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TREATISE 


HUMAN  PHYSIOLOGY. 


FOR  THE  USE  OF 


STUDENTS  AND  PRACTITIONERS  OF  MEDICINE. 


BY 

HEXRY  C.  CHAPMAN,  M.D., 

PROFESSOR  OF  INSTITUTES  OF  MEDICINE  AND  MEDICAL  JURISPRUDENCE  IN  THE  JEFFERSON  MEDICAL  COLLEGE 

OF  PHILADELPHIA  ;    MEMBER  OF  THE  COLLEGE  OF  PHYSICIANS  OF  PHILADELPHIA,   OF  THE  ACADEMY 

OF  NATURAL  SCIENCES  OF  PHILADELPHIA,  OF  THE  AMERICAN  PHILOSOPHICAL  SOCIETY*, 

AND  OF  THE  ZOOLOGICAL  SOCIETY  OF  PHILADELPHIA. 


PHILADELPHIA: 

LEA  BROTHERS  &  CO 

1887. 


Entered  according  to  Act  of  Congress  in  the  year  1887,  by 

LEA  BROTHEES  &  CO., 

In  the  Office  of  the  Librarian  of  Congress  at  Washington.    All  rights  reserved. 


DORNAN,  PR1NTKR. 


TO 


MY  WIFE 


THIS  WORK  IS  AFFECTIONATELY  DEDICATED 


AS  A  SMALL  ACKNOWLEDGMENT  OF  THE  INTEREST  EVINCED  AND 


ENCOURAGEMENT  EXTENDED  IN  ITS  COMPLETION, 


THE  AUTHOR, 


PREFACE. 


To  those  familiar  with  the  many  excellent  German,  French,  and 
English  treatises  upon  Physiology,  it  may  appear  strange  that  the 
author  should  feel  it  incumbent  upon  himself  to  offer  one  more  con- 
tribution upon  such  a  well-worn  theme.  The  experience,  however,  of 
the  past  eight  years,  as  Professor  of  the  Institutes  of  Medicine  or 
Physiology  in  the  Jefferson  Medical  College  of  Philadelphia,  has 
convinced  the  author  that  there  is  a  want  felt  by  students  and  prac- 
titioners of  medicine  for  a  systematic  work,  representing  the  existing 
state  of  physiology  and  its  methods  of  investigation,  and  based  upon 
comparative  and  pathological  anatomy,  clinical  medicine,  physics, 
and  chemistry,  as  well  as  upon  experimental  research.  It  is  the 
hope  of  the  author  that  the  present  work,  embodying  essentially  his 
teaching,  Avill  not  only  supply  such  a  want,  but  will  facilitate  and 
stimulate  the  study  of  this  most  important  branch,  the  institutes, 
that  is  to  say,  the  foundation  of  all  rational  medicine.  The  author 
takes  much  pleasure  in  here  expressing  his  acknowledgments  to  Dr. 
A.  P.  Brubaker,  Demonstrator  of  Physiology  in  the  Jefferson  Medical 
College,  for  the  assistance  rendered  in  the  performance  of  the  experi- 
mental part  of  the  work  ;  to  Arthur  E.  Brown,  Esq.,  Superintendent 
of  the  Zoological  Garden,  of  Philadelphia,  for  the  many  facilities  and 
courtesies  extended  in  the  dissection  of  the  rare  animals  that  have 
died  at  the  Garden,  the  results  of  which  are  frequently  made  use  of 
in  the  work,  and  to  Dr.  Lawrence  Wolff,  Demonstrator  of  Chemistry 
in  the  Jefferson  Medical  College,  for  the  favor  of  seeing  the  work 
through  the  press. 

HENRY  C.  CHAPMAN. 

Philadelphia,  October  10.  1887. 


CONTENTS. 


PAGE 

Introduction 33-42 


CHAPTER  I. 

GENERAL  STRUCTURE  OF  THE  BODY,  PHYSICALLY  AND  CHEMICALLY. 
PROXIMATE  PRINCIPLES  OP  INORGANIC  ORIGIN. 

Organs — Tissues — Cells — Water — Sodium  Chloride — Potassium  Chloride 
— Calcium  Phosphate — Calcium  Carbonate— Sodium  Carbonate  .     43-54 

CHAPTER  II. 

NON-NITROGENOUS  PROXIMATE  PRINCIPLES  OF  ORGANIC  ORIGIN. 

Starch— Sugar— Fat 55-65 

CHAPTER  III. 

NITROGENOUS  PROXIMATE  PRINCIPLES  OF  ORGANIC  ORIGIN. 

Albuminose — Fibrin  —  Casein — Mucosin — Pancreatin  — Pepsin — Ostein 
— Cartilagin— Globulin,  Crystallin,  Musculin — Elasticin  and  Keratin — 
Haematin — Melanin — Biliverdin — Urrosacin — Resume        .         .         .     66-79 

CHAPTER  IV. 

FOOD. 

Hunger  and  Thirst— Use  of  Food— Kinds  of  Food         ....     80-87 

CHAPTER  V. 

QUALITY  AND  QUANTITY  OF  FOOD. 

Tea    and    Coffee — Tobacco — Alcohol — Distilled    Liquors — Wine — Malt 

Liquors 88-98 


Vlll  CONTENTS. 

CHAPTER  VI. 

DIGESTION. 

PAGE 

The  Teeth— Mastication— Enamel— Cement— Tooth  Pulp— Maxillary 
Bones  and  Temporo-maxillary  Articulation — Intermaxillary  Bone — 
Muscles  of  Mastication — Resume        .......  99-113 

CHAPTER  VII. 

[NSALIVATION  AND  DEGLUTITION. 

Insalivation — Deglutition 114-123 

CHAPTER  VIII. 

GASTRIC  DIGESTION. 

Function  of  the  Stomach — Experiments  on  Digestion — Mucous  Mem- 
brane of  Stomach — Gastric  Glands — Gastric  Juice   ....     124-136 

CHAPTER  IX. 

GASTRIC  DIGESTION. — ( Continued.) 
Composition  of  Gastric  Juice 137-146 

CHAPTER  X. 

INTESTINAL  DIGESTION.      INTESTINAL  JUICE.       PANCREATIC  JUICE.      LIVER. 
GLYCOGEN.      BILE.      FECES.       DEFECATION. 

Intestinal  Juice — Pancreatic  Juice — The  Bile — The  Large  Intestine — 
The  Contents  of  the  Large  Intestine — Defecation — Resume  of 
Digestion 147-187 

CHAPTER  XL 

ABSORPTION. 

Lacteals,  Thoracic  Duct,  etc. — Lymphatic  System — Lymph  and  Chyle 
— Structure  of  Villi — Chyle — Venous  Absorption — Absorption  by 
Stomach  and  Rectum 188-201 

CHAPTER  XH. 

OSMOSIS. 

Endosmometer — Capillary  Attraction — Miscibility  of  Liquids — Condi- 
tions favoring  Absorption — Resume  of  Absorption  ....     202-211 


CONTENTS.  IX 

CHAPTER  XIII. 

THE  BLOOD. 

PAGE 

Quantity  of  Blood  in  Human  Body — Red  Corpuscles — Diameters  of 
Red  Blood-corpuscles — Red  Blood  corpuscles  of  Vertebrates  .         .     212-221 

CHAPTER  XIV. 

the  blood. — (Continued.) 

White  Corpuscles — Structure  of  Solitary  and  Lymphatic  Grlands — 
Structure  of  Spleen—Production  of  White  Corpuscles— Thymus 
Grland— Elementary  Corpuscles 223-235 

CHAPTER  XV. 

THE  BLOOD. — I  Continued.) 
Coagulation  of  the  Blood 236-241 

CHAPTER  XVI. 

THE  BLOOD. — {Continued.) 

Composition  of  the  Blood — Composition  of  the  Corpuscles  .         .         .     242-247 

CHAPTER  XVII. 

THE  BLOOD.  —  I  <  'nn tinned.) 

Haemoglobin — Hajmatin — Gases  of  the  Blood — Arterial  and  Venous 
Blood— Salts  of  the  Blood— Transfusion 248-263 

CHAPTER  XVIII. 

CIRCULATION  OF  THE  BLOOD. 

The  Heart — Rhythm  of  Motion  of  Heart — Vibrator — Capacity  of 

Heart 264-277 

CHAPTER  XIX. 

THE  HEART. 

Cardiograph— Work  Done  by  the  Heart — Cause  of  Sounds  of  Heart 
— Conditions  Influencing  Heart's  Action — Conditions  Influencing 
Pulse — Cause  of  Heart's  Contraction — Stimulus  to  Heart's  Action.     278-292 

CHAPTER  XX. 

THE  ARTERIES. 

Flow  of  Liquids  through  Tubes — Elasticity  and  Contractility  of  Arteries ' 
—Dilatation  of  Arteries 293-300 


PAGE 


X  CONTENTS. 

CHAPTER  XXI. 

the  arteries. — ( Continued. ) 
Sphygmograph — Arterial  Schema 3(11-312 

CHAPTER  XXII. 

PRESSURE  AND  VELOCITY  OP  THE  BLOOD  IN  THE  ARTERIES. 

Pressure  of  Liquids — Hydrostatic  Paradox — Hydrostatic  Bellows — 
Blood  Pressure — Haemodynamometer — Arterial  Pressure — Aortic 
Pressure— Kymograph — Blood  Pressure  in  Turtle  and  Frag — Differ- 
ential Manometer — Spring  Kymograph — Hocmodromonieter —  Stro- 
mubr — Hsemodromograph— Traces  of  Pressure  and  Velocity  of 
Blood 313-345 

CHAPTER  XXIII. 

THE  CAPILLARIES. 

Structure  of  Capillaries— Capacity  of  Capillary  System — Phenomena 
of  Capillary  Circulation — Velocity  of  Blood  in  Capillaries — Plethys- 
mograph — Pressure  of  Blood  in  Capillaries— Capillary  Force  .        .     346-360 

CHAPTER  XXIV. 

THE  VEINS. 

Capacity  of  Venous  System — Venous  Pressure — Causes  of  Flow  of 
Blood  in  Veins — Rapidity  of  Circulation 361-371 

CHAPTER  XXV. 

HISTORY  OF  THE  DISCOVERY  OF  THE  CIRCULATION  OF  THE  BLOOD. 

Knowledge  of  the  Ancients — Demonstration  of  the  Function  of  Arteries 
— Discovery  of  Pulmonary  Circulation — Discovery  of  Systematic 
Circulation — Knowledge  at  the  End  of  the  Sixteenth  Century — 
Appearance  of  Harvey's  Work — Discovery  of  the  Capillaries — 
Demonstration  of  Circulation  by  Injections 372-390 

CHAPTER  XXVI. 

RESPIRATION. 

Respiration  in  Invertebrata— Structure  of  Larynx — Structure  of 
Trachea — Apparatus  of  Calliburces — Structure  of  Pleura — Inspira- 
tion and  Expiration 391-403 

CHAPTER  XXVII. 

MUSCLES  OF  RESPIRATION. 

Inspiration — Expiration 404-415 


CONTENTS  xi 

CHAPTER  XXVIII. 

RESPIRATORY  MOVEMENTS  AS  STUDIED  BY  THE  GRAPHIC  METHOD. 

PAGE 

Mechanical  Work  Performed  during  Respiration — Breathing  Capacity.     416-437 

CHAPTER  XXIX. 

ABSORPTION  OF  OXYGEN — EXHALATION  OF   CARBONIC  ACID. 

Valentin  and  Brunner's  Apparatus — Amount  of  Oxygen  Absorbed — 
Regnault's  Respiration  Apparatus — Lud wig's  Respiration  Appa- 
ratus— Carbonic  Acid  Exhaled — Voit's  Respiration  Apparatus — 
Determination  of  Carbonic  Acid  Exhaled         .....     438-455 

CHAPTER  XXX. 

CONDITIONS  [NFLUENCING  PRODUCTION  OF  CARBONIC  ACID,  EXHALATION  OF 
WATERY  VAPOR,  ORGANIC  MATTER,  AND  VENTILATION. 

Per  Cent,  of  Carbonic  Acid  in  Exhaled  Air — Exhalation  of  Carbonic 
Acid — Production  of  Carbonic  Acid — Exhalation  of  Water — Organic 
Matter  Exhaled— Asphyxia 456-469 

CHAPTER  XXXI. 

ANIMAL  HEAT. 

Age  and  Sex — Daily  Variations — Food — Muscular  and   Mental  and 

Glandular  Action — Surrounding  Temperature  .....     470-483 

CHAPTER  XXXII. 

PRODUCTION  OF  ANIMAL  HEAT. 

The  Calorimeter — Specific  Heat  of  Tissues — Heat  Produced  in  Twenty- 
four  Hours— Heat  Value  of  Foods  .......     484-498 

CHAPTER  XXXIII. 

EXPENDITURE  AND  REGULATION  OF  HEAT. 

Correlation  of  Heat  and  Mechanical  Work — Conditions  Influencing 
Expenditure  of  Heat — Influence  of  Baths  and  Clothing — Regula- 
tion of  Heat  Produced  and  Expended 499-507 

CHAPTER  XXXIV. 

THE  KIDNEYS  AND  URINE. 

Structure  of  Kidney — The  Urine — Constituents  of  the  Urine — Deter- 
mination of  Urea — Influence  of  Muscular  Exercise — Origin  of  Urea.     508-523 


Xll  CONTENTS. 


CHAPTER  XXXV. 

THE  URINE. 

PAGE 

Origin  of  Uric  Acid — Origin  of  Hippuric  Acid — Excretion  of  Urine — 
Formation  of  Alkaline  Urine 524r-533 

CHAPTER  XXXVI. 

STRUCTURE  OF  NERVOl  S  SYSTEM. 

Medullated  Nerve  Fibres — Axis-cylinder  of  Nerves— Gelatinous  Nerve 
Fibres — Peripheral  Distribution  of  Nerves — Composition  of  Nervous 
System 534-544 

CHAPTER  XXXVII. 

BATTERIES.  OH.m's  LAW.  INDUCTION  APPARATUS.  PENDULUM  MYOGRAPH. 
SPRING    MYOGRAPH.      WHIPPE.       LATENT    PERIOD.      VELOCITY    OF    NERVE 

FORCE,  ETC. 

Polarization — Potential — Electromotive  Force,  etc. — Resistance-box — 
Influence  of  Resistance — Induction  Apparatus — Unipolar  Induction 
— Helmholtz's  Induction  Apparatus — Traces  of  Muscular  Contraction 
—  Marking  Lever — Pendulum  Myograph  —  Spring  Myograph  — 
Rapidity  of  Tnnsmission  of  Nerve  Force — Muscular  and  Nervous 
Force 545-571 

CHAPTER  XXXVIII. 

GALVANOMETERS.  NON-POLARIZABLE  ELECTRODES.  ELECTRICAL  CURRENT. 
RESISTANCE.  ELECTROMOTIVE  FORCE  OF  NERVE.  CAUSE  OF  ELECTRICAL 
CURRENT  OF  NERVE. 

Multiplier — Scale  and  Lamp  for  Galvanometer—  Wiedemann's  Gal- 
vanometer— Telescope  and  Scale  for  Galvanometer — Disposition  of 
Diverting  Vessels — Physiological  Rheoscope — Resistance  of  Nerve 
— Electromotive  Force — Graduation  Constant— Round  Compensator 
— Double  Dipolar  Molecules— Static  and  Dynamic  Electricity  .         .     572-595 

CHAPTER  XXXIX. 

NECA  XTVE  VARIATION.      RAPIDITY  OF  ITS  PROGRESSION.      ELECTROTONIC 
CURRENTS.      ELECTROTOM  S. 

Negative  Variation — Differential  Rheotome  —  Rheocord — Rate  of 
Propagation  of  Negative  Variation — Wave  of  Negative  Variation 
— Effect  of  Constant  Current — Electromotive  Molecules — Passage 
of  Electrical  Current,  etc — Electrotonic  Currents — Electrotonus — 
Effect  of  Strength  of  Constant  Current — Ritter's  Law    .         .        .     596-622 


CONTENTS.  Xlll 


CHAPTER  XL. 

THE  SPINAL  CORD,  ITS  STRUCTURE  AND  FUNCTIONS  AS  A  CONDUCTOR  OF 
MOTOR  AND  SENSORY  IMPULSES. 

PAGE 

Course  of  Nerve  Fibres — Medulla  Oblongata — Functions  of  Anterior 
and  Posterior  Roots — Degeneration  of  the  Nerve  Fibres — Decussa- 
tion of  Nerve  Fibres — Distribution  of  Spinal  Nerves       .         .        .     623-638 

CHAPTER  XLT. 

THE  SPINAL  CORD  AS  A  NERVOUS  CENTRE.      REFLEX  ACTION. 

The  Spinal  Cord  as  a  Nervous  Centre — Nervous  System  of  Sea  Hare 
and  Centipede — Ratio  of  Brain  to  Spinal  Cord — Nature  of  a  Reflex 
Action — Spinal  Nerve  Centres .     639-650 

CHAPTER  XLIL 

THE  MEDULLARY  NERVES. 

Third  Nerve  ;  Motor  Oculi  Communis — Fourth  Nerve  ;  Patheticus — 
Fifth  Nerve ;  Trigeminal — Seventh  Nerve ;  Portio  Dura,  Facial — 
Ninth  Nerve;  Glossopharyngeal — Tenth  Nerve;  Pneumogastric — 
Eleventh  Nerve;  Spinal  Accessory — Twelfth  Nerve ;  Hypoglossal  .     651-687 

CHAPTER  XLIII. 

THE  PONS  VAROLII.      CRURA  CEREBRI.      CORPORA  STRIATA.      THALAMI   OPTICI. 
CORPORA  QUADRIGEMINA.      CEREBELLUM. 

Crura  Cerebri— Corpora  Striata — Thalami  Optici — Function  of  Corpora 

Quadrigemina — Cerebellum — Coordinating  Power  of  Cerebellum    .     688-701 

CHAPTER  XLIV. 

THE  CEREBRAL  HEMISPHERES. 

Cerebral  Fissures  and  Convolutions  —  Cerebral  Tissues — Weight  of 
Brain — Injury  to  the  Cerebral  Hemispheres — Comparative  Devel- 
opment of  the  Brain — Localization  of  Functions — Aphasia — Causa- 
tion of  Sleep — Functions  of  Cerebral  Hemispheres  ....     702-723 

CHAPTER  XLY. 

SYMPATHETIC  NERVOUS  SYSTEM. 

Sympathetic  Nerve — Cervical  Ganglia  and  Cardiac  Nerves — Lumbar 
and  Sacral  Ganglia — Effects  of  Division  of  Cervical  Sympathetic — 
Vaso-dilator  Nerves — Oncometer     .......     724-736 


XIV  CONTENTS. 

CHAPTER  XLVI. 

THE  SKIN  AND  ITS  APPENDAGES.      PERSPIRATION.      GENERAL    LND  TACTILE 

SENSIBILITY. 

PAOE 

The   Skin — The   Nails — The    Hairs —Sebaceous    Glands— Mammary 

Glands  and  Milk — Sudoriferous  Glands — Perspiration      .         .         .     737-760 

CHAPTER  XLVII. 

THE  NOSE  AND  OLFACTION.      THE  TONGUE  AND  GUSTATION. 
Olfaction — The  Tongue  and  Gustation  ......     761-768 

CHAPTER  XLVIII. 

THE  EYE  AND  VISION. 

The  Eyeball — The  Sclerotic  and  Cornea — The  Choroid — Ciliary  Pro- 
cesses—  Ciliary  Muscle  —  The  Iris  —  The  Retina  —  The  Vitreous 
Humor  and  Hyaloid  Tunic — The  Crystalline  Lens — The  Aqueous 
Humor 769-782 

CHAPTER  XLIX. 

PHYSIOLOGICAL  OPTICS. 
Refraction  and  Accommodation 783-805 

CHAPTER  L. 

BINOCULAR  VISION.      SENSATION  AND  PERCEPTION  OF  SIGHT.      PROTECTIVE 
APPENDAGES  OF  THE  EYE. 

Sensation  of   Sight — Perception  by  Sight — Protective   Appendages, 

etc.,  of  the  Eye 806-821 

CHAPTER  LT. 

PHYSIOLOGICAL  ACOUSTICS. 

Intensity  of  Sound — Pitch  of  Sound— Quality  of  Sound     .         .         .     822-839 

CHAPTER  LIT. 

THE  LARYNX,  AND  THE  PRODUCTION  OF  THE  VOICE  AND  SPEECH. 

The  Larynx — Production  of  the  Voice — Speech  ....     840-854 

CHAPTER  LIII. 

THE  STRUCTURE  OF  THE  EAR,  AND  THE  SENSATION  OF  HEARING. 

The  Structure  and  Functions  of  the  External  Ear — The  Structure  of 
the  Middle  Ear— Functions  of  the  Middle  Ear- Structure  of  the 
Internal  Ear — Functions  of  the  Internal  Ear 855-874 


CONTENTS.  XV 

CHAPTER  LIV. 

MUSCULAR  CONTRACTILITY. 

PAGE 

Muscular  Contractility 875-884 

CHAPTER  LV. 

REPRODUCTION. 

Spontaneous  Generation — Fissiparous,  Gem mi  parous,  and  Sexual  Gen- 
eration— Female  Generative  Apparatus — Corpus  Luteum  of  Men- 
struation and  Pregnancy — Menstruation — The  Male  Generative 
Apparatus 885-899 

CHAPTER  LVI. 

REPRODUCTION. — ( Concluded.) 

Impregnation  of  the  Ovum  and  Development  of  Embryo — Formation 
of  Blastodermic  Membrane — Development  of  Primitive  Trace — 
Development  of  Primitive  Organs— Development  of  Amnion,  Allan- 
tois,  and  Umbilical  Vesicle — Development  of  the  Nervous  System 
— Development  of  Alimentary  Canal  and  its  Appendages — De- 
velopment of  the  Vascular  System — Development  of  Respiratory 
Organs — Development  of  the  Genito-urinary  Organs — Development 
of  Extremities — Development  of  the  Placenta         ....     900-931 


PHYSIOLOGY. 


INTRODUCTION. 

Physiology,  from  the  Greek  ?vo/c  and  >■'->:"<:,  literally  means  a  discourse 
on  Nature.  At  the  present  day,  however,  the  word  has  not  such  an 
extended  significance,  physiology  as  understood  by  naturalists  and  phy- 
sicians meaning  the  study  of  the  functions  or  uses  of  the  parts  of  which 
living  beings  consist. 

I  use  the  word  parts,  in  preference  to  that  of  structures,  inasmuch  as 
there  are  beings  like  the  monera,  simple  masses  of  a  jelly-like  substance 
or  protoplasm,  which  are  so  structureless  and  unorganized  that  great 
difficulty  is  experienced  in  classifying  them,  it  being  questionable 
whether  they  should  be  ranged  among  plants  or  animals,  or  relegated 
to  an  intermediate  kingdom,  the  u  Protistenreich  "  of  Hteckel,1  or,  as 
Huxley2  expresses  it,  a  sort  of  a  biological  "no  man's  land."  Indeed 
it  has  been  doubted  whether  the  term  living  at  all  could  be  properly 
applied  to  the  monera  in  the  same  sense  in  which  that  word  is  used  in 
reference  to  the  higher  animals.  As  the  totality  of  the  functions  or 
uses  of  the  parts,  structures,  or  organs  of  which  living  beings  consist, 
constitute  their  life,  I  may  define  Physiology  therefore  as  the  study  of 
life  or  of  function. 

Necessarily  from  the  definition,  Physiology  presupposes  a  knowledge 
of  anatomy  or  structure.  The  relation  of  the  two  may  be  compared  to 
the  study  of  a  clock  when  at  rest  and  when  going. 

The  anatomist  studies  the  form  and  relation  of  the  weights,  the  pen- 
dulum, the  hands,  etc.,  at  rest ;  the  physiologist,  the  fall  of  the  weight, 
the  swinging  of  the  pendulum,  the  movement  of  the  hands.  Anatomy 
is  the  statical,  physiology  the  dynamical,  part  of  biology. 

As  well  might  the  mechanician  hope  to  understand  the  movements 
of  the  clock  and  to  regulate  it  without  a  knowledge  of  the  parts  com- 
posing it,  as  for  the  physiologist  to  understand  the  motions  of  the  living 
body  without  a  previous  knowledge  of  its  structure. 

Anatomy  and  physiology  are  so  intimately  associated  that,  philo- 
sophically, they  should  be  studied  together ;  indeed,  to  separate  them, 
except  for  the  convenience  of  teaching,  is  highly  illogical. 

As  Hyrtl3  well  observes,  "Anatomy,  unassociated  with  phvsiology,  is 
a  mindless  study  and  does  not  deserve  the  name  of  a  science.  Can  one 
study  the  arrangement  of  a  machine  without  any  reference  to  its  object  ? 

1  Generelle  .Mur|ilml,i2ie.  I!.l    j.  S.  x\ii.     Berlin,  18(56. 

-  Physical  Basis  of  Life,  p.  129.     Lay  Sermons.     New  York,  1871. 

3  Lehrbuch  tier  Auatoniie,  S.  18.     Wien,  1881. 

3 


34  INTRODUCTION. 

It  is  possible  simply  to  view  the  harmoniously  arranged  parts  of  a  whole, 
simply  to  stare  at  it  without  reflection.  The  anatomist  can  undertake 
no  investigation  without  considering  the  physiological  questions  in- 
volved. The  paths  of  both  sciences  meet  and  cross  each  other  in  so 
many  places  that  there  are  but  few  divergent  points." 

In  beginning  the  study  of  any  subject  not  only  is  it  indispensable 
that  the  object  of  the  investigation  should  be  clearly  defined,  but  it  is 
proper  that  relation  to  knowledge  in  general  should  be  pointed  out. 

The  classification  of  the  sciences  has  been  a  vexed. one  from  the  time 
of  Bacon1  to  Comte.2  This,  from  the  nature  of  things,  might  have 
been  expected;  for  there  are  no  sharply  defined  lines  in  nature;  one 
science  encroaches  so  upon  another  that  it  is  impossible  to  say  where 
the  one  ends  and  the  other  begins.  All  classification,  therefore,  must 
be  imperfect.  The  following  one,  that  of  Comte,  is  open  to  many 
criticisms,  as  shown  in  the  masterly  essay  of  Spencer.3 

Table  I. 

Mathematics. 

Astronomy. 

Physics 

Chemistry.       (    p 

Biology.  <     y  ..-,    "*'      f    Anatomy. 

Sociology.        (  &J-     ^    Physiology. 


Classification 
of 
Knowledge 


Admitting  its  manv  faults,  I  make  use  of  it  here  on  account  of  its 
brevity  simply  to  indicate  the  position  of  Physiology  relatively  to  that 
of  other  kinds  of  knowledge. 

It  will  be  seen,  from  the  table,  that  the  study  of  plants  and  animals 
constitutes  the  subject-matter  of  Biology. 

The  second  division  of  this  grand  science  comprehends  all  that  is 
known  of  the  structure,  functions,  habits,  geographical  and  geological 
distribution  of  animals  :  therefore,  the  study  of  animal  functions  or 
animal  physiology  is  a  subdivision  of  Zoology.  In  the  same  manner, 
vegetal  physiology  forms  a  part  of  Botany.  Human  physiology,  a  part 
of  general  animal  physiology,  forms  the  subject  of  this  work. 

If  the  sciences  are  studied  in  the  order  in  which  they  follow  each 
other  in  Table  I.,  then  the  inorganic  will  precede  the  organic.  This  is 
the  logical  order  and  historically  the  one  in  which  they  were,  generally 
speaking,  cultivated,  for  the  phenomena  of  the  inorganic  world  are  less 
complex  and  more  easily  generalized  than  those  of  the  organic,  and, 
therefore,  more  readily  investigated.  Wherever  practicable,  the  his- 
torical order  will  be  found  to  be  the  best  one  to  pursue  in  the  study  of 
any  science;  indeed,  as  we  proceed,  it  will  be  seen  that  the  phenomena 
of  physiology  depend  upon  physical  and  chemical  laws,  and  that  probably, 
with  the  advance  of  knowledge,  the  whole  subject  will  be  treated  as  a 
branch  of  molecular  physics — hence  the  indispensability  to  the  student 
of  physiology  of  a  knowledge  ot  physical  and  chemical  science. 
Ample  illustrations  of  the  value  of  such  knowledge  will  be  given  when 

i  De  Augmentis  Scientiarum.  -  fours  de  Philosophie  Positive. 

*  Genesis  of  Science.     Essays.    London,  1868. 


INTRODUCTION.  35 

the  special  functions  are  considered.  The  special  senses  of  sight  and 
hearing,  for  example,  depend  for  their  successful  study  upon  familiarity 
with  optics  and  acoustics  ;  the  investigation  of  the  circulation  is  a  ques- 
tion of  hydraulics  ;  that  of  secretion,  of  organic  chemistry. 

By  referring  to  Table  I.,  it  will  be  observed  that  Botany  comes  before 
Zoology  ;  where  practicable,  its  study  should  precede  that  of  Zoology, 
for  plants  serve  to  bridge  over,  to  a  certain  extent,  the  gap  between  the 
mineral  and  animal  world,  and  at  different  points  touch  the  confines 
of  these  two  kingdoms.  Further,  with  some  exceptions,  plants  are 
destitute  of  a  nervous  system,  and  even  if  extended  investigation  should 
show  that  their  nervous  system  is  more  developed  than  now  it  is  sup- 
posed to  be,  it  would  exercise  a  small  influence  as  compared  with  that 
of  the  higher  animals.  Plants,  therefore,  offer  a  favorable  opportunity 
of  examining  the  processes  of  nutrition  uninfluenced  by  the  nervous 
system. 

When  we  come  to  examine  the  circulation,  digestion,  etc.,  in  man, 
we  shall  see  that  these  functions  are  greatly  modified  by  the  nervous 
system  ;  hence  the  advantage  of  studying  nutrition  in  lower  organiza- 
tions where  these  disturbing  elements  are  eliminated. 

Having  endeavored  to  define  the  object  of  our  study,  and  to  indicate 
its  limits  and  relation  to  knowledge  in  general,  let  me  now  consider  the 
different  methods  by  which  human  physiology  can  be  investigated — and, 
first,  a  great  deal  can  be  learned  of  the  functions  of  the  human  body 
by  careful  i-eflection  on  the  structure  of  the  same.  Bailer1  says  :  "  and 
first  the  fabric  of  the  human  body  is  to  be  learned,  whose  parts  are 
almost  infinite.  Those  who-  would  study  physiology  separately  from 
anatomy  certainly  seem  to  me,  can  be  compared  with  mathematicians 
who  undertake  to  express,  by  calculation,  the  forces  and  functions  of  a 
certain  machine  of  which  they  have  learned  neither  disks,  wheels, 
measures,  nor  material.  Truly  I  am  persuaded  that  we  know  scarcely 
anything  of  physiology  unless  we  have  learned  it  through  anatomy." 

Undoubtedly,  the  functions  of  many  organs  might  be  inferred  from 
the  thorough  studv  of  their  structure.  As  a  matter  of  historv,  the 
demonstration  of  the  valves  in  the  veins  by  Fabricius  to  Harvey  was 
one  of  the  important  facts  that  first  suggested  to  the  latter  to  investigate 
the  flow  of  the  blood. 

The  functions  of  certain  nerves  Avill  probably  be  never  definitely 
settled  until  anatomy  has  determined  whether  they  terminate  in  muscle, 
gland,  or  sensory  organs. 

Those  grand  old  anatomists,  Eustachius,  Fallopius,  Vesalius,  with 
their  physiological  followers,  Harvey,  Haller,  and  Hunter,  have  well 
illustrated  in  their  works  the  important  relations  of  anatomy  to  physi- 
ology. 

Not  only,  however,  is  a  knowledge  of  general  descriptive  anatomy 
necessary,  but  it  is  indispensable  also  that  the  student  who  hopes  to 
cultivate  physiology  with  any  success,  must  have  a  thorough  training  in 
histology,  or  the  science  which  has  for  its  object  the  study  of  the  tissues. 

The  necessity  of   a  thorough  knowledge   of  structure,   in  order  to 

1  Elementa  Physiologist-.    Lausanna?,  MDCC'LVII.     Preface,  p.  1. 


36  INTRODUCTION. 

understand  function,  is  so  obvious  that  it  seems  superfluous  to  dwell 
further  upon  it.  Pathology  furnishes  valuable  data  to  the  student  of 
human  physiology.  Where  disease  is  restricted  to  one  organ,  and  when 
it  is  noticed  that  with  the  destruction  of  the  tissues  composing  it  a  par- 
ticular function  gradually  weakens  and  finally  disappears,  it  is  a  logical 
inference  that  the  loss  of  function  is  dependent  upon  the  loss  of  struc- 
ture. In  this  way  the  uses  of  many  parts  might  be  ascertained — hence, 
the  importance  of  carefully  kept  clinical  records  and  thorough  post- 
mortem examination. 

Suppose,  for  example,  that,  associated  with  loss  or  want  of  speech, 
in  the  majority  of  instances  it  is  found,  after  death,  that  a  particular 
convolution  in  the  hemisphere  of  the  brain  is  either  wanting,  unde- 
veloped, or  diseased — it  would  be  a  fair  conclusion  that  the  faculty  of 
speech  was  connected,  in  some  way,  with  this  particular  convolution, 
especially  if  it  was  clearly  shown  that  the  facts  were  not  mere  coinci- 
dence, but  bore  the  relation  of  cause  and  effect.  Or  take  the  case  of 
a  human  being  suddenly  paralyzed  upon  one  side  of  the  body  both  with 
reference  to  sensation  and  motion,  and  post-mortem  examination  re- 
vealed that  certain  parts  of  the  opposite  side  of  the  brain  were  affected, 
as  in  apoplexy,  for  example.  It  would  be  natural  then,  to  consider 
that  the  parts  affected  in  the  one  side  of  the  brain  presided  over  the 
opposite  side  of  the  body  and  extremities — or,  take  the  case  of  a  man 
suddenly  stabbed  in  the  back-bone,  the  instrument  penetrating  only 
half-way  through  the  spinal  cord,  and  the  patient  loses  voluntary  motion 
on  the  side  of  the  wound,  and  sensation  on  the  opposite  side — the  view 
that  the  sensory  fibres  decussate  in  the  cord,  and  the  motor  one  in  the 
medulla  would  be  confirmed. 

While,  according  to  many  thinkers,  clinical  medicine  and  morbid 
anatomy  alone  will  not  furnish  data  sufficient  to  deduce  a  physiology 
and  a  rational  pathology,  undoubtedly  such  facts  as  the  above  are  in- 
valuable as  aids  in  throwing  light  upon  the  still  obscure  functions  of  the 
nervous  system  and  the  uses  of  other  structures  in  the  human  body. 

The  admirable  observations  of  Beaumont1  and  Budge2  upon  human 
beings,  in  whom  the  stomach  and  intestine  had  been  wounded  in  such  a 
manner  as  to  render  them  susceptible  of  experiment,  are  illustrations  of 
the  application  of  pathological  cases  to  the  study  of  physiology. 

When  the  vast  complexity  of  structure  exhibited  by  the  human 
organization  is  considered,  it  becomes  evident  that  any  investigation  of 
its  function,  however  extended,  if  it  be  confined  to  man  alone,  can  lead 
to  but  very  limited  results. 

Comparative  anatomy  has  shown,  however,  that  the  life  of  the  animal 
kingdom  is  a  grand  panorama,  each  fleeting  form,  as  it  passes  before 
the  view,  recalling  that  which  has  just  passed,  foreshadowing  that  which 
is  to  come;  the  simplest  of  living  beings,  so  lowly  organized  and 
transparent  that  their  entire  life  processes  can  be  observed  by  the 
microscope,  leading  through  intermediate  forms  to  higher  types  of  life, 
closely  approaching  that  of  man  himself.  With  the  development  of 
additional  structures,  we  find  correspondingly  increased  functions,  and 
infer  that  the  new  function  is  due  to  the  new  structure. 

1  Experiments  and  Observations.     Plattsburg,  1833.  -  Vircbow's  Arcbiv,  Bd.  xiv.  S.  140. 


INTRODUCTION.  37 

The  comparative  method  of  investigation  is  therefore  the  opposite  of 
the  pathological  one,  by  which,  as  we  have  seen,  the  use  of  a  structure 
is  inferred  from  loss  of  function  dependent  upon  the  loss  of  structure. 

In  the  hands  of  Harvey,  Hunter,  Cuvier,  Muller,  Milne,  Edwards, 
Owen,  comparative  anatomy  has  proved  of  invaluable  service  in  the 
study  of  physiology. 

In  his  great  work,  Harvey1  states  "  that  if  anatomists  had  given  to 
the  organization  of  the  inferior  animals  the  same  attention  that  they 
devote  to  the  structure  of  the  human  body,  the  question  of  the  circula- 
tion would  long  since  have  been  determined." 

Observations  upon  the  enlargement  of  the  collateral  vessels  in  the 
horns  of  the  deer  when  in  the  velvet  after  ligature  of  the  carotid,  sug- 
gested to  the  great  physiological  surgeon,  John  Hunter,2  the  idea  of  the 
collateral  vessels  maintaining  the  circulation  in  the  thigh  after  ligature 
of  the  main  trunk. 

The  ligation  of  the  carotid  in  the  dog,3  and  of  the  femoral  in  the 
same  animal,  done  by  Home4  at  the  suggestion  of  Hunter,  having 
further  convinced  the  latter  of  the  feasibility  of  ligation  as  a  cure  for 
aneurism,  Hunter  tied  the  femoral  artery  in  the  celebrated  case  of  the 
coachman  suffering  from  popliteal  aneurism  and  thereby  introduced  a 
most  capital  improvement  in  surgery.5 

To  study  the  physiology  of  man  without  the  slightest  knowledge  of 
life  as  exhibited  in  the  lower  animals  is  as  if  one  would  attempt  to 
master  the  steam  engine  without  any  acquaintance  with  the  elementary 
laws  of  heat  or  mechanics,  or  to  investigate  a  magnetic  apparatus  with- 
out knowing  anything  about  the  simple  facts  of  electricity. 

As  the  study  of  comparative  anatomy,  in  its  application  to  human 
physiology,  at  the  present  day,  is  very  much  neglected,  it  may  not  be 
superfluous  to  offer  a  few  instances  as  illustrations  of  the  importance  of 
the  study  in  this  respect.  For  example,  from  the  fact  of  the  bile  and 
pancreatic  juice  passing  into  the  alimentary  canal  at  the  same  point  in 
man,  it  is  impossible  to  say  to  which  of  these  fluids  the  changes  ex- 
hibited after  their  mixture  with  the  food  are  due. 

By  examining  the  rabbit  or  the  beaver,  however,  we  find  that  the 
opening  of  the  pancreatic  duct  into  the  intestine  is  situated  twelve 
inches  and  more  below  that  of  the  bile-duct.  Hence,  the  different 
changes  exhibited  by  the  food  as  it  is  successively  affected  by  these 
secretions,  can  be  perfectly  observed  by  killing  a  rabbit  or  beaver  in 
full  digestion.  Indeed,  as  we  shall  see,  it  is  in  this  way  the  emulsifying 
power  of  the  pancreas  is  usually  demonstrated.6  Again,  the  question 
as  to  whether  the  bile  is  a  secretion  or  an  excretion  finds  its  answer  in 
the  structure  of  the  doris,7  a  little  mollusk  in  which  the  liver  has  two 
ducts,  one  of  which  carries  the  bile  into  the  alimentary  canal,  where  it 
mixes  with  the  food,  while  the  other  removes  it  at  once  from  the  body, 
showing  that  the  bile,  in  this  case  at  least,  is  both  a  secretion  and  an 
excretion. 

i  De  Motu  Cordis,  p.  33.     Frankfort,  1628.  -  Works,  edited  by  Palmer,  vol.  iii.  p.  201. 

8  Ibid.,  vol.  i.  p.  444.  *  Ibid.,  vol.  iii.  p.  597. 

5  Experimental  Physiology,  p.  39.     Owen      Loudon,  1882. 

6  Bernard  :  Physiologie  Experimental,  tome  ii.  p.  179.     Paris,  1856. 

7  Cuvier:  Memoires  Pour  Servir  a  THistoire  et  a  l'Anatomie  des  Mollusquez.     Paris,  1817.     Memoire 
sur  le  Genre  Doris,  p.  16. 


38  INTRODUCTION. 

One  of  the  best  established  facts  in  physiology  is  that  the  intellectual 
faculties  depend  upon  the  development  of  the  brain,  both  in  reference 
to  quantity  and  to  quality.  This  is  well  seen  when  the  brains  in  a 
series  of  animals  are  compared  with  reference  to  their  intelligence.  With 
the  gradual  addition  of  certain  parts  of  the  brain  there  is  a  correspond- 
ing increase  in  mental  activity — and  in  this  way,  to  a  considerable 
extent,  the  functions  of  certain  parts  of  the  brain  have  been  made  out. 

Embryology,  or  the  study  of  the  transitory  phases  through  which 
every  animal  passes  in  its  development  from  the  stage  of  the  egg  to 
that  of  the  adult,  and  which  might  be  called  the  comparative  anatomy 
of  the  individual,  has  already  proved  to  be  of  service  in  throwing  light 
on  the  functions  of  the  human  body,  and  which  the  future  will,  no 
doubt,  show  to  be  susceptible  of  even  a  wider  application  than  is  made 
of  it  at  present,  for  the  embryo  of  animals,  with  the  exception  of  the 
lowest,  consists  of  three  germinal  layers,  of  which  the  upper  one  gives 
rise  to  the  epidermis  and  central  nervous  system,  the  lower  one  to  the 
epithelium  of  the  alimentary  canal  and  its  appendages,  the  middle  one 
to  bone,  muscle,  vessel,  etc.  These  germinal  layers,  even  at  the  start, 
can  be  readily  distinguished,  the  cells  composing  them  being  differently 
affected  by  physical  and  chemical  influences.  Some  of  the  lower  ani- 
mals, for  example,  the  hydrozoa,  never  get  beyond  this  layered  stage, 
the  inner  layer  acting  as  stomach,  the  outer  as  skin.  If  a  tissue  in  the 
adult  can  be  shown  to  have  been  derived  from  one  of  these  layers  in  its 
embryonic  stage  its  function  could  almost  be  predicted.  Indeed  the 
whole  modern  pathological  histology  is  an  application  of  this  view.  The 
older  pathologists,  like  Morgagni,1  confined  themselves  to  the  study  of 
the  organs  as  affected  by  disease. 

Bichat,2  in  investigating  the  tissues  of  which  the  organs  are  composed, 
created  histology ;  Schleiden3  first  showed  that  vegetable  tissues  consist 
of  cells,  and  Schwann/  following  his  lead,  applied  Schleiden's  view  to 
the  tissues  of  animals.  The  embryologists,  Reichert,5  Kolliker,6  Remak,7 
etc.,  then  proved  that  the  cells  composing  the  tissues  were  the  modified 
cells  of  the  original  mulberry  mass  of  cells  into  which  the  egg  or  primitive 
cell  segments.  The  obvious  corollary  of  these  generalizations  followed 
when  Virchow,8  Billroth,9  Paget,lu  Rindfleisch,11  etc.,  showed  that  path- 
ological structures  were  the  still  further  modified  cells  composing  the 
tissues  of  the  organ,  and  that  morbid  growths  were  really  physiological 
ones,  exhibiting  themselves  under  conditions  otherwise  than  normal; 
while  with  the  development  of  teratology,  through  the  works  of  Geoffrey 
St.  Hilaire,12  and  others,  the  explanation  of  the  production  of  monsters 
lusus  naturae  became  possible.  That  which  is  pathological  at  one  stage 
of  growth  was  shown  to  be  physiological  at  another ;  that  which  is 
normal  in  one  animal  is  abnormal  in  another.  Gradually  the  strict 
demarcation  between  physiology  and  pathology  has  been  broken  down, 

1  De  Sedibus  Morbornm,  17G1.  -  Anatoniie  Generate,  1801. 

■'  Miiller's  Archiv,  18:W.  4  Mikroskopische  Unternuchungen,  1839. 

5  Entwickelung  in  Wirbelthiere,  1840.  ''  Entwickelung  der  Cephalopoden,  1844. 

i  Entwickelung  der  Wirbelthiere,  1852  *  Cellular  Pathologie,  1854. 

9  Allgenieine  Pathologie,  1872.  10  Surgical  Pathology,  1870. , 

11  Pathologische  Anatoniie,  1873. 

12  Histoire  Generate  et  Particuliere  des  Anomalies  de  ['organization,  1837. 


INTRODUCTION.  39 

and,  with  the  fusion  of  the  two  studies,  a  rational  pathology  and  rational 
treatment  are  being  slowly  developed. 

Notwithstanding  the  importance  of  a  knowledge  of  general  physics 
and  chemistry,  anatomy,  embryology,  and  pathology  in  the  study  of  the 
functions  of  the  human  body,  nevertheless,  the  study  of  human  physi- 
ology is  often  almost  entirely  based  on  experiments  made  upon  living 
animals :  the  study  of  the  circulation  and  respiration  by  means  of  the 
graphic  method,  the  making  of  gastric  fistulas,  the  introduction  into  the 
system  of  an  animal  of  various  substances,  toxic  and  narcotic,  the 
removal  of  various  parts  of  the  nervous  system,  are  examples  of  the 
kind  of  work  often  exclusively  done  in  physiological  laboratories. 

The  student  of  physiology,  however,  should  not  confine  himself  to  the 
experimental  methods,  however  invaluable  and  indispensable  they  may 
be  as  a  means  of  investigation,  but  should  avail  himself,  as  far  as  possi- 
ble, of  the  other  methods  of  research  just  referred  to,  studying  the  sub- 
ject from  all  the  different  points  of  view  possible  and  comparing  the 
results  obtained  by  the  various  methods  made  use  of. 

As  objections  are  often  made  to  the  experimental  study  of  physiology, 
it  will  not,  I  hope,  be  considered  superfluous  if  I,  for  a  moment,  consider 
some  of  the  most  important  of  those  usually  advanced.  It  is  often  urged 
as  an  objection  to  a  vivisection,  that  the  pain  inflicted  so  disturbs  the 
normal  condition  that  any  result  as  to  the  function  of  a  part  determined 
in  this  way  is  valueless ;  the  suffering  entailed  vitiating  any  conclusion 
as  to  the  healthy  function  of  the  part  examined.  This  objection  is,  of 
course,  not  made  if  anaesthetics  are  used.  There  are,  however,  experi- 
ments performed  in  which  it  is  necessary  that  the  animal  should  be  in 
the  full  possession  of  its  faculties  and  which,  from  the  conditions  of  the 
investigations,  make  the  use  of  anaesthetics  impossible.  As  regards 
such  investigations  it  may  be  said,  without  doubt,  that  animals  suffer 
far  less  from  the  pain  inflicted  in  a  vivisection  than  man  does  from  a 
similar  wound  due  to  an  accident  or  the  knife  of  the  surgeon.  This  is 
due  to  several  causes;  the  animal  is  in  ignorance  of  what  is  going  to  be 
done,  forgets  the  operation  almost  immediately,  his  nervous  organization 
is  less  susceptible  than  that  of  the  human  being,  and  his  wounds  heal  up 
more  quickly.  The  influence  of  pain,  though  less  in  an  animal  than 
man,  must  nevertheless  be  always  taken  into  consideration. 

Whenever  the  vivisection  is  performed  without  an  anaesthetic,  the 
physiologist  ought  not  to  draw  any  conclusion  from  the  experiment 
until  the  animal  has  had  time  to  recover  from  the  effects  of  the  shock, 
hemorrhage,  etc.,  and  has  so  far  returned  to  his  normal  condition  that 
the  influence  of  pain,  if  any  still  exists,  is  so  small  in  amount  that  it 
cannot  be  considered  as  interfering  with  the  function  of  the  structure 
examined.  It  is  evident,  therefore,  that  if  the  physiologist  had  no 
higher  motive,  selfishness  would  induce  him  to  be  as  merciful  as  possible 
and  to  eliminate,  so  far  as  he  is  able,  pain,  as  a  possible  source  of  fallacy 
in  his  conclusions. 

The  animal,  both  during  and  after  vivisection,  should  be  treated  just 
as  a  patient  undergoing  an  operation  would  be  by  a  wise  surgeon  ;  the 
object  in  both  cases  being  to  restore,  as  rapidly  as  possible,  the  physio- 
logical conditions — the  conditions  of  health.    As  an  illustration  of  what 


40  INTRODUCTION. 

has  just  been  said,  as  regards  the  amount  of  permanent  disturbance 
produced  in  an  animal  by  a  vivisection,  let  me  mention  that  Blondlot's 
pointer  dog,  in  which  a  gastric  fistula  had  been  made,  was  used,  after 
her  recovery,  by  her  master  for  eight  years  in  the  field  for  hunting 
purposes,  and  in  the  laboratory  for  obtaining  gastric  juice,  and  that 
during  that  period  the  dog  had  two  litters  of  pups. 

The  Canadian  St.  Martin,  on  whom  the  gastric  fistula  was  caused 
by  a  gunshot  wound,  producing  far  more  dangerous  effects  than  the 
vivisection  just  referred  to,  lived  to  be  eighty-four  years  old,  enjoyed 
good  health  all  his  life,  married  and  had  children,  performed  the  duties 
of  a  servant,  and  was  during  this  time  frequently  of  inestimable  value 
to  science,  as  affording  Dr.  Beaumont  and  others  the  rare  opportunity 
of  observing  gastric  digestion  in  man  under  the  most  favorable  circum- 
stances. 

One  might  as  well  object  that  the  pain  suffered  by  St.  Martin,  after 
the  explosion  of  the  gun,  vitiated  the  conclusions  drawn  by  Beaumont, 
as  to  object  to  the  conclusions  of  Blondlot  because  the  making  of  a 
gastric  fistula  in  a  dog  involved  the  giving  of  the  animal  pain.  A  far 
more  important  objection  than  that  just  referred  to  is  that,  as  animals 
differ  very  much  in  their  organization,  conclusions  drawn  from  experi- 
ments made  upon  one  kind  of  an  animal  cannot  be  applied  to  another 
kind ;  digestion  in  a  dog,  for  example,  not  being  exactly  the  same  as 
in  a  man. 

It  is  undoubtedly  true  that,  while  frogs,  turtles,  pigeons,  rabbits, 
dogs,  horses,  etc.,  agree  anatomically  in  many  respects  with  each  other 
and  man,  they  disagree  to  such  an  extent  that  the  result  of  experiments 
made  upon  one  of  these  animals  is  often  utterly  inapplicable  to  the  other, 
and  entirely  worthless  as  applied  to  man.  Indeed,  the  most  striking 
differences  in  the  effect  of  certain  substances  are  observed  even  in  closely 
allied  animals,  varieties  of  the  same  species.  Thus  the  black  rhinoceros 
feeds  upon  the  euphorbia,  which  poisons  the  white  species ;  goats  and 
lambs  avoid  most  of  the  solanaceous  plants ;  the  ox  and  the  rabbit  will 
eat  belladonna ;  the  goat,  the  hemlock  ;  the  horse,  aconite. 

Such  differences  should  be  always  taken  into  consideration  when  the 
results  of  a  vivisection  upon  one  animal  are  to  be  applied  to  the  deter- 
mination of  the  function  of  a  structure  in  another.  It  must  be  always 
proved  that  the  structure  and  functions  compared  are  homologous. 
Further,  a  careful  post-mortem  examination  should  be  always  made 
after  the  vivisection,  in  order  to  learn  exactly  what  has  been  done,  to 
show  that  no  structure  has  been  involved  which  would  modify  the  results 
except  the  one  examined.  It  is  the  neglect  of  such  precautions,  the 
indifference  to  the  infliction  of  pain,  the  comparing  of  utterly  unlike 
conditions,  the  absence  of  the  test  of  post-mortem  examination,  the  want 
of  controlling  experiments,  and  of  comparison  of  the  results  obtained 
with  the  facts  of  pathology  and  comparative  anatomy  that  has  brought 
vivisection  into  the  disrepute  in  which  it  is  held  at  the  present  day  by 
many  even  educated  persons.  Crude  generalizations,  based  upon  im- 
perfect experiments  performed  upon  animals  illogically  applied  to  man, 
have  made  even  medical  men  doubt  altogether  of  the  efficiency  of  this 
method,  and  account  for  their  sympathizing  with  the  well-meaning,  no 


INTRODUCTION.  41 

doubt,  but  ill-judged  efforts  to  suppress  experimental  investigation  alto- 
gether ;  and  yet  if  vivisection  should  be  banished  from  the  laboratory, 
the  physiologist  would  be  deprived  of  one  of  his  most  fertile  methods  of 
research.  The  history  of  physiology  proves  not  only  the  importance  of 
vivisection,  but  its  indispensability  as  a  means  of  present  research. 
Indeed,  it  is  no  exaggeration  to  say  that  there  is  not  an  organ  in  the 
human  body  whose  functions  have  not  been  learned,  in  part  at  least,  by 
vivisections.     Let  me  illustrate  this  statement  by  a  few  examples. 

Consider  the  history  of  the  circulation  of  the  blood,  and  we  shall  see 
that  every  important  advance  made  in  a  knowledge  of  the  phenomena 
was  due  to  a  vivisection.  Thus,  Galen  demonstrated  by  vivisection 
that  the  artery  contained  blood  and  not  air,  as  its  etymology  would  in- 
dicate. It  was  by  a  vivisection  that  Harvey  proved  that  the  blood  flowed 
from  the  heart  to  the  periphery  through  the  arteries,  and  from  the 
periphery  back  to  the  heart  through  the  veins.  Finally,  it  was  through 
a  vivisection  that  Malpighi  saw,  for  the  first  time,  the  blood  actually  flow- 
ing from  the  arteries  into  the  veins  through  the  intermediate  vessels, 
the  capillaries.  One  of  the  most  important  discoveries  ever  made  in 
physiology,  that  of  the  functions  of  the  roots  of  the  spinal  nerves,  that 
the  anterior  are  motor  and  the  posterior  are  sensory,  was  demonstrated 
by  Majendie  upon  a  living  animal.  The  influence  of  the  nervous  sys- 
tem upon  the  heart,  so  far  as  is  known,  has  been  entirely  learned  by 
the  experimental  investigations  made  upon  animals  by  the  Webers,  Von 
Bezold,  Ludwig,  Cyon,  etc.  The  beautiful  investigations  of  Bernard 
upon  the  salivary  glands,  the  pancreas,  the  liver,  by  means  of  vivi- 
sections, have  demonstrated  certain  peculiarities  in  reference  to  the 
secretion  of  these  organs,  that  could  never  have  been  learned  by  any 
other  method.  By  means  of  vivisection  Brown-Sequard  showed  the 
influence  of  the  sympathetic  nerve  in  diminishing  the  calibre  of  the 
bloodvessels,  and  thence  discovered  the  vasomotor  nerves,  by  which  the 
distribution  of  the  blood  to  the  tissues  is  regulated.  It  is  needless 
to  multiply  examples  of  the  importance  of  vivisection  as  a  means  of 
research,  as  nearly  every  chapter  in  this  work  will  afford  such.  It  must 
not  be  forgotten,  however,  that  vivisection  is  but  one  means  of  physio- 
logical research,  and  that  however  important  may  be  the  results  obtained 
by  it,  the  latter,  as  already  mentioned,  should  be  always  compared  with 
such  facts  of  comparative  anatomy  and  pathology  as  have  a  bearing 
upon  the  function  investigated,  so  that  so  far  as  possible  all  sources  of 
fallacy  may  be  eliminated. 

To  those  familiar  with  the  history  of  medicine  any  agument  to  prove 
the  importance  of  the  study  of  physiology  would  be  superfluous.  Phy- 
siology has  always  been,  and  is  still,  the  corner-stone  of  medicine.  The 
doctrines  of  Hippocrates,  Galen,  Sydenham,  Beerhave,  Hunter,  and 
Virchow,  reflect  as  a  mirror  the  physiology  of  the  day.  It  is  self- 
evident  that  to  understand  disease  and  its  cure  one  must  first  understand 
health.  The  study  of  physiology  must  precede  that  of  pathology  and 
therapeutics.  Hand  in  hand  they  advance  together,  the  progress  of  the 
one  depending  upon  that  of  the  other.  There  is  no  better  illustration 
of  the  truth  of  this  view  of  the  dependence  of  pathology  and  therapeutics 
upon  physiology  than  ophthalmic  medicine,  the  most  developed  and 


42  INTRODUCTION. 

finished  of  all  branches  of  medicine,  whose  present  perfected  condition 
is  entirely  due  to  the  comparatively  thorough  understanding  of  the 
structure  and  function  of  the  healthy  eye. 

On  the  other  hand,  diseases,  like  those  of  the  nervous  system,  are  in 
a  proportionally  backward  condition  owing  to  the  imperfect  knowledge 
of  the  normal  anatomy  and  physiology  of  the  parts  involved. 

Having  denned  the  subject  of  physiology,  considered  the  methods  by 
which  it  is  studied,  and  its  importance  to  medicine,  it  only  remains  now 
in  conclusion  to  indicate,  generally,  the  order  in  which  the  study  will 
be  pursued,  and  here  nature  will  be  our  guide.  Our  first  sensations  are 
those  of  hunger  and  thirst — hence  the  taking  of  food.  We  will, 
therefore,  after  describing  the  general  physical  and  chemical  structure 
of  the  body,  begin  with  the  study  of  digestion  and  absorption,  the 
elaboration  of  the  food  into  the  blood,  and  its  circulation  will  be  then 
described,  the  consideration  of  excretion,  animal  heat,  completing  the 
study  of  nutrition. 

But  man  is  more  than  a  vegetable,  he  feels,  thinks,  moves.  Impres- 
sions of  the  outer  world  made  upon  his  nervous  system  awaken  in  him 
consciousness,  the  inner  world  of  mind.  Through  his  nervous  system 
man  not  only  becomes  aware  of  the  existence  of  an  environment,  but 
adjusts  his  actions  with  reference  to  it.  Finally,  though  the  individual 
perishes  in  the  reproduction  of  his  kind,  the  race,  temporarily  at  least, 
survives,  hence  the  study  of  development.  We  will  begin,  therefore, 
with  the  study  of  nutrition,  consider  next  the  nervous  system,  concluding 
with  an  account  of  reproduction. 


CHAPTER    I. 

GENERAL  STRUCTURE  OF  THE  BODY,  PHYSICALLY 
AND  CHEMICALLY. 

Before  taking  up  the  stud)7  of  the  functions,  specifically,  it  will  be 
well  to  consider,  from  a  general  point  of  view,  of  what  the  human  body 
consists,  physically  and  chemically  speaking,  to  obtain  some  general 
knowledge  of  its  organization,  of  which  the  functions  are  the  living 
expression. 

As  is  known  to  every  one,  the  human  body,  like  that  of  a  domestic 
animal,  is  made  up  of  skin,  muscles,  bone;  of  various  viscera,  such  as 
the  heart,  lungs,  liver,  stomach  ;  of  nerves,  arteries,  etc. 

The  old  anatomists  busied  themselves  almost  entirely  with  the  descrip- 
tion of  such  organs,  their  number,  size,  color,  relative  position,  etc. 
This  kind  of  study  may  be  said  to  have  culminated  in  Cuvier,  who,  as 
regards  the  exactness,  extent,  and  variety  of  his  knowledge  stands 
without  a  rival  as  an  anatomist.  If,  however,  any  one  organ  is  examined 
somewhat  closely,  it  will  be  found  to  be  far  from  homogeneous.  Thus 
the  stomach  consists  of  several  layers,  mucous,  fibrous,  muscular,  etc. ; 
the  heart,  of  muscular,  connective,  adipose,  nervous  tissue,  etc.  Such 
tissues,  combined  in  greater  or  less  proportions,  make  up  the  different 
organs  of  which  the  body  is  composed ;  the  same  tissue,  for  example, 
the  connective,  being  found  in  different  organs,  just  as  the  substance 
wood  may  be  applied  to  making  a  chair,  sofa,  bed,  or  bookcase  fur- 
nishing a  room. 

The  investigation  of  the  tissues,  the  creation  of,  histology,  is  due  to 
the  genius  of  Bichat.  If  now  any  tissue  be  studied  in  detail,  it  can 
be  still  further  resolved  into  simpler  ultimate  physical  elements  or  what 
are  commonly  called  cells,  or  their  modifications.  This  last  analysis 
was  made  by  Schleiden  and  Schwann.  Through  the  progress  of  or- 
ganic chemistry  it  has  also  become  possible  to  state,  with  tolerable 
accuracy,  of  what  the  body  is  composed  chemically.  When  the  analysis 
is  a  proximate  one,  the  result  gives  such  principles  as  water,  common 
salt,  salts  of  lime ;  starch,  sugar,  fat ;  albumen,  fibrin,  casein,  etc. 
These  principles  exist  as  such  in  the  human  body,  and  are  called  proxi- 
mate principles,  being  the  result  of  a  proximate  analysis.  If  now  these 
principles  be  analyzed,  they  will  bj  found  to  consist  of  hydrogen,  oxy- 
gen, sodium,  chlorine,  carbon,  nitrogen,  phosphorus,  etc.  In  this  way 
it  is  shown  that  the  human  body  consists,  ultimately,  of  the  ordinary 
chemical  elements.  A  human  being  then  consists,  ultimately,  of  myriads 
of  cells  composed  of  the  ordinary  chemical  elements.  Certain  cells  form 
tissues,  certain  tissues  act  together  as  organs,  and  the  organs  harmo- 
niously working  together  constitute  a  living,  healthy  man.     The  chem- 


44 


GENERAL    STRUCTURE    OF    THE    BODY. 


ical  elements  composing  the  cells  also  act  in  concert,  as  proximate 
principles.  A  resume  of  the  above  physical  and  chemical  facts  may  be 
seen  thrown  together  synoptically  under  Table  II. 

Table  II.1 — The  Human  Body  Consists 

PHYSICALLY.  CHEMICALLY 


of  Organs. 
The  organs  of  tissues. 
The  tissues  of  cells. 
The  cells  of  elements. 


Examples  of  Cells. 

1.  Cells  floating  in  a  liquid:    blood 

corpuscles,  lymph  corpuscles. 

2.  Cells  in  layers:   epidermis,  epithe- 

lium, enamel. 

3.  Cells   in  masses :    adipose  tissue, 

medulla  of  hair. 

4.  Cells  imbedded  in  non-cellular  sub- 

stance :  cartilage,  bone. 

5.  Cells  forming  fusiform  bands  :  un- 

striated  muscular  fibre. 

6.  Cells  transformed  into  tubes:  cap- 

illaries, nerves,  dentine. 


of  Principles. 


The  principles  of  elements. 
Proximate  principles. 

Of  1st  Class. 
Water,     sodium     chloride,     calcium 
phosphate,  calcium  carbonate,  etc. 

of  'Id  Class. 
Starch,  sugar,  oils,  fats. 

of  3d  Class. 
Albumen,  fibrin,  casein,  etc. 

Ultimate  Elements. 
Oxygen,  hydrogen,  carbon,  nitrogen, 
chlorine,    phosphorus,    sulphur, 
calcium,  sodium,  potassium,  mag- 
nesium, iron,  fluorine,  silicon. 


7.  Cells  transformed  into  filaments: 
fibrous  tissue,  elastic  tissue. 

A  cell  may  consist,  in  its  wall,  of 
membrane ;  in  its  contents,  of 
liquid  and  granules ;  in  its  ap- 
pendages, of  filaments. 

Let  me  now  take  up  somewhat  more  in  detail  what  is  known  of  cells 
and  proximate  principles.  A  cell  may  be  defined  as  the  ultimate  ele- 
mentary living  unit,  a  mass  of  living  matter,  varying  from  the  3-oVo"th 
to  the  yxijth  of  an  inch  in  diameter.  It  may  consist  of  a  cell  wall,  in- 
closing cell  contents  of  a  liquid,  semi-liquid,  or  granular  character. 
The  granules  in  some  cells  are  united,  according  to  many  histologists, 
by  filaments  or  threads ;  the  cell  contents  consisting  then  of  a  network. 
Often  among  the  cell  contents  can  be  distinguished  a  still  smaller  cell, 
the  nucleus,  and,  within  this,  the  nucleolus.  Sometimes  the  cell  wall  is 
elongated  into  an  appendage,  a  cilia.  Great  difference  still  prevails,  as 
may  be  seen  from  the  views  of  Kolliker,  Leydig,  Schultze,  Brucke, 
Hteckel,  Gegenbaur,  Beale,  etc.,  as  to  the  relative  importance  of  the 
nucleus  and  nucleolus  of  the  cell  contents  and  cell  Avail. 

According  to  some  observers,  the  all  important  element  in  cell  life  is 
the  nucleus,  while  others  maintain  that  it  is  the  cell  contents.  The 
cell  wall  and  even  the  nucleus  are  regarded  by  some  as  the  cell  contents 
in  a  state  of  retrograde  metamorphosis. 

As  we  proceed  in  our  studies,  it  will  be  seen  that  there  are  cells,  like 


1  Partly  taken  from  Leidy's  Anatomy,  p.  32. 


CELLS. 


45 


the  blood  corpuscles,  which  have  neither  nucleus  nor  cell  Avail  ;  that  the 
first  step  in  the  division  of  the  egg  or  primitive  cell  consists  in  the  dis- 
appearance of  the  germinal  vesicle  or  nucleus,  and  that  the  mulberry 
mass  of  cells,  the  result  of  that  division,  are  at  first  without  a  cell  wall. 
Further,  there  are  protoplasmic  beings,  like  the  monera,  of  which  the  pro- 
tamoeba  (Fig.  1)  is  an  example  which,  through  life,  never  exhibit  either 


Fig.  1. 


Fig.  2. 


Protamoeba.     (H.eckel.) 

nucleus  or  cell  wall.  Such  facts 
prove  that  in  certain  cases,  at 
least,  neither  the  nucleus  nor  cell 
wall  is  an  indispensable  element 
to  the  life  of  cells,  and  should 
make  physiologists  cautious  in 
attributing  positive  functions  to 
this  or  that  element  of  a  cell. 
Indeed,  I  cannot  say  that  the 
relative  significance  of  either 
nucleus,  nucleolus,  cell  wall,  or  cell  centents,  is  as  yet  definitely  under- 
stood.    As  examples  of  cells,  attention  may  be  called  to  those  lining  the 


Buccal  and  glandular  epithelium,  with  granular  mat- 
ter and  oil-globules  ;  deposited  as  sediment  from  human 
saliva.     (Dalton.) 


Fig.  3. 


Fig.  4. 


Columnar  ciliated  epithelium  cells  from  the 
human  nasal  membrane  ;  magnified  300  diam- 
eters.    (Quain  and  Shaepey.) 

uriniferous  tubules  of  the  kidney, 
to  the  cells  of  the  enamel,  to 
those  of  the  epithelium  of  the 
mouth  (Fig.  2),  of  the  columnar 

epithelium     Of    the     intestine,     tO         Human  blood-globules       a.   Red  globules,  seen   flat- 
the  multipolar  Cell  found  in  nei'-    Wise-    «>•  R^  globules,  seen  edgewise,    c.  AVhite  globule. 
r  ,...,.      (Dalton.) 

vous  tissues,  to  the  ciliated  epi- 
thelial cells  from  the  pulmonary  mucous  membrane  (Fig.  3),  to  blood 
cells  (Fig.  4),  to  unstriated  muscular  fibre  cells. 


46 


GENERAL    STRUCTURE    OF    THE    BODY. 


As  I  take  up  the  different  organs,  the  cells  composing  their  tissues 
will  be  described  more  in  detail;  so  the  above  examples  will,  therefore, 
suffice  for  the  present  in  giving  a  general  idea  of  the  form  of  cells. 

While  there  is  still  some  doubt  as  to  the  exact  use  of  the  different 
parts  of  the  cells,  there  is  no  doubt  that  the  life  of  the  organism  resides 
in  the  cells  composing  it.  Among  other  reasons  for  supposing  so,  may 
be  mentioned  the  fact  that  the  life  of  the  human  being  begins  as  the 
ovum,  a  cell,  and  that  the  tissues  of  the  embryo,  out  of  which  are  built 
up  the  organs  of  the  adult,  consist  of  modified  cells,  the  lineal  de- 
scendants of  this  primitive  cell  or  ovum,  and  inheriting  its  life  charac- 
teristics, the  life  of  the  organism  being  the  resultant  of  the  lives  of  the 
individual  cells  composing  it. 

The  independent  life  of  cells  is  well  seen  in  some  of  the  lower  animals, 
whose  blood  corpuscles  can  be  observed  actually  feeding  upon  sub- 
stances artificially  introduced  into  the  circulation,  and  in  the  embryonic 
state  can  be  observed  dividing  and  subdividing,  and  so  reproducing 
themselves.  Gland  cells,  like  those  of  the  liver,  kidney,  etc.,  in  taking 
from  the  blood  the  materials  out  of  which  their  respective  secretions  are 
elaborated,  show  their  independent  activities.  Pathological  processes 
often  present  chances  for  observing  this  independent  cell  life,  in  the 
wandering  of  the  white  and  red  blood-cells  out  of  the  vessels,  in  the 
rapid  proliferation  of  cells  seen  in  the  development  of  various  morbid 
growths,  etc.  The  protozoa  and  protophyta,  or  the  simplest  of  animals 
and  plants,  however,  offer  the  most  favorable  opportunities  for  observing 
the  life  history  of  cells ;  for  these  simple  beings 
never  get  beyond  the  one-cell  stage  of  life,  indeed 
neither  tissues  nor  organs  are  ever  developed  in 
them  in  the  same  sense  that  these  are  in  the 
higher  animals.  The  entire  life  cycle  of  these 
minute  plants  and  animals  can  be  often  followed 
under  the  microscope.  The  manner  in  which  cells 
take  food,  move  about,  their  mode  of  reproduction 
— usually  through  simple  division,  though  some- 
times endogeneously  and  by  gemmation  and  con- 
jugation—  can  be  readily  observed  by  an  examina- 
tion of  the  greenish  matter  on  damp  bricks,  stones, 
etc.,  consisting  usually  of  palmoglea,  micrococcus, 
or  the  greenish  film-like  spirogyra  seen  covering 
the  ditches  and  ponds  in  the  neighborhood  of  the 
city,  and  which  also  usually  contain  specimens  of 
unicellular  protozoa  paramoecium  (Fig.  5),  stentor, 
as  well  as  desmidiacese,  of  which  Fig.  6  is  an  ex- 
ample. These  researches,  always  interesting  to 
the  mere  microscopist  on  account  of  the  beauty  of 
the  vegetable  and  activity  of  the  animal  forms,  have  a  deep  meaning  to 
the  philosophical  physiologist.  For  it  is  reasonable  to  suppose  that  the 
life  of  man  or  the  higher  animals,  when  in  the  one-cell  or  ovum  stage 
(Fig.  7),  is  similar  to  that  of  these  beings  which  pass  beyond  this  uni- 
cellular stage.  Hence,  we  may  conclude  that  the  human  ovum,  or  any 
of  the  cells  descended  from  it,  absorbs  and  assimilates  nutriment,  like 


Fig.  5. 


i>-'-W 


''M. 


■40, 


■■/, 


Parama'cium     caudatum. 
a,  a.  Contractile  vesicles.    6. 

Mouth.     (Carpenter.) 


CELLS, 


47 


the  unicellular  beings  just  referred  to.     The  segmentation  of  the  egg 
in  the  higher  animals  corresponds  also  to  the  division  of  the  cell  seen  in 


Fig.  6. 


F  I G . 


Pediastrum  pertusum. 

(Carpenter.) 


Human  ovum,  magnified  85  diaoi.   a.  Vitelline  membrane.  6.  Vitellus 
c.  Germinative  vesicle,   d.  Germinative  spot.     (Dalton.) 


the  reproduction  of  these  minute  beings,  the  manner  in  which  the 
nucleus  divides  first  into  two  halves  and  the  cell  contents  or  protoplasm 
constricts  around  the  new  nuclei  being  essentially  the  same  in  both 
cases ;  the  only  difference  being,  as  we  shall  see  hereafter,  that  in  the 


Division  of  the  yelk  of  Ascaris.     A,  B,  C  (from  Kiilliker),  ovum  of  Ascaris  nigrovenosa;  D  ami  E.  that 
of  Ascaris  acuminata  (from  Bagge).     (Quain  and  Sharpey  ) 


former  the  new  cells  hold  together  and  are  transformed  into  tissue,  in 
the  latter  the  new  cells  are  scattered,  constituting  the  next  generation 
of  cells.     This  distinction  may  be  seen  by  comparing  the  segmentation 


Fig.  9. 


Development  of  protococcus  pluvialis.     (Carpenter.) 

of  ascaris  (Fig.  8)  with  the  reproduction  of  protococcus  through  con- 
tinued subdivision  (Fig.  9).     In  either  case,  however,  the  life  of  the  re- 


48  GENERAL    STRUCTURE    OF    THE    BODY. 

sultant  cells  is  that  inherited  by  them  from  the  parent  cell.  The  cells 
resulting  from  the  segmentation  of  the  mammalian  ovum  or  egg  are  at 
first  very  similar,  hut  soon  a  marked  difference  between  them  can  be 
observed.  If  the  researches  of  Van  Beneden1  on  the  rabbit  are  con- 
firmed, the  difference  is  noticeable  even  in  the  two  first  segmentation 
cells.  However  this  may  be,  the  cells  soon  begin  to  differ  in  size,  shape, 
and  the  manner  in  which  they  are  affected  by  chemical  agents.  Some 
dispose  themselves  so  as  to  form  the  epiblast,  others  the  hypoblast,  and 
between  these  two  layers  a  third  appears,  the  mesoblast. 

The  modification  of  the  cells  and  the  further  development  of  these 
three  layers  will  be  considered  when  I  take  up  the  subject  of  reproduc- 
tion. It  will  be  seen  then  that  through  the  processes  incidental  to 
development,  cells  often  lose  their  originally  round  form,  becoming 
sometimes  flattened  or  scale-like,  and  often  of  a  prismatic  and  columnar 
shape.  Sometimes  the  cells  float  free  in  a  liquid,  like  the  blood 
corpuscles ;  or  they  may  arrange  themselves  in  layers,  like  those  of  the 
enamel ;  or  in  masses,  as  seen  in  the  medulla  of  hairs.  They  may  be 
imbedded  in  a  solid  non-cellular  matrix,  as  in  cartilage.  Cells  are 
sometimes  flattened  into  bands,  as  in  the  unstriated  muscular  fibre,  or 
a  number  are,  through  the  dissolution  of  their  adjacent  walls,  metamor- 
phosed into  tubes,  of  which  the  capillaries  and  dentine  are  examples,  or 
they  may  be  converted  into  fibrous  tissue.  These  modifications  are  seen 
in  Table  II.,  synoptically  arranged.  The  various  substances  elaborated 
by  cells  in  different  parts  of  the  adult  economy  will  be  more  appro- 
priately considered  as  the  functions  of  the  organs  are  taken  up.  It 
will  be  seen  that  the  life  of  the  body  is,  therefore,  the  resultant  life  of 
the  cells  composing  it;  that  the  body  is  a  living  republic  of  cells. 

Let  us  now  return  to  the  chemical  composition  of  the  body,  or  of  the 
cells  of  which  it  consists.  We  have  seen  that  the  human  body  consists 
of  chemical  elements  acting  as  proximate  principles.  Before  considering 
these,  let  us  see  what  is  meant  by  a  proximate  principle. 

A  proximate  principle  may  be  defined  as  a  principle,  simple  or  com- 
pound, which  exists  and  acts  as  such  in  the  human  body.  Thus, 
sodium  chloride  is  a  proximate  principle.  Neither  the  rare  metal 
sodium,  nor  the  offensive  greenish  gas  chlorine,  however,  are  proximate 
principles,  for  they  do  not  exist  or  act  as  such  in  the  body.  Calcium 
phosphate  is  an  example  of  a  proximate  principle ;  but  the  metal 
calcium,  and  the  phosphoric  acid,  not  existing  or  acting  separately,  as 
calcium  and  phosphoric  acid,  in  the  body,  cannot  be  regarded  as  proxi- 
mate principles.  The  purely  analytical  chemist  would  resolve  such 
proximate  principles  as  fat,  albumen,  into  their  ultimate  elements, 
carbon,  hydrogen,  oxygen,  and  carbon,  hydrogen,  oxygen,  nitrogen, 
phosphorus,  respectively.  The  physiological  chemist,  however,  would 
study  these  principles  without  further  decomposition,  investigating  the 
part  that  fat  and  albumen  play  as  such  in  the  economy,  without  any 
reference  to  their  ultimate  chemical  composition.  The  proximate  prin- 
ciples— leaving  out  of  consideration,  for  the  present,  the  gases,  which 
can  be  more  conveniently  treated  of  under  the  subjects  of  respiration 

1  Bulletin  de  l'Acad.  Belgiijue,  1874. 


WATER.  49 

and  the  blood,  and  the  various  effete  matters  whose  elimination  from 
the  economy  constitutes  the  function — divide  themselves  naturally  into 
those  of  inorganic  and  organic  origin  ;  the  latter  are  further  distinguished 
by  those  containing  nitrogen  and  those  which  do  not,  Table  II.  gives 
some  typical  examples  of  these  three  classes  of  the  proximate  principles  ; 
and  of  their  ultimate  chemical  elements,  manganese,  iodine,  and  bromine, 
though  not  existing  in  man,  have  been  found,  however,  in  other  organized 
bodies. 

By  referring  to  Tables  III.  and  IX.  a  list  of  the  most  important  of 
the  proximate  principles  may  be  seen,  and  the  parts  of  the  body  in 
which  they  usually  occur.  Let  me  now  take  up  somewhat  in  detail  the 
consideration  of  these  principles,  beginning  with  those  of  inorganic 
origin. 

Table  III.1 — Proximate  Principles  of  the  First  Class,  or  those  of 
Inorganic  Origin. 

Substances.  Where  found. 

Water     .......  Universal. 

Sodium  chloride     .....  Universal,  except  enamel. 

Potassium  chloride         ....  Muscles,    blood,    milk,    saliva,    bile, 

gastric  juice. 

Calcium  pbospbate         ....  Universal. 

Calcium  carbonate         ....  Bones,  teeth,  cartilage. 

Sodium  carbonate  ....  Blood,  saliva,  lymph. 

Potassium  carbonate      ....  Bones,  lymph. 

Magnesium  phosphate  ....  Universal. 

Sodium  phosphate  ....  Universal. 

Potassium  phosphate     ....  Universal. 

Sodium  sulphate    .....  Universal,  except  milk. 

Potassium  sulphate        ....  Bile,  gastric  juice.     Same  as  sodium 

sulphate. 

Calcium  sulphate  .....  Blood,  feces. 

Ammonium  chloride      ....  Gastric  juice,  saliva,  tears. 

Magnesium  carbonate    ....  Blood,  sebaceous  matter. 

Sodium  bicarbonate        ....  Blood. 

As  implied  in  the  definition,  the  principles  of  this  class  are  inorganic 
in  origin,  being  found  in  the  rocks  forming  the  crust  of  the  earth,  in  sea 
water,  springs,  etc.  They  have  a  definite  chemical  composition,  and 
are  crystallizable.  With  the  exception  of  calcium  carbonate,  of  which 
the  otoliths  of  the  ear  consist,  they  are  combined  in  the  body  with  the 
organic  principles.  This  union  is  so  intimate  that  as  the  organic  prin- 
ciples become  effete,  and  are  eliminated,  the  inorganic  substances  are 
cast  out  with  them.  Some  of  these  substances  play  a  more  important 
r6le  than  others,  and  are  found  in  greater  or  less  quantities  in  the 
economy. 

Let  us  consider  now  the  most  important  of  these  substances,  where 
they  occur,  and  their  principal  uses. 

Water,  H20. — In  the  maintenance  of  life,  none  of  the  proximate 
principles,  whether  inorganic  or  organic,  surpass  in  importance  water. 
When  it  is  learned,  however,  that  it  constitutes  nearly  three-fifths  by 
weight  of  the  whole  body,  this  will  no  longer  be  a  subject  of  surprise. 

1  Robin  et  Verdeil :  Traite  de  Chimie  Anatomique,  tome  denxieme,  \>.  5.     Paris,  1853. 

4      " 


50  GENERAL    STRUCTURE    OF    THE    BODY. 

In  the  course  of  our  studies  we  shall  find  that  water  exists  in  all  parts 
of  the  body:  in  solids,  like  hone  and  enamel;  in  fluids,  like  the  tears, 
perspiration,  etc.  Its  uses  in  the  economy  are  manifold.  It  gives  con- 
sistence and  general  resiliency  to  the  body,  pliability  to  tendons,  elasticity 
to  cartilage,  resistance  to  the  bones.  Various  substances,  like  articles 
of  food  and  the  effete  matters,  find  their  way  into  and  out  of  the  body 
through  their  solubility  in  water.  The  importance  of  water  is  at  once 
seen  if  the  system  is  deprived  of  it.  The  tissues  become  shrivelled  and 
dried  up  and  inflexible,  the  liquids  become  thick,  inspissated,  lose  their 
fluidity.  On  the  other  hand,  an  excess  of  water  gives  rise  to  general 
debility,  muscular  weakness,  dropsies,  etc. 

In  the  living  body  water  exists  as  "  water  of  composition" — that  is,  it 
constitutes  an  integral  part  of  the  tissues.  The  water  is  not  taken  up 
by  the  tissues,  like  a  sponge,  but  really  forms  a  part  of  its  substance, 
the  union  being  a  chemical  one. 

Table  IV.' — Quantity  of  Water. 

Substance. 

Enamel 

Epithelium 

Teeth 

Bones 

Tendons     . 

Cartilages  . 

Skin  .... 

Liver. 

Muscles 

Ligaments 

Blood 

The  relative  amount  of  water  is,  in  the  tissues,  regulated  by  the  salts. 
Thus,  when  water  is  added  to  the  blood,  the  corpuscles  become  swollen, 
and  finally  are  dissolved  away ;  but  if  a  strong  solution  of  salt  be  added 
instead,  the  corpuscles  lose  their  water  and  shrivel  up.  Most  of  the 
water  found  in  the  system  is  taken  in  as  part  of  the  solid  and  fluid  articles 
of  the  food.  As  we  shall  see  hereafter,  however,  about  500  grammes, 
or  7500  grains,  are  formed  in  the  system  through  the  combustion  of  carbo- 
hydrates. The  daily  amount  of  Avater  necessary  for  the  healthy  adult 
has  been  estimated,  by  Dalton,2  at  about  four  and  one-half  pounds. 
This,  of  course,  includes  the  water  entering  into  the  solid  articles  of 
food.  About  fifty-two  per  cent,  of  the  water,  after  it  has  played  its  part 
in  the  economy,  is  discharged  by  the  skin  and  lungs,  the  rest  by  the 
kidneys  and  with  the  feces.  It  has  been  calculated  that  nearly  one 
pound  passes  off  by  the  skin,  about  a  pound  by  the  lungs,  and  a  little 
over  three  pounds  by  the  kidneys.  When,  however,  the  skin  is  not 
active,  as  in  the  winter  time,  then  the  kidneys  act  very  freely  ;  in  the 
summer  the  reverse  is  the  case.  Diuretics  favor  the  one  set  of  emunc- 
tories,  diaphoretics  the  other. 

By  glancing  at  Table  IV.  it  may  be  seen  how  universally  water  is 
found  in  the  tissues,  and  its  relative  amount.     Thus,  while  we  find  that 

1  Robin  et  Verdeil,  op.  cit  ,  p.  115.  -  Physiology. 


Part,  perlOOO. 

Su'istance. 

Parte  per  1000. 

2 

Milk       . 

.     887 

'.         37 

Chyle     . 

.     004 

.     100 

Bile 

.     905 

.     130 

Urine 

.     933 

.     500 

Lymph  . 

.    960 

.     550 

Saliva     . 

.     983 

.     575 

Gastric  juice  . 

.     984 

.     618 

Perspiration    . 

.     986 

.     725 

Tears 

.     990 

.     768 

Pulmonary  vapor  . 

.     997 

.     780 

SODIUM    CHLORIDE  51 

a  thousand  parts  of  pulmonary  vapor  contain  nine  hundred  and  ninety- 
seven  parts  of  water,  it  will  be  seen  there  are  only  two  parts  of  water 
in  a  thousand  of  enamel,  and  that  a  substance,  like  tendon,  so  different 
from  either  of  those  just  mentioned,  is  half  made  up  of  water.  The 
great  importance  of  water  in  health,  and  still  more  in  disease,  cannot  be 
too  much  dwelt  upon  by  the  physiologist  and  practising  physician. 

Sodium  Chloride',  NaCl. — Next  to  water,  common  salt  is  the  most 
important  of  the  inorganic  proximate  principles,  being  found,  like  water, 
almost  universally,  even  in  the  ovum.  With  the  exception  of  the  enamel, 
in  which  it  has  not  yet  been  discovered,  salt  is  found  in  all  the  solids 
and  fluids  of  the  body.  The  absolute  amount,  however,  has  not  yet 
been  determined.  The  saltish  taste  of  the  tears  and  perspiration  is  due 
to  the  presence  of  this  principle.  It  is  found  in  the  largest  proportion 
in  fluids.  The  relative  quantity  of  sodium  chloride  found  in  some  of 
the  fluids  of  the  body  may  be  seen  by  looking  at  Table  Y. 

Table  V.1 — Quantity  or  Sodium  Chloride. 

Substance.  Parts  per  1000.       Substance.  Parts  per  1000. 

Blood 4.2  Saliva 1.5 

Chyle 5.3  Perspiration    ....  3.4 

Lymph        .         .         .         .         .4.1  Urine       .*....  4.4 

Milk 0.8  Feces 3.0 

Salt  is  introduced  into  the  system  through  the  different  articles  of 
animal  and  vegetable  food  which  always  contain  it ;  in  addition,  salt  as 
such  is  added  to  the  food  of  man  and  the  herbivora ;  the  amount  con- 
tained in  their  food  not  being  sufficient  for  the  wants  of  the  economy. 
Salt,  like  all  other  inorganic  principles,  passes  ultimately  through  the 
body,  and  is  carried  out  of  it  in  the  urine,  feces,  perspiration,  etc.  The 
uses  of  salt  in  the  system  are  manifold.  The  phenomena  of  osmosis, 
or  the  passage  of  fluids  and  gases  through  the  animal  membranes,  are 
greatly  modified  by  the  amount  of  salt  present,  a  solution  of  salt  osmosing 
through  a  membrane  much  less  readily  than  pure  water.  Absorption 
is  influenced  by  it.  It  increases  the  solubility  of  albumen ;  this  prin- 
ciple being  coagulated  much  less  quickly  by  heat  in  a  solution  of  sodium 
chloride  than  in  water.  The  coagulability  of  fibrin  may  be  prevented 
by  a  strong  saline  solution.  The  forms  of  tissues  are  preserved  through 
the  presence  of  salt,  as  in  the  case  of  blood-corpuscles  just  referred  to. 
Nutrition  is  undoubtedly  affected  in  other  Avays  by, salt,  as  yet  not  per- 
fectly understood.  The  experiments  of  Boussingault2  upon  bullocks,  and 
of  Dailly3  upon  sheep,  showed  what  a  deleterious  effect  was  produced  in 
their  general  appearance  when  these  animals  were  deprived  of  salt.  It 
is  well  known  how  the  wild  buffalo  is  found  by  the  salt  licks  of  the 
Northwest,  and  how  the  hunter  in  Southern  Africa  avails  himself  of  his 
knowledge  of  the  habits  of  wild  animals  collecting  near  salt  springs,  to 
kill  his  game.  Every  one  is  familiar  with  the  fact  of  how  cattle  run  to 
any  one  who  will  give  them  salt.  It  is  said  that  fugitives  from  iustice 
will  often  risk  capture  and  their  lives  to  obtain  salt.     Facts  like  the 

1  Robin  et  Verdeil,  op.  oit.,  p.  176.  2  Chimie  Agricole,  p.  27L     Paris,  1854. 

3  Longet :  Traitg  de  Phyaiologie,  tome  i.  p.  70. 


02  GENERAL    STRUCTURE    OF    THE    BODY. 

0 

above  show  what  a  deep-seated  want  is  felt  by  man  ami  beast  alike, 
when  deprived  of  salt. 

Potassium  CHLORIDE,  KC1. — This  principle  is  found  in  the  muscles, 
blood,  saliva,  bile,  gastric  juice,  urine,  etc.  A  greater  part  of  it  is  intro- 
duced into  the  system  with  the  food,  though  probably  some  is  produced 
through  the  double  decomposition  of  the  potassium  phosphate  and  sodium 
chloride  existing  in  the  blood,  sodium  phosphate  and  potassium  chloride 
resulting.  The  uses  of  potassium  chloride  and  sodium  chloride  are 
probably  the  same  in  the  economy.  This  principle  is  discharged  from 
the  body  in  the  mucus  and  the  urine. 

Calcium  Phosphate,  Ca3(P04)2. — This  very  important  principle  is 
found  in  all  the  solids  and  fluids  of  the  body.  By  looking  at  Table  VI. 
it  will  be  seen,  however,  that  calcium  phosphate  exists  in  much  larger 
proportions  in  the  solids  than  in  the  fluids.  Only  traces  are  found  in 
blood,  saliva,  etc.,  whereas  a  thousand  parts  of  enamel  will  contain 
nearly  nine  hundred  parts  of  this  principle.  Calcium  phosphate,  while 
insoluble  in  water,  is  held  in  solution  in  certain  parts  of  the  system  by 
the  free  carbonic  acid,  the  bicarbonates  and  the  sodium  chloride — in  the 
urine,  for  example,  by  the  acid  sodium  phosphate.  On  the  other  hand,  this 
principle  is  in  a  solid  condition  in  bones,  teeth,  cartilage,  etc.  Calcium 
phosphate  forms  one  Of  the  ingredients  of  our  food  and  so  gets  into  the 
system;  it  is  eliminated  in  the  feces  and  urine.  Its  use  in  the  economy 
is  to  give  strength  and  solidity.  Hence  the  large  amount  present  in 
the  bones,  and  more  especially  in  the  enamel,  the  hardest  of  all  known 
organic  substances.  It  is  very  abundant  in  the  lower  extremities,  which 
support  the  weight  of  the  body.  The  ribs  contain  less  calcium  phos- 
phate than  the  upper  extremities,  hence  their  greater  elasticity. 

Table  VI.1 — Quantity  of  Calcium  Phosphate. 

Substance. 

Blood      . 

Milk 

Soliva 

Urine 

Excrements     . 

Bone 

The  amount  of  calcium  phosphate  found  in  any  organ  or  tissue  differs 
often  according  to  age;  thus  it  will  be  seen  from  Table  VI.  that  in  the 
teeth  of  a  very  old  man,  in  a  thousand  parts  there  are  one  hundred  and 
fifty  parts  more  than  in  an  infant,  and  fifty  more  than  in  an  adult. 
Rickets  is  due  to  a  want  of  the  proper  amount  of  calcium  phosphate. 
The  liability  of  pregnant  women  to  meet  with  fractures,  and  the  delay 
of  union  in  these  cases,  are  due  to  their  offspring  taking  from  the  mother 
so  much  calcium  phosphate,  necessary  in  the  development  of  the  new 
being.  The  calcium  phosphate  in  a  bone  can  be  all  dissolved  out  by 
hydrochloric  acid  ;  such  a  bone  retains  its  form,  but  if  it  be  the  fibula, 
is  so  pliable  that  it  can  be  tied  in  a  knot,  a  good  illustration  of  the  im- 
portance of  this  salt  to  the  system.    If  animals  be  deprived  of  their  proper 

i  Robin  et  Verdeil,  op.  cit.,  p.  287. 


Parts  per  1000. 

Substance.                                         Pa 

rts  per  1000. 

0.7 

Teeth  of  infant    . 

510.0 

2.5 

Teeth  of  adult     . 

610.0 

0.6 

Teeth  of  man  at  81  years    . 

660.0 

.       25.0 

Enamel         .         .         .         . 

885.0 

.       4O.0 

Bachitic  bone 

136.0 

.     400.0 

CALCIUM    CARBONATE,    SODIUM    CARBONATE.  53 

amount  of  calcium  phosphate  their  bones  soften,  as  seen  in  Chossat's 
experiments  on  pigeons. 

Calcium  Carbonate,  CaCO.,. — This  principle  is  found  in  the  blood, 
teeth,  cartilage,  and  bones.  In  the  latter  it  is  not  as  abundant  as  the 
phosphate,  but  exists  in  the  proportion  of  a  hundred  parts  to  the  thou- 
sand (see  Table  VII.). 

Table  VII.1 — Quantity  of  Calcium  Carbonate. 

Substance.  Parts  per  1000. 

Bone 102.0 

Teeth  of  infant 140  0 

Teeth  of  adult 100.0 

Teeth  of  man  at  eighty-one  years         ....  10.0 

As  before  mentioned,  calcium  carbonate  is  the  only  inorganic  principle 
which  exists  in  a  crystalline  form  and  uncombined  in  the  body.  As 
such,  it  is  found  in  the  otoliths  of  the  internal  ear.  Calcium  carbonate 
is  found  in  our  food,  and  in  this  way  is  introduced  into  the  system. 
It  is  held  in  solution  by  carbonic  acid.  Some  of  the  calcium  carbonate 
found  in  the  system  is  no  doubt  due  to  the  decomposition  of  the  malates, 
citrates,  tartrates,  acetates  present  in  the  food,  into  carbonic  acid.  It 
passes  out  of  the  body  in  the  urine,  probably  transformed  into  the  phos- 
phate. The  uses  of  calcium  carbonate  in  the  economy  are  the  same 
essentially  as  those  of  the  phosphate. 

Sodium  Carbonate,  Na2Co3. — Sodium  carbonate  is  found  (Tabic 
AT  1 1.)  in  the  blood,  saliva,  etc.,  the  alkalinity  of  these  fluids  beino- 
due  to  its  presence.  It  is  not  introduced  from  without,  but  is  formed  in 
the  system  through  the  decomposition  into  carbonic  acid,  of  the  malates, 
tartrates,  etc.,  found  in  fruits.  Some  of  it  occasionally  passes  away  in 
the  urine,  but  a  greater  part  is  decomposed  by  the  acid  of  the  lungs  ; 
the  carbonic  acid  set  free  behm  exhaled. 

Table  VIII. z — Quantity  of  Sodium  Carbonate. 

Substance.  Parts  per  1000. 

Blood 1.6 

Lymph 0.."> 

Cephalo  fluid 0.6 

Compact  tissue  of  bone 2.0 

Spongy  tissue  of  bone 0.7 

Sodium  carbonate  seems  to  maintain  the  albumen  and  fibrin  of  the 
blood  in  a  fluid  condition,  and  is  of  use  also  in  preserving  the  form  of 
the  blood  corpuscles.  What  has  just  been  said  of  sodium  carbonate 
applies  equally  well  to  potassium  carbonate  (K2C03),  sodium  phos- 
phate, etc. 

Sodium  phosphate  (Na,HP04),  magnesium  phosphate  (MgHP04), 
and  potassium  phosphate  (K2HP04),  are  found  in  small  quantities 
all  through  the  body.  They  exist  in  our  food,  and  are  discharged  in 
the  urine  and  feces.  Their  use  seems  to  be  similar  to  that  of  calcium 
phosphate. 

1  Robin  et  Verdeil,  op.  cit,  p.  223.  -  Robin  et  Verdeil,  op.  cit.,  p.  258. 


54  GENERAL    STRUCTURE    OF    THE    BODY. 

There  are  found  in  the  blood,  and  some  other  of  the  fluids  and  solids 
of  the  body  also,  sodium  sulphate  (Na2S< ).,),  potassium  sulphate  (K2S(  >,), 
and  calcium  sulphate  (CaS04).  The  first  two  of  these  salts  are  intro- 
duced in  the  food  and  are  discharged  in  the  urine.  Their  functions 
seem  to  lie  the  same  as  the  sodium  carbonate.  The  calcium  sulphate  is 
found  in  drinking  water,  and  is  evacuated  in  the  feces;  its  function  is 
unknown.  Magnesium  carbonate  (MgCOs)  and  sodium  bicarbonate 
(NaHC03)have  been  found  in  the  blood.  Finally,  ammonium  chloride 
(NH4G)  is  found  in  the  tears,  saliva;  its  origin  and  use  are  very 
obscure. 

Some  physiological  chemists  subdivide  the  inorganic  proximate  prin- 
ciples into  two  classes :  those  which  appear  indispensable  to  the  constitu- 
tion of  the  tissues,  as  water,  calcium  phosphate,  etc.,  and  those  which 
influence  the  processes  of  nutrition  without  absolutely  entering  into  the 
composition  of  the  tissues,  like  the  chlorides. 

It  appears  to  me  however,  that  at  present,  at  least,  no  such  sharp 
lines  of  demarcation  can  be  drawn  between  these  principles.  Water, 
for  example,  while  existing  in  many  tissues  in  a  molecular  state  of  com- 
bination, no  doubt  influences  the  processes  of  nutrition.  On  the  other 
hand,  while  common  salt  plays  an  important  role  in  nutrition,  under 
certain  conditions,  it  seems  to  be  as  much  a  tissue  element  as  calcium 
phosphate. 

In  the  present  state  of  physiological  chemistry,  it  seems  premature, 
therefore,  to  draw  any  very  fine  distinctions  as  to  the  relative  impor- 
tance of  this  or  that  inorganic  principle,  or  do  more  than  point  out,  as  I 
endeavored  to  do  in  a  general  way,  their  uses  in  the  human  economy. 


CHAPTER   II. 


PROXIMATE  PRINCIPLES  OF  ORGANIC  ORIGIN. 


As  has  been  already  stated,  in  addition  to  the  inorganic  proximate 
principles,  the  human  body  contains  many  of  organic  origin — that  is, 
principles  elaborated  by  organized  bodies,  plants,  or  animals;  some  of 
these  principles  have  already  been  prepared  artificially  by  chemists,  and 
there  is  no  reason  why  in  time  they  should  not  all  be.  They  naturally 
arrange  themselves  into  two  classes,  those  containing  no  nitrogen  and 
those  in  which  this  principle  is  present.  Table  IX.  gives  some  of 
these  principles  and  where  they  are  found.  Let  us  consider  the  former 
class  first. 

Table  IX. — Organic  Principles. 


( 'until ining  no  Nitrogen. 


Substances 

Starch    . 
Sugar     . 
Fat 
Pneumic  acid 


Albumen 

Fibrin    . 

Albuminose 

Casein    . 

Mucosin 

Pancreatin 

Pepsin  . 

Globulin 

Musculin 

Ostein    . 

Cartilagin 

Elasticin 

Keratin 

Crystallin 

Hiematin 

Melanin 

Biliverdin 

Urrosacin 


Containing  A 


Where  found. 
Brain. 
Milk. 

Almost  universal. 
Lungs. 


iroge/i. 

I 
i 


Blood,  chyle,  lymph. 

Chyme,  blood. 
Milk. 

Mucus. 

Pancreatic  juice. 

Gastric  juice. 

Blood  corpuscles. 

Muscles. 

Bone. 

Cartilage. 

Elastic  tissue. 

Nails. 

Lens. 

Blood. 

Pigment. 

Bile. 

Urine. 


Non-nitrogenous  Principles  of  Organic  Origin. — This  class  of 
proximate  principles  is  represented  by  the  starches,  sugars,  fats,  fatty 
acids,  and  oils,  lactic  acid  and  lactates,  pneumic  acid  and  sodium  pneu- 
mate :  but,  as  already  mentioned,  when  not  obtained  artificially,  are 
produced  only  by  plants  and  animals.  These  substances  do  not  form  a 
part  of  the  mineral  world,  like  such  principles  as  salt,  calcium  phos- 
phate, etc.,  just  considered.     They  agree  with  the  organic  proximate 


5b' 


PROXIMATE    PRINCIPLES    OF    ORGANIC    ORIGIN 


principles  in  having  ;i  definite  chemical  composition,  and,  with  the  excep- 
tion of  starch,  are  crystallizable.     In  striking  contrast  with  the  principles 

of  the  first  class,  with  the  exception  of  the  butter  and  sugar  of  milk  of 
lactation,  those  of  the  second  class  are  never  discharged  from  the  body 
while  in  a  state  of  health.  The  principles  of  the  second  class  differ 
from  those  of  the  third  not  only  in  the  absence  of  nitrogen,  but,  as  we 
shall  see,  these  latter  are  not  crystallizable. 

By  glancing  at  Table  X.   it  will  be  seen  that  of  these  principles, 
starch,  sugar,  and  stearin — a  form  of  fat,  consist  of  carbon,  hydrogen, 
#and  oxygen. 

Tahle  X. — Composition  of 


Water 

Starch 
Cane  sugar 
Grape  sugar 
Stearin 
Albumen . 


H,  O. 

^1kH30  Oi5. 

C,2H22  On. 
C6  H„  06. 
C57HU0O6. 

C72H112022N18S. 


These  particular  principles  are  often  known  as  the  carbohydrates 
The  term,  however,  is  only  applicable  to  the  starch  and  sugar,  since 
it  is  only  in  the  latter  that  the  hydrogen  and  oxygen  exist  in  the  pro- 
portion to  form  water,  the  hydrogen  being  largely  in  excess  of  the  oxy- 
gen in  the  fats.  Let  us  begin  our  study  of  the  second  class  of  proximate 
principles  with  starch. 

Starch,  C18H30O15. — Starch  exists  in  the  human  body  as  the  corpora 
amylacea,  the  starch  granules  that  are  found  in  the  walls  of  the  lateral 


Fiu.  10. 


Fig.  11. 


Starch  grains  from  wall  of  lateral  ventricles  ; 
from  a  woman  aged  thirty-five,.     (Dalton.) 


Grains  of  potato  starch.     (Dalton.) 


ventricles  of  the  brain,  in  the  fornix,  septum  lucidum,  etc.,  described  by 
Kolliker1  and  Yirchow.2     They  resemble  (Fig.  10),  to  a  considerable 


i  Handbuch  der  Gewebelehre,  1852,  S.  311. 

2  Cellular  Pathology.     Translated  by  Chance.     7th  edit  ,  p.  313. 


STARCH.  57 

extent,  the  starch  grains  of  Indian  corn.  They  are  transparent  and 
colorless,  like  the  starch  granules  of  plants  generally.  They  average 
about  the  18100th  of  an  inch  in  size,  present  a  hilus,  are  slightly  lami- 
nated, and  give  the  characteristic  blue  color  when  treated  with  iodine. 
Although  not  crystallizable,  starch  is  far  from  being  an  amorphous 
powder,  as  seen  from  the  above  description  of  the  corpora  amylacea,  but 
the  characteristic  structure  of  the  starch  granule  is  better  seen  in  that 
of  the  potato  (Fig.  11),  where  the  laminations  and  the  hilus  of  the  gran- 
ules are  well  marked.  Starch  exists  abundantly  (see  Table  XI.)  in 
corn,  wheat,  oats,  rice,  potatoes,  and  indeed  in  almost  all  vegetable  food. 
Tapioca,  arrowroot,  etc.,  so  useful  as  articles  of  diet,  under  certain  cir- 
cumstances, are  varieties  of  starch. 

Table  XI.1 — Quantity  of  Starch  in  100  Parts  in 

Bice 88.65  Peas 37.30 

Indian  corn     ....  67.55  Beans 33.00 

Barley 66.43  Flaxseed          ....     23.40 

Oats 60.59  Potatoes 20.00 

Bve 64.65  Sweet  potatoes         .         .         .     16.05 

Wheat 57.88  Chocolate        .         .         .        .11.00 

AVhatever  may  be  the  source  from  which  starch  is  derived,  it  is 
chemically  the  same,  and  is  produced  in  growing  vegetables,  under  the 
influence  of  solar  light,  by  a  process  of  deoxidation  of  carbonic  acid,  as 
shown  by  the  following  formula  : 

Carbonic  acid.     Oxygen.  Starch.  Water. 

6H2C03  —  120  =  C6H10O5  +  H20 

The  principle  of  the  development  of  starch  through  the  deoxidation 
of  carbonic  acid  may  be  roughly  illustrated  in  the  following  manner: 
A  bunch  of  fresh  mint  being  placed  within  a  cylindrical  tube  containing 
dilute  carbonic  acid  water  standing  over  the  pneumatic  trough  is  ex- 
posed to  sunlight.  Soon  the  leaves  of  the  mint  will  be  seen  covered 
with  minute  beads  of  gas,  a  small  quantity  of  the  latter  accumulating 
at  the  top  of  the  cylindrical  tube.  By  withdrawing  the  mint  and  pass- 
ing up  a  few  bubbles  of  nitric  oxide,  a  dark  brown  vapor  will  appear  at 
the  top  of  the  tube,  proving  that  the  contained  gas  was  oxygen. 
Starch  is  insoluble  in  cold  water,  but  by  boiling  the  granules  are 
liquefied,  and,  on  cooling,  remain  fused  together  as  a  whitish,  oxaline, 
homogeneous  mass.  In  this  condition,  it  is  said  to  be  tkhydrated." 
The  most  important  property  of  starch  for  the  physiologist,  however, 
is  the  readiness  with  which  it  is  converted  into  sugar.  This  might  be 
inferred  from  their  relative  composition,  the  only  difference  being  in 
the  amount  of  water  (see  Table  X.).  Thus,  if  human  saliva  lie  added 
to  boiled  starch  and  the  mixture  be  maintained  at  a  temperature  of 
100°  F.,  in  a  few  minutes  it  will  be  found  to  have  been  converted  into 
suo-ar  as  shown  by  the  following  formula  : 

Starch.  AVater.  Glucose. 

C6H10O5  +  H,0  =  C6H1206 

1  Dalton:  Physiology,  18S2,  p.  52.     Payen:  Substances  Alimentaires,  p.  -265.     P;uis,  1SG5. 


58  PROXIMATE    PRINCIPLES    OF    ORGANIC    ORIGIN. 

All  of  the  starch  in  the  food  is  soon  converted  into  glucose  in  the  ali- 
mentary canal  by  the  digestive  processes,  and  in  this  form  disappears 
from  the  economy.  The  use  of  starch  leads  us  naturally  to  the  con- 
sideration of  sugar  or  the  form  in  which  it  appears,  with  the  exception 
of  the  corpora  amylacea,  in  the  body. 

Sugar. — This  principle  is  found  in  the  alimentary  canal  during 
digestion,  under  the  form  of  glucose,  C6H1206,  as  milk  sugar,  C12H22Ou 
+  H20,  during  lactation  The  liver  also  contains  glycogen,  C6H1()05, 
a  substance  readily  converted  into  sugar,  which  passes  into  the  hepatic 
veins,  and  from  there  to  the  vena  cava  and  heart.  In  the  muscles  are 
found  inosite,  C6H1206-f  2H20,  and  a  substance  similar  to  grape  sugar. 
Sugar  exists  in  the  economy  combined  with  other  proximate  principles. 
Thus,  in  the  blood  we  find  the  sugar  dissolved  in  water  combined  with 
the  albumen,  sodium  chloride,  etc. 

These  animal  sugars  are  closely  related,  chemically,  and  are  readily 
converted  into  one  another.  While  sugar  is  produced  in  man  by  the 
liver  and  mammary  glands,  etc.,  by  far  the  greater  part  is  derived  from 
the  food  either  in  the  form  of  cane  sugar,  C12H22Ou,  or  that  contained 
in  fruits,  grape  sugar,  C6H1206,  or  from  the  easily  transformed  starch. 

Table  XII.1 — Quantity  of  Sugar  in  100  Parts  cn 


Cherries  .... 

.     18.12 

Goats'  milk 

.     5.80 

Juice  of  sugar  cane 

.     18.00 

Cows'  milk 

.     5.20 

Apricots  .... 

.     16.48 

Indian  corn-meal 

.     3.71 

Peaches  .... 

.     11.61 

Rye  flour 

.     3.46 

Pears       .... 

.     11.52 

Barley  meal 

.     3.04 

Sweet  potatoes 

.     10.20 

Wheat  flour 

.     2.33 

Beet  roots 

.       8.00 

Oatmeal    . 

.     2.19 

Parsnips 

.      4.50 

Beef's  liver 

.     1.79 

The  vegetable  sugars  only  differ  from  the  animal  varieties  in  the 
proportion  of  water  they  contain,  and  when  we  come  to  study  digestion 
and  absorption  we  shall  see  that  the  vegetable  sugars  are  all  metamor- 
phosed into  the  animal  kind  before  they  are  taken  up  by  the  system. 
While  the  two  classes  of  sugars  have  many  affinities,  yet  they  differ  in 
the  effects  produced  upon  them  by  alkalies  and  acids.  Cane  sugar, 
when  boiled  with  an  acid,  is  converted  into  the  animal  variety,  the 
addition  of  alkalies  having  no  effect.  On  the  other  hand,  the  acids 
have  no  effect  upon  the  animal  sugars,  whereas  melasic  acid  results  from 
boiling  with  an  alkali.  Under  certain  circumstances,  sugar  (C6H12Ofi) 
becomes  lactic  acid,  2(C3HG03) ;  the  significance  of  this  chemical  change 
we  shall  see  presently.  A  convenient  test  for  sugar  is  that  known  as 
Trommer's  test.  The  suspected  liquid  is  placed  in  a  test-tube,  to  this 
are  added  one  or  two  drops  of  sulphate  of  copper ;  then  the  mixture  is 
made  distinctly  alkaline  by  the  addition  of  a  solution  of  caustic  potash. 
The  mixture  will  become  blue,  particularly  if  sugar  is  present.  Now 
heat  the  test-tube  till  just  before  boiling  point,  when,  if  sugar  is  present,  a 
reddish  precipitate  will  appear  just  in  the  upper  part  of  the  tube,  and  will 
gradually  be  seen  in  the  whole  liquid.  The  reaction  is  due  to  the  cupric 
oxide  being  reduced  to  the  condition  of  a  cuprous  oxide  by  the  oxidation  of 

1  From  Dalton,  op.  cit. ,  p.  54.     Payen,  op.  nit. 


FAT.  59 

the  sugar.  The  solution  to  be  examined  should  be  clear.  This  can  be 
accomplished  by  boiling  the  suspected  tissue,  finely  divided,  with  water 
and  sulphate  of  soda  and  filtering.  The  organic  and  coloring  matters 
will  be  retained,  and  a  clear  extract  will  pass  through,  the  soda  not 
interfering  with  the  test.  Milk,  liver,  and  grape  sugar  and  glucose 
respond  to  Trommer's  test.  Cane,  maple,  and  beet  sugar,  however, 
must  be  boiled  with  very  weak  sulphuric  acid  to  convert  them  into 
glucose  before  the  test  will  be  applicable.  There  are  substances  in  the 
healthy  urine  which  interfere  with  the  reaction  in  the  reduction  of  the 
copper,  though  sugar  be  added  in  considerable  quantity.  Of  course, 
this  does  not  apply  to  diabetic  urine.  Albuminose,  which,  as  we  shall 
see  hereafter,  is  produced  dirring  gastric  digestion,  interferes  also  with 
Trommer's  test,  as  noted  by  Longet,1  though  Dalton2  pointed  out  first 
the  fact  of  the  products  of  stomach  digestion  having  this  curious  effect. 
With  the  above  qualifications,  Trommer's  test  is  very  reliable  and 
easily  applied.  Other  tests,  such  as  those  of  Moore,  Barreswil's,  Mau- 
merie,  Bottger's,  Fehling's,  the  fermentation  test,  and  that  of  torulse, 
etc.,  are  also  used.  Notwithstanding  the  amount  of  sugar  introduced 
into  the  economy  in  the  food  and  produced  independently  in  the  system, 
none  appears  in  the  excretions  in  health ;  the  presence  of  sugar  in  the 
urine,  for  example,  being  a  sign  of  the  disease  diabetes.  With  the 
exception  of  the  places  indicated,  sugar  is  not  found  in  the  system,  it 
being  destroyed  almost  as  rapidly  as  produced,  being  burnt  up  and 
oxidized,  and  passing  out  of  the  economy  principally  through  the  lungs, 
transformed  into  carbonic  acid  gas  and  water  thus : 

Glucose.  Oxygen.       Carbonic  acid  gas.  Water. 

C6H,A    +     120    =    6(C02)      +     6(H20) 

Through  its  combustion  it  is  one  great  source  of  heat,  and  hence  its 
importance  to  man  as  a  source  of  fuel  and  force.  Its  relations  in  this 
respect  will  be  again  pointed  out  when  the  subjects  of  food  and  animal 
heat  are  considered.  At  all  periods  of  life  sugar  is  a  most  important 
principle.  In  the  foetus,  even  at  an  early  period  of  intrauterine  life, 
the  fluids  contain  it,  and  in  a  greater  proportion  than  after  birth. 

Fat. — Fat  is  an  almost  universal  constituent  of  the  body;  it  is 
absent,  however,  in  the  bones,  teeth,  the  eyelids,  and  scrotum,  elastic 
and  unelastic  fibrous  tissue.  It  is  always  present,  even  in  extreme 
cases  of  emaciation,  in  the  orbit,  and  around  the  kidneys.  The  amount, 
however,  varies  very  considerably  in  the  different  tissues,  as  may  be 
seen  from  Table  XIII. 

Table  XIII.3—  Quantity  of  Fat  ix  100  Parts  of  Tissue. 

Sweat 0.001  Liver 2.4 

Saliva 0.02  Muscles 3.3 

Lymph 0.05  Hair 4.2 

Chyle 0.2  Milk 4.3 

Mucus 0.3  Cortex  of  brain         .         .         .8.0 

Blood 0.4  Medulla 20.0 

Cartilage          ....  1.3  Nerves 22.1 

Bone        .         .         .         .         .1.4  Spinal  cord        ....  23.(3 

Crystalline  lens       .         .         .  2.0  Adipose  tissue  ....  82.7 

i  Gazette  Heb.,  1855.  -'  Amer.  Journ.  Med.  Sri.,  1854.  :s  Carpenter:   Physiology,  1881,  p.  88. 


60 


PROXIMATE    PRINCIPLES    OF    ORGANIC    ORIGIN 


Thus,  while  in  the  sweat,  lymph,  saliva,  etc.,  there  is  ;i  more  trace  of 
fat,  more  than  twenty  per  cent,  is  found  in  the  nervous  system,  and 
over  eighty  in  adipose  tissue.  The  whole  amount  of  fat,  according  to 
Burdach,1  in  the  body  of  a  man  weighing  17<>  pounds  was  N.8  pounds, 
or  5/1  pounds  of  fat  to  every  101)  of  body. 

Fat  exists  in  the  adipose  tissue,  for  example,  in  the  form  of  vesicles 
which  are  transparent  and  contain  the  oily  matters,  and  in  certain 
tissues,  like  the  liver,  cartilages,  etc.,  an  excess  of  the  production  of  fat 
in  liver  cells  constitutes  fatty  liver  globules.  Chemically  speaking,  fat 
consists  of  a  mixture  of  the  principles  known  to  chemists  as  stearin, 
palmitin,  margarin,2  and  olein.  The  first  two  are  solid  at  the  tem- 
perature of  the  body,  but  are  held  in  solution  by  the  olein.  They 
crystallize  (Fig.  12)  in  needle-like  forms,  assuming  a  beautiful  radiatory 

Fig.  12. 


Stearin  crystallized  from  a  warm  solution  in  olein.     (Dai/ton.) 

or  arborescent  appearance,  where  fluid,  fatty,  oily  substances  under  the 
microscope  have  the  appearance  of  round  globules,  bright  in  the  centre, 
and  dark  at  the  edges.  With  the  exception  of  the  phosphorized  fat  of 
nervous  tissues,  fat  does  not  exist  combined  with  the  other  proximate 
principles,  like  we  found  was  the  case  with  the  inorganic  principles 
and  the  sugars ;  there  is  no  such  molecular  union  of  fat  with  any  prin- 
ciple. There  is  no  difficulty,  therefore,  in  extracting  it  from  the  system 
in  a  state  of  purity.  Pressure  is  often  the  only  process  needed,  the  oil 
being  squeezed  out  of  the  interstices  of  the  tissues  of  the  organ  con- 
taining it.  The  general  composition  of  fat  may  be  illustrated  by  that 
of  stearin,  C57Hu0O6,  and  it  will  be  observed  that  while  fat,  like  the 
carbohydrates,  consists  of  carbon,  hydrogen,  and  oxygen,  the  last  two 
elements  do  not  exist  in  fat  in  the  proportions  to  form  water. 


1  Traits  de  Pliysiologie,  tome  viii.  p.  80.    Paris,  1857. 

-  Margarin  probably  consists  of  a  mixture  of  stearin  and  palmitin. 


FAT.  61 

Table  XIV.1 — Quantity  of  Fat  in  100  Parts  of  Food. 

Chocolate  nut  ....  49.00  Salmon 4.85 

Sweet  almonds  ....  24.28  Cows'  milk         ....  3.70 

Indian  corn       .         .         .         .8.80  Deans 2.50 

Fowls'  eggs       ....     7.00  Wheat 2.10 

•Mackerel 6  70  Peas 2.10 

Calf  s  liver        ....     5.58  Oysters 1.51 

Beef's  flesh        ....     5.19  Potatoes 0.11 

The  fat  of  the  body  is,  to  a  great  extent  no  doubt,  derived  from  the 
fat  of  the  food,  somewhat  modified,  however,  after  being  introduced  into 
the  system,  since  the  fat  of  the  body  neither  in  man  nor  animals  is  iden- 
tical with  that  of  their  food.  In  most  cases,  however,  more  fat  is  pro- 
duced in  the  system  than  can  be  accounted  for  by  the  fat  derived  from 
the  food.  The  experiments  of  Persoz,2  Boussingault,3  Thomson,4  Lawes5 
and  Gilbert,  and  others,  upon  geese,  ducks,  pigs,  cows,  etc.,  with  refer- 
ence to  this  point  are  conclusive. 

In  the  case  of  a  cow,  for  example,  under  the  observation  of  Voit,  and 
to  be  referred  to  again  in  a  moment,  it  was  observed  that  of  the  202-4 
grammes  of  fat  in  the  milk,  only  1658  could  have  been  derived  from 
the  fat  of  the  feed.  Now,  from  such  facts  as  the  starch  of  plants  be- 
coming oil,  and  of  sugar  being  readily  transformed  into  alcohol  and 
other  fats  during  fermentation,  as  shown  by  the  formula 

Glucose.  Alcuhol.         Carbonic  acid  gas. 

C6H1206     =     2C,H60     +     2C02 

of  carbohydrate  principles  constituting  a  part  of  a  fattening  food,  of 
the  negroes  and  cattle  getting  fat  during  the  time  that  the  cane  is 
being  collected  and  the  sugar  extracted,  etc.,  one  would  be  naturally 
led  to  suppose,  as  indeed  held  by  Liebig,  that  the  fat  produced  in  the 
system  over  and  above  that  absorbed  from  the  food,  was  derived  from 
its  carbohydrate  principles.  On  the  other  hand,  it  is  a  matter  of 
every  day  observation  that  animals  are  fattened  best  on  a  feed  consisting 
of  albuminous  as  well  as  of  carbohydrate  principles  apart  from  the 
fatty  matters  contained  in  it;  and  while  there  is  no  difficulty  in  under- 
standing how,  through  the  abstraction  of  oxygen,  as  just  shown,  a  fat, 
like  alcohol,  may  be  derived  from  a  carbohydrate,  it  does  not  follow  that 
fat  is  actually  so  produced  in  the  system.  On  the  contrary,  as  shown 
by  Pettenkoffer6  and  Voit,  so  tar  from  the  fat  produced  being  propor- 
tional to  the  carbohydrate  principles,  which  ought  to  be  the  case  on 
such  a  supposition,  the  fat  deposited  is  proportional  to  the  amount  of 
albumen  destroyed  Thus,  as  will  be  seen  from  the  following  experi- 
ments made  upon  dogs  fed  with  starch  : 

Experiment  of  Feeding  a  Dog  upon  Starch. 

c        .      -  -     .  Meat  of  body  Fat  Carbonic  acid 

.taren  ot  loou.  destroyed.  deposited.  produced. 

No.  1.    379  grammes  ...     211  24  546 

"     2.    608         "  .    "     .         .     1!»3  22  799 

1  Dalton,  op.  cit.,  p.  62.     Payen,  op.  cit. 

-  Annales  de  Chiniie  et  Physique  (:i),  t.  xiv.  p.  408,  1845.  3  Ibid.,  p.  419,  1845 

<  Aim.  de  Chimie  u.  Phar.,  Hand  Ixi.  S.  228,  1847. 

•'•  Report  of  the  British  Association  lor  the  Advance  of  Science,  1852. 

6  Zeits.  fur  Biologie,  Band  ix.  S.  435,  1873.    Hermann  :  Physiologie,  Sechster  Band,  1681.  S.  252. 


Meat   !<'.-troycil. 

Fat  deposited 

211  <.f  body. 

'   24 

COS  I     of 

55 

469  i  food. 

112 

62  PROXIMATE    PRINCIPLES    OF    ORGANIC    ORIGIN. 

that  while  the  amount  of  fat  deposited  differed  but  little,  the  amount  of 
starch  taken  as  food  was  much  greater  in  the  one  case  than  the  other. 
This  is  as  might  have  been  expected,  since  the  starch,  after  being 
transformed  within  the  system  into  sugar,  is  then  ultimately  oxidized, 
and,  as  we  shall  see,  constituting  an  important  source  of  heat,  cannot, 
therefore,  be  a  source  of  fat.  The  meat  destroyed,  it  may  be  men- 
tioned in  the  above  experiments,  was  that  of  the  body,  since  none  was 
given  as  food.     On  the  other  hand,  in  the  three  following  experiments : 

Experiment  of  Feeding  a  Dog  upon  Starch  and  Meat. 

Starch  of  food. 

No.  1.    379  srammes 
"     2.    379"      " 
"     3.    379         "  ... 

also  made  upon  dogs  fed  with  starch,  and  in  the  second  and  third  ex- 
periments with  meat  also,  it  will  be  observed  that  while  the  amount  of 
starch  remained  the  same,  that  of  the  meat  consumed  differed  con- 
siderably, nearly  seven  times  more  meat  being  destroyed  in  the  third 
example  than  in  the  first,  and  nearly  five  times  as  much  fat  deposited. 
Not  only,  however,  has  it  been  shown  that  the  meat  or  its  contained 
albumen,  when  broken  up,  accounts  for  the  production  of  fat  in  a  car- 
nivorous animal,  as  the  dog,  but  also  in  a  herbivorous  one,  like  the  cow. 
Thus,  according  to  Voit,2  as  has  already  been  mentioned,  of  the  2024 
grammes  of  fat  in  the  milk  of  a  cow,  1658.40  grammes  are  clearly 
derived  from  the  fat  of  the  feed,  1851  grammes  are  developed  out  of 
the  breaking  up  of  3602  o-rammes  of  albumen,  which,  together  with 
that  of  the  feed,  more  than  accounts  for  that  found  in  the  milk,  as 
shown  in  detail  from  the  following  experiments  : 

Production  of  Fat  in  Milk  of  Cowt. 


In  feed 

In  feces 

.     2757. 74  grammes  fat, 
.     1099.33 

Absorbed 
Out  of  3602  grammes  of  albumen 

.     1658.40 
.     1851.00 

Available 
In  milk        ..... 

.     3509.00 
.     2024.00 

1485.00 

When  the  chemical  composition  of  albumen  is  considered,  consisting, 
as  we  shall  see  as  it  does,  of  CHONS,  it  becomes  perfectly  apparent 
how,  in  being  decomposed  in  the  system,  it  can  split  into  two  sub- 
stances, a  non-nitrogenous  one,  consisting  of  CHOS,  and  a  nitro- 
genous one,  CON2H4,  urea,  the  former,  excluding  the  sulphur,  being 
retained  in  the  system  as  fat,  the  latter  being  eliminated,  as  we  shall 
see,  in  the  urine.  Suppose,  for  example,  that  540  grains  (about  34 
grammes)  of  urea  have  been  excreted  by  a  man  in  the  urine,  involving 
a  destruction  of  about  three  times  as  much  albumen  ;  while  all  of  the 

1  Hermann,  op.  cit.,  S.  255. 


FAT.  63 

nitrogen  of  the  albumen  destroyed  passes  practically  out  of  the  body  as 
urea,  only  108  grains  of  the  804  grains  of  the  carbon  of  the  albumen 
leave  the  body  in  that  form  ;  756  grains  of  carbon  are,  therefore, 
retained  in  the  body,  available  for  the  production  of  fat,  as  may  be  seen 
from  the  following  formula: 


c 

H 

N 

0 

864 

112 

252 

352 

108 

36 

252 

144 

Albumen  . 
Urea 

Fat 756  76  ...  208 

or  dividing  by  atomic  weights. 

C6;  HT6  Ol3 

It  is  not  to  be  supposed,  however,  that  all  of  the  756  grains  of  the 
carbon  are  converted  into  fat,  since  probably  two-thirds  are  exhaled 
from  the  body  in  the  form  of  carbonic  acid.  The  above  theoretical 
consideration  is  fully  borne  out  by  the  experiments  of  Pettenkofer  and 
Voit1  made  upon  dogs  fed  with  meat.  In  one  instance,  for  example, 
when  a  dog  had  eaten  2000  grammes  of  meat  (about  400  of  albumen) 
43  grammes  of  carbon  Avere  retained  in  the  system  in  the  form  of  58 
grammes  of  fat,  corresponding  to  12  percent,  of  the  albumen  destroyed. 
The  details  of  the  experiment  are  as  follows  : 

Experiment  of  Fattening  a  Dog  on  Meat. 

2000  grammes  of  meat 

Urine 
Feces 
Respiration 


Apart  from  the  experimental  evidence  such  as  that  just  offered,  there 
are  a  number  of  general  facts  which  go  to  show  that  in  many  cases 
albumen  becomes  fat,  as,  for  example,  in  the  fatty  degeneration  of  the 
tissues,  the  conversion  of  .dead  bodies  into  adipocere,  the  development  of 
fat  out  of  peptones  during  fermentation  ;  that  milk,  after  standing,  con- 
tains albumen  and  less  fat;  that  in  phosphorous  poisoning,  as  the  fat 
increases  the  albumen  diminishes,  etc.  Many  more  instances  might 
be  mentioned,  but  enough  has  been  said  to  leave  no  reasonable  doubt 
that  fat,  to  a  certain  extent  at  least,  is  developed  out  of  albumen. 
The  only  question  that  still  remains  undecided  is  as  to  what  extent 
albumen  becomes  fat.  In  many  instances,  according  to  Voit,2  even  if 
as  little  as  ten  per  cent,  of  fat  (fifty  per  cent,  being  the  maximum)  is 
developed  out  of  albumen,  the  amount  so  developed,  together  with  the 
fat  present  in  the  food,  is  more  than  enough  to  cover  the  fat  produced 

i  Zeit.  fur  Biologie.,  v.  S.  106,  1869;  vi.  S.  371,  1870;  vii.  S.  489,  1871. 
2  Hermann  :   Physiologie,  Sechster  Band,  S.  -lib. 


N 

C 

68.0 

250.4 

66.5 

39.9 

1.4 

9.2 

0.0 

158.3 

67.9 

2(17.4 

43  C  retained 

64         PROXIMATE    PRINCIPLES    OF     ORGANIC    ORIGIN. 

by  the  animal.  On  the  other  hand,  there  is  no  positive  evidence  what- 
ever that  carbohydrate  principles  are  transformed  within  the  body 
into  fat.  As  a  matter  of  fact,  they  cannot  be  drawn  upon  for  that  pur- 
pose to  any  extent,  leaving  the  body  as  carbonic  acid  and  water  after 
having  been  oxidized  in  the  system.  General  considerations  and  expe- 
riments showing  then  that  the  fat  deposited  in  the  body  over  and  above 
that  absorbed  from  the  food  is  derived  from  albumen,  it  may  be  asked 
of  what  use  are  the  carbohydrate  principles  always  present  in  fat- 
tening diet;  in  what  way  do  they  contribute  toward  the  production  of 
fat  ?  Regarding  these  principles  as  a  source  of  heat  to  the  economy, 
their  role  as  a  part  of  fattening  diet  becomes  perfectly  clear,  since  in 
being  burned  they  save  the  fat  otherwise  derived  and  which  would  be 
drawn  upon  for  the  same  purpose  if  they  were  absent.  Hence,  the  fact 
of  a  dog  fed  on  sugar  and  meat,  excreting  less  urea  and  getting  fatter 
than  when  fed  on  meat  alone,  of  the  negroes,  etc.,  already  referred  to, 
getting  fat  during  the  extraction  of  the  sugar  from  the  cane ;  of  dogs 
fed  on  meat  and  rubol,1  palm  oil,2  or  stearin,  getting  fat,  and  without 
a  trace  of  these  substances  being  found  in  the  excreta,  the  sugar  or  oil 
given  with  the  food  in  these  instances  saving  the  fat  otherwise  pro- 
duced from  the  albumen  from  being  burned.  The  carbohydrate  prin- 
ciples evidently  then  play  in  the  production  of  fat  this  secondary  role 
of  saving  the  fat,  otherwise  produced,  from  being  consumed,  and  only 
in  the  event  of  it  being  shown  that  the  fat  deposited  cannot  be  accounted 
for  by  the  destruction  of  the  albumen  being  overestimated,  can  these 
principles  be  regarded  as  a  source  directly  of  fat,  of  which  at  present,  I 
repeat,  there  is  no  evidence.  If  the  viewT  of  the  origin  of  fat,  just  re- 
ferred to,  essentially  that  of  Voit,3  be  accepted,  it  becomes  intelligible 
why  individuals  become  fat  whatever  they  eat,  and  that  if  the  fat  of  the 
body  is  to  be  reduced,  all  kinds  of  food  must  be  diminished,  as  little 
eaten  as  possible,  to  cut  off  the  supply,  and  plenty  of  active  exercise 
taken  to  quicken  the  circulation  and  respiration,  and  in  that  way  burn 
off  that  already  deposited.  Fat  is  never  discharged  from  the  body  in 
health  except  in  the  butter  of  milk,  but  is  destroyed,  burnt,  passing 
away  as  carbonic  acid  gas  and  water ;  and,  therefore,  like  sugar,  being 
a  source  of  heat  and  force : 

Fat.  Oxygen.     Carbonic  acid  gas.  Water. 

C57H110O6    +    0163    =    57(C02)    +    55(H20) 

Fat  is  useful  also  as  serving  to  support  the  organs,  like  the  eye  and 
kidney.  It  fills  up  the  spaces  between  vessels,  bones,  and  muscles, 
rounding  oft'  the  trunk  and  extremities  into  the  graceful  curves  of  the 
human  form. 

It  prevents  the  loss  of  heat  through  its  bad  conductive  power.  This 
function  of  fat  is  well  shown  in  the  cetacea,  of  which  the  whale,  dolphin, 
and  porpoise  are  examples.  In  these  animals,  just  under  the  skin, 
there  is  an  immense  amount  of  blubber  or  fat.  If  it  were  not  for  this 
layer  of  fat  these  marine  animals  would  lose  a  great  quantity  of  heat. 

1  Radziejewsky  :   Yin-how's  Archiv,  xliii.  S.  268. 
'-'  Subuotin  Zeits.  ftir  Bmlugie,  Baud  vi.  S.73,  1870. 
3  Hermann  :  Physioloeie,  Sechster  Band,  S.  235. 


FAT.  65 

It  is  well  known  that  when  fat  is  boiled  with  an  alkali  and  water,  part 
of  the  water  is  appropriated  and  the  fat  breaks  up  into  glycerin  and 
oleic,  palmitic,  or  stearic  acid,  according  to  the  kind  of  fat  used,  the  acid 
further  uniting  with  the  alkali  to  form  soap.  This  process  is  called 
saponification,  but  the  terra  also  includes  the  breaking  up,  simply,  of 
fat.  in  the  presence  of  water,  into  glycerin  and  an  acid,  as  seen  in  the 
following  formula  : 

Stearin.  Water.  Stearic  acid.  Glycerin. 

C57H110O6    +    3H,0    =    C54H108O6    -  ■    C3H803 

This  can  be  accomplished  by  passing  the  vapor  of  water  through  fat 
heated  to  572°  F.  In  this  way.  sodium  oleate  and  palmitate  and  oleic 
and  palmitic  acids  are  formed.  1  mention  these  principles,  as  they  have 
been  found  in  small  quantities  in  the  blood,  bile,  and  lymph.  The  odor 
in  the  axilla  and  feet  is  probably  due  to  the  combination  of  fatty  acids 
with  alkali.  The  oleates  and  margarates  may  serve  to  hold  in  solution 
the  small  amounts  of  fat  and  fatty  acids  found  in  the  blood.  Some  of 
the  fat  introduced  in  the  economy  probably  disappears  through  this  pro- 
cess of  saponification.  As  regards  the  remaining  proximate  principles  of 
the  second  class,  lactic  acid,  pneumic  acid,  and  sodium  pneumate.  little 
need  be  said.  Lactic  acid  is  developed  in  the  economy  through  the 
"acid  fermentation"  of  sugar,  especially  that  of  milk:  as  seen,  for 
example,  in  the  souring  of  milk.  It  is  found  in  the  muscles  and  often 
in  the  gastric  iuice.  Pneumic  acid  is  restricted  to  the  lungs.  Pneumate 
of  soda  is  formed  through  the  decomposition  of  the  carbonates  in  the 
blood  as  the  latter  pass  through  the  lungs. 


CHAPTER   III. 

PROXIMATE   PRINCIPLES  OF  THE  THIRD  CLASS. 

This  class  includes  such  substances  as  albumen,  fibrin,  casein,  pepsin, 
globulin,  ostein,  etc.  They  agree  with  the  principles  of  the  second 
class,  in  being  of  organic  origin — that  is,  elaborated  by  plants  and 
animals,  organized  bodies.  The  water,  carbonic  acid,  and  salts  found 
in  the  mineral  inorganic  world,  constituting  the  food  of  plants,  with 
some  exceptions,  like  the  fungi,  are  converted  by  the  plant  through  the 
agency  of  the  sun's  light  and  heat  into  such  principles  as  starch,  sugar, 
vegetable  albumen,  fibrin,  and  casein,  etc.  The  plants  in  time  serve 
as  food  for  herbivorous  animals,  •which  are  eaten  by  the  carnivorous 
ones,  while,  as  we  shall  soon  see,  all  three,  plants,  herbivora,  and 
carnivora,  together  with  the  inorganic  principles,  enter  into  the  food  of 
man. 

It  will  be  seen,  therefore,  that,  so  far  as  the  organic  principles  are 
concerned  in  nature,  the  plant  is  indispensable  as  preparing  the  food  for 
the  animal ;  the  former  living  on  carbonic  acid,  salts,  etc.,  which  would 
be  starvation  to  the  latter. 

While  the  organic  principles  are  usually  developed  in  the  order  indi- 
cated, it  must  be  mentioned,  however,  that  chemists  have  succeeded  in 
artificially  preparing  some  of  the  principles  of  the  third  class,  as  well  as 
those  of  the  second,  from  the  direct  combination  of  the  inorganic  ele- 
ments in  their  laboratory  by  purely  physico-chemical  processes,  without 
invoking  in  any  way  either  plant  or  animal  agency. 

Just  as  no  sharp  line  of  demarcation  can  now  be  drawn  between  plants 
and  animals,  so  the  distinction  between  the  organic  and  inorganic  worlds 
is  daily  becoming  fainter.  Indeed,  no  one  can  say  positively  where  the 
one  ends  and  the  other  begins. 

The  proximate  principles  of  the  third  class,  with  the  exception  of 
lecithin,  cerebrin,  leucin,  tyrosin,  to  be  described  hereafter,  differ  from 
those  of  the  first  and  second  in  not  being  crystallizable.  They  may 
coagulate,  but  they  never  assume  regular  crystalline  form. 

It  is  usually  assumed  in  works  on  physiology  that  such  substances 
as  albumen,  fibrin,  etc.,  have  not  a  definite  chemical  composition  and 
therefore  differ  in  this  respect  from  water,  salt,  sugar,  etc.  Chemistry 
teaches  that  a  definite  quantity  by  weight  of  oxygen  and  hydrogen  unite 
to  form  a  definite  quantity  of  water;  that  a  certain  quantity  of  sodium 
chloride  consists  of  just  so  much  sodium  and  chlorine  ;  that  carbon, 
hydrogen,  and  oxygen  combine  in  certain  proportions  to  form  a  definite 
quantity  of  sugar.  If,  however,  any  of  the  elements  entering  into  the 
composition  of  these  substances  be  either  increased  or  decreased,  the 
substance  will  cease  to  exist  as  such  :   a  priori  then  it  is  highly  improb- 


PROXIMATE     PRINCIPLES    OF    THE    THIRD    CLASS.         67 

able  that  albumen,  for  example,  consisting  of  C72H112N18022S,  should  be 
an  exception  to  this  law  of  definite  combining  proportions.  It  seems  to 
me  more  likely  that  albumen  differs  in  its  composition  in  individuals 
and  is  constantly  changing  even  in  the  same  person,  and  that  these  albu- 
mens, while  resembling  the  one  whose  formula  has  just  been  given,  if 
carefully  analyzed  would  be  found  to  consist  of  different  amounts  of 
carbon,  hydrogen,  oxygen,  nitrogen,  and  sulphur,  with  different  proper- 
ties, than  to  suppose  that  the  composition  of  a  substance  like  albumen 
can  be  altered  without  affecting  its  properties,  and  that  it  has  no  definite 
chemical  composition.  That  such  is  the  case  seems  confirmed  by  the 
fact  of  chemists  having  described  at  least  sixteen  kinds  of  albumen. 

The  truth  seems  to  be  that  any  one  of  these  albumens,  with  a  little 
more  or  a  little  less  of  this  or  that  element  of  composition,  is  not  so 
changed  as  to  render  it  unfit  for  playing  the  ordinary  rdle  of  albumen 
in  the  economy.  In  other  words,  that  these  albumens,  though  slightly 
differing  chemically,  are  readily  converted  into  one  another,  the  function 
of  albumen  in  the  system  being  performed  by  any  of  them. 

This,  however,  is  quite  a  different  statement  from  that  usually  made, 
that  these  principles  are  of  indefinite  chemical  composition. 

The  proximate  principles  of  the  third  class,  however,  are  distinguished 
in  a  marked  degree  from  those  of  the  first  and  second  in  containing 
nitrogen.  This  element  seems  indispensable  to  the  composition  of  a 
body  exhibiting  life.  As  is  well  known,  those  substances  which  are 
very  changeable,  decomposing  suddenly,  like  nitrogen  iodide,  nitrogen 
chloride,  nitroglycerin,  fulminating  salts,  gunpowder,  etc.,  owe  their 
peculiar  properties  to  the  nitrogen  they  contain. 

As  we  proceed  in  our  studies,  Ave  shall  see  that  the  essence  of  life  is 
in  change.  To  make  use  of  a  homely  simile,  nitrogen  seems  to  play 
the  same  part  in  the  living  body  as  that  by  a  restless,  excitable  spirit 
in  the  living  community  :  ever  ready  himself  to  be  affected  by  slight 
changes  and  to  influence  in  the  same  way  those  around  him. 

Thus  an  important  feature  of  the  nitrogenized  proximate  principles 
is  the  readiness  with  which  they  induce  such  changes  as  fermentation 
and  putrefaction — the  latter  being  brought  about  by  the  growth  and 
multiplication  of  a  minute  protist,  the  Bacterium  termo  (Fig-  13),  just  as 
sugar  is  decomposed  into  alcohol  and  carbonic  acid  through  the  influence 
of  the  yeast  cell.  Like  the  latter,  the  bacterium  cells  in  inducing  putre- 
faction neither  give  up  nor  take  away  any  chemical  elements,  acting 
by  their  presence  alone  in  a  way  which  must  be  admitted  is  not  as  yet 
understood.  The  effect  of  the  bacterium  cells  in  inducing  putrefaction 
in  this  manner,  like  that  of  the  saccharomyees  or  yeast  cell  (Fig.  14)  in 
producing  fermentation,  is  usually  said  to  be  due  to  catalysis.  The 
word  catalysis  meaning  literally  to  dissolve,  break  up,  while  frequently 
made  use  of  in  speaking  of  those  actions  in  the  economy  which  are  of 
this  character,  is,  however,  only  a  word,  not  an  explanation — in  fact, 
merely  a  convenient  way  of  expressing  our  ignorance  of  the  phenomena 
to  be  explained. 

The  susceptibility  of  these  organic  principles  to  change,  in  and  out 
of  the  In idv,  is  not  only  due  to  the  nitrogen  they  contain,  but  to  the 
great  number  of  atoms  entering  into  their  composition. 


68 


PROXIMATE    PRINCIPLES    OF    THE    THIRD    CLASS. 


It  is  more  Datura!  that  albumen,  for  example,  consisting  of  225  atoms, 
should  break  up  into  its  constituent  parts  on  the  slightest  change  taking 
place  in  the  surrounding  conditions,  than  sodium  chloride  or  water,  com- 
posed of  two  or  three  atoms  respectively.  It  is  easier  for  two  or  three 
persons  to  get  along  together  than  :i25,  especially  when  among  the  latter 
there  arc  22  (the  nitrogenous  atoms)  most  unstable  ones. 

Another  property  of  these  principles  is  their  hygrometricity — that  is, 
their  capacity  for  taking  up  their  water  of  composition  by  contact  after 
it  has  been  driven  off  by  heat,  when  the  principles  are  said  to  have  been 
desiccated. 

Fig.  13. 


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Cells  of  Bacterium  termo  ;  from  a  putrefying  infusion.     (Daliun.  i 

The  organic  principles  of  this  class  are  always  combined  with  the 
inorganic  ones,  the  union  being  most  intimate,  so  much  so  that  as  the 
first  are  used  up  and  become  effete,  and  are  cast  out  of  the  body,  the 
inorganic  principles  go  with  them.  Like  the  principles  of  the  second 
class,  those  of  the  third  class  are  destroyed  in  the  system,  never  appear- 
ing in  the  excretions  in  health  (with  the  exception  of  casein  of  milk, 
mucus,  epithelium,  and  epidermis).  Being  transformed  into  carbonic 
acid,  water,  urea,  etc.,  through  a  process  of  splitting,  with  subsequent 
oxidation,  they  are  also  a  source  of  heat  to  the  economy  like  the  prin- 
ciples of  the  second  class.  The  different  principles  of  this  class,  and 
some  of  the  situations  in  which  they  are  found  in  the  human  body,  may 
be  seen  in 


Table  XV.' — Quantity  of  Albumen. 

Substance. 

Parts  per  1000. 

Substance.                                      Part 

per  1000. 

Cerebro-spinal  fluid 

.       0.9 

Chyle       .... 

40.1) 

Aqueous  humor 

.       1.4 

Spinal  cord 

74.9 

Liquor  amnii  . 

.       7.0 

Brain       .... 

86.3 

Intestinal  juice 

.       9.5 

Liver        .... 

117.4 

Pericardial  fluid 

.     23.6 

Muscle     .... 

161.8 

Lymph    . 

.     24.6 

Blood       .... 

195.6 

Pancreatic  juice 

.     33.3 

Middle  coat  of  arteries   . 

273.3 

Synovia 

.     39.1 

( Irystalline  lens 

383.0 

Milk 

.     3!  ».4 

1  Carpenter,  op.  < -i t . ,  p.  GO 


ALBUM  EX.  69 

Their  relative  amount,  as  may  be  seen,  varies  greatly ;  thus  in  a 
thousand  parts  of  cerebrospinal  fluid  there  are  only  traces  of  albumi- 
nous compounds,  over  30  parts  in  the  same  amount  of  chyle,  and 
nearly  200  in  blood.  In  the  brain,  over  80  parts  to  the  thousand,  over 
160  in  muscle,  and  nearly  400  in  the  crystalline  lens,  in  round  num- 
bers. The  principles  of  this  class  all  agree  in  their  general  aspects:  a 
few  words  will  suffice  for  their  individual  peculiarities. 

Albumen. — Albumen,  which  the  white  of  egg  closely  resembles,  is 
the  type  of  the  other  principles  of  this  class,  and  out  of  which  they  are 
all  elaborated.  It  is  found  in  all  parts  of  the  system,  at  all  periods  of 
life,  in  greatest  abundance  in  the  blood,  is  present  in  the  lymph,  chyle, 
serous  secretions,  milk,  intermuscular  fluid.  Albumen  can  be  obtained 
from  the  system,  in  which  it  exists  in  the  fluid  condition,  by  coagula- 
tion. This  can  be  readily  done  by  heating,  or  adding  alcohol  to  the 
liquid  containing  the  albumen,  and  filtering.  Mineral  acids,  and  some 
of  the  metallic  salts,  have  the  same  effect. 

The  ordinary  method  of  testing  for  albumen  consists  in  heating  the 
suspected  liquid — urine,  for  example — in  a  test-tube,  when,  if  albumen 
be  present,  an  opacity  makes  its  appearance  in  the  upper  part  of  the 
tube  first,  which  afterward  extends  downward,  an  insoluble  precipitate 
is  formed,  which  often  becomes  solidified. 

If  it  be  thought  that  the  opacity  be  due  to  an  excess  of  earthy  phos- 
phates, add  hydrochloric  acid,  which  has  no  effect  on  coagulated  albu- 
men, but  which  will  dissolve  the  phosphates.  On  the  other  hand,  caustic 
potash  will  dissolve  coagulated  albumen  in  urine,  but  has  no  effect  on 
the  phosphates.  In  adding  nitric  acid  to  urine  it  may  be  mentioned 
that  the  cloudiness  is  often  due  to  urates ;  this  will  disappear  in  an 
excess  of  nitric  acid,  which,  however,  will  not  take  place  if  the  cloudi- 
ness be  due  to  coagulated  albumen,  and  it  should  be  added  that,  in 
making  use  of  the  heat  test,  etc.,  the  liquid  to  be  tested,  if  alkaline, 
will  not  respond,  even  though  it  should  contain  albumen;  under  such 
circumstances  it  is  necessary  to  add  a  few  drops  of  acetic  acid. 

The  albumen  of  the  blood  is  derived  from  the  albuminous  substances 
of  the  food,  the  latter,  as  we  shall  see,  being  transformed  during  diges- 
tion into  albuminose,  an  albumen  intermediate  between  food  albumen 
and  blood  albumen. 

Blood  albumen,  the  great  nutritive  element  of  the  blood,  is  carried 
by  the  latter  medium  to  all  parts  of  the  system.  In  this  way  the  tissues 
arc  supplied  with  fresh  nitrogenized  material,  replacing  that  which 
becomes  effete. 

The  actual  process  by  which  the  albumen  of  the  blood  is  transformed 
into  the  albuminous  principles  of  the  tissues  during  growth,  or  in  adult 
life,  has  not  yet  been  made  out.  There  is  no  reason  to  doubt,  however, 
that,  like  all  other  so-called  vital  phenomena,  it  is  a  physico-chemical 
one. 

Albumen,  after  splitting  up  into  simpler  compounds,  and  subsequent 
oxidation  of  the  latter,  leaves  the  body  as  urea,  carbonic  acid  gas,  and 
water.  It  is.  therefore,  a  source  of  heat  and  force  to  the  economy  as 
well  as  a  tissue-maker,  and  this  is  true  of  the  albuminoids  generally. 

Adopting  at    least  provisionally,    the  formula  for  albumen   already 


70        PROXIMATE    PRINCIPLES    OF    THE    THIRD    CLASS. 

given,  and  deducting  its  nitrogen  as  representing  so  much  urea,  it  will 
be  at  once  seen  that  the  remainder  of  the  albumen,  through  oxidation, 
will  finally  be  transformed  into  carbonic  acid,  water,  and  sulphuric  acid, 
even  if  it  be  supposed  that  part  of  the  albumen  is  retained  temporarily 
as  fat,  as  follows: 

Albumen  C72  Hm  Nl8  0.22  S 

9  Urea  (CH4N.,0)     (',,*  H%"  Nia  (\_ 

C63     II;,;       0  013    S 

C63  HTB  013  S  +  Om  =  63CO,  +  38H20  +  SO:i 

It  is  obvious  also,  that  if  the  fat  developed  out  of  the  albumen  be 
finally  burned,  nevertheless  the  combustion  of  albumen  will  be  far  loss 
perfect  than  that  of  sugar  or  fat,  since  thirty-two  per  cent,  of  the  albu- 
men passes,  unburned,  as  urea,  out  of  the  body.  Albumen,  as  a  source 
of  heat  to  the  economy  is,  therefore,  an  expensive  fuel,  so  to  speak,  as 
compared  with  sugar  or  fat,  which  are  as  perfectly  burned  within  the 
body  as  out  of  it ;  apart,  also,  from  the  fact  of  less  heat  being  developed 
through  the  burning  of  albumen  than  of  equal  parts  of  fat  or  sugar. 

Albuminose. — Albuminose,  or  the  modified  food  albumen,  is  found 
in  the  stomach  and  small  intestine  during  digestion,  and  immediately 
afterward  in  the  blood  in  small  quantities.  It  differs  from  the  albumen 
of  the  blood  in  not  being  coagulable  by  heat,  and  imperfectly  by  nitric 
acid,  and  from  the  albumen  of  the  food  in  being  endosmotic — that  is, 
capable  of  passing  through  membranes,  and  so  of  being  absorbed  and 
getting  into  the  circulation. 

White  of  egg,  though  not  identical  with  albumen,  but  closely  resem- 
bling it,  was  shown  by  Bernard1  to  be  rejected  by  the  kidneys  when 
injected  into  the  veins,  due  probably  to  its  not  being  endosmotic.2  When 
the  white  of  egg  has  been  digested,  however,  and  converted  into  albu- 
minose, it  is  then  readily  absorbed. 

Albuminose  does  not  remain  long  as  such  in  the  blood,  being  rapidly 
transformed  into  blood  albumen. 

Fibrin. — It  is  questionable  whether  the  substance  commonly  called 
fibrin  exists  as  such,  as  a  proximate  principle  in  the  system.  When 
the  blood  coagulates,  and  the  red  corpuscles  are  removed  from  the  clot, 
there  remains  a  whitish,  stringy,  fibrous  substance  called  fibrin,  and 
which  is  supposed  by  some  chemists  to  exist  as  such  in  the  blood  in  a 
fluid  condition;  by  others,  to  be  only  an  albumen,  modified  through 
changed  conditions ;  another  view  favored  by  many,  is  that  fibrin  is 
due  to  the  union  through  a  ferment  of  two  principles — fibrinogen,  found 
in  the  liquor  sanguinis,  and  paraglobulin,  found  in  the  blood  corpuscles. 

There  is  much  to  be  said  in  favor  of  all  these  views,  but,  as  we  shall 
see  later,  as  yet  the  origin  of  fibrin  cannot  be  said  to  have  been  posi- 
tively determined. 

This  substance  is  found  in  the  lymph  and  chyle  as  well  as  in  the 
blood,  but  in  less  quantity.  It  is  composed  ultimately  of  the  same  ele- 
ments as  albumen,  and  must,  therefore,  be  derived,  remotely,  from  the 
nitrogenized  principles  of  the  food. 

1  Bernard:  Liquides  de  l'Organisnie,  tome  i.  p.  4f>7.     Paris,  L859. 
-  Mialhe  :  Chimie  Applique  a  la  physiologie,  p.  125.     Paris,  1856. 


FIBRIN,    CASEIN,    MUCOSIN,    ETC.  71 

Whatever  its  condition  may  be  in  the  blood,  in  the  system  fibrin  is 
destroyed;  thus  it  is  not  found,  for  example,  in  the  renal  or  hepatic 
veins,  the  liver  and  kidney  transforming  it  in  a  way  not  yet  understood. 

Fibrin  is  interesting  to  the  pathologist,  as  constituting  the  false 
membrane  of  croup,  and  as  supplying  the  material  for  the  spontaneous 
;ii  rest  of  hemorrhage  in  small  vessels  which  have  been  opened  from  any 
cause. 

Casein. — This  principle  is  found  only  in  the  milk,  being  derived 
from  the  albumen  by  the  action  of  the  mammary  glands,  and  is  there- 
fore present  in  the  system  only  during  lactation. 

It  is  very  important,  however,  as  constituting  the  principal  nitro- 
genized  food  for  the  infant,  being  readily  converted  in  the  child  into 
albuminose,  which  is  carried  into  its  blood  and  is  then  transformed  into 
blood  albumen. 

It  is  one  of  the  few  principles  of  this  class  which  are  discharged  from 
the  body  in  health.  It  differs  from  albumen  in  not  being  coagulated 
by  heat,  but  by  the  weak  vegetable  acids. 

The  coagulation  of  casein  occurs  when  sugar  of  milk  is  converted 
into  lactic  acid  by  hydration,  the  milk  becoming  then  sour,  the  reaction 
being  as  follows  : 

Milk  sugar.         Water.         Lactic  acid. 

C12H.,2Ou  +  H20  =  4C,H603 

Casein  is  kept  in  a  fluid  condition  in  milk  through  sodium  carbonate. 

Mucosin,  Pancreatine  Pepsin. — Mucosin  is  found  in  the  secre- 
tions of  mucous  membranes,  differing  slightly  in  composition  according 
to  the  situation  from  which  it  is  obtained.  It  is  very  like  albumen; 
indeed,  the  white  of  the  egg  is  generally  taken  as  the  type  of  albumen, 
though  it  is  really  mucosin,  being  secreted  by  the  mucous  membrane 
of  the  oviduct  of  the  hen.  White  of  egg  differs  from  ordinary  mucosin, 
however,  in  usually  containing  sulphur.  Mucosin  is  one  of  the  few 
principles  of  the  third  class  dischai'ged  in  health. 

Pancreatin  is  the  active  principle  of  the  pancreatic  juice.  It  differs 
from  albumen  in  being  coagulated  by  magnesium  sulphate.  Its  proper- 
ties with  those  of  pepsin,  the  nitrogenized  element  of  the  gastric  juice, 
will  be  considered  when  the  subject  of  digestion  is  taken  up. 

Ostein  AXD  Cartilagin. — This  principle,  which  is  solid,  is  found 
only  in  bones,  in  combination  with  the  earthy  salts.  When  bone  is 
treated  with  dilute  hydrochloric  acid  the  mineral  salts  are  dissolved 
out  and  almost  pure  ostein  remains. 

When  bones  are  boiled  they  are  converted  into  gelatin.  This,  how- 
ever, is  not  a  proximate  principle,  as  it  does  not  exist  as  such  in  the 
system. 

Cartilao-in  is  to  cartilage  what  ostein  is  to  bone.  When  cartilagin 
is  boiled  it  becomes  chondrin.  This  goes  to  show  that  the  development 
of  bone  from  cartilage  is  more  than  the  addition  of  lime  salts  ;  the 
organic  principle  cartilagin  being  probably  metamorphosed  at  the 
same  time  into  ostein. 

Globulin,  Crystallin,  Musculin. — Globulin  and  crystallin  exist 
in  a  semisolid  state  in  the  blood  corpuscles,  and  crystalline  lens  of  the 


72        PROXIMATE    PRINCIPLES    OF    THE    THIRD    CLASS. 

eye  respectively.  Musculin  is  found  also  .semisolid  in  muscles,  com- 
bined with  inorganic  principles.  It  is  the  most  important  nitrogenized 
element  of  the  food,  and  through  its  metamorphosis  into  albumen  in  the 
system  supplies,  to  a  great  extent,  the  economy  with  that  important 
principle. 

Elasticin  and  Keratin. — Elasticin  is  found  in  the  yellow  elastic 
tissue  and  the  membrane  which  envelops  the  muscular  fibres.  Keratin 
is  present  in  the  nails  and  hair. 

ELematin,  Melanin,  Biliverdin,  Urrosacin.—  Hamatin  gives 
the  blood  its  red  color,  and  is  found  in  the  corpuscles  combined  with 
globulin.      One  of  its  most  important  constituents  is  iron. 

When  hsematin  is  deficient  in  the  system  as  seen  in  anaemia,  the 
exhibition  of  iron  will  always  reproduce  it. 

To  demonstrate  iron  in  hsematin,  add  one  drop  of  nitric  acid  to  blood 
in  a  watch  glass,  and  evaporate  over  a  lamp.  The  iron  is  converted 
into  a  peroxide  (the  acid  giving  up  oxygen),  to  this  add  the  potassium 
sulphocyanide,  when  the  characteristic  red  color  will  appear,  due  to  the 
formation  of  the  ferric  sulphocyanide. 

Melanin  is  the  organic  principle  of  pigment  found  in  the  choroid 
and  iris  of  the  eye,  hair,  and  epidermis.  It  is  probably  developed 
through  the  transformation  of  haematin. 

Biliverdin,  the  coloring  matter  of  the  bile,  and  urrosacin,  the  modi- 
fied pigment  of  the  urine,  will  be  again  referred  to  under  the  subjects 
of  the  liver  and  kidneys. 

To  avoid  repetition,  as  well  as  for  convenience,  the  remaining  proxi- 
mate principles  entering  into  the  composition  of  the  tissues  and  secre- 
tions of  the  body,  and  not  mentioned  in  the  general  introductory  just 
given,  will  be  considered  as  the  latter  are  successively  treated  of. 

While  there  is  no  doubt  that  the  urea,  carbonic  acid,  and  water  of 
the  excreta  are  derived  from  albuminous  principles,  there  is  still  a  dif- 
ference of  opinion  as  to  whether  the  albumen  whose  breaking  up  and 
oxidation  gives  rise  to  urea,  etc.,  is  that  of  the  tissues  or  that  of  the 
food,  or  of  both,  and,  if  the  latter,  how  much  of  the  urea  produced  is  to 
be  attributed  to  the  breaking  up  of  the  tissue-albumen  and  how  much  to 
food-albumen. 

That  the  urea  cannot  be  entirely  derived  from  the  breaking  up  of  the 
albumen  of  the  tissues,  organic  albumen,  is  shown  from  the  amount  pro- 
duced in  starvation  being  so  much  smaller  than  when  nitrogenous  food, 
circulating  albumen,  is  taken  ;  fifteen  times  as  much  urea  being  pro- 
duced, according  to  Voit,1  in  the  latter  case  as  in  the  former.  Unless 
this  large  amount  of  urea  is  derived  from  the  food  it  is  difficult  to  account 
for  it,  for  although  the  albumen  of  the  body  exists  in  greater  amount 
than  that  of  the  food,  as  a  matter  of  fact  in  starvation  but  a  fractional 
part  of  it  is  destroyed;   in  a  dog,  for  example,  about  one  per  cent. 

It  is  true  that  it  is  held  by  many  physiologists  that  the  albuminous 
principles  of  the  food  displace  those  of  the  tissues,  either  entirely  or  in 
part,  the  latter  giving  rise  to  the  urea,,  according  to  the  view  that  urea 

1  Hermann  :   Physiologif,  Sechster  Band,  S.  302. 


DERIVATION    OF    UREA.  73 

is  derived  from  the  tissue  whether  albuminous  food  be  taken  or  not,  all 
albuminous  food  becoming  tissue  before  being  destroyed.  If  such  be 
the  case,  however,  the  whole  body  of  a  dog,  for  example,  would  be 
destroyed  and  built  up  again  in  a  few  days,1  which  is  much  more  im- 
probable than  that  its  albuminous  food  taken  during  the  same  time 
should  be  broken  up  and  oxidized  into  urea,  etc.  Indeed,  as  a  matter 
of  fact,  there  is  no  evidence  to  show  that  under  any  circumstances  the 
disintegration  and  oxidation  of  the  body  proper,  apart  from  that  of  the 
food  absorbed,  go  on  to  anything  like  the  extent  usually  assumed  and 
embodied  in  the  popular  idea  of  the  whole  body  being  entirely  changed 
in  some  given  period. 

Apart  from  the  daily  destruction  and  renewal  of  the  cells  of  the  epi- 
dermis and  its  appendages,  hair,  nails,  etc.,  of  the  epithelial  cells  of  the 
mucous  membrane  of  the  nose,  trachea,  alimentary  canal,  and  its  glan- 
dular appendages,  of  the  blood  corpuscles,  there  is  little  or  no  evidence 
of  the  total  destruction  of  the  cells,  the  constituent  elements  of  the 
tissues. 

Even  in  starvation,  where  the  muscles  and  liver  may  diminish  one- 
half  in  weight,  under  the  microscope  the  same  number  of  muscular 
fibres,  the  same  number  of  liver  cells  are  visible,  though  diminished  in 
volume  through  loss  of  their  contents,  just  as  an  amoeba  paramoecium  or 
any  unicellular  being  may  be  empty  or  distended  according  as  it  is 
supplied  with  food;  cells,  the  structural  elements,  as  we  have  seen, 
being  essentially  distinguished  from  extraneous  matters  which  they  may 
or  may  not  absorb. 

That  a  disintegration  and  renewal  of  the  tissues  may  go  on  is  seen 
in  the  formation  of  bony  cavities,  in  the  production  and  absorption  of 
callus,  in  the  disappearance  of  the  alveolar  ridge  of  the  jaw,  in  the  repro- 
duction of  parts  that  are  lost.  Such  processes,  as  we  know,  are,  how- 
ever, very  slow,  while  under  certain  circumstances  there  does  not  appear 
to  be  any  change  taking  place  at  all,  depression  in  the  crystalline  lens 
of  the  eye,  cicatrices,  peculiar  markings  in  the  skin,  etc.,  persisting 
through  life. 

This  hypothesis  of  the  destruction  of  the  albuminous  tissues  and  the 
derivation  of  urea  from  the  latter  is  an  illustration  among  many  of  the 
vast  influence  of  LiebigV  views  upon  animal  chemistry. 

That  distinguished  chemist  held  that  force  was  developed  at  the  ex- 
pense of  the  albuminous  tissues,  the  loss  being  continually  repaired  by 
albuminous  food;  that  muscular  activity  was  the  cause  of  the  decom- 
position of  tissue-albumen,  and  consequent  production  of  urea,  and  that 
the  amount  of  tissue-albumen  destroyed  is  a  measure  of  tissue  change  or 
"  stoflf-wechsel "  as  he  called  it — that  is,  the  breaking  up  of  the  albu- 
minous tissues  with  the  production  of  urea  and  the  rebuilding  of  the 
same  through  albuminous  food.  Any  albumen  present  in  the  food,  over 
and  above  that  destroyed  through  muscular  activity,  was  deposited, 
according  to  Liebig,  in  the  body — that  is,  the  amount  of  urea  produced 
depended  upon  the  muscular  work  and  not  upon  albuminous  food. 

1  Voit  in  Hermann,  op.  cit.,  S.  277. 

2  Die  Organische  Chimie,  1842.  Ann.  d.  Chimie  und  Phar.,  xli.,  1842  :  liii.,  1845  ;  lviii.,  1846  :  lxx., 
1849  ;  lxxix.^  1851. 


74        PROXIMATE    PRINCIPLES    OF    THE    THIRD    CLASS. 

The  remaining  carbohydrate  principles,  etc.,  of  the  food  in  being 
oxidized  were  regarded  solely  as  sources  of  heat,  their  transformations 
not  constituting  a  part  of  the  true  stoff-wechsel,  that  being  limited  to 
the  changes  in  the  albuminous  tissues. 

With  the  establishment,  however,  of  the  fact  that  the  amount  of  urea 
was  increased  by  albuminous  food,  independently  of  muscular  activity,, 
the  celebrated  theory  of  Liebig  as  such  was  no  longer  tenable.  So 
deeply  rooted,  however,  was  this  theory,  that  it  was  still  defended, 
though  in  a  somewhat  modified  form,  by  Lehmann,1  Frerichs,2  Bidder,3 
and  Schmidt. 

Those  experimenters  who  first  showed  that  urea  is  increased  by  nitro- 
genous food  impressed  with  the  improbability  of  any  great  quantity  of 
the  latter  becoming  first  tissue  and  then  urea,  assumed  that  all  of  the 
albumen  of  the  food  over  and  above  that  destroyed  in  starvation  (the 
minimum,  and  derived  from  the  body)  was  in  excess,  was  a  luxus,  so  to 
speak,  and  was  directly  oxidized  in  the  blood,  like  the  carbohydrate 
principles,  etc.  Hence  the  theory  so  widely  known  as  that  of  "luxus 
consumption." 

As  there  is  not  the  slightest  evidence,  however,  that  the  albuminous 
principles  of  the  food  are  directly  oxidized  in  the  blood,  and,  as  we 
shall  see,  muscular  action  does  not  increase  the  amount  of  urea,  and  as 
the  amount  of  albumen  destroyed  in  starvation  is  no  measure  of  that 
destroyed  in  health,  the  celebrated  theory  of  ''luxus  consumption"  of 
Bidder  and  Schmidt  falls  to  the  ground  with  that  of  the  "  stoff-wechsel " 
of  Liebig,  of  which  it  is  merely  a  modification. 

As  there  is  little  or  no  evidence  of  the  rapid  destruction  of  the  in- 
tegral part  of  the  tissues  implied  in  the  view  of  the  albumen  of  the  food 
becoming  tissue  first  and  afterward  urea ;  or,  it  may  be  added,  of  the 
urea  being  developed  synthetically  out  of  simpler  principles  resulting 
from  the  destruction  of  the  tissues,  it  will  be  assumed,  for  the  present, 
at  least,  that  by  far  the  greatest  amount  of  urea  is  produced  through 
the  splitting  up  of  the  nitrogenous  food  into  simpler  compounds,  and 
subsequent  oxidation  of  the  latter. 

By  oxidation,  whether  of  food  or  of  tissue,  it  may  be  here  as  well  as 
elsewhere  mentioned,  that  it  is  not  to  be  understood  that  there  is  a 
direct  combination  of  oxygen  with  food  or  tissue,  but  that  just  as  in  the 
case  of  oil  burning  in  a  lamp,  or  of  wood  in  a  stove,  there  is  a  splitting 
up  of  these  substances  at  a  certain  temperature  into  simpler  ones,  the 
latter  of  which  are  oxidized,  so  do  the  albumen  and  fat  of  the  body  split 
up  into  simpler  principles,  which  by  subsequent  oxidation  pass  out  of 
the  system  as  urea,  carbonic  acid,  and  water,  and  just  as  in  the  im- 
perfect combustion  of  oil  or  wood  through  the  want  of  oxygen  there 
arise  various  products,  so  the  imperfect  combustion  of  albumen,  sugar, 
etc.,  gives  rise  to  the  production  of  fat,  uric  ucid,  diabetic  sugar,  etc. 

That  the  breaking  up  of  food  or  tissue  in  the  body  cannot  be  due  to 
direct  oxidation,  as  held  by  Lavoisier,  is  shown  by  many  facts,  such  as 
that  the  oxidation  of  substances  within  the  system  does  not  follow  the 
same  order  as  without  it ;   that  animals  do  not  breathe  more  oxygen 

i  Wagner:  Handworterbuch,  1884,  ii.  S.  18.  -  Archiv  f.  Anat.  und  Phys.,  1848,  S.  4G9. 

3  Die  Verdauungsafte,  1852,  8.  348. 


DESTRUCTIVE    CHANGES    OF     FOOD    AND    TISSUE.  75 

when  in  an  atmosphere  containing  a  greater  quantity  than  that  existing 
in  the  ordinary  air,  or  ahsorb  more  oxygen  even  though  the  haemo- 
globin be  saturated  with  it,  that  carbonic  acid  is  exhaled  by  a  body  or 
part  of  the  same  in  an  atmosphere  in  which  oxygen  is  absent.  Indeed, 
there  is  no  more  reason  to  suppose  that  the  destructive  changes  of  food 
or  tissue  going  on  in  the  body  are  entirely  dependent  upon  direct  oxi- 
dation, than  that  the  combustion  of  wood  or  coal  in  a  stove  depends 
entirely  upon  the  draught.  The  construction  of  the  body,  like  that  of 
the  stove,  must  exercise  a  great  influence  upon  the  burning  of  the  sub- 
stances placed  within  it. 

Inasmuch  as  the  destructive  changes  of  food  or  tissue,  or  of  both, 
going  on  in  the  body,  and  upon  which  the  maintenance  of  life  depends, 
are  not  due  to  direct  oxidation,  as  held  by  Lavoisier,  nor  to  muscular 
activity  and  oxidation,  as  supposed  by  Liebig.  Bidder,  Schmidt,  etc.,  it 
remains  for  us  now  to  offer  some  hypothesis  which  can  be  provisionally 
accepted,  if  for  nothing  more  than  that  by  it  facts  can  be  connected 
together,  woven  into  something  like  a  theory,  suggestive  not  only  of 
new  discoveries  but  to  be  tested  by  them. 

From  time  immemorial  physiologists  have  been  impressed  with  the 
similarity  existing  between  the  phenomena  of  fermentation,  putrefaction, 
and  those  of  life,  and  with  every  advance  in  knowledge  the  resemblance 
becomes  more  and  more  striking.  Thus,  as  we  shall  see,  the  change  of 
starch  into  glucose  bv  the  saliva,  of  albumen  into  albuminose  by  the 
gastric  juice,  the  splitting  up  of  fat  in  the  presence  of  water  into  glycerin 
and  fatty  acid,  etc.,  by  the  pancreatic  juice,  are  due  to  the  ferment-like 
action  of  the  ptyalin,  pepsin,  pancreatin,  of  these  secretions. 

These  changes  are,  however,  but  the  first  of  a  series  experienced  by 
the  food  in  its  gradual  transformation  into  urea,  carbonic  acid,  and 
water;  the  intermediate,  subsequent  stages  taking  place  in  the  tissues 
themselves  and  not  in  the  fluids  bathing  them.  At  least  there  is  no 
evidence  that  the  further  breaking  up  and  oxidation  of  the  food  modi- 
fied during  digestion  and  absorption,  go  on  in  the  blood,  lymph,  or 
chyle,  these  fluids  appearing  to  be  rather  the  means  of  transportation 
of  the  nourishing  food  to  the  tissues  where  the  so-called  vital  changes 
take  place  and  of  removing  the  effete  matters  to  the  excretory  organs, 
by  means  of  which  they  are  eliminated  from  the  body. 

That  the  fluids  of  the  body,  such  as  the  blood,  lymph,  etc.,  cannot 
be  indispensable  in  the  effecting  of  those  changes  which  constitute  life, 
apart  from  carrying  to  the  tissue  the  material  to  be  changed,  is  shown 
from  the  fact  that  such  changes  go  on  in  an  economy  in  the  absence  of 
blood,  etc.,  as  in  the  absorption  of  oxygen  and  carbonic  acid  by  unicel- 
lular organisms,  and  the  lower  forms  of  animal  life  in  which  a  vascular 
system  is  absent.  In  insects  also,  in  which  the  breathing  being  accom- 
plished by  trachea?,  the  oxygen  is  absorbed  directly  by  the  cells  of  the 
organs  surrounding  the  latter,  and,  as  we  shall  see  later,  the  embryo 
bird,  consisting,  as  it  does,  essentially  of  a  mass  of  but  little  differ- 
entiated cells,  absorbs  oxygen  and  exhales  carbonic  acid  in  the  absence 
of  a  vascular  system. 

Facts  like  those  just  mentioned  of  the  fermentative  changes  taking 
place  in  the  alimentary  canal,  and  elsewhere,  as  we  shall  see,  of  the  far 


76 


PROXIMATE     PRINCIPLES    OF    THE    THIRD    CLASS 


greater  functional  activity  of  the  tissues,  as  compared  with  that  of  the 
fluids  of  the  body,  of  the  relative  stability  of  the  tissues,  as  contrasted 
with  the  albuminous  and  carbohydrate  principles  of  the  food  brought 
to  them  in  the  fluids,  point  to  the  general  conclusion  thai  vital  changes 
are  brought  about  in  the  tissues  by  some  kind  of  ferment  action  together 
with  oxidation.  The  tissues,  through  virtue  of  the  cells  of  which  they 
consist,  act  upon  the  food  brought  to  them,  as  the  yeast  cell,  saccharo- 


Fxa.  14. 


Fro.  15. 


Saccharomyces  cerevisiae,  in  its  quiescent  con- 
dition ;  from  deposit  of  beer-yeast,  after  fermenta 
tion.     (Dalton.) 


Saccharomyces  cerevisiae  in  active  germina- 
tion. From  fermenting  saccharine  solution. 
(Dalton.) 


myces  cerevisire  (Figs.  14,  15),  acts  upon  sugar,  breaking  it  up  into 
carbonic  acid  gas  and  alcohol,  as  shown  by  the  formula  : 


Glucose. 

(V.LL.O,, 


Alcohol.  Carbonic  acid  gas. 

2C.H60    +     2C02 


the  changes  undergone  by  the  food  in  passing  through  the  economy 
not  any  more  necessarily  involving  the  destruction  of  the  tissues  than 
the  changes  in  the  sugar  induced  by  the  yeast  cells  involve  the  de- 
struction of  the  latter ;  though  the  cells  of  the  tissue,  like  those  of  the 
yeast,  have  a  certain  limit  to  their  action.  It  would  appear,  there- 
fore, that  life  is  rather  maintained  through  the  destruction  of  the  food 
by  the  cells  of  the  tissue  through  fermentation  and  oxidation  than 
at  the  expense  of  the  tissues  themselves.  Such  at  least  is  essentially 
the  view  so  well  developed  by  Voit,1  one  of  the  highest  living  authorities 
on  the  subject  of  nutrition,  and  by  which  many  striking  facts  in  nutri- 
tion, whether  during  starvation  or  upon  a  diet  of  one  one  or  more 
articles  of  food,  may  be  explained. 

Thus  while  a  starving  man  lives  at  the  expense  principally  of  the 
albumen  and  fat  stored  up  in  the  tissues  of  his  own  body,  there  not 
being  enough  of  these  principles  in  the  fluids  to  account  for  what  is 
destroyed  as  measured  by  the  excreta,  nevertheless,  the  albumen  and 


1  Physiologie  der  Allgemeinen  StonVechsel  und  der  Ernahrang,  Hermann,  op.  cit.,  Sechster  Band. 


DESTRUCTION     OF     FOOD     BY    CELLS.  77 

fat  of  the  tissues,  etc.,  are  not,  as  such,  used  as  food,  but  are  trans- 
formed into  circulating  or  food  albumen,  and  in  this  form  are  carried 
to  the  other  tissues,  and  there  destroyed,  one  part  of  the  body  being 
sacrificed,  therefore,  to  nourish  another.  That  the  latter  is  the  case,  is 
evident  from  such  facts  as  that  the  heart  and  central  nervous  system, 
for  example,  during  starvation  lose  but  little  in  -weight,  whereas  the 
muscular  system  may  be  reduced  over  forty  per  cent.,  that  the  bones  of 
the  extremities  do  not  suffer  for  want  of  lime  salts,  the  latter  being  sup- 
plied from  the  bones  of  the  sternum  and  skull,  the  latter  becoming,  in 
consequence,  very  thin,  of  the  starving  mother  secreting  milk  in  volume, 
etc.,  far  exceeding  that  of  the  mammary  gland  itself. 

As  regards  also  the  destruction  of  different  kinds  of  nutritive  prin- 
ples,  whether  derived  from  the  tissues  of  the  body  or  from  food,  it  is 
evident  that  the  cells  destroy  more  readily  certain  principles  than  others  : 
albumen  more  readily  than  sugar,  sugar  more  readily  than  fat  whether 
derived  from  food  or  albumen.  The  amount  of  such  substances  de- 
stroyed or  deposited  will  depend  then  on  the  relative  amounts  in  which 
they  are  presented  to  the  tissues,  whether  in  starvation  or  in  health. 

Hence,  on  an  excessively  rich  nitrogenous  diet  the  cells  exhausting 
themselves  in  destroying  albumen,  fat  will  be  deposited ;  the  same  will 
be  the  case  if  sugar  be  given  with  albumen,  the  former  being  destroyed 
in  preference  to  the  fat  derived  from  the  albumen. 

Resume. — We  have  seen  that  the  proximate  principles  of  the  third 
class  consist  ultimately  of  carbon,  hydrogen,  oxygen,  nitrogen,  sulphur 
(and,  in  some  animals,  of  phosphorus).  That  such  principles  as  albumen, 
fibrin,  casein,  etc.,  should  be  composed  of  these  chemical  elements  to 
the  exclusion  of  the  remaining  sixty  or  seventy,  is  not  meaningless. 
Spencer1  has  shown  that  the  elements  composing  living  bodies  have 
mobility  enough  to  enable  them  to  get  rid  of  their  effete  material  and 
to  change  continuously  and  actively  their  intimate  parts.  On  the  other 
hand,  through  the  combination  of  a  great  number  of  atoms,  these  prin- 
ciples, through  their  inertia,  become  relatively  immobile  and  possess 
fixity  enough  to  resist  disintegration.  There  must  be  fluidity  and  yet 
solidity  in  a  living  body.  These  conditions  are  fulfilled  in  the  fact  that 
three  of  the  important  elements  entering  into  the  composition  of  albu- 
men, fibrin,  etc.,  are  mobile  gases,  oxygen,  hydrogen,  and  nitrogen, 
hence  the  readiness  with  which  these  matters  change  the  arrangement  of 
their  parts  or  development,  and  the  rapidity  of  those  transformations  of 
motion  or  function. 

It  can  be  shown  on  mechanical  principles  that  as  the  masses  of  the 
atoms  increase,  their  mobility  decreases,  hence  the  comparative  cohesive- 
ness  of  such  principles  as  albumen,  etc. 

Many  interesting  illustrations  are  brought  forward  by  Spencer  in 
favor  of  the  above  view.  Briefly,  it  may  be  said  here  that  the  chemical 
and  physical  contrasts  of  the  carbon,  hydrogen,  oxygen,  and  nitrogen 
are  such  as,  a  priori,  would  be  required  of  the  elements  entering  into 
the  composition  of  living  bodies. 

While  admitting  that  the  proximate  principles  of  the  third  class  are 

1  Principles  of  Biology. 


78        PROXIMATE    PRINCIPLES    OF    THE    THIRD    CLASS. 

indispensable  to  the  production  of  life,  it  seems  to  me,  however,  that 
we  are  not  justified  in  restricting  vitality  to  them  as  is  often  done  by 
physiologists.  The  fact  is  that  the  tissues  as  they  exist  in  the  living 
body  are  not  composed  of  albuminous  principles  alone.  What  would 
bone  be  without  its  calcareous  salts,  nervous  tissue  without  phosphorized 
fats,  how  much  life  would  be  left  in  a  body  after  the  water  had  been 
removed,  of  what  use  would  the  pepsin  be  in  the  gastric  juice  without 
the  acid,  the  blood  without  its  salts,  iron,  etc.  ? 

It  is  often  said  that  the  albuminous  principles  impart  their  life  to  the 
inorganic  ones.  This  is  a  mere  assumption,  for  the  former  principles 
are  always  intimately  associated  with  the  latter,  being  taken  into  the 
body  to  be  digested,  assimilated,  and  excreted  together. 

You  cannot  separate  the  inorganic  principles  from  the  albuminous 
ones  and  leave  the  latter  living.  Deprive  an  animal  of  water  and  salt 
and  it  will  die  as  surely  as  if  deprived  of  albuminous  food. 

If  there  are  any  strictly  vital  principles  in  a  living  body  to  the  exclu- 
sion of  others  not  vital,  it  does  not  seem  to  me  that  they  can,  at  present, 
at  least,  be  isolated.  A  simple  statement  of  the  fact  is,  that  life  consists 
of  a  series  of  changes  exhibited  by  certain  inorganic  and  organic  prin- 
ciples composed  of  chemical  elements  combined  in  a  certain  way  under 
certain  conditions. 

The  more  complex  the  materials  and  their  mode  of  combination,  the 
more  complex  the  resultant  life. 

A  substance  consisting  of  two  chemical  elements,  one  atom  of  each 
only  in  combination,  possesses  fewer  properties  than  one  consisting  of 
numerous  elements  and  hundreds  of  atoms.  Water,  H20,  has  fewer 
properties  than  potassium  ferricyanide,  Fe^'K^CN),.,  seen  crystal- 
lized in  definite  mathematical  form  in  every  apothecary's  window,  and 
neither  can  be  compared  as  regards  their  possibilities  with  living  matter 
consisting  of  an  infinite  number  of  atoms  of  albuminous,  carbohydrate, 
and  inorganic  principles. 

Believing  that  the  properties  of  water  and  those  of  potassium  ferri- 
cyanide are  the  resultant  of  the  properties  of  the  chemical  elements  of 
which  they  consist,  logically  it  must  follow  also  that  life  results  from 
the  properties  of  the  elements  composing  the  substances  exhibiting  the 
life,  the  question  in  each  instance  being  one  of  the  redistribution  of 
matter  and  force.  It  should  be  mentioned  also  that  the  connection 
between  the  elements  and  the  properties  exhibited  by  their  union  are 
at  present  as  little  understood  in  the  first  two  cases  as  in  the  last,  mol- 
ecular physics  not  yet  having  given  an  explanation.  Vital  phenomena 
are  not,  therefore,  more  mysterious  than  any  other  kind  of  phenomena, 
and  can  be  investigated  to  the  same  extent  and  in  the  same  sense  as 
those  of  gravitation,  chemical  affinity,  etc.  No  more,  no  less.  Facts 
obtained  and  laws  generalized  from  them.  The  essence  of  phenomena, 
the  ultimate  cause  of  gravity,  chemical  affinity,  vitality,  or  any  other 
mode  of  force  being  unknowable. 

We  have  seen  that  the  proximate  principles  of  the  human  body  are 
derived  directly  or  indirectly  from  the  food.  When  we  come  to  study 
the  blood  we  shall  find  that  it  is  by  means  of  this  fluid  that  these  prin- 
ciples are  carried  to  all  parts  of  the  economy.     As  the  living  body  is 


RESUME    OF    PROXIMATE    PRINCIPLES..  79 

nourished  by  its  blood,  and  as  the  blood  is  being  continually  renewed  by 
the  food,  it  is  natural  that  all  three,  body,  blood,  and  food,  should  con- 
tain essentially  the  same  principles.  We  shall  soon  see  that  this  is  the 
case.  As  the  nutritive  principles  exist,  however,  in  the  food  in  a  con- 
dition different  from  that  found  in  the  blood,  they  are  first  subjected  to 
certain  processes  in  the  alimentary  canal  that  render  them  susceptible 
of  absorption  by  this  fluid  and  the  lymph  ;  whence  carried  to  the  tissues 
they  are  further  elaborated,  assimilated,  or  decomposed  by  the  cells  of 
the  same,  supplying  the  latter  with  material  for  growth  and  develop- 
ment or  the  production  of  force. 

The  life  of  the  body,  as  already  stated,  being  the  total  life  of  the 
cells  composing  it,  it  is  in  the  cells  or  their  modifications  that  the 
elaboration,  combination,  and  decomposing  of  the  chemical  principles 
take  place,  the  total  resultant  of  which  constitutes  life.  To  the  first  of 
such  vital  processes,  digestion,  let  us  now  turn,  commencing  with  the 
subject  of  food. 


CHAPTER   IY. 

FOOD. 

Vital,  like  all  other  work,  implies  waste.  Our  thoughts,  our  words, 
our  gestures  are  all  accomplished  at  the  expense  of  the  food  and  tissues 
of  our  bodies.  Portions  of  our  tissues,  and  the  food  appropriated  by 
them,  are  being  slowly  but  constantly  consumed,  being  transformed 
into  substances  which  will  ultimately  become  carbonic  acid,  water,  and 
urea. 

Life  depends  upon  this  continual  and  incessant  waste  and  change  of 
food  and  tissue.  It  is  literally  true  that  "in  the  midst  of  life  we  are  in 
death."  Every  mental  and  muscular  effort  is  accompanied  with  the 
destruction  of  so  much  food,  brain,  and  muscular  substance,  and  the  loss 
of  heat.  The  carbonic  acid  and  water  exhaled  at  every  breath  are  evidence 
of  so  much  food  and  tissue  consumed.  This  daily,  hourly,  momentary 
death  of  the  tissues  and  destruction  of  food  demand  the  constant  renewal 
of  the  matters  of  which  they  are  composed.  Hence  the  necessity  of  food, 
by  which  I  mean  any  substance,  inorganic  or  organic,  solid  or  liquid, 
that  will  nourish  the  body ;  renewing  the  material  destroyed  in  produc- 
ing the  phenomena  of  life. 

Hunger  and  Thirst. — The  effects  of  withholding  food  entirely  or 
of  giving  it  in  too  small  quantities  are  seen  in  cases  of  starvation  and 
inanition. 

Under  ordinary  circumstances  the  sensations  of  hunger  and  thirst  are 
the  first  indications  that  solid  and  liquid  food  are  required  by  the  system. 
These  sensations  seem  to  be  due  to  a  certain  condition  of  the  stomach 
and  mouth  induced  by  the  want  of  food  experienced  by  the  general 
system.  That  such  is  the  case  seems  to  be  justified  by  facts  like  the 
following.  It  is  well  known  that  the  sensations  of  hunger  and  thirst 
can  be  relieved  by  introducing  food  into  the  system  through  fistular 
openings  made  in  the  body  by  disease  or  wounds.  Thus  food  taken  into 
the  system  through  an  opening  in  the  intestine,  as  is  wrell  known,  will  not 
only  relieve  the  sensation  of  hunger  but  sustain  life,1  and  in  the  case  of 
an  opening  into  the  oesophagus,  Avhen  water  and  spirit  were  injected 
into  the  stomach,  the  thirst  was  relieved.2  It  is  also  well  known  that 
bathing  and  wringing  the  clothes  in  salt  water  have  been  the  means  of 
temporarily  relieving  the  thirst  of  shipwrecked  sailors. 

On  the  other  hand,  if  the  food  is  not  absorbed,  the  sensations  of 
hunger  in  the  stomach  and  of  thirst  in  the  mouth  are  only  temporarily 
relieved;  even  though  solid  food  may  be  eaten  and  water  be  drank  in 
large  quantities,  the  general  wants  of  the  system  in  such  cases  not  being 
satisfied. 

1  Busch  :  Virchow's  Arctaiv,  1858.  -  Gairdncr  :  Edinburgh  Medical  and  Surgical  Journal,  1S20. 


HUNGER    AND    THIRST.  81 

The  consideration  of  death  from  hunger  and  thirst  belongs  rather  to 
the  subject  of  pathology.  As  an  illustration,  however,  of  how  life  de- 
pends upon  waste,  and  of  the  manner  and  relative  quantities  in  which 
the  tissues  are  destroyed  to  maintain  life,  the  records  of  death  from  want 
of  food,  solid  and  liquid,  become  of  interest  to  the  physiologist.  For  a 
starving  man  is  living  upon  himself,  and  as  nature  is  always  economical 
in  her  expenditures,  one  may  feel  sure  that  the  very  best  disposition 
possible  under  such  circumstances  is  made  of  the  material  available  in 
maintaining  life.  In  the  wasting  away  that  takes  place  in  these  cases 
we  have  a  guide  as  to  the  character  of  the  nourishment  that  the  system 
would  have  taken  had  food  been  supplied  from  without  instead  of  from 
within,  and  can  so  deduce  some  conclusions  as  to  the  use  of  food 
generally. 

Shipwrecks,  prolonged  sieges,  imprisonments,  forced  marches,  etc., 
furnish  the  data  by  which  some  idea  may  be  obtained  of  the  state  of 
nutrition  and  of  the  agonies  and  horrors  in  cases  of  death  from  starva- 
tion. Among  the  symptoms  of  starvation  ma}'  be  mentioned,  first, 
severe  pain  in  the  epigastrium,  which  usually  passes  away  in  a  day  or 
so,  then  an  indescribable  feeling  of  weakness,  a  sort  of  sinking,  in  the 
same  parts  is  experienced.  The  face  becomes  pale  and  cadaverous,  and 
there  is  a  wild  look  in  the  eye.  General  emaciation  follows,  an  offensive 
odor  is  noticed  about  the  body,  which  is  covered  with  a  brownish  secre- 
tion. The  voice  becomes  weak,  muscular  effort  is  almost  impossible,  the 
intelligence  can  with  difficulty  only  be  aroused.  Finally  death  takes 
place,  usually  in  eight  or  ten  days,  often  accompanied  with  mania  and 
convulsions. 

( )n  post-mortem  examination  the  most  striking  facts  usually  noticed 
are  the  diminution  in  the  weight  of  the  body,  almost  entire  absence  of 
fat  and  blood,  and  the  loss  in  bulk  of  the  most  important  viscera.  The 
coats  of  the  intestine  are  so  thinned  as  to  be  almost  transparent,  the 
gall-bladder  is  distended  with  bile,  and  decomposition  sets  in  very 
rapidly. 

Death  from  inanition  or  insufficient  food,  though  more  prolonged  than 
that  from  actual  starvation,  is  essentially  the  same  process  only  slower. 
being  characterized  by  the  same  symptoms,  and  the  same  post-mortem 
changes.  Many  babies  and  young  children  in  large  cities  and  even  in 
the  country  die  from  inanition — actually  starved  to  death,  undoubtedly 
through  ignorance  in  some  cases ;  but  in  others,  however,  the  length  of 
time  in  death  from  inanition  varying  so,  and  being  often  so  extended, 
advantage  is  frequently  taken  of  this  to  obscure  and  mask  the  true 
cause  of  death  by  those  interested  in  escaping  from  the  penalties  of  their 
criminal  neglect  of  the  children  placed  in  their  charge. 

As  already  observed,  one  of  the  most  prominent  symptoms  of  starva- 
tion is  the  loss  of  weight.  It  may  be  generally  stated  that  when  this 
loss  exceeds  forty  per  cent.,  or  from  twenty  to  fifty  per  cent,  according 
to  Voit,  of  the  weight  of  the  body,  death  takes  place. 


82 


FOOD. 


Table  XVI. —  Relative  Loss  ov  Tissric  in  Starvation  jx  Joo  Parts. 


In  doves,  accord-    In  <  :ate,  accord- 
ing to  ' Ihossat.1       iug  tci  \ 'nil.- 


Fat         .... 

Blood    .... 

Spleen  .... 

Pancreas 

Liver     .... 

Heart     .... 

Intestines 

Muscles 

Muscular  coal  of  stomach 

Pharynx  and  oesophagus 

Skin       .... 

Kidneys 

Respiratory  apparatus  . 

Osseous  system 

Eyes      .... 

Nervous  system      . 


93.3 

97 

75.0 

27 

71.4 

67 

64.1 

17 

52.0 

.".4 

44.8 

3 

42.4 

18 

42.3 

31 

39.7 

34.2 

:;:;.:: 

21 

31.9 

26 

22.2 

18 

16.7 

14 

10.0 

1.9 

3 

By  looking  at  Table  XVI.,  taken  from  the  excellent  works  of  Chossat 
and  Voit,  it  will  be  noticed  that  the  difference  in  the  relative  loss  of  the 
tissues  is  very  considerable.  Thus  the  nervous  system  loses  only  a  little 
over  one  per  cent.,  the  muscles  over  forty  per  cent.,  while  more  than 
ninety  per  cent,  of  the  fat  disappears. 

Now  it  has  been  noticed  that  in  starvation  the  temperature  falls,  and 
most  rapidly  as  death  approaches;  this  is  so  evident  that  the  immediate 
cause  of  death  is  undoubtedly  cold.  When  it  is  remembered  that  one 
of  the  principal  uses  of  the  fatty  principles  is  to  produce  heat  through 
their  combustion,  the  large  loss  of  fat  in  such  cases  becomes  intelligible, 
the  animal  using  up  its  own  fat  as  so  much  fuel. 

Inasmuch  as  no  food  has  been  introduced  into  the  body  there  is 
nothing  for  the  economy  to  make  blood  out  of,  hence  the  small  quantity 
found  in  the  body  after  death  from  starvation.  Further,  what  there  is 
of  it  is  of  the  most  inferior  quality,  rather  injurious  than  otherwise;  for 
through  the  impeded  circulation  the  worn-out  and  effete  matters  which 
are  excreted  and  carried  out  of  the  system  so  rapidly  in  health  accumu- 
late in  the  stagnating  inspissated  fluid  and  represent  so  much  poison. 

Even  though  one  should  recover  from  the  effects  of  long  deprivation 
of  food,  the  system  for  weeks  afterward  remains  in  a  bad  condition 
peculiarly  favorable  to  the  reception  of  any  zymotic  poison.  Hence, 
from  time  immemorial,  famine  has  been  the  harbinger,  the  forerunner 
of  epidemics,  the  plague,  etc.  Almost  invariably  after  a  long  siege, 
where  there  has  been  insufficient  food,  unless  careful  measures  are  taken, 
disease  breaks  out  and  carries  off  many  of  those  spared  by  the  sword. 
In  the  often-quoted  words  of  Chossat,  "  inanition  is  a  cause  of  death 
which  advances  in  the  front  and  in  silence  in  every  disease  in  which 
alimentation  is  not  in  a  normal  condition." 

Terrible  as  the  pangs  of  hunger  are,  those  of  thirst  are  worse.  Man 
and  animals  will  live  longer  without  solid  food  than  when  deprived  of 
water,  man  dying  usually  in  a  few  days  when  no  water  at  all  has  been 


i  Recherches  Experimentales  sur  1"  Inanition,  p.  92. 
2  Hermann  :  Physiologic,  Band  vi.  S.  97. 


USE     OF     FOOD.  83 

.aken.  When  it  is  remembered  that  about  three-fifths  of  the  body  con- 
sist of  water  this  is  readily  accounted  for. 

The  sensation  of  thirst,  though  caused  by  this  general  want  of  the 
system  for  water,  is  referred  to  the  mouth  and  throat,  which  are  first 
sensibly  affected.  These  parts  become  very  dry  and  hot  and  there  is 
an  agonizing  feeling  of  constriction,  fever  sets  in,  the  blood  is  very  much 
diminished  in  quantity  and  becomes  thickened,  the  urine  is  scanty  and 
burns,  the  viscera  may  be  said  to  be  almost  inflamed,  delirium  generally 
precedes  death. 

The  importance  of  giving  water  freely,  internally  and  externally,  in 
health  and  disease  cannot  be  too  much  insisted  upon.  No  detailed 
argument  is  necessary  to  prove  this  point.  The  simple  fact  that  some- 
times within  four  days,  even,  men  have  died  when  entirely  deprived  of 
water  speaks  for  itself. 

There  are  cases  sometimes  mentioned  of  human  beings  who  have  lived 
for  very  long  periods  of  time  without  eating  or  drinking  anything. 
When  the  evidence  of  such  cases,  however,  is  examined  critically  it 
generally  turns  out  (with  some  exceptions  to  be  mentioned  shortly)  that 
a  morsel  of  food  or  a  little  water  has  been  taken  at  some  time,  and  that 
the  exceptions  are  usually  only  apparent. 

Use  of  Food. — We  have  seen  that  the  body,  both  in  health  and 
starvation,  wastes  that  it  may  live.  The  rate  of  waste,  however,  varies 
in  different  classes  of  animals,  and  in  different  individuals  of  the  same 
species.  Thus,  mammals  and  birds,  living  a  more  active  life  than  rep- 
tiles or  batrachians,  waste  more  tissue  and  food.  A  man  who  lives  a 
fast  life — using  the  term  in  its  physiological  sense — wastes  more  rapidly 
than  one  who  lives  a  moderate  one.  Hence  the  difference  in  the  amount 
and  quality  of  the  food  required  and  the  frequency  in  taking  it  observed 
in  different  animals,  and  by  the  same  animal  at  different  periods  of  its 
life.  Thus  the  boa  constrictor  may  feed  only  once  in  three  or  four 
months,  while  man  eats,  usually,  three  times  a  day. 

Further,  the  food  of  the  inhabitants  of  the  polar  regions,  consisting 
principally  of  fatty,  oleaginous  principles,  that  of  the  people  of  tropical 
countries,  of  rice,  dates,  etc.,  shows  that  the  food,  in  addition  to  repairing 
the  waste  of  the  tissues,  fulfils  other  conditions  essential  to  life. 

Every  one  is  sensible  of  the  change  of  the  seasons,  feeling  that  icy 
winter  is  melting  into  spring,  that  budding  spring  is  unfolding  into 
summer.  The  traveller,  journeying  from  temperate  to  polar  or  tropical 
regions,  appreciates  the  increasing  cold  of  the  one,  or  heat  of  the  other, 
and  yet  the  average  temperature  of  man  remains  about  the  same, 
98.6°  F.,  at  all  seasons,  in  all  climates. 

The  temperature  may  rise  as  high  as  110°  in  certain  diseases,  like 
tetanus,  and  even  to  1*22°  F.,  as  in  a  case  of  injury  to  the  spine,  and 
which  may  be  mentioned,  ended  in  recovery;1  or,  under  certain  con- 
ditions, may  fall  as  low  as  83°  F.,  or  lower,  as  in  cholera.  These 
extremes  if  maintained,  however,  are  soon  followed  by  death. 

How  can  this  constant  heat  in  the  human  body  be  accounted  for? 

We  have  seen  that  the  sugars  and  fats,  and  albuminous  principles  of 

1  Lancet,  March  G,  1875. 


84  FOOD. 

which  the  body  is  composed,  and  which  are  derived  from  the  food,  are 
consumed  in  the  economy,  and  produce  heat.  Thus  food  is  so  much 
fuel  for  the  system.  The  question  of  some  of  the  food  being  directly 
burnt  up  as  such,  as  so  much  coal,  or  indirectly  by  first  becoming  tissue, 
and  which  lias  Keen  already  considered,  does  not  affect  the  fact  of  the 
food  being  the  source  of  heat  to  the  economy.1 

The  use  of  food  then  is  to  repair  not  only  the  waste  of  the  tissues, 
but  also  to  supply  the  fuel  for  the  production  of  heat  and  force.  In  the 
child,  however,  the  food  not  only  supplies  these  two  wants,  but  also 
furnishes  the  materials  for  its  growth,  hence  the  large  and  constant 
amounts  of  food  demanded  by  an  active,  healthy  child.  This  fact 
should  never  be  forgotten  by  the  physician,  for  many  persons  seem  to 
think  that  a  child  can  be  built  up  out  of  nothing.  There  is  quite  as 
much  danger  in  giving  a  baby  or  child  too  little  food  as  too  much,  for 
more  of  them  die  of  starvation  than  of  repletion. 

Again,  the  food  of  the  female  during  gestation,  must  furnish  the 
materials  out  of  which  the  child  is  developed,  as  well  as  supply  her  own 
wants.  The  food,  under  these  circumstances,  ought  to  be  most  generous, 
both  in  quantity  and  quality,  that  neither  mother  nor  child  should 
suffer. 

Striking  contrasts  are  offered,  according  to  the  particular  use  made 
of  the  food  in  one  or  more  of  the  ways  just  mentioned  by  different 
classes  of  living  beings,  or  of  an  animal  at  different  periods  of  its  exist- 
ence. Thus  in  trees,  making  no  muscular  or  nervous  effort  and,  there- 
fore, wasting  but  little,  and  having  no  constant  temperature  to  maintain, 
all  their  food  can  be  applied  to  increase  their  size,  hence  their  indefinite 
growth.  Insects,  on  the  contrary,  being  most  active,  are  usually  small 
animals,  the  greater  portion  of  their  food  being  used  up  in  producing 
their  various  actions,  and  little  left  for  growth.  In  the  foetal  state  of 
man  the  food  is  applied  to  growth,  in  the  adult,  for  the  purposes  men- 
tioned above  ;  hence  a  man  cannot  grow  indefinitely,  his  food  being 
used  for  the  development  of  mental  and  muscular  force,  there  will  be 
none  left  that  can  be  appropriated  for  growth.  Inasmuch  as  the  quantity 
of  food  that  can  be  taken  by  an  animal  is  limited  by  the  capacity  of  its 
alimentary  canal,  it  might  be  inferred,  a  priori,  that  if  the  greater  part 
of  the  food  is  applied  to  one  particular  use,  there  will  be  little  or  none 
left  for  any  other. 

Hot-blooded  animals  require  more  food  than  cold-blooded  ones,  in 
order  to  maintain  their  higher  temperature,  and  their  more  active  life. 
When  hot-blooded  animals,  however,  hibernate — that  is,  sleep  for  months 
at  a  time — they  pass  into  a  sort  of  cold-blooded  state,  taking  no  food, 
existing  by  living  upon  themselves :  they  always  weigh  less  at  the  end 
of  their  sleep  than  at  its  beginning;  the  waste,  however,  is  comparatively 
small,  they  living  so  quietly  during  the  hibernating  period. 

By  bearing  in  mind  these  facts,  it  becomes  intelligible  how  individuals 
have  been  able  to  sustain  life  without  taking  food,  water  excepted,  for 
many  days   beyond  the  period  when  ordinarily  death  from  starvation 

1  The  various  conditions  winch  influence  the  regulation  and  distribution  of  beat,  and  the  cause  of  its 
production,  will  be  deterred  until  we  consider  the  subject  of  animal  heat. 


KINDS    OF    FOOD. 


85 


ensues.  By  taking  little  or  no  exercise,  in  passing  most  of  the  time  in 
sleep,  and  residing  in  a  tropical  climate,  or  in  a  temperate  one  during 
the  hottest  summer  months,  while  the  experiment  lasts,  it  will  be  found 
that  the  system  needs  but  little  food,  the  waste  of  the  tissues  being 
reduced  to  a  minimum,  and  there  being  but  little  need  for  the  heat  pro- 
duced on  account  of  the  high  temperature  of  the  surroundings.  By 
living  in  this  way,  man  can  transform  himself  almost  into  a  cold-blooded 
or  hot-blooded  hibernating  animal.  Under  such  circumstances  he  lives 
upon  himself,  and  continually  loses  weight.  When,  as  regards  this  loss 
of  weight,  a  certain  limit  is  reached,  which  varies  according  to  the  con- 
dition, previous  mode  of  life,  and  peculiarities  of  the  individual,  he  will 
certainly  die  of  starvation  unless  food  be  taken,  death  from  starvation 
being  only  a  question  of  time  if  the  system  be  deprived  of  food. 


Table  XVII.1— Composition  of  Blood. 


Water 
Globulin 

Albumen    . 

Fibrin 

Serolin 

Cholesterin 

Sodium 

Potassium 

Sodium 

Magnesium 

Sodium 
Potassium 

Free  soda 

Magnesium 


I  ( Ueate 

Margarate 
|  Stearate 

) 

-  Chloride 

J 

(  ( !arbonate 
-,'  Sulphate 
(  Phosphate 


(  Sulphate 
i  Phosphate 

Calcium  phosphate    . 

Iron    .         .         .         .         . 

Extractives  undetermined 


781 .600 

135.000 

70.000 

2.500 

0.025 

0.125 

1.400 


:  j.  5(i0 


2..S5H 


.       0.550 
.       2.450 

1000. ooo 


Kinds  of  Food. — At  the  conclusion  of  the  last  chapter  it  was  stated 
that,  as  the  principles  of  which  the  body  is  composed  are  derived  from 
the  blood,  and  the  blood  from  the  food,  the  same  principles  will  be  found 
in  all  three.  By  glancing  at  Table  XVII.,  drawn  up  from  Becquerel 
and  Rodier,  it  will  be  seen  that  the  blood  contains  water,  sodium  chloride, 
phosphates,  fats,  albuminous  principles,  etc.,  while  any  of  the  ordinary 
animal  or  vegetable  foods,  like  fish,  eggs,  milk,  flour,  or  potatoes,  etc., 
will  be  seen  from  Tables  XVIII.  and  XIX.  to  consist  of  essentially 
these  same  principles.  Indeed,  the  food  of  man  naturally  divides  itself, 
like  the  proximate  principles,  into  three  classes,  the  albuminous,  carbo- 
hydrate, and  inorganic.  Liebig's  classification  into  tissue-making  and 
heat-producing  food  is  correct,  so  far  as  in  that  some  kinds  of  food 


1  Becquerel  and  Rodier  :  Traite  de  Chiinie,  Pathologique,  p, 


Paris,  1854. 


80  FOOD. 

are  especially  useful  in  producing  heat.  It  must  be  remembered,  how- 
ever, that  the  combustion  <>f  all  tissue  produces  heat,  and  that  heat- 
making  substances  like  fat,  and  the  inorganic  principles,  make  tissue  as 
well  as  the  albuminous  ones.  There  is,  therefore,  no  such  sharp  line 
of  demarcation  as  heat-  and  tissue-making  foods  as  Liebig's  classification 
implies. 

It  may  appear  strange  that  inorganic  principles  like  calcium  phos- 
phate, salt,  water,  etc.,  are  classed  as  food,  but  as  we  have  seen  that  the 
body  is  composed  of  inorganic  as  well  as  organic  principles,  we  must 
regard  as  a  food  any  substance  that  will  furnish  these  principles.  The 
chemical  analysis  of  such  substances  as  are  seen  in  Tables  XVIII.  and 
XIX.  explains  why  mankind  makes  use  of  eggs,  fish,  flour,  potatoes 
etc.,  as  food,  these  articles  containing  the  inorganic  and  organic  prin- 
ciples of  which  the  body  consists. 

Table  XVIII.1— Animal  Foods. 

In  1000  parts  Mammals.  Birds.  Fish.  Eggs.  Milk. 

Water     .  .  728.75  729.83  740.82  735.04  861.53 

Albumen  .  174.22  202.61  137.40  134.34  39.43 

Collagen  .  31.59  14.00  43.88  

Fat.         .  .  37.15  19.46  45.97  116.37  49.89 

Carbohydrates  42.23 

Extractives  .  16.90  21.11  16.97  3.74  .... 

Salts        .  .  11.39  12.99  14.96  10.51  5.92 


Table  XIX.2 — Vegetable  Foods. 


( lorn  flour. 

Peas  (dried>. 

Potatoes. 

Beet  root. 

150.00 

760 

822.50 

132.50 

280 

10 

20.40 

.  606.80 

573 

180 

54.80 

122.60 

,     26.60 

'76 

'46 

25.60 

,     16.80 

,     12.50 

'38 

'id 

*8.90 

In  1000  parts 

Water       . 
Albumen  . 
Starch 
Sugar 
Cellulose  . 
Fat  . 
Salts 


From  the  fact  of  the  inorganic  principles  being  usually  combined  in 
sufficient  quantities  with  the  organic,  their  indispensable  use  as  food  is 
often  overlooked.  The  albuminous  principles  of  the  food  that  in  the 
economy  are  converted  into  the  albumen  of  the  blood,  are  found  both 
in  the  animal  and  vegetable  foods.  Thus  we  have  albumen  as  musculin 
forming  the  basis  of  muscle,  in  various  meats,  beef,  mutton,  venison, 
lamb,  etc.,  in  the  white  of  the  egg,  as  casein  in  cheese,  in  birds,  fish, 
oysters,  and  milk,  as  may  be  seen  from  Tables  XVIII. ,  XXL,  and 
XXII. 

In  vegetables,  albumen  exists  as  vegetable  albumen,  readily  converted 
into  that  of  the  blood.  It  is  present  in  peas,  potatoes,  beets,  flour,  etc., 
as  shown  in  Tables  XIX.  and  XX. 

1  Moieschott,  referred  to  by  Carpenter,  Principles  of  Human  Physiology,  1881,  p.  97. 
-  Carpenter,  op.  cit. 


KINDS    OF    FOOD. 


Table  XX.1 — Composition  of  the  Potato. 


Water         .... 

66.875 

Starch         .... 

30.469 

Albumen    .... 

0.503 

Gluten        .... 

0.055 

Fat 

0.056 

Gum  ..... 

0.020 

Asparagin  .... 

0.063 

Extractives 

0.921 

Potassium  chloride     . 

0.176 

Iron                    ~\ 

Man-anesium    j    Silicates           ) 

Aluminium       ,    1Ml      hates              .... 
I0*1™                  Citrates            j 

0.815 

Potassium 

Calcium             J 

Free  citric  acid           ....... 

0.047 

100.000 

Table  XXI.2 — Composition  of  Ox  Flesh. 

Water 

77.17 

Muscular  fibre,  vessels,  nerves  .... 

15.80 

Tendinous  tissue        ...... 

1.90 

Albumen    ........ 

2.20 

Substances  soluble  in  water       .... 

1.05 

Substances  soluble  in  alcohol     .... 

1.80 

Calcium  phosphate    ...... 

0.08 

100.00 

Table  XXII.3 — Composition  of  the  Oyster. 

Water 

.     80.385 

Nitrogenized  substances     . 

.     14.010 

Fat 

.       1.515 

Salts 

.       2.695 

Loss    ..... 

.       1.395 

100.000 

Starch  is  found  in  vegetables,  in  greater  proportions,  for  example,  in 
wheat,  corn,  rice,  potatoes,  beans  and  peas,  etc.,  than  in  turnips,  cab- 
bages, cauliflowers.     Sugar  is  derived  from  animals,  as  milk  and  liver, 

i  1 

sugar  and  sugar  of  honey  ;  and  from  vegetables  as  cane  and  grape 
sugar.  Fats  and  oils  are  found  both  in  the  animal  and  vegetable  foods. 
By  looking  at  the  above  Tables  the  relative  proportions  of  the  carbo- 
hydrate to  the  albuminous  principles  in  the  substances  usually  used  as 
food  may  be  seen,  and  the  large  quantity  of  water  and  constant  presence 
of  salts  are  especially  noticeable. 

Of  the  salts,  amounting  in  twenty-four  hours  to  about  twenty 
grammes  (three  hundred  grains),  the  most  widely  distributed  are  the 
sodium  chloride  and  calcium  phosphate,  these  being  present  both  in  the 
vegetable  and  animal  foods.  Iron,  a  most  important  principle,  is  found 
in  ego;s  and  milk.  It  is  not  necessary  to  dwell  further  upon  the  in- 
organic  kinds  of  food,  sufficient  attention  having  been  paid  to  them 
wdien  treating  of  their  use  in  the  system  as  proximate  principles. 


1  Pereira  :  Treatise  on  Food  and  -  »I.-t .    Nc\ 
8  Payen  :  Substances  Alimentaires,  p.  221. 


Y.. ik.  1843. 
Paris,  ISO"). 


Flint:  Physiology,  vol    ii.  l>.  71. 


CHAPTER  Y. 

QUALITY  AND  QUANTITY  OF  FOOD. 

It  might  be  supposed  from  looking  at  Tables  XVIII.  and  XIX.  that 
it  was  immaterial  whether  man  lived  upon  animal  or  vegetable  food, 
since  they  both  contain  essentially  the  same  substances,  and.  this  would 
receive  confirmation  when  it  was  remembered  that  while  many  savage 
tribes  on  the  one  hand  subsist  almost  entirely  upon  meat,  the  food  of 
others  on  the  other  consists  principally  of  the  date,  rice,  etc.,  with  little 
or  no  animal  food.  As  a  matter  of  fact,  life  can  be  sustained  on  either 
an  animal  or  vegetable  diet,  the  processes  of  digestion  converting  in- 
differently the  albumen  into  albuminose,  whether  it  be  derived  from  beef 
or  potatoes,  and  assimilating  the  fats  and  salts  whether  they  are  fur- 
nished by  fish  or  bread.  Living  upon  either  animal  or  vegetable  food, 
alone,  however,  is  far  from  being  an  economical  mode  of  diet,  at  least 
under  ordinary  circumstances. 

It  might  be  naturally  inferred  from  the  fact  of  man  possessing  at  the 
present  day  incisor,  canine,  and  molar  or  grinding  teeth,  that  from  time 
immemorial  he  had  been  accustomed  to  live  on  both  kinds  of  food,  for 
had  he  limited  himself  to  one  or  the  other,  certain  teeth  would  have 
probably  disappeared  or  at  least  have  become  smaller  through  disuse. 
Diminution  in  size  has  actually  taken  place  in  the  posterior  molar  teeth 
through  the  effects  of  eating  cooked  food. 

The  alimentary  canal  of  man,  as  we  shall  see,  is  not  so  long  or  com- 
plicated as  that  of  the  herbivora,  and  yet  not  so  simple  as  that  of  the 
carnivora,  being  rather  a  mean  between  the  two.  A  fair  conclusion 
from  this  comparison  would  be  that  a  mixed  diet  is  better  adapted  to 
the  human  system  than  an  exclusively  animal  or  vegetable  one.  The 
chemistry  of  the  excretions  not  only  confirms  this  view,  but  offers  the 
explanation  why  it  should  be  so. 

Table  XXIII.1 

4600  grs.  of  carbon  to  300  grs.  of  nitrogen  in  excreta,  or  15  C  to  1  N. 

30,000  grs.  of  bread  contain  9000  grs.  of  carbon  to  300  nitrogen,  or  30  C  to  1  N. 

46,000  grs.  of  meat  contain  4600  C,  1380  N,  or  3  C  to  1  N. 

about  2    lbs.  of  bread  contain  < !  4630  grs.       N  154  grs. 

"       f  lb.  of  meat  contains  C    463  grs.       N  154  grs. 

"     21  lbs.  of  bread  and  meat  contain  C  5093  grs.       N  308  grs. 
or  C  16  grs.  N  1  gr. 

In  a  state  of  health  there  are  found  in  the  excreta  for  one  grain  of 
nitrogen  fifteen  grains  of  carbon  (Table  XXIII.).      If  a  man   should 

i  Carpenter:  Physiology,  1881,  p   96. 


COMPOSITION    OF    FOOD.  89 

confine  himself  to  vegetable  food,  say  bread,  for  example,  for  every 
grain  of  nitrogen  that  he  ate  he  would  take  in  not  only  fifteen  grains 
of  carbon,  that  are  necessary,  but  fifteen  grains  too  much  ;  in  eating 
meat  alone,  while  he  obtains  the  one  grain  of  nitrogen,  he  gets  only  about 
three  grains  of  carbon,  twelve  grains  too  little.  He  must  eat,  therefore, 
nearly  five  times  as  much  meat  as  is  necessary,  so  far  as  the  amount  of 
nitrogen  is  concerned,  in  order  to  get  the  fifteen  grains  of  carbon,  and 
in  so  doing  he  loads  his  system  with  five  times  too  much  nitrogen.  In 
eating  bread  you  get  twice  as  much  carbon  as  is  needed,  and  in  eating 
meat  four  times  too  little.  In  diminishing  the  amount  of  bread  you 
get  too  little  nitrogen,  and  in  increasing  the  amount  of  meat  too  much. 
If.  however,  the  bread  and  meat  are  taken  together  in  proper  propor- 
tions we  will  get,  according  to  the  above  calculation,  the  ratio  of  16  of 
carbon  to  1  of  nitrogen  in  the  excretions,  which  differs  but  little  from 
that  actually  found,  1  to  15,  and  which  can  be  accounted  for  by  re- 
membering that  the  food  of  man  consists  not  only  of  bread  and  meat, 
but  of  other  substances  containing  carbon  and  nitrogen. 

Of  the  chemical  elements  entering  into  the  composition  of  food,  car- 
bon and  nitrogen  are  the  most  important  with  reference  to  the  compari- 
son to  be  made  hereafter  between  the  ingesta  and  the  egesta  in  the 
determination  of  the  origin  of  the  latter,  the  source  of  animal  heat,  etc. 
The  various  methods  adopted  by  chemists  for  determining  the  composi- 
tion of  foods  will  be  found  in  the  standard  general  and  special  treatises 
pertaining  to  that  subject.  It  may  be  mentioned,  however,  incidentally 
here,  that  the  determination  of  the  carbon,  hydrogen,  and  nitrogen 
entering  into  the  composition  of  food  is  essentially  accomplished  by 
burning  the  substance  in  suitable  apparatus,  and  of  so  converting  its 
carbon,  hydrogen,  and  nitrogen  into  carbonic  acid,  water,  and  ammonia, 
and  of  deducing  the  amounts  of  carbon,  hydrogen,  and  nitrogen  m  the 
food  examined  from  the  carbonic  acid,  water,  and  ammonia  produced, 
the  remainder  giving  the  amount  of  oxygen.  Should  the  food  contain 
sulphur  and  phosphorus  in  addition  to  the  other  elements  just  men- 
tioned, their  amount  can  be  similarly  determined  by  their  conversion 
into  sulphuric  and  phosphoric  acids  respectively.  Table  XXIY.  gives 
the  amount  of  carbon,  hydrogen,  nitrogen,  etc.  in  the  daily  food. 

Table  XXIV.1 


c 

H 

0 

X 

s 

Albuminoids,     130 

grammes 

70 

10 

29 

20 

1 

Hvdroearbons,  300 

" 

L34 

18 

148 

Fat,                      100 

" 

70 

12 

12 

Mineral  salts,       20 

<< 

Water,               2000 

it 

2X0  40  L89 


The  study  of  the  teeth,  alimentary  canal,  and  the  excretions  explains 
what  experience  teaches,  that  generally  a  mixed  diet  is  best  adapted  to 


i  Dalton,  7th  ed.,  1882,  p.  132. 


90  QUALITY    AND    QUANTITY    OF    FOOD. 

the  wants  of  man.  There  arc  circumstances,  however,  when  although 
the  diet,  strictly  speaking,  is  mixed,  it  consists  to  a  great  extent  of 
either  animal  or  vegetable  foods ;  the  external  condition  being  such  thai 
the  wants  of  the  system  are  better  supplied  by  the  one  than  the  other. 

Thus  the  Guachos  in  South  America,  spending  their  life  in  the  saddle, 
and  the  climate  being  bot,  live  upon  beef,  there  being  little  necessity 
for  taking  heat-making  food,  enough  heat  being  generated  through  the 
c bustion  of  the  beef  indispensable  as  supplying  the  force  and  re- 
placing the  tissue  wasted  in  their  active  life. 

The  people  inhabiting  the  Arctic  regions,  living  in  a  temperature 
where  the  thermometer  falls  lower  even  than  — 40°,  would  freeze  to 
death  were  it  not  for  the  oily  matters  that  are  found  in  the  whales  and 
seals  serving  as  articles  of  food,  and  winch  in  their  combustion  produce 
so  much  heat.  In  tropical  countries,  however,  the  demand  for  carbon- 
aceous food  is  at  its  minimum,  the  heat  being  intense,  hence,  the  prin- 
cipal food  consists  of  rice,  etc.,  which  contains  relatively  little  carbon. 

The  obvious  corollary  from  the  above  facts  is,  that  travellers  should 
accustom  themselves  as  soon  as  possible  to  eat  the  food  of  the  country 
they  may  happen  to  be  passing  through,  and  not  invariably  try  to 
stick  to  the  diet  they  have  been  accustomed  to  at  home.  Further,  as 
the  seasons  change  in  any  one  particular  place,  the  diet  should  be 
altered.  Fats  and  sugars  are  more  needed  by  the  system  in  January 
than  in  July,  and  more  exercise  being  taken  in  winter  than  in  summer, 
tissue  is  wasted  in  this  way  in  addition  to  that  consumed  to  produce 
heat.  The  food  should  differ,  therefore,  both  in  quality  and  quantity 
in  cold  and  hot  weather. 

This  subject  of  food  is  of  great  importance  to  the  practical  physician, 
for  improper  food  is  a  fertile  source  of  disease. 

The  bilious  diarrhoeas  so  common  in  the  autumn  are  undoubtedly 
efforts  of  nature  to  relieve  the  system  of  the  superfluous  material  that 
has  accumulated  in  the  system  during  the  summer  to  such  an  extent 
that  it  can  not  be  burnt  up.  The  liver  diseases  that  foreigners  con- 
tract in  the  tropics  are  due,  probably,  to  the  same  cause.  An  excess 
of  albuminous  food  gives  rise  to  gravel,  gout,  etc.,  through  the  imper- 
fect combustion  of  the  urates. 

Rheumatism,  etc.,  seems  to  be  due  to  acidity  resulting  from  the  modi- 
fication of  the  starch  and  sugars  of  vegetable  food  taken  in  too  large 
quantities.  A  deficiency  of  oil  on  the  one  hand,  and  of  fresh  vege- 
tables on  the  other,  produces  phthisis  and  scurvy  respectively.  In  such 
cases  the  treatment  is  simply  to  diminish  the  article  in  excess  and  to 
supply  that  which  is  deficient. 

The  benefit  derived  from  cod-liver  oil  in  consumption  is  well  known, 
and  the  improvement  in  gouty  disease  through  entire  change  of  diet  and 
mode  of  life  is  often  marked. 

Theory  and  practice  both  agree,  therefore,  in  showing  that  food  must 
consist  of  a  proper  mixture  of  albuminous,  oleaginous,  saccharine,  and 
saline  principles,  and  just  in  proportion  as  any  single  food  contains 
these  principles  will  it  be  nutritious  as  an  article  of  diet  when  used 
alone.  The  potato,  for  this  reason,  is  invaluable  as  a  food,  containing 
as  it  does  so  manv  different  substances,  Table  XX.     Bread  has  been 


COMPOSITION    OF    FOOD.  91 

called  the  staff"  of  life,  it  entering  so  largely  into  the  food  of  all  classes 
of  society.      Table  XX Y.,  giving  the  composition   of  flour,   explains 

Table  XXV.1 — Composition  of  Flour. 

Water        .........  2.25  ounces. 

Gluten 2.00         " 

Albumen 0.25        " 

Starch 9.50         " 

Sugar 1.00 

Gum 0.25 

Fat 0.125       " 

Fibre 0.25 

Ash 0.25 

15.975       " 

why  it  fulfils  the  wants  of  the  system  to  so  great  an  extent.  But 
"man  cannot  live  by  bread  alone,"  and  experience  has  shown  that  this 
is  true  of  any  one  article  of  food ;  the  disgust  and  loathing  when  re- 
stricted to  one  article  of  diet  for  any  length  of  time  becoming  so  intense 
that  animals  will  even  starve  rather  than  touch  the  food  under  such  cir- 
cumstances. 

Indeed,  it  is  not  only  impossible  for  a  man  to  subsist  for  any  length 
of  time  upon  a  meat  diet,  but  a  carnivorous  animal,  a  dog,  for  example, 
whose  alimentary  apparatus  is  especially  adapted  to  the  digestion  of 
meat,  soon  succumbs  when  fed  upon  pure  flesh  alone,  unless  the  body 
be  well  supplied  with  fat,  an  albuminous  diet  being  in  fact  the  same 
as  a  starvation  one  in  which,  as  we  have  seen,  the  man  or  animal  lives 
upon  the  flesh  and  fat  of  the  body.  On  the  other  hand,  if  the  food 
consists  of  fat  alone,  man  or  beast  will  live  but  a  short  time,  and  it  is 
worthy  of  mention  that  on  such  a  diet  less  urea  is  excreted  than  in  the 
starving  condition,  the  albuminous  tissues,  the  source  of  the  urea,  being 
spared  through  the  oxidation  of  the  fat.  If  more  fat,  however,  be 
taken  than  can  be  disposed  of  in  this  way,  as  shown  by  the  retention  of 
carbon  in  the  system,  then  fat  is  stored  up  and  the  albuminous  tissues 
destroyed.  The  effect  of  a  carbohydrate  diet  is  essentially  the  same  as 
a  fatty  one,  sugar  or  transformed  starch  being,  however,  more  readily 
oxidized  than  fat,  seventeen  parts  of  sugar  being  equal  to  ten  parts  of 
fat  in  this  respect ;  less  urea  is,  therefore,  excreted  upon  a  carbohydrate 
diet  than  upon  a  fatty  one.  A  certain  amount  of  body  fat  appears  to  be 
also  destroyed  upon  a  carbohydrate  diet. 

Of  all  foods,  milk  (Table  XXA'I.)  is  the  one  which  combines  in 
itself  to  the  greatest  extent  the  proper  substances  in  quantity  and 
quality  for  the  nutrition  of  the  body,  and  were  life  limited  to  its  early 
periods,  we  might  say  that  milk  is  an  exception  to  the  rule  just  stated, 
but  as  the  child  develops  into  the  adult  necessity  is  felt  for  other  kinds 
of  food  as  well.  All  through  life,  however,  milk  constitutes  a  most 
important  article  of  diet,  and  can  be  more  relied  upon,  both  in  sickness 
and  in  health,  than  any  other  kind  of  food. 

1  Lankester  Guide  to  the  Food  Collections  in  the  South  Kensington  Museum,  p.  39. 


chloride 


0.15 


92  QUALITY    AND    QUANTITY    OF    FOOD. 

Table  XXVI.1 — Composition  of  Cow's  Milk. 

Water 86.40 

Nitrogenized  substances t.30 

Lactose 5.20 

Butter ,  8.70 

Calcium       1 

Magnesium  V  phosphate       .......       0.25 

Ferric  j 

Potassium 

Sodium         { 

Sodium  phosphate 

Sodium  lactate 

Traces  of  coloring  and  aromatic  matters. 

100.00 

The  qantity  of  food  that  a  man  can  eat  and  live,  is  very  different 
from  that  which  he  should  eat.  Mentioning  incidentally  that  a  young 
Esquimaux  is  said  to  have  eaten  thirty-five  pounds  of  food,  including 
tallow  candles,  in  twenty-four  hours,  and  a  Hindoo  a  whole  sheep  at  a 
time,  and  that  Cornaro  lived  for  fifty-eight  years  on  only  twelve  ounces 
of  vegetable  matter  and  fourteen  ounces  of  light  wine,  and  Thomas 
Wood  for  eighteen  years  on  sixteen  ounces  of  flour  made  into  a  pudding 
with  water2  (a  very  exceptional  case),  let  us  ascertain,  if  possible,  what 
is  the  proper  amount  of  food  for  the  average  man  in  twenty-four  hours. 

According  to  Prof.  Dalton,3  "  the  entire  quantity  of  food  required 
during  twenty-four  hours,  by  a  man  in  full  health  and  taking  free  exer- 
cise in  the  open  air,  is  as  follows : 

Table  XXVII. — Food  Required  in  24  Hours. 

Meat 453  grammes  (16  ounces). 

Bread 540       ""         (19      "      ). 

Butter  or  fat 100         "         (3 J       "      ). 

Water 1530         "         (52  fiuidounces). 

"  That  is  to  say,  rather  less  than  two  and  a  half  pounds  of  solid 
food  and  rather  over  three  pints  of  liquid."  It  is  desirable,  indeed 
nece-sary,  if  health  .is  to  be  maintained,  that  such  articles  as  fresh 
vegetables,  tea,  coffee,  milk,  sugar,  and  fruit  should  be  added  from  time 
to  time  to  those  just  mentioned. 

It  will  be  observed  from  a  comparison  of  Tables  XXIII.  and 
XXVII.,  that  on  a  bread  and  meat  diet  more  bread  is  eaten  than  when 
oil  is  also  taken  with  them  as  part  of  the  daily  food.  In  the  latter  case 
the  oil  supplying  part  of  the  carbon,  less  bread  is  required. 

Table  XXVIII.4 — Daily  Ration  of  the  United  States  Soldier. 


Bread  or  flour       ..... 

22   ounces 

Fresh  or  salt  beef        .... 

20         " 

Pork  or  bacon      ..... 

12 

Potatoes  (three  times  a  week) 

16 

Rice     ....... 

1.6     " 

Coffee  (or  tea  0.24  oz.) 

1.6     " 

Sugar   ....... 

2.4     " 

Beans  ....... 

0.64  gill. 

Vinegar        ...... 

0.32    " 

Salt 

0.16    " 

1  Paven  :  Substances  Alimentaires,  p.  139.     Paris,  1865. 

2  Carpenter'* 

Physiology,  p.  1 

3  Physiology,  p.  97. 

4  Physiology, 

vol.  ii.  p.  126. 

TEA     AND    COFFEE.  93 

Prof.  Flint  considers  the  United  States  army  ration,  Table  XXVIII., 

as  the  most  generous  in   the  world.      "The  bread,  meat,  and  potatoes 

contain  9.28  of  carbon  and  4.68  of  nitrogenized  matter,  in  addition  to 

which  are  the  alimentary  principles  contained  in  the  rice,  beans,  sugar, 

-and  coffee,  with  the  peculiar  stimulant  effect  of  the  coffee.'' 

According  to  Payen,1  thesoup  used  in  the  great  Paris  hospitals,  and 
which  is  very  nutritious,  may  be  appropriately  mentioned  here  as  serving 
also  as  a  guide  in  forming  a  diet  scale  for  charitable  institutions  generally. 
Its  composition  maybe  seen  from  Table  XXIX. 

Table  XXIX.'2 — Formula  for  Making  Soup. 

Water     .........  20  gallons. 

Meat  with  bones 68  lbs    10  oz. 

Vegetables 13    "    10    " 

Salt           .          .          .     _     .          .          .                    .          .  1     "     12:j    " 

Burnt  onions  (baked  in  oven  until  desiccated)       .  0     "      7jj   " 

In  concluding  this  general  account  of  the  subject  of  food,  it  may  be 
stated  that  the  effects  of  cooking  food  are  three :  First,  to  make  it  more 
palatable :  second,  to  utilize  it  thoroughly  ;  third,  to  improve  its  digesti- 
bility. Food  which  is  agreeable  to  the  taste  is  eaten  with  more  relish; 
and,  therefore,  better  digested  than  if  unpalatable.  If  the  food  were 
not  cooked,  much  of  it  would  be  unfit  to  eat  and  wasted,  and  even  if  it 
could  be  eaten  much  would  be  undigested. 

There  are  a  number  of  substances  which  cannot  be  regarded  as  food 
in  the  same  sense  as  those  already  referred  to,  but  as  they  are  consumed 
to  an  enormous  extent,  in  one  form  or  another,  by  the  majority  of  man- 
kind, some  reference  must  at  least  be  made  to  them  in  this  connection. 
I  refer  to  tea  and  coffee,  tobacco,  distilled  and  fermented  liquors. 

Tea  and  Coffee. — As  the  composition  and  principal  actions  of  tea 
and  coffee  are  the  same,  they  may  be  studied  together.  Tea  and  coffee 
are  obtained  from  the  Thea  chinensis  and  Caffea  Arabica,  the  tea  and 
coffee  plant  respectively.  As  seen  from  Table  XXX.,  they  are  com- 
posed of  the  same  principles,  united  in  different  proportions. 

Table  XXX.3 — Composition  of  Tea  and  Coffee. 

Tea.  Coffee. 

Water 5  12 

Theine 3  1.75 

Casein 15  13 

Gum 18  9 

Sugar       ........       3  6.5 

Tanic  acid 26.2-">  4 

Aromatic  oil 0.75  0.002 

Fibre 20  35.048 

Fat 4  12 

Mineral  substances 5  6.7 


100.00         100.000 

The   active   principles   are   usually  distinguished  as  theine  and  caf- 
feine.     These    alkaloids,    however,    and    the    active    principle    of  the 

1  Substances  Alimentaires,  p   101.  -  Flint,  op.  cit.,  p.  87. 

i  arpenter:  Physiology,  1870,  p.  120. 


94  QUALITY     AND    QUANTITY    OF    FOOD. 

Paraguay  tea,  made  from  a  shrub,  have  the  same  chemical  compositions 

(C8lf1()N402  +  2II20). 

In  making  good  tea  there  are  usually  allowed  "  i spoonful  for  each 

person  and  one  for  the  pot,"  so  each  person  gets  then  say  about  100 
grains  of  tea.  We  see,  however,  from  Table  XXX.,  that  the  quan- 
tity of  theine,  the  active  principle  of  tea,  amounts  to  only  three  per 
cent.;  it  must  be  admitted,  therefore,  that  its  nutritive  powers,  either  as 
a  tissue-  or  heat-making  food,  must  be  very  small.  How  account,  there- 
fore, for  the  value  of  tea  as  an  article  of  diet,  as  daily  experienced  by 
hundreds  of  millions  of  people  ?  The  explanation  of  the  effect  of  tea 
depends  upon  the  fact  of  its  increasing  the  amount  of  carbonic  acid 
expired,  and  of  waste;  as  first  shown  by  Mr.  Edward  Smith.1  Tea  is 
a  respiratory  stimulant,  and  therefore  powerfully  promotes  "those  vital 
changes  in  food  which  ultimately  produce  the  carbonic  acid  to  be 
evolved."  Instead,  therefore,  of  supplying  nutritive  matter,  it  causes 
the  assimilation  and  transformation  of  that  already  taken.  The  effect 
is  not  proportionate  to  the  quantity  of  tea  taken,  and  in  this  respect  it 
is  analogous  to  the  action  of  a  ferment.  The  sense  of  ease  in  respiration 
and  increase  of  general  comfort  after  taking  tea  are  well  known,  as  is  also 
the  fact  that  tea  tends  to  induce  perspiration  and  thereby  to  cool  the 
body.  Hence,  in  reference  to  nutrition,  we  may  say  that  tea  increases 
waste,  since  it  promotes  the  transformation  of  food  without  supplying 
nutriment,  and  increases  the  loss  of  heat  without  supplying  fuel.  It 
is  better  adapted,  therefore,  to  those  who  are  well  fed  than  to  the  poor 
and  fasting. 

The  effects  of  tea  upon  the  mind  are  well  known  :  wakefulness,  clear- 
ness and  activity  of  thought,  disposition  for  muscular  exertion,  etc. 
The  exhaustion  and  nervousness  which  sometimes  follow  the  excessive 
use  of  tea  appear  to  be  due  to  the  loss  of  sleep  and  waste  of  tissue 
rather  than  to  any  poisonous  action  of  its  active  principle.  The  effects 
of  coffee  and  tea,  in  many  respects,  are  the  same.  Coffee,  however, 
differs  from  tea  by  diminishing  the  action  of  the  skin.  It  lessens  also 
the  loss  of  heat  of  the  body,  but  increases  the  vis  a  tergo,  and,  therefore, 
the  heart's  action  and  the  fulness  of  the  pulse,  and  excites  the  mucous 
membranes.  The  conditions,  therefore,  under  which  coffee  may  be 
taken  are  very  different  from  those  suited  to  tea.  It  is  more  suited 
than  tea  for  the  poor  and  feeble.  It  is  also  more  fitted  for  breakfast, 
inasmuch  as  the  skin  is  then  active  and  the  heart's  action  feeble,  whilst 
in  good  health  and  with  sufficient  food  it  is  not  needful  after  dinner, 
but  if  then  drank  should  be  taken  soon  after  the  meal. 

It  was  formerly  stated  that  the  action  of  coffee,  tea,  etc.,  was  an  ex- 
ception to  the  rule  that  increased  vital  activity  is  accompanied  by  waste, 
these  substances  being  said  to  increase  force  but  to  diminish  waste,  the 
urea,  which  diminishes  under  the  use  of  coffee,  being  supposed  to  be  the 
measure  of  tissue  change.  It  is  now  known  that  the  emission  of  car- 
bonic  acid  by  the  lungs  is  rather  the  true  measure  of  muscular  exertion, 
and  this  being  increased  by  coffee  and  tea,  the  objection  just  mentioned 
is  no  longer  of  weight. 

1  Philosophical  Transactions,  1859. 


ALCOHOL.  95 

Tobacco. — As  the  employment  of  tobacco  is  most  extensive  in  all 
classes  of  society,  a  few  voids  on  its  effect  upon  the  system  in  this  con- 
nection appear  appropriate  The  active  principle  of  tobacco  is  a 
poisonous  alkaloid,  nicotia,  consisting  of  C10H]4N2.  The  results  of  Dr. 
Hammond's  experiments  seem  to  show  that  under  the  use  of  tobacco 
the  elimination  by  the  kidneys  of  the  uric  and  phosphoric  acids  is  in- 
creased, but  that  the  feces  and  urine  are  diminished,  the  exhalation  of 
carbonic  acid  being  only  slightly  affected.  While  the  excessive  use  of 
tobacco  no  doubt  produces  a  state  of  wakefulness,  trembling,  and  nervous 
excitement,  it  cannot  be  denied  that  when  moderately  used  it  is  often 
very  beneficial,  quieting  and  soothing  the  nervous  system  when  ex- 
hausted by  bodily  and  mental  effort,  and  even  in  ordinary  circumstances 
producing  a  general  tranquillizing  effect. 

Tobacco  seems  also  to  promote  digestion,  stimulating  the  secretion  of 
the  gastric  juice,  perhaps  by  reflex  action,  hence  the  common  custom  of 
smoking  a  cigar  after  breakfast  or  dinner. 

Alcohol. — Before  considering  the  use  of  wines,  malt  liquors,  and 
spirits,  it  is  necessary  to  learn,  if  possible,  the  effects  of  pure  alcohol 
upon  the  human  body,  since  this  principle  is  contained  in  large  or  small 
quantities  in  all  such  fluids.  Alcohol  chemically  consists  of  C2H60, 
and  the  first  question  to  be  investigated  is.  What  becomes  of  it  when 
taken  into  the  system?  Some  experimenters,  like  Anstie  and  Dupre, 
found  very  little  alcohol  in  the  excretions,  it  appearing  to  be  oxidized, 
burnt  up;  according  to  others,  however,  like  Percy,  Lallemand,  Perrin, 
and  Ducroy,1  alcohol  is  found  in  the  ventricles  of  the  brain  unchanged, 
and  is  eliminated  by  the  lungs,  skin,  and  kidneys. 
'  It  is  possible  that  these  contradictory  results  may  be  due  to  the  dif- 
ferent amounts  of  alcohol  given,  to  the  length  of  time  that  it  has  been 
in  the  system,  and  that  under  certain  circumstances  it  is  in  part  con- 
sumed and  in  part  excreted.  In  either  case,  however,  alcohol  can  be  of 
no  benefit  to  the  system,  for  if  it  is  found  as  such  untransformed  in  the 
organs  or  excreted  unchanged,  it  cannot  supply  any  want,  simply  passing 
through  the  system,  and  if  it  is  burnt  up  it  must  interfere  with  the 
oxidation  of  other  substances,  such  as  fat,  etc.,  which  under  ordinary 
circumstances  would,  through  combustion,  disappear.  If  this  view  be 
correct,  Ave  have  an  explanation  of  hard  drinkers  becoming  often  so  fat, 
the  alcohol  being  burnt  in  preference  to  their  fat,  and  so  allowing  their 
fat  to  accumulate  in  the  muscles,  in  the  liver,  heart,  etc.,  or,  what  is 
more  likely,  the  alcohol  in  some  way  interferes  with  that  splitting  of 
food  or  tissue  that  normally  precedes  its  oxidation. 

Alcohol  can  never  substitute  the  natural  drink  of  man,  water.  Many 
substances  which  are  soluble  in  the  latter  are  precipitated  by  the  former, 
and.  hence,  useless  to  the  system  ;  further,  it  does  not  supply  any  prin- 
ciple to  the  tissues. 

Alcohol,  in  diminishing  the  amount  of  urea  excreted  and  the  action 
of  the  skin,  and  in  interfering  with  natural  combustion,  perverts  the 
whole  nutrition  of  the  body.  The  active  changes  and  the  rapid  removal 
of  the  effete  matters,  so  characteristic  of  healthy  life,  are  retarded  by 

1  Carpenter' d  Physiology,  1876,  p.  107. 


96  QUALITY    AND    QUANTITY    OF    FOOD. 

alcohol;  hence,  the  susceptibility  to  zymotic  poisoning  of  the  dram 
drinker  and  his  chronic  diseases.  It  is  well  known  also  that  less  food 
is  taken  when  alcohol  is  used,  and  so  alimentation  is  affected.  It  is 
often  urged  that  alcohol  "  will  keep  the  cold  out,"  but  as  the  cutaneous 
vessels  dilate  under  the  use  of  alcohol  through  paralysis  of  the  vaso- 
constrictor nerves  more  blood,  and  therefore  more  heat,  comes  to  the 
surface,  which  instead  of  being  retained  within  the  body  as  it  would 
otherwise  be,  escapes,  the  natural  effect  of  the  cold  being  to  contract 
the  vessels  and  of  so  keeping  the  heat  in  the  body.  Whether  this  be 
the  true  explanation  or  not,  the  fact  remains  the  same,  that  Arctic 
voyagers  keep  the  cold  out  far  better  without  .the  use  of  alcohol  than 
with  it.1  Finally,  in  addition  to  these  facts,  when  it  is  remembered 
that  many  persons  preserve  their  mental  and  bodily  health  perfectly 
without  ever  touching  alcohol,  it  is  difficult  to  offer  a  single  good  phy- 
siological reason  for  the  use  of  alcohol  at  any  time,  the  body  being  in 
health. 

It  must  not  be  forgotten,  however,  that  almost  every  people,  savage 
or  civilized,  use  alcohol  in  some  form  or  another.  Whether  some,  as 
yet  unknown,  want  is  supplied  to  the  system  by  alcohol,  or  whether  it 
is  used  merely  to  drown  sorrow  or  to  relieve  ennui,  is  an  undecided 
question.  Among  civilized  people  life  is  so  artificial  and  man  is  so 
harassed  bodily  and  mentally  that,  unfortunately,  perfect  health  is  far 
from  being  common.  Life  at  times  becomes  weary,  the  heart  feels 
oppressed,  digestion  is  sluggish,  the  circulation  impeded,  muscular 
languor  is  present,  then  alcohol  is  useful,  for  it  is  a  nervo-muscular 
stimulant.  The  action  of  the  heart  is  accelerated,  the  blood  flows  more 
rapidly,  the  heart  is  relieved,  and  good  results  from  its  use.  Every 
physician  knows  that  in  those  dark  hours  when  life  hangs  upon  a 
thread,  that  alcohol  is  often  the  only  remedy  that  has  dragged  the  poor 
sufferer  out  of  the  jaws  of  death — the  good  effects  of  its  temporary 
action  bridging  over  such  critical  periods.  As  a  medicine,  alcohol  is 
indispensable ;  when  used  for  any  other  purpose,  little  or  nothing  can 
be  said  in  its  favor. 

The  action  of  alcohol  is  different  in  many  respects  from  tea  or  coffee. 
Alcohol  narcotizes  the  sympathetic,  tea  and  coffee  excite  the  cerebro- 
spinal nervous  system  ;  the  former  stupefies,  while  the  latter  brightens 
the  intellect:  the  one  inebriates  and  destroys,  the  other  cheers  and 
preserves. 

Distilled  Liquors,  Wine,  Malt  Liquors. — The  distilled  hquors 
most  commonly  used  are  brandy,  wdiiskey,  gin,  and  rum.  They 
contain,  as  a  rule,  a  little  more  than  50  per  cent,  of  alcohol,  and  hence, 
when  abused,  their  bad  effects.  Brandy,  the  most  valuable  of  them  as 
a  medicine,  is  obtained  by  the  distillation  of  wine ;  whiskey  from  rye, 
wheat,  etc. ;  gin,  from  different  grains  rectified  by  juniper,  and  rum 
from  molasses.  Brandy,  wdiiskey,  and  gin  diminish  the  amount  of 
carbonic  acid  exhaled,  and  so  interfere  with  vital  processes.  Rum, 
however,   increases  the   carbonic  acid   exhaled,  and,   therefore,   is  less 

1   I  lays  :  American  Journal  of  the  Medical  Sciences,  1850. 


DISTILLED    LIQUOES,    WINE,    MALT    LIQUORS.  97 

hurtful  in  its  effects.     It  has  long  been  noticed  that  the  rum-drinker 
lives  longer  than  the  brandy  or  gin-drinker. 

Table  XXXI.1—  Composition  of  Wine. 

Water. 

Alcohol. 

Bouquet. 

Sugar. 

Gum. 

Extractives. 

Gluten  (except  where  tannin  is  present). 

Acetic  acid. 

Bitartrate  of  potassium. 

Tartrate  of  potassium  and  aluminium  (in  German  wines). 

Sulphate  of  potassium. 

Potassium  and  sodium  chlorides. 

£a?ni.n  f+     }  in  red  wines. 

Coloring  matter  j     • 

Carbonic  acid  (in  champagne). 

Wine,  or  the  fermented  juice  of  the  grape,  is  called  full-bodied  or 
light,  according  to  the  amount  of  alcohol  present.  There  is  always  less 
alcohol  in  wines  than  in  the  distilled  liquors  just  mentioned  ;  thus  port, 
Madeira,  and  sherry  contain  from  15  to  25  per  cent,  of  alcohol ;  claret, 
sauterne,  hock,  about  10  to  15  per  cent.  In  countries  where  the  light 
wines  are  used  by  all  classes  of  society,  the  horrible  effects  of  spirituous 
liquors  are  almost  unknown,  the  per  cent,  of  alcohol  being  so  small  in 
light  wines. 

Wine,  as  seen  from  Table  XXXI.,  contains,  in  addition  to  alcohol, 
sugar,  gluten,,  and  a  number  of  salts,  etc.  Wine  is  nutritious  in 
proportion  to  the  amount  in  which  these  substances  are  present.  In 
the  preparation  of  many  wines,  like  champagne,  the  amount  of  carbonic 
acid  is  increased  ;  hence,  their  great  use  as  diffusible  stimulants  in  those 
cases  where  the  vital  powers  demand  prompt  and  active  stimulation. 
Under  such  circumstances  there  is  no  better  medicine  than  champagne. 


Table  XXXII.2 — Composition  of  Beee. 


Water  .... 

Alcohol       .... 
Dextrin,  glucose,  etc. 
Nitrogenized  substances     . 
Mineral  salts 
Bitter  principle  not  determined 


947.00 

4.50 

41.40 

5.26 

1.84 


1000.00 


Beer,  ale,  and  porter  are  made  from  malted  barley,  with  the  addition 
of  hops.  All  malt  liquors  contain  alcohol ;  about  1  to  4  per  cent,  in 
the  weaker,  and  from  6  to  8  per  cent,  in  the  stronger  kinds.  Even  as 
much  as  12  per  cent,  is  found  in  the  heavy  English  beers. 

Table  XXXII.  gives  the    composition  of  the  ordinary  French  beer, 


1  Pereira  :  A  Treatise  on  Food  and  Diet,  1843,  p.  502. 

-  Payen:  Substances  Alimentaires,  p.  462.     In  the  original  table  of  Payen,  957  is  given,  instead  of  947, 
probably  a  typographical  error. 


98  QUALITY    AND    QUANTITY    OF    FOOD. 

whioh  will  serve  as  an  example  of  malt  liquors  generally.  A  most 
noticeable  feature  is  the  small  amount  of  alcohol,  and  the  very  large 
quantity  of  glucose,  etc.  There  are  also  nitrogenized  substances, 
mineral  salts,  and  a  bitter  principle.  Apart  from  the  alcohol  they 
contain,  malt  liquors  are  nutritious  on  account  of  these  carbohydrate 
and  nitrogenized  and  inorganic  principles.  They  are  often  of  great 
service  to  persons  who  have  run  down,  are  debilitated,  or  who  are  slowly 
recovering  from  some  exhausting,  low  type  of  disease,  being  taken 
then  as  medicine.  In  such  cases  the  small  quantity  of  alcohol  in  the 
malt  liquor  is  beneficial,  acting  as  a  stimulant,  the  hops  are  useful  as 
a  tonic,  and  the  remaining  principles  as  food. 

It  will  be  seen  from  what  has  been  said  of  alcohol  that  the  evil 
resulting  from  the  abuse  of  liquors  of  all  kinds  is  proportional  to  the 
amount  that  is  present  of  this  principle,  that  malt  liquors  and  light 
wines  are  less  injurious  than  brandy  and  whiskey,  and  that  beer,  ale, 
etc.,  containing  so  many  nutritious  principles,  closely  approximate  to 
the  true  idea  of  a  food.  The  importance,  however,  of  remembering  that 
the  malt  liquors  also  contain  alcohol,  and  in  sufficient  quantities  to  do 
mischief  if  too  freely  partaken  of,  will  be  appreciated  when  it  is  learned 
that  1,076,844,942  gallons  of  beer  were  consumed  in  1873  in  Great 
Britain,  in  addition,  to  spirits,  wine,  cider,  etc. 

Alcohol  cost  the  United  States,  in  ten  years,  directly,  $600,000,000; 
indirectly,  $600,000,000  more ;  destroyed  300,000  lives,  sent  150,000 
people  to  prisons  and  work-houses,  100,000  children  to  the  poor-house, 
drove  1000  insane,  determined  2000  suicides,  caused  loss  by  fire  or 
violence  of  $10,000,000  of  property,  made  200,000  widows,  and 
1,000,000  orphans.1 

With  such  an  array  of  figures  it  cannot  be  considered  superfluous 
that  attention  has  been  called  to  the  effect  of  alcohol  in  its  relation  with 
food. 

1  De  Marmon  :  New  York  Medical  Journal,  December,  1870. 


CHAPTEE    YI. 


DIGESTION. 


In  order  that  the  food  should  fulfil  its  functions  in  the  economy  it 
must  be  assimilated,  and  before  that  can  be  accomplished  the  food  must 
be  first  digested  and  then  absorbed.  Digestion  should,  therefore,  be 
studied  first. 

Under  the  general  term  digestion  are  included  several  processes : 
the  prehension  of  food,  its  mastication  and  insalivation,  deglutition,  the 
changes  effected  in  the  food  during  its  passage  through  the  stomach, 
the  small  and  large  intestine,  and  defecation. 

While  the  various  and  often  complicated  ways  in  which  the  lower 
animals  take  their  food  are  interesting  to  the  comparative  physiologist, 
the  description  of  which  would  require  a  detailed  account  of  the  organs 
involved,  it  is  unnecessary  for  me  to  dwell  upon  the  simple  process  as 
observed  in  man.  In  sucking,  however,  it  may  be  mentioned  that  this 
process  is  due  to  the  tongue  acting  like  a  piston,  since  when  the  velum 
is  applied  to  the  back  of  the  tongue  and  the  mouth  closed  posteriorly  a 
tendency  to  a  vacuum  is  made,  the  lips  at  the  same  time  closing  around 
the  nipples  anteriorly.  In  drinking  the  action  is  essentially  the  same, 
except  where  the  head,  being  thrown  back  and  the  liquid  poured  in,  it 
is,  so  to  speak,  tossed  off.    « 

Mastication. 

The  chewing  of  food,  or  mastication,  is  effected  by  the  teeth,  which, 
in  the  adult  condition,  are  thirty-two  in  number,  viz.,  eight  incisors, 
four  canines,  eight  premolars,  and  twelve  molars.  A  tooth  is  usually 
described  as  having  three  parts.  That  portion  which  is  seen  in  the 
mouth  is  called  the  crown.  The  tapering  portion  inserted  in  the  socket, 
or  alveolus  of  the  jaw,  is  the  root  or  fang,  and  is  held  in  position  by 
fibrous  tissue  continuous  with  the  periosteum  of  the  jaw  and  submucous 
tissue  of  the  gum.  The  intermediate  constricted  part  of  the  tooth 
between  the  crown  and  the  fang  is  known  as  the  neck,  the  accumulation 
of  fibrous  tissue  at  this  position  being  called  the  dental  ligament. 

The  incisor  or  cutting  teeth  (Fig.  16)  four  in  each  jaw,  are  nearest 
to  the  middle  line  in  front  of  the  jaw.  They  are  inserted  in  their 
sockets  by  a  single  fang.  The  crown  of  the  tooth  is  Avedge-shaped, 
and  presents  a  wide,  sharp,  and  chisel-like  edge,  its  lingual  or  inner 
surface  is  concave  from  above  downward.  In  the  upper  jaw  the  central 
incisors  are  larger  than  the  lateral  ones,  whereas,  in  the  lower  jaw  the 
lateral  are  larger  than  the  central  ones.  The  incisors  are  well  adapted 
to  cut  and  bite  the  food. 


100 


DIGESTION, 


The  tooth  next  to  the  lateral  incisors  in  both  jaws  is  called  the  canine 
(Fig.  17),  and  corresponds  to   the  large  tearing  and   holding  tooth  in 


Fig.  16. 


Fig.  17. 


Incisor  teeth  of  the  upper  and  lower  jaws. 
a.  Front  view  of  the  upper  and  lower  middle  in- 
cisors. 6.  Front  view  of  the  upper  and  lower 
lateral  incisors,  c.  Lateral  view  of  the  upper 
and  lower  middle  incisors,  showing  the  chisel 
shape  of  the  crown  ;  a  groove  is  seen  marking 
slightly  the  fang  of  the  lower  tooth.    (Quain.) 


Fig.  19. 


Canine  tooth    of  the  upper  jaw.     a.  Front  view.     b. 
Lateral  view,  showing  the  long  fang  grooved  on  the  side. 

the  dog,  and  hence  its  name.  The 
canine  teeth,  four  in  number,  are  larger 
than  the  incisor  teeth.  The  crown  is 
conical  and  bevelled  behind,  the  fang 
is  longer  than  in  any  of  the  other  teeth, 
and  laterally  exhibits  a  slight  furrow, 
as  if  indicating  a  tendency  to  subdivide 
into  two.  The  upper  canine  or  eye 
teeth  are  larger  and  longer  than  the 
lower  ones.  The  latter  are  often 
called  the  stomach  teeth.  The  canine  teeth  assist 
the  incisors  in  dividing  the  food. 

The  premolars,  two  in  each  jaw  (Fig.  18),  succeed 
the  canine.  They  are  shorter  and  thicker  than  the 
latter.      The  crown   is  cuboidal,  convex   externally 

and  internally,  and  exhibits  upon 

the  triturating  surface  two   emi- 
nences or  cusps,  hence  their  name 

of  bicuspids.     The  fang  is  conical 

and  flattened,  and  deeply  grooved. 

The  upper  premolars  are  larger 

than    the    lower  ones,  and  their 

fang  is  more  or  less  subdivided 

into  two. 

The    premolar    teeth   are  suc- 
ceeded  by  the   twelve  molar    or 

grinding  teeth,  six  in  each  jaw. 

The  molar  tooth  (Fig.  19)  has  a 

cuboid  crown.       The  triturating 

surface  in  the  upper  molars  at  the 

four  angles  is  elevated  into  four 

tubercles  with  a  diagonal    ridge 


Fig.  18. 


First  bicuspid  tooth  of 
the  lower  jaw.  a.  Front 
view.  6  Lateral  view, 
showing  the  lateral 
groove  of  the  fang  and 
the  tendency  in  the 
upper  to  division.  (Quain 
and  Sharpey.) 


First  molar  tooth  of 
the  upper  and  lower 
jaws.  They  are  viewed 
from  the  outer  aspect. 
(Quain  and  Sharpey.) 


MASTICATION.  101 

connecting  two  of  them.  In  the  lower  molars  there  are  five  tubercles 
or  cusps,  two  on  the  inner  side  and  three  on  the  outer.  The  upper  molars 
are  inserted  in  their  sockets  by  a  pair  of  conical  fangs,  the  lower  ones 
by  three  fangs,  two  external  and  one  internal,  the  latter  is  the  largest 
and  grooved.  The  first  molar  tooth — that  is,  the  one  most  anteriorly 
situated — is  the  largest,  the  third,  or  the  wisdom  tooth,  the  smallest. 
Often,  however,  in  the  savage  races  of  mankind,  in  the  milk  teeth  of 
civilized  races,  in  the  fossil  man,  and  in  the  monkeys,  the  last  molar 
is  the  largest.  It  is  by  means  of  the  molar  teeth  that  the  food  is 
crushed  and  ground  up. 

During  mastication  the  external  tubercles  of  the  lower  molars  are 
opposed  to  those  of  the  upper  ones,  and  through  the  lateral  motion  of 
the  lower  jaw  inward,  the  external  tubercles  pass  down  the  inclined 
surfaces  of  the  external  ones  and  up  those  of  the  internal  tubercles  of 
the  upper  teeth,  crushing  the  substances  between  them. 

The  teeth  are  arranged  in  the  jaw  somewhat  in  the  form  of  a  curve. 
In  savage  races,  on  account  of  the  prominence  of  the  canine  teeth,  the 
curve  is  rather  of  an  oblong  form,  and  in  civilized  races  the  curve  is 
often  V-shaped.  The  incisor  teeth  of  the  upper  jaw  overlap  those  of 
the  lower,  and  the  external  cusps  of  the  premolars  and  molar  teeth 
close  outside  those  of  the  lower  jaw.  It  will  be  also  observed  that  the 
central  incisors  of  the  upper  jaw  extend  over  the  central  and  half  of  the 
lateral  incisors  of  the  lower  jaw,  whilst  the  upper  lateral  incisors  come 
in  contact  with  the  outer  half  of  the  lower  laterals  and  the  anterior  half 
of  the  lower  canines.  The  canine  teeth  of  the  upper  jaw  extend  over 
half  of  the  lower  canines  and  half  of  the  lower  first  premolars.  The 
first  premolar  of  the  upper  jaw  is  opposed  to  the  half  of  the  first  pre- 
molar and  half  of  the  second  premolar  of  the  lower  jaw,  whilst  the 
second  upper  premolars  impinge  upon  the  posterior  half  of  the  second 
premolar  and  anterior  half  of  the  first  molar  of  the  lower  jaw.  The 
first  molar  of  the  upper  jaw  is  opposed  to  the  posterior  two-thirds  of  the 

Fig.  20. 


Skull  of  lion.     (Owes.) 


first  molar  and  anterior  third  of  the  second  molar  of  the  lower  jaw. 
The  second  upper  molar  impinges  upon  the  posterior  third  of  the  second 
and  anterior  third  of  the  last  molar  of  the  lower  jaw.  The  last  molar 
in  the  upper  jaw  is  opposed  by  that  part  of  the  third  molar  in  the  lower 
jaw  which  remains  uncovered  by  the  second  upper  molar. 


102 


DIGESTION, 


Skull  of  Indian  rhinoceros.     (Owen.) 


By  this  disposition  it  will  be  seen  that  no  two  teeth  are  opposed  to 
each  other  only,  and  that,  with  the  exception  of  the  last  molar,  ouch 

tooth  in  the  upper  jaw  is  op- 
posed to  two  teeth  in  the  lower 
one.  If  a  tooth  is  lost,  or  even 
two  alternate  ones,  the  remain- 
ing teeth  will  therefore  he  still 
useful. 

If  the  teeth  of  man  be  com- 
pared with  those  of  a  carnivor- 
ous animal,  like  a  lion  (Fig. 
20),  or  with  those  of  a  herbiv- 
orous one,  like  a  rhinoceros 
(Fig.  21),  it  will  be  noticed  that 
in  man  the  teeth  are  both  of 
the  carnivorous  and  herbivor- 
ous kinds,  and  pretty  evenly 
developed,  whereas,  in  the  lion,  on  the  one  hand,  the  teeth  are  all  of 
the  biting,  cutting,  and  tearing  character;  while  in  the  rhinoceros, 
on  the  other  hand,  the  largest  teeth  are  of  the  grinding  and  crushing 
character.     The  teeth  of  the  carnivorous  lion  and  herbivorous  rhinoceros 

are  in  harmony  with  the  nature 
Fig.  22.  of  their  food. 

One  would  infer  from  the  fact 
of  man  possessing  both  incisor 
and  molar  teeth  that  his  food  had 
consisted  from  time  immemorial 
of  both  animal  and  vegetable 
origin.  This  confirms  what  we 
have  already  learned  from  the 
chemistry  of  the  food,  that  the 
diet  of  man  should  be  a  mixed 
one. 

On  making  a  longitudinal  sec- 
tion  of  a  tooth,  of  a  molar  for 
example  (Fig.  22),  it  will  be  ob- 
served that  there  is  a  cavity 
within  the  crown  of  the  tooth 
which  extends  into  and  through 
the  fangs  opening  by  a  small 
aperture  at  their  apices.  This 
space  is  the  pulp  cavity,  and 
contains,  in  the  living  tooth,  the 
pulp.  The  tooth  will  be  also 
seen  from  such  a  section  to  con- 
sist of  three  parts,  dentine  or  ivory,  a  yellowish-white  substance  border- 
ing the  pulp  cavity,  enamel,  a  harder  and  whitish  substance  capping 
the  crown,  cement,  a  translucent  bony-like  layer  encrusting  the  roots. 

The  dentine  constitutes  the  great  bulk  of  the  tooth,  chemically  it  con- 
sists of  about  twenty-eight  parts  of  animal  matter  (tooth  cartilage),  and 
seventy-two  of  earthy  salts,  among  the  latter  are  principally  found  cal- 


Section  of  human  molar  tooth  magnified     (Owen.) 


ENAMEL. 


108 


cium  phosphate,  some  calcium  carbonate  and  magnesium  phosphate. 
When  examined  with  the  microscope  dentine  (Fig.  23)  is  seen  to  consist 
of  an  amorphous  translucent  matrix,  in  which  are  imbedded  numerous 
canals  or  tubes,  whose  walls  are  distinct  from  the  matrix.  These  latter 
are  the  dental  or  dentinal  tubules,  and  average  in  diameter  at  their  com- 
mencement 45100th  of  an  inch.  The  intermediate  space  between  the 
adjacent  tubules  is  about  three  times 
their  diameter.      The  dental    tubules  ^IG-  2?>- 

open  at  their  inner  ends  or  begin- 
nings into  the  pulp  cavity,  outwardly 
they  pass  to  the  periphery  of  the  tooth. 
The  tubules  run  generally  in  a  parallel, 
but  somewhat  wavy  course.  As  they 
pass  outward  they  become  gradually 
narrower,  dividing  and  subdividing, 
giving  off  innumerable  small  branches, 

Fig.  24. 


a.  Dentine,     b.  Odontoblastic  cells,     c.  Fibres. 
(Tomes.) 

which  anastomose  or  end  blindly. 
Some  of  the  terminal  branches  pass 
into  the  canalicula  of  the  cement,  others 
into  the  so-called  interglobular  spaces, 
irregular  cell-like  cavities  in  the  ma- 
trix. The  walls  of  the  dental  tubules 
are  about  as  thick  as  their  calibre.  In 
the  living  tooth  the  dental  tubules  are 
filled  with  the  dental  fibres,  which  are 
prolongations  from  the  odontoblastic 
cells  of  the  pulp  (Fig.  24).  These 
dental  fibres  are  possibly  the  terminal  filaments  of  the  nerves  supplying 
the  tooth.  The  contour  markings  observed  in  the  teeth  are  due  to 
irregularities  in  the  matrix  or  intertubular  substance. 

As  age  advances  there  is  deposited  upon  the  inner  surface  of  the 
dentine  a  secondary  kind  of  dentine,  known  as  osteo-dentine,  which 
resembles  both  dentine  and  bone.  This  appears  to  be  due  to  a  sort  of 
ossification  of  the  pulp,  the  effect  of  which  is  gradually  to  obliterate 
the  latter  and  the  pulp  cavity. 

Enamel. — The  crown  of  the  tooth  is  covered  with  the  enamel,  the 
hardest  of  organic  substances.  It  is,  however,  gradually  worn  down 
by  protracted  use.     The  enamel  is  thickest  upon  that  part  of  the  tooth 


Section  of  fang,  parallel  to  the  dentinal 
tubules  (human  canine).  Magnified  300  diam- 
eters. 1.  Cement,  with  large  hone-lacuna; 
and  indications  of  lamella;.  2.  Granular 
layer  of  Purkinje  (interglobular  spaces).  3. 
Dentinal  tubules.     (Waldeyer.) 


104 


DIGESTION. 


Fig.  25. 


:£?> 


most  used  in  trituration,  here  it  exists  in  several  layers ;  it  is  thinnest 
at  the  roots,  where  it  gradually  disappears. 

Chemically,  enamel  consists  of  about  five  parts  of  animal  matter,  and 
ninety-five  of  earthy  constituents,  the  latter  being  mostly  calcium  phos- 
phate. Microscopically,  enamel  consists  of  solid  six-sided  prisms,  the 
enamel  fibres  having  an  average  diameter  of  g  fo  0th  of  an  inch,  and  a 
length  of  101()0th  of  an  inch.  Each  prism  rests  by  its  inner  end  upon 
the  dentine,  the  outer  end  being  covered  with  the  cuticle  of  the  teeth. 
Usually  there  are  sevei'al  layers  of  enamel  prisms, 
the  outer  layer  being  then  covered  with  the  cuticle. 
The  prisms,  while  arranged  in  a  parallel  manner, 
do  not  run  in  an  exactly  straight  direction,  the 
course  being  rather  an  undulating  one.  The 
prisms,  when  viewed  horizontally  from  their  outer 
ends,  present  a  tessellated  appearance  (Fig.  25). 
The  so-called  cuticle  of  the  teeth,  or  membrane  of 
Nasmyth,  just  referred  to  as  covering  the  outer 
ends  of  the  enamel  prisms  or  fibres,  averages  about 
the  15  ^00th  to  the  -3  oWo~th  of  an  inch  in  thickness. 
It  acts  as  a  protective  covering  to  the  enamel. 
By  some  histologists  the  cuticle  of  the  teeth  is 
regarded  as  a  very  thin  cement. 

Cement. — The  crusta  petrosa  or  cement  covers  the  roots  of  the  teeth, 
beginning  at  the  neck  as  a  thin  layer  and  becoming  gradually  thicker 


Section  of  enamel,  highly 
magnified,  at  right  angles  to 
the  course  of  its  columns  ; 
exhibiting  the  six-sided  char- 
acter of  the  latter     (Leidy.) 


Fig.  20. 


ace 


a.i 


pi 


Mnlar  tooth  of  horse  ae.  Antero-external  ;  pe,  Postero-external  ; 
ai  Anter. .-internal  ;  pi.  Postero-external  or  principal  cusps  respec- 
tively. ;/.  External  vertical  rib.  x.  An  anterior  cingular  cusp. 
ace,  pec.  Anterior  and  posterior  cross-crests.     (Wortman.i 

at  the  fan£S.  It  adheres  verv  closely  to  the 
dentine  and  to  the  periosteal  lining  of  the 
alveoli.  Cement  differs  from  bone  in  its 
lacunae  being  more  variable  in  their  form  and 
size,  and  their  canicula  being  larger  and  more 
numerous.  In  many  animals,  like  the  cat, 
dog,  and  hog,  the  dentine,  cement,  and  enamel  are  disposed  as  in  man. 
In  the  grinding  teeth  of  the  herbivora,  however,  as  in  those  of  the 
elephant  (Fig.  26),  horse  (Fig.  27),  the  dentine,  enamel,  and  cement 


Molar  tooth  of  African  elephant. 
e.  Enamel,  d.  Dentine,  c.  Cement. 
(Owen.) 


MAXILLARY    BONES.  105 

alternate  with  each  other  in  such  a  way  that  as  the  teeth  are  worn  an 
uneven  triturating  surface  is  always  maintained. 

Tooth  Pulp. — The  pulp  of  the  tooth  situated  in  the  pulp  cavity  is 
not  only  the  formative  organ  of  the  tooth,  but  the  source  of  its  vascular 
.and  nervous  supply ;  the  tooth-pulp  consisting  of  cells,  bloodvessels, 
nerves,  and  a  small  quantity  of  connective  tissue. 

The  cells  are  most  numerous  on  the  surface  of  the  pulp.  In  this 
position  they  are  known  as  odontoblasts  and  the  layers  formed  by 
them  as  the  membrana  eboris.  The  odontoblastic  cells  exhibit  three 
kinds  of  processes :  Those  passing  internally  into  the  pulp,  others 
which  serve  to  connect  adjacent  cells,  and  those  already  referred  to  as 
being  prolonged  into  the  dentinal  tubules.  The  bloodvessels  pass  in 
and  out  by  the  openings  in  the  apex  of  the  tooth,  forming  beneath  the 
odontoblastic  layer  a  capillary  network.  The  nerves  enter  by  the  fang 
of  the  tooth  and  after  giving  off  a  few  branches  form  a  plexus  beneath 
the  odontoblastic  layer.  The  exact  manner,  however,  in  which  the 
nerves  terminate  in  the  teeth  is  not  known,  unless,  as  already  men- 
tioned, the  dental  fibres  are  of  a  nervous  character.  The  teeth  of  the 
upper  jaw  are  supplied  by  branches  from  the  superior  maxillary  nerve, 
those  of  the  lower  by  the  inferior  maxillary. 

No  lymphatics,  as  yet,  have  been  found  in  the  tooth  pulp,  or  in  other 
parts  of  the  teeth.  As  age  advances,  the  pulp  of  the  tooth  diminishes 
in  size  through  its  gradual  calcification,  the  odontoblastic  layer  atrophies, 
the  connective  tissue  increases,  the  capillary  network  disappears,  the 
nerves  exhibit  a  fatty  degeneration,  and  the  pulp  ultimately  becomes  a 
dried-up,  insensitive  mass. 

Although  the  pulp  may  lose  entirely  its  vitality,  yet  the  enamel  and 
dentine  may  remain  serviceable,  they  appearing  to  be  perfected  struc- 
tures. These  are,  however,  never  reproduced  when  destroyed  by  wear 
or  decay  or  by  loss  of  the  tooth,  with  the  rare  exception  of  where  a  tooth 
is  reproduced  for  the  third  time. 

The  way  in  which  the  teeth  are  developed  and  the  manner  in  which 
the  permanent  teeth  are  preceded  by  the  deciduous  or  milk  set,  will  be 
considered  under  the  subject  of  reproduction. 

Maxillary  Bones  and  Temporo-maxillary  Articulation. — 
The  teeth  in  man  and  mammalia  are  confined  to  the  maxillary  bones,  in 
which  they  are  imbedded,  the  bone  being  moulded  so  to  speak,  around 
the  roots  of  the  teeth  after  these  are  developed  and  so  forming  the 
sockets.  Between  the  jaw  and  the  tooth  there  is  a  space  which  in  the 
living  tooth  is  filled  up  by  the  alveodental  periosteum.  Through  the 
elasticity  of  this  root  membrane  the  tooth  possesses  a  certain  amount  of 
motion.  Were  the  teeth  immovably  fixed  in  their  sockets  some  shock 
would  be  felt  during  mastication.  This  alveodental  periosteum,  which 
passes  imperceptibly  into  the  gum  and  periosteum,  consists  of  connective 
tissue  in  which  are  found  nerves  and  vessels.  There  is  also  no  sharp 
line  of  demarcation  between  the  gum  and  the  mucous  membrane  of  the 
mouth  on  the  one  hand  and  the  periosteum  on  the  other. 

Of  the  maxillary  bones  the  superior,  from  being  immovably  articulated 
with  the  other  bones  of  the  head,  are  only  passive  in  mastication.  The 
upper  teeth,  however,  offer  fixed  surfaces,  against  which  those  of  the 
lower  jaw  are  brought  into  apposition. 


106 


DIGESTION, 


Intermaxillary  Bone. — If  the  inner  surface  of  the  superior  max- 
illary bone  be  examined  between  the  middle  line  and  alveolar  margin, 
in  most  instances  a  suture  will  be  readily  recognized  running  downward 
and  outward  from  the  anterior  palatine  foramen  to  the  outer  margin  of 
the  second  incisor  tooth.  This  suture  is  interesting  from  several  points 
of  view,  among  others,  as  indicating  in  the  embryo  the  distinction  ex- 
isting between  the  true  superior  maxillary  bones  and  the  intermaxillary 
bones,  the  latter  being  characterized  by  carrying  the  incisor  teeth.  As 
development  advances,  however,  in  man  and  to  a  great  extent  also  in 
monkeys,  the  superior  maxillaries  coalesce  to  such  an  extent  with  the 
intermaxillaries  that  the  primitive  distinction  between  the  bones  is 
almost  entirely  lost,  in  some  instances  the  suture  itself  even  disappearing. 
In  the  other  mammalia,  however,  the  intermaxillaries  remain  quite 
distinct  from  the  superior  maxillaries  and  each  other,  and  are  readily 
disarticulated.     It  was  this  latter  circumstance  that  led  Goethe,1  equally 

Pig.  28. 


Antero-posterior  section  of  the  temporo-maxillary  articulation  of  the  right  siile.     (A.  T  )  }£.     (Quain.) 

great  as  a  poet  and  naturalist,  to  look  for  and  discover  the  intermaxillary 
bone  in  man,  so  convinced  was  he  that  the  skull  consisted  of  the  same 
bones  in  all  the  mammalia. 

The  inferior  maxillary  bone,  mandible  or  lower  jaw,  consists  in  the 
adult  of  a  single  piece  movably  articulated  with  the  temporal  bone 
(Fig.  28).  This  articulation  is  really  a  double  joint,  since  there  is 
interposed  between  the  condyle  and  the  glenoid  cavity  a  biconcave 
oblong  piece  of  fibro-cartilage  to  the  edges  of  which  is  attached  the 
capsular  ligament.  The  spaces  on  either  side  of  the  cartilage  are  lined 
with  synovial  membrane,  and  there  is  no  connection  between  the  two 
cavities  unless  the  cartilage  is  perforated.  When  the  jaw  is  simply 
depressed,  the  joint  acts  as  a  hinge.  Through  the  movement  of  the 
condyle  on  the  eminentia  articularis,  the  forward  and  lateral  motions  of 
the  jaw  are  affected.      The  mechanism  of  the  temporo-maxillary  articu- 


1  Sammtliche  Werke,  Baud  vi.,  Osteologie,  S.  65. 


INTERMAXILLARY    BONE. 


107 


lation  is  therefore  such  as  to  insure  great  freedom  of  motion  to  the  lower 
jaw.  The  lateral,  forward,  and  depressing  actions  of  the  jaw  either  suc- 
ceed each  other  or  are  variously  combined  during  the  mastication  of  food. 

Fig.  29. 


Jaws  of  tiger 

Fig.  30. 


Condyle. 


Upper  and  lower  jaw  of  sheep.     (Owen.  I 


If  the  condyle  of  the  jaw  in  a  carnivorous  animal  be  examined,  in  a 
tiger,  for  example  (Fig.  29),  it  will  be  noticed  that  its  long  diameter  is 
transverse,  and  that  the  glenoid  cavity  is  grooved,  hollowed  out,  so  as 


108 


DIGESTION 


to  receive  it.  This  disposition  is  carried  out  to  such  an  extent  in  the 
badger  that  the  lower  jaw  will  remain  depressed,  interlocked,  within  the 
glenoid  cavity,  even  though  all  the  ligaments  be  cut  away.  The  motion 
of  the  lower  jaw  in  many  of  the  carnivora  is  almost  exclusively  of  an 
up  and  down  character,  there  being  little  or  no  lateral  motion.  In  the 
herbivora,  however,  as  in  the  sheep,  rhinoceros,  etc.,  it  is  the  lateral 
motion  of  the  lower  jaw  that  is  evident  in  chewing.  In  such  animals 
the  glenoid  cavity  is  rather  shallow  and  the  condyle  oblong  or  ovate 
(Fig.  30).  The  motion  of  the  jaw  in  the  rodentia  differs  from  that 
observed  both  in  the  carnivora  and  herbivora,  being  backward  and  for- 
ward, like  that  seen  in  the  gnawing  action  of  a  rat.  This  motion  is 
rendered  possible  in  such  animals  through  the  long  diameter  of  the 
condyle  and  the  glenoid  cavity  having  an  antero-posterior  direction,  as 
in  the  capvbara  (Fig.  31). 

Fig.  31. 

. «.— c 


('.  Condyle,  and  G.  Glenoid  cavity  of  the  capybaia.     (Tomes.) 

The  temporo-maxillary  articulation,  combining  in  man,  as  we  have 
seen,  to  a  great  extent,  in  one  joint,  the  peculiarities  just  noticed  in  the 
temporo-maxillary  articulation  of  the  carnivora,  herbivora,  and  rodent 
types  of  the  mammalia,  furnishes  another  proof  of  the  natural  diet  of 
man  being  a  mixed  one. 

The  various  movements  of  the  lower  jaw  are  effected  by  a  number  of 
different  muscles ;  to  the  consideration  of  these  let  us  now  turn. 

Muscles  of  Mastication. — These  muscles  naturally  divide  them- 
selves into  two  groups,  Table  XXXIII. ,  one  of  which  elevates  the  lower 
jaw,  moves  it  laterally  or  in  an  antero-posterior  direction  ;  the  other 
depresses  it.     Let  us  begin  with  the  former  group  first. 

Table  XXXIII.— Principal  Muscles  of  Mastication. 


Elevators,  etc 

Temporal. 
Masseter. 
External  1 
Internal  I 


pterygoid. 


Depressors. 

Digastric. 
Mylo-hyoid. 
Geniohyoid. 
Platysma  myoides. 


The  action  of  the  muscles  becomes  quite  apparent  when  their  anatomy 
is  understood.  The  temporal  (Fig.  32)  arising  from  the  temporal  fossa 
and  inserted  into  the  coronoid  process  raises  the  lower  jaw  against  the 
upper.  The  action  of  the  temporal  is  aided  by  the  contraction  of  the 
masseter  and  internal  pterygoid,  the  former  muscle  (Fig.  33)  arising 
from  the  zygomatic  arch  and  passing  backward  into  the  lower  border  of 


MUSCLES    OF    MASTICATION 
Fig.  32. 


L09 


The  temporal  muscle,  the  zygoma  and  masseter  having  been  removed.     (Gray.) 

Fig.  33. 


Sketch  of  a  superficial  dissection  of  the  face,  showing  the  position  of  the  parotid  and  submaxillary 
glands  (Allen  Thomson).  Two-fifths  the  natural  size.  _p.  The  main  part  of  the  parotid  gland,  p'.  The 
small  part,  which  lies  alongside  the  duct,  on  the  masseter  muscle  d.  The  duct  of  Stenson  before  it  per- 
forates the  buccinator  muscle,  a.  Transverse  facial  artery,  n,  n.  Branches  of  the  facial  nerve  emerging 
from  below  the  gland.  /.  The  facial  artery  passing  out  of  a  groove  in  the  submaxillary  gland  and 
ascending  on  the  face,  s  m.  Superficial  larger  portion  of  the  submaxillary  gland  lying  over  the  pos- 
terior part  of  the  mylo-hyoid  muscle,     d  d.  Digastric  muscle.     (Quain  and  Sharpey.) 


110 


DIGESTION. 


the  jaw,  the  latter  (Fig  34)  having  its  origin  in  the  pterygoid  fossa  and 
its  insertion  in  the  lower  and  back  part  of  the  inner  side  of  the  jaw. 
The  action  of  these  muscles  is  well  seen  in  the  carnivora,  in  which  they 
are  very  large.     The  maximum  effect  of  the  masseter  can  also  he  we'll 


Fig.  34. 


Fig. 


View  of  the  pterygoid  muscle  from  the  outer  side. 
~%.     1.   External  pterygoid.     2.   Internal  pterygoid. 

(QUAIN.) 


View  of  the  pterygoid  muscle  from  the  inner 
side.  34-  1-  External  pterygoid.  2.  Internal 
pterygoid.     (Quain.) 


observed  in  the  rodentia,  the  muscle  being  enormously  developed  in 
these  animals.  The  lateral  and  forward  motion  of  the  lower  jaw  is  due 
to  the  action  of  the  external  pterygoid.  This  muscle  (Fig  35)  arises  from 
the  sphenoid,  palate,  and  superior  maxillary  bones,  and  passing  backward 
and  outward  is  inserted  into  the  neck  of  the  condyle  of  the  lower  jaw 
and  into  the  inter-articular  fibro-cartilage.  If  the  condyle  of  the  jaw  on 
one  side,  the  left  for  example,  be  fixed,  it  will  he  seen  from  the  direction 
of  the  fibres  of  the  external  pterygoid  that  if  the  muscle  of  the  opposite 
side  contracts  it  will  draw  the  lower  jaw  forward  and  laterally  in  an 
inward  direction,  the  condyle  playing  upon  the  articular  eminence,  the 
cartilage  being  interposed,  it  having  been  also  drawn  forward  by  the 
muscle.  This  alternate  lateral  motion  of  the  lower  jaw  is  very  evident 
in  the  chewing  of  the  food,  particularly  well  seen  in  the  herbivora,  in 

which  order  the  external  pterygoid  muscle  is 
relatively  much  developed.  If  the  external 
pterygoid,  however,  act  together,  the  lower 
jaw  is  drawn  forward  along  the  diagonal  A  D 
of  the  parallelogram,  the  two  sides  of  which, 
ABA  C  (Fig.  36),  are  the  directions  taken 
by  the  jaw  when  alternately  acted  upon  by  the 
external  pterygoids. 

As  regards  the  second  group  of  the  masti- 
catory muscles  there  can  be  no  doubt  as  to  the 
function  of  the  mylo-hyoid  (Fig.  37)  genio- 
hyoid, and  platysma  myoides  muscles.  The 
two  former  muscles  passing  from  the  hyoid  bone  to  the  mylo-hyoid 
ridge  and  genial  tubercle  of  the  lower  jaw  respectively  will  depress  the 
jaw  when  the  hyoid  bone  is  fixed.  The  same  effect  is  produced  by 
the  platysma,  it  being  partly  inserted  into  the  lower  border  of  the  jaw. 
The  action  of  the  digastric  muscle  is  not  so  simple  as  that  of  the  other 


MUSCLES    OF    MASTICATION, 


111 


Fig.  37. 


depressors ;  indeed,  its  action  in  depressing  the  lower  jaw  was  denied  by 
the  elder  Monro.1  This  view  gave  rise  to  his  memorable  discussion,  in 
the  last  century,  with  Winslow,2  in  which  Ferrein3  later  took  part,  who 
agreed  with  Winslow  in  holding  that  the  digastric  was  a  depressor. 

The  digastric  muscle,  as  its  name  implies,  is  double-bellied,  consisting 
of  an  anterior  and  posterior  muscular  part  with  an  intervening  tendin- 
ous portion.  The  tendon  often  passes 
through  the  stylo-hyoid  muscle,  glid- 
ing through  a  small  synovial  bursa,  * 
"  and  is  connected  with  the  body  and 
great  cornu  of  the  os  hyoides  by  a 
broad  band  of  aponeurotic  fibres  in 
the  form  of  a  loop  and  lined  with  syno- 
vial membrane.'"5  The  posterior  belly 
of  the  digastric  muscle  passes  upward, 
backward,  and  outward  from  the  tendon 
to  the  digastric  groove  of  the  temporal 
bone,  the  anterior  belly  upward  and 
forward  to  the  inner  surface  of  the  jaw, 
near  the  symphysis.  An  interesting 
fact  to  be  noticed  is  that  the  anterior 
belly  is  supplied  by  the  mylo-hyoid 
branch  of  the  inferior  maxillary  branch 
of  the  fifth  nerve,  the  posterior  belly 
by  the  facial,  as  we  shall  see  when  we 
come  to  study  the  nervous  system  ;  this 
shows  that  the  muscle  is  essentially  a 
double  one. 

Such  being  the  disposition  of  the 
digastric  muscle,  it  follows  that  if  the 
jaw  be  fixed  and  the  anterior  belly 
alone  contracts,  the  hyoid  bone  will 
be  elevated  anteriorly,  as  it  is  by  the  genio-hyoid  and  mylo-hyoid 
muscles  in  the  first  stage  of  deglutition.  If,  however,  the  posterior  belly 
alone  contracts,  the  hyoid  bone  will  be  raised  upward  and  backward,  its 
action  being  similar  to  that  of  the  stylo-hyoid  muscle.  Should  both 
bellies  contract,  then  the  hyoid  bone  will  be  elevated  almost  perpen- 
dicularly. On  the  other  hand,  should  the  hyoid  bone  be  fixed  by  its 
depressor  muscles,  the  lower  jaw  will  be  slightly  depressed  if  the  anterior 
belly  of  the  digastric  muscle  acts  alone;  should  the  posterior  belly  act 
independently,  then  the  mastoid  process  will  be  drawn  downward,  and 
with  it  the  back  of  the  head,  thereby  elevating  the  upper  jaw  and  open- 
ing slightly  the  mouth.  This  action  of  the  posterior  belly  alone,  or  with 
the  anterior  one  acting  with  it,  is  no  doubt  aided  by  the  deep  muscles  of 
the  neck.     While  it  is  possible  that  the  lower  jaw  can  be  depressed  by 


A.  The  lower  jaw  and  hyoid  bone,  from 
below,  with  the  mylo-hyoid  muscles  attached. 
B.  The  same  from  behind,  with  the  mylo- 
hyoid  and    genio-hvoid    muscles    attached. 

(a.t.).   yz. 


1  Remarks  on  the  Articulation,  etc.,  of  the  Lower  Jaw,  p.  341. 
Ediiiluigli,  1781      Also  Medical  Essays,  1783. 

2  Mem.  de  l'Acad.  Roy.  des  Sciences,  1742,  tome  59,  p.  176. 

3  Ibid.,  tome  xli.  pp   427,  509. 

*   Hyrtl  :  Lehrbuch  der  Anatomic,  Elfte  Aufl.,  S.  402. 
5   Quain's  Anatomy,  8th  ed.,  vol.  i.  p.  282, 


The  works  of  Alexander  M<  nro,  M.D. 


112  DIGESTION. 

the  anterior  belly  of  the  digastric  acting  alone,  it  is  most  probable  that 
the  posterior  belly  acts  with  the  anterior  one  in  producing  this  effect, 
the  muscle  acting  in  the  reverse  direction  of  that  just  referred  to  pro- 
ducing the  movement  of  the  back  of  the  head.  This  view  is  confirmed 
by  the  fact  pointed  out  by  Winslow1  that  in  several  animals  the  anterior 
belly  of  the  digastric  muscle  is  wanting,  the  posterior  alone  being  present 
and  being  then  inserted  into  the  angle  of  the  jaw.  Owen2  called  atten- 
tion to  this  being  the  case  in  the  orang,  and  the  author  has  confirmed  the 
observation.3  Occasionally  the  anterior  belly  is  absent  in  man.  Under 
such  circumstances  the  posterior  is  inserted  into  the  ramus  of  the  jaw. 
Were  not  the  anterior  belly  normally  present  it  is  possible  that,  as 
Hyrtl4  suggests,  the  forward  and  lateral  movements  of  the  jaw  might  be 
seriously  interfered  with.  That  the  mouth  is  to  a  certain  extent  opened 
by  the  elevation  of  the  upper  jaw  through  the  backward  motion  of  the 
head  due  to  the  contraction  of  the  posterior  belly  of  the  digastric  and 
of  the  muscles  of  the  neck,  may  be  shown  in  various  ways.  For  exam- 
ple, when  the  chin  is  placed  upon  a  table,  the  lower  jaw  being  then 
immovable,  or  when  the  lower  jaw  is  firmly  fixed,  as  in  certain  surgical 
operations,  it  will  be  observed  that  the  mouth  can  be  slightly  opened, 
though  the  lower  jaw  cannot  be  depressed.  The  experiment  suggested 
to  Monro5  by  his  former  pupil,  Pringle,  of  putting  the  blade  of  a  knife 
or  his  own  nail  opposite  to  the  conjoined  edges  of  the  teeth  when  the 
mouth  is  shut,  which  knife  being  held  unmoved  while  the  mouth  is 
opened,  he  may,  by  the  help  of  a  mirror,  see  the  upper  teeth  raised, 
remarkably,  at  every  operation  he  performs,"  is  very  convincing. 

It  must  be  admitted,  however,  that  the  movement  of  the  upper  jaw 
in  this  respect  has  not  much  significance,  as  the  opening  of  the  mouth 
is  essentially  due  to  the  depression  of  the  lower  jaw.  Indeed,  the  move- 
ment of  the  upper  jaw  in  the  opening  of  the  mouth  was  denied  altogether 
by  Winslow.6  In  this  respect,  however,  Ferrein  agreed  with  Monro, 
although  the  former  attributed  the  action  of  the  upper  jaw  to  the  digas- 
tric, the  latter  to  the  muscles  of  the  neck. 

Of  the  muscles  of  mastication,  as  we  shall  see  hereafter,  the  temporal, 
masseter,  pterygoid,  mylo-hyoid,  and  anterior  belly  of  the  digastric  are 
supplied  by  branches  of  the  fifth  pair  of  nerves ;  the  platysma  myoides 
and  posterior  belly  of  the  digastric  by  the  facial,  and  the  genio-hyoid  by 
the  hypoglossal. 

Resume. — The  effect  of  mastication  is  that  the  solid  food  taken  into  the 
mouth  is  cut  and  crushed  and  ground  up  by  the  teeth.  The  little  pieces 
that  ooze  out  between  the  teeth  and  the  cheeks  are  pushed  under  the  teeth 
again  by  the  muscular  action  of  the  cheeks  and  lips,  while  the  fragments 
that  escape  within  the  inner  side  of  the  teeth  are  forced  back  by  the  tongue. 
The  importance  in  man  of  the  action  of  the  cheeks,  lips,  and  tongue  in 
mastication  is  well  seen  when  there  is  a  paralysis  of  the  facial  or  hypo- 
glossal nerves.  In  such  cases  the  food  accumulates  between  the  cheeks 
and  the  teeth,  and  the  want  of  action  of  the  tongue  is  seen  both  in  the 
difficulty  of  mastication  and  deglutition.      The  same  effect  can  be  pro- 

1  Op.  cit.  -  Proc.  Zool.  Sue.  Lond.,  1830,  p.  29. 

3  Proc.  Acad,  of  Nat.  Sciences,  Philadelphia,  1880.  *  Topograph  Anat..  Fiinfte  Aufl.,  S.  438. 

*  Op.  cit.,  p.  239.  6  Panizza  :  Gaz.  Med.,  1835,  p.  419. 


MUSCLES    OF    MASTICATION.  113 

duce<l  by  cutting  the  corresponding  nerves  in  animals.1  The  thorough 
mastication  of  the  food  insures  its  further  digestion.  Indeed,  a  most 
fertile  source  of  dyspepsia  is  the  too  common  custom  of  bolting  the  food. 
In  the  latter  part  of  the  last  century  it  was  shown  by  Spallanzani2  that 
different  kinds  of  meat  when  enclosed  in  perforated  tubes  and  so  swal- 
lowed, passed  through  his  alimentary  canal  comparatively  undigested. 
When  the  meats,  however,  were  first  broken  up  and  then  placed  within 
the  tubes  very  little  undigested  matter  was  found  in  them  when  passed 
by  the  anus. 

In  gramnivorous  birds,  like  the  common  fowl,  for  example,  the  want 
of  teeth  is  supplied  by  pebbles  swallowed  with  the  food,  the  gizzard 
triturating  the  food  by  means  of  the  pebbles. 

Mastication  should  be  kept  up  until  the  food  is  thoroughly  ground 
up.  The  teeth  are  so  exquisitely  sensible  to  the  presence  of  any  hard 
matter  that  we  are  enabled  by  them  to  know  at  once  whether  the  pro- 
cess of  mastication  is  completed.  During  mastication  not  only  is  the 
food  thoroughly  triturated,  but  it  becomes  gradually  incorporated  with 
the  saliva.  To  the  consideration  of  the  production  and  effects  of  this 
secretion  let  us  now  turn. 

i  Panizza  :  Gaz.  Med.,  is  ::.,  p.  419. 

-  Fisica  Animale  et  Vegetabile,  tomo  seccmdo,  p.  52.     Venezia,  1782. 


CHAPTER    VII. 


INSALIVATION  AND  DEGLUTITION. 
Insalivation. 

The  saliva  consists  of  a  mixture  of  the  secretion  of  the  parotid,  sub- 
maxillary, and  sublingual  glands,  usually  known  as  the  salivary  glands 
(Fig.  38),  and  also  of  the  labial,  buccal,  lingual,  molar,  and  pharyngeal 
glands.  These  glands  are  structurally  examples  of  the  racemose  or 
grape-like  type  of  gland,  so  called  from  the  secreting  portion  of  the 
gland  with  its  efferent  duct  resembling  a  bunch  of  grapes  attached  to 
the  stem  (Fig.  39.) 

The  dilatations  or  diverticula  from  the  duct  are  lined  with  cells  in 
which  the  secreting  power  resides. 

Let  us  now  consider  some  of  the  peculiarities  of  the  saliva  secreted 
by  these  different  glands.     In  man  the  secretion  of  the  parotid  is  more 


Fig.  38. 


Fig.  39. 


Minute  structure  of  a  racemose  gland  of  the 
parotid.     (Mii.nk  Edwards.) 

abundant  than  that  from  any  of 
the  other  salivary  glands.  Gases 
of  salivary  fistula  occurring  in 
man  from  time  to  time  have 
given  physiologists  like  Jarjarvay 
Mialhe1  the  opportunity  of  examining,  separately,  the  parotid  saliva, 
while  Dalton2  and  Schiff3  have  obtained  it  directly  by  introducing  a 
tube  into  the  duct  of  Steno.  According  to  Dalton,  the  parotid  saliva 
is  alkaline,  clear,  and  watery,  which  enables  it  to  mix  readily  with 
and  soften  the  food.     Its  flow  is  most  active  during  mastication,  about 


The  salivary  gland."    (Gray.) 


1  Berard  :  Physiologie,  tome  ii.  p.  403,  note.     Paris,  1849. 

3  Physiologie  de  la  Digestion,  tome  i.  p.  183.     Florence,  1867. 


Physiology,  1864,  p.  1'25. 


IXSALIVATION. 


115 


three  times  as  much  saliva  being  secreted  on  the  masticating. side  of 
the  mouth  as  on  the  opposite  one.  These  facts,  taken  into  consideration 
with  that  of  the  orifice  of  the  duct  of  Steno  being  so  situated  that  the 
saliva  at  once  comes  in  contact  with  the  food  that  is  being  masticated, 
suggest  the  view  that  the  function  of  the  parotid  saliva  is  directly 
connected  with  that  of  mastication. 

The  facts  of  comparative  physiology  lead  to  the  same  conclusion. 
Thus,  in  the  ruminantia,  -which  chew  their  food  very  thoroughly,  the 
parotid  glands   are  very  large; 

on    the    other    hand    they    are  Fig.  40. 

usually  absent  in  the  cetacea, 
whales,  dolphins,  etc.,  and  but 
little  developed  in  the  otter, 
seal,  hippopotamus,  the  latter 
not  needing  parotid  glands,  the 
water  in  which  they  live  or  pass 
much  of  their  time  sufficiently 
moistening  their  food.  Bernard1 
has  also  shown  that  if  the  duct 
of  Steno  be  divided  in  the  horse, 
the  time  required  in  chewing  a 
feed  of  oats  is  three  times  as  much 
as  under  ordinary  circumstances. 
The  food  is  also  swallowed  with 
difficulty  under  such  circum- 
stances, through  the  want  of  its 
proper  admixture  with  the  saliva. 
It  is  well  known  also  that  less 
saliva  is  produced  in  the  horse 
on  a  feed  of  oats  than  on  one  of 
hay  or  straw,  and  that  food 
already  moistened  excites  little 
if  any  flow  at  all. 

In  experimenting  upon  ani- 
mals, more  particularly  on  dogs, 
Bernard  noticing;  after  inserting 
a  tube  into  the  duct  of  Wharton, 
and  placing  a  sapid  substance 
like  pepper  upon  the  tongue, 
that  there  was  an  abundant  flow 
of  submaxillary  saliva,  concluded 
that  the  function  of  this  kind  of 
saliva  was  connected  with  the 
sense  of  taste.  To  a  certain  ex- 
tent this  view  is  probably  true. 
Reflection,  however,  upon  the  relative  development  of  the  submaxillary 
glands  in  different  kinds  of  mammals,  in  connection  with  the  habits  of 
the  same,  leads  to  the  conclusion  that  one  of  the  uses,  at  least,  of  the 


o 


Salivary  gland  and  Madder,  armadillo. 


1  Physiologie  Experimentale,  tome  ii.  pp.  49,  147.     Ibid.,  p.  74. 


116  INSALIVATION    AND    DEGLUTITION. 

submaxillary  saliva  is  that  of  a  lubricating  kind.  Thus  in  the  carnivora, 
in  which  the  food  is  rather  bolted  than  chewed,  the  submaxillary  glands 
are  large,  whereas  the  parotids  are  small.  In  the  great  ant-eater,  also, 
Myrmeeophaga  jubata,  while  the  parotid  gland  is  so  small  that  it 
escaped  even  the  notice  of  Cuvier,  the  submaxillary  gland  is  sixteen 
inches  in  length  and  secretes  an  extremely  viscid,  tenacious  saliva 
which  lubricates  the  prehensile  and  extensible  tongue,  to  which  the 
ants  adhere,  and  on  which  the  animal  subsists.  The  submaxillary 
glands  are  also  very  large  in  the  armadillo  and  echidna  (Fig.  40). 

That  the  function  of  the  submaxillary  saliva  is  of  a  lubricating 
character  in  man  is  further  shown  by  its  viscidity,  the  consistence  being- 
such  that  it  coats  but  does  not  penetrate  the  bolus  of  food ;  and  by 
another  significant  fact,  that  before  the  submaxillary  saliva  passes  into 
the  mouth,  it  mixes  with  part  of  the  viscid  secretion  of  the  sublingual 
gland,  the  duct  of  Bartholin  joining  the  duct  of  Wharton,  the  rest  of 
the  sublingual  saliva  passing  into  the  mouth  directly  by  the  ducts  of 
Rivinus. 

The  sublingual  saliva  is  more  viscid,  even,  than  the  submaxillary, 
and  was  considered  by  Bernard1  to  be  directly  related  to  deglutition. 
It  would  appear,  however,  from  what  has  been  said,  that  both  the  sub- 
maxillary and  sublingual  saliva  are  connected  in  deglutition.  There  is 
no  reason,  however,  why  the  submaxillary  saliva  should  not  be  also 
connected  with  gustation,  since  insapid  substances  will  be  usually  re- 
jected ;  whereas,  sapid  ones  will,  after  being  tasted,  be  then  swallowed. 
If  the  secretion  aids  deglutition,  it  is  natural  to  suppose  its  flow  will  be 
influenced  by  the  stimulus  of  the  exciting  sapid  substance,  and  which 
we  shall  hereafter  see  to  be  the  case. 

The  fluids  secreted  by  the  labial,  buccal,  or  molar  glands,  etc.,  have 
never  been  studied  separately  in  man.  In  animals  in  which  the  ducts 
of  the  parotid,  submaxillary,  and  sublingual  glands  have  been  ligated, 
the  fluid  still  secreted  by  the  mouth  comes  from  the  glands  just  men- 
tioned, and  consists  of  a  thick,  opaque,  grayish  mucus,  containing 
salivary  corpuscles,  desquamated  epithelial  cells,  etc.  The  turbidness 
of  the  mixed  saliva  is  due  to  this  secretion,  that  from  the  salivary  glands 
proper  being  transparent. 

It  has  been  learned  from  the  researches  of  Heidenhain,2  Lavdowsky,3 
and  others,  that  the  minute  structure  of  the  salivary  glands  differs  con- 
siderably according  as  they  are  examined  after  a  period  of  rest  or 
activity,  and  that  such  differences  are  more  marked  in  the  so-called 
mucous  glands,  like  the  submaxillary,  in  which  the  secretion  is  viscid, 
mucin-like,  than  in  the  serous  ones,  like  the  parotid,  in  which  the  secre- 
tion is  limpid.  Thus,  if,  after  a  period  of  rest,  a  section  of  a  "  mucous" 
gland — the  submaxillary  gland  of  the  dog,  for  example — be  examined, 
the  cells  of  an  alveolus  (Fig.  41,  A)  will  be  found  to  stain  with  carmine 
more  readily  in  certain  parts  than  in  others.  The  nuclei  and  surround- 
ing protoplasm,  and  the  demilune  cells — apparently  young  cells  lying 
next  to  the  basement    membrane — become   deeply  tinged,  while    the 

1  Comptes  Rendns,  1852,  tome  xxxiv.  p.  237. 

2  Hermann  :  Physiologie,  Funfter  Band,  S.  58.     Leipzig,  1880.  , 
8  Archives  of  Mic.  Anat.,  1877,  xiii.  S.  281. 


INSALIVATION. 


117 


remaining  portion  of  the  cell  remains  uncolored,  due  apparently  to  its 
protoplasm  in  this  situation  having  been  converted  into  a  mucin-like 
substance.  If,  however,  similar  sections  of  the  gland  be  made  after  a 
period  of  activity  induced  by  stimulation,  as  we  shall  see  of  the  chorda 
tympani  nerve,  it  will  be  observed  (Fig.  41,  B)  that  but  a  small  portion, 


Fig.  41. 


~?^ 


.SS# 


■W 


d 

Section  of  a  "mucous"  gland.  A.  In  a  state  of  rest.  B.  After  it  has  been  for  some  time  actively 
secreting,  a.  Demilune  cells,  c.  Leucocytes  lying  in  the  interalveolar  spaces.  The  darker  shading  in 
both  figures  is  intended  to  indicate  the  amount  of  staining.     (After  Lavpowsky.) 

if  indeed  any  part,  of  the  cell  has  resisted  coloration  with  carmine,  and 
that  the  cells  have  diminished  in  size. 

If  sections  of  a  "serous"  gland — the  parotid  gland  of  a  rabbit,  for 
example — after  periods  of  rest  and  activity,  be  treated  in  the  same  way 
with  carmine,  differences  of  the  same  kind  will  be  observed.  Tims, 
after  rest  the  cells  of  the  parotid  (Fig.  42,  A)  will  be  found  to  be  pale, 
transparent,  with  few  granules,  staining  by  carmine  with  difficulty,  the 
nuclei  irregular  in  outline,  apparently  as  if  shrunken.      After  a  period 

Fig.  42. 


Section  of  a  "serous"'  gland  :  the  parotid  of  the  rabbit.     A.  At  rest.     B.  After  stimulation  of  the 
cervical  sympathetic.     (After  Heidenhain.) 

of  activity,  on  the  other  hand  (Fig.  42,  B),  from  stimulation  by  the 
sympathetic  nerve,  the  cells  will  be  seen  to  have  become  turbid,  full  of 
granules,  staining  readily  with  carmine,  the  nuclei  large  and  round, 
with  conspicuous  nucleoli,  and  the  cells,  as  a  whole,  smaller.  Such 
facts  lead  us  naturally  to  conclude  that  during  a  period  of  rest  the  cells 
of  the  salivary  glands  arc  elaborating  from  the  blood  their  characteristic 


118  INSALIVATION    AND    DEGLUTITION. 

secretion,  the  elements  of  the  latter  existing  in  the  blood,  but  not  the 
secretion  itself,  as  such  ;  that  the  secretion,  as  formed,  is  stored  up  (the 
part  not  staining  with  carmine)  until  needed,  when  at  the  proper  moment 
it  is  forced  into  the  interior  of  the  gland  and  thence  passes  into  the 
duct,  the  normal  stimulus  to  the  secretion  being,  as  we  shall  see  here- 
after, impressions  made  upon  the  tongue,  etc.,  and  which  are  trans- 
mitted by  the  appropriate  nerves  supplying  the  glands.  That  the 
process  of  the  secretion  of  saliva  by  the  salivary  glands  is  not  one  of 
mere  filtration  of  the  secretion  from  the  blood,  apart  from  the  former 
not  exbting  as  such  in  the  latter,  is  shown  by  the  fact  of  the  submaxil- 
lary secretion — of  the  dog,  for  example — passing  into  the  duct  under  a 
pressure  of  about  200  millimetres  (8  inches),  or  about  twice  as  great  as 
that  of  the  blood-pressure  in  the  carotid  artery  of  the  same  side.  Were 
pressure  the  only  influence  at  work  in  the  secretion  of  the  saliva,  the 
latter  would  flow  back  to  the  blood  whence  its  elements  came,  rather 
than  into  the  excretory  duct.  That  during  the  process  of  secretion 
chemical  action  is  going  on,  is  also  shown  by  the  temperature  of  the 
saliva  and  venous  blood  coming  from  the  gland  being  1.5°  C.  higher 
than  that  of  the  arterial  blood  supplying  the  gland,1  and  that  the  pro- 
duction of  carbonic  acid  is  increased.2 

Inasmuch  as,  under  ordinary  circumstances,  it  is  the  mixed  saliva 
which  modifies  the  food,  it  will  not  be  necessary  to  dwell  upon  the 
chemical  or  physical  peculiarities  of  any  one  particular  kind  of  it. 

Table  XXXIV. — Composition  of  Human  Saliva. 

Water 995.16 

Epithelium           .........  1.62 

Organic  matter,  soluble        .......  1.34 

Potassium  sulphocyanide     .......  0.06 

Sodium  | 

Calcium                phosphate           ......  0.98 

Magnesium     j 

Sodium  1      i  i     ■  i  a  o  i 

r>  ,      •   m        [    chloride 0.84 

Potassium       ) 


1000.00 


The  saliva  as  we  find  it  in  the  mouth,  consisting  then  of  a  mixture  of 
all  the  different  kinds  of  saliva,  is  an  alkaline,  colorless,  somewhat 
opaque,  viscid  fluid,  with  a  specific  gravity  of  from  1.004  to  1.000;  its 
composition  is  given  in  Table  XXXIV.  Like  all  the  secretions,  the 
saliva  consists  largely  of  water,  some  organic  matter,  and  a  small 
quantity  of  salts.  In  1831,  Leuchs1  discovered  that  hydrated  starch, 
when  mixed  with  warm  saliva,  was  liquefied  and  converted  into  sugar. 
Since  then,  numerous  experiments  have  been  performed  on  animals, 
especially  dogs,  with  the  object  of  showing  that  their  saliva  has  not  this 
effect  upon  starch.  While  these  observations  are  interesting  from  a 
general  physiological  point  of  view,  they  have  no  bearing  whatever  upon 
the  question  of  the  effect  of  human  saliva  upon  starch.  Anyone  can 
convince  himself  that  starch  is  converted  i  lto  sugar  in  the  mouth  by 

1  Ludwig  and  Spieas :  Sitz.  d.  Wiener,  Acad.  Math.  Nat.  Classe,  1857,  xxv.  S.  548. 

2  Pliuger  :  Pfluger's  Archiv,  1868,  Band  i.  S.  686. 


INSALIVATION.  119 

taking  a  little  boiled  starch,  mixing  it  thoroughly  with  his  saliva,  and 
then  testing  for  sugar.  The  mixture  will  not  then  give  a  blue  color  on 
the  addition  of  iodine,  but  at  first  a  red  or  violet  one,  showing  that  the 
starch  has  become  partly  dextrin  ;  the  latter  is,  however,  soon  also 
transformed  into  glucose  or  grape  sugar,  as  can  be  shown  by  Trommer's 
test.  Saliva  has  the  same  effect  on  raw  starch,  only  a  longer  time  is 
required  to  produce  it.  It  has  been  ascertained  by  experimenting  with 
the  different  substances  entering  into  the  composition  of  the  mixed 
saliva,  that  it  is  a  portion  of  the  albuminous  organic  matter  which  pos- 
sesses this  transforming  effect,  and  that  the  different  kinds  of  saliva 
have,  as  well  as  the  mixed  saliva,  the  property  of  converting  starch  into 
sugar.  The  phenomenon  appears  to  be  one  of  fermentation  with  hydra- 
tion, as  may  be  seen  from  the  following  reaction  : 

Starch.  Water.  Glucose.  Dextrin.  Water. 

C18H30O13    +     3H20    -    1(C6H1206)  2(C6H10O5)     +    2(H20). 

Dextrin.  Water.  Glucose. 

2(C6H10O5)  +  2(H,0)    =     2(C6H12Q6). 
3(C6H1206). 

The  action  appears  to  be  due  to  a  kind  of  ferment,  the  so-called 
ptvalin  of  Berzelius,  which  can  be  isolated  by  precipitation  by  alcohol, 
the  exact  nature  of  which,  however,  at  present  is  not  thoroughly  under- 
stood. According  to  Mialhe1  one  part  of  ptvalin  will  effect  the  trans- 
formation of  more  than  two  thousand  parts  of  starch.  It  will  be  seen 
from  this  that  its  action  must  be  very  energetic.  Nevertheless,  as  the 
large  quantity  of  starch  present  in  the  food  remains  but  a  short  time  in 
the  mouth,  it  is  questionable  whether  any  great  amount  of  it  is  con- 
verted into  sugar  in  the  mouth,  notwithstanding  the  admitted  rapidity 
of  the  action  of  the  saliva.  We  shall  see,  however,  that  the  transform- 
ing effect  of  the  saliva  upon  starch  is  continued  even  after  the  food  has 
passed  into  the  stomach,  the  gastric  juice  not  interfering  with  the  action, 
and,  as  the  food  remains  for  some  time  in  that  organ,  no  doubt  a  con- 
siderable quantity  of  sugar  is  produced  there  in  this  manner. 

The  importance  of  the  saliva,  however,  in  this  respect,  must  not  be 
exaggerated,  as  we  shall  see  that  the  intestinal  and  pancreatic  juices 
transform  starch  into  sugar  as  efficiently  as  the  saliva,  and  it  is  well 
known  that  the  serum  of  the  blood,  mucus,  the  fluid  from  cysts,  etc., 
have  the  same  property,  though  not  in  as  great  a  degree  as  the  fluids 
first  referred  to.  The  significance  of  the  potassium  sulphocyanide, 
which  appears  to  be  always  present  in  the  saliva,  is  not  apparent.  The 
remaining  salts,  while  rendering  the  saliva  alkaline,  have  not  been 
shown  as  yet  to  serve  any  particular  purpose  in  digestion. 

"While  one  of  the  uses  of  the  saliva  in  man  is  certainly  the  transform- 
ation of  starch  into  sugar,  undoubtedly  its  most  important  function  is 
that  of  aiding  mastication  and  deglutition,  the  secretion  of  the  parotid 
gland  being  specially  connected  with  the  former  function,  that  of  the 
submaxillary  and  sublingual  glands  with  the  latter,  as  we  have  seen  in 
speaking  of  the  secretions  separately.     The  amount  of  saliva  secreted 

1  Chimie  applique  a  la  Pliysiulogie,  p.  43.     Taris,  1856. 


120  INSALIVATION    AND    DEGLUTITION. 

during  twenty-four  hours  in  man  has  never  been  exactly  determined. 
As  the  saliva  is  constantly  being  reabsorbed,  a  source  of  error  in  any 
calculation  as  to  the  amount  secreted  in  a  given  time  would  be  the  risk 
of  counting  the  same  saliva,  or,  at  least,  the  elements  entering  into  its 
composition  more  than  once.  According  to  Dalton,1  31.1  grammes, 
about  478  grains,  of  saliva  can  be  obtained  from  the  mouth  in  twenty 
minutes  without  any  artificial  stimulus.  The  natural  stimulus  to  the 
secretion  of  the  saliva,  however,  is  the  presence  of  food  in  the  mouth ; 
indeed,  the  sight,  or  even  the  thought  of  food,  in  some  individuals  will 
make  the  mouth  "water."  The  amount  of  saliva  secreted  will  depend, 
therefore,  on  the  quantity  and  quality  of  the  food.  According  to 
Dalton,2  wheaten  bread  will  gain  during  mastication  fifty-five  per  cent, 
in  weight,  lean  meat  forty-eight  per  cent.  Assuming  that  about  sixteen 
ounces  of  meat  and  nineteen  of  bread  are  eaten  in  the  twenty-four 
hours,  and  adding  the  saliva  absorbed  by  this  amount  of  food  to  that 
secreted  during  the  intervals  of  digestion  deduced  from  Dalton's  experi- 
ments, it  can  be  estimated,  approximately,  that  1280  grammes,  a  little 
less  than  three  pounds  avoirdupois,  of  saliva  are  secreted  in  the  twenty- 
four  hours. 

After  the  food  has  been  thoroughly  masticated  and  mixed  with  the 
saliva,  the  secretion  of  the  parotid  gland  penetrating  the  bolus,  while 
that  of  the  submaxillary,  sublingual,  and  remaining  glands  of  the  mouth 
rather  coating  it  externally,  it  is  swallowed.  As  the  bolus  of  food  passes 
down  the  pharynx  it  receives  another  coating  from  the  secretions  of  the 
glands  in  that  situation,  and  so  deglutition  is  further  facilitated.  In  con- 
cluding our  account  of  the  saliva  there  may  be  mentioned  appropriately 
in  this  connection  the  peculiarity  it  possesses  of  attracting  or  entangling 
bubbles  of  air  in  the  mass  of  food.  The  effect  of  this  is  that  stomach 
digestion  is  facilitated  through  the  easy  access  afforded  to  the  gastric 
juice  when  the  food  comes  in  contact  with  this  secretion.  Moist,  heavy 
bread  is  not  readily  acted  upon  by  the  secretions,  through  its  not  being 
permeated  with  air  in  the  manner  just  referred  to.  Let  us  now  consider 
the  manner  in  which  deglutition  is  effected. 

Deglutition. — The  act  of  swallowing,  or  deglutition,  is  often  divided 
arbitrarily  by  physiologists  into  three  stages  or  periods,  though  these 
stages  are  strictly  continuous.  During  the  first  stage  the  food  passes 
backward  to  the  isthmus  of  the  fauces.  The  second  stage  is  occupied 
by  the  passage  of  the  food  through  the  palate  from  the  isthmus  into  the 
oesophagus,  while  the  third  stage  consists  in  the  food  passing  from  the 
oesophagus  into  the  stomach.  After  the  food  has  been  thoroughly 
chewed,  the  mouth  being  closed,  the  first  stage  of  deglutition  begins  by 
the  tongue,  more  especially  its  point  aided  by  the  cheek,  collecting  the 
particles  of  the  food  into  a  mass  or  bolus.  Through  the  action  of  the 
hyoglossal  muscles  (Fig.  43)  the  tongue  is  then  moved  forward  and 
upward;  the  effect  of  this  is  that  the  bolus  of  food  is  pressed  against  the 
hard  palate,  and  thence  into  the  fauces,  through  the  tongue  being  some- 
what elevated  at  the  sides  and  depressed  in  the  centre,  while  the  soft 
palate  is  applied  at  the  base  probably.     Probably  some  slight  suction 

i  Physiology,  188-_»,  p.  144.  2  Qp.  cit.,  p   146. 


DEGLUTITION 


121 


force  is  exercised  in  the  swallowing  of  liquid  and  soft  articles  during 
the  first  stage  of  deglutition. 

Fig.  43. 


Base  of  cranium. 


Pharynx. 


Tongue. 

--  Salivary  glands 
Hyoid  bone. 

W Larynx. 

Thyroid  gland. 

(Esophagus.  Trachea. 

Vertical  section  of  mouth  and  pharynx.     (Milne  Edwards.) 

The  tongue  is  as  important  in  deglutition  as  we  have  seen  it  to  be 
in  mastication.      The  results  of  dividing  the  hypoglossal  in  animals, 


Fin.  44. 


already  referred  to,  and  the  cases 
observed  in  man  where  the  tongue 
has  been  amputated,  or  congeni- 
tally  deficient,  show  that  without 
the  action  of  the  tongue  degluti- 
tion is  impossible. 

In  amputation  of  the  tongue 
there  is  usually  left  a  portion  of 
the  base  sufficient  to  press  against 
the  palate,  making  deglutition  pos- 
sible. The  action  of  swallowing 
during  the  first  stage  is  usually  per- 
formed unconsciously  ;  in  reality, 
however,  it  is  a  voluntary  one.  As 
the  food  passes  through  the  fauces, 
the  tongue  being  drawn  upward 
and  backward  by  the  contraction 
of  the  stylo-glossal  muscles  the  en- 
trance to  the  fauces  is  thereby 
narrowed,  then  the  posterior  half 
arches  of  the  palate  approach  each 
other  through  the  action  of  the 
palatopharyngeal  muscles,  while 
the  interval  between  them  is  filled 
up  by  the  uvula  (Fig.  44),  at  the 
same  time  the  soft  palate  is  rendered  tense  by  the  tensor  palati  and 
elevated  by  the  levator  palati;  the  natural  communication  between  the 
pharynx  and  posterior  nares  being  then  cut  off,  the  food  passes  from 
the  isthmus  of  the  fauces  into  the  pharynx,  the  superior  constrictor  of 


Uvula,     h  b.  Anterior  half  arches,     c  c.  Posterior 
half  arches.    //.  Tonsils.     (Valentin.) 


122  INSALIVATION    AND    DEGLUTITION. 

which  grasps  the  bolus  of  food  and  the  soft  palate.  The  pharynx,  in  the 
meantime,  is  elevated  with  the  larynx  through  the  contraction  of  the 
stylo-pharyngeal,  stylo-hyoid,  genio-hyoid,  mylo-hyoid,  probably  the  thy- 
roid and  the  digastric  muscles,  the  latter  acting  more  especially  through 
its  anterior  belly,  the  lower  jaw,  it  need  not  be  said,  being  now  fixed. 
In  this  way  the  cavity  of  the  pharynx  is  widened,  at  the  same  time  the 
entrance  to  the  larynx  is  closed,  being  elevated  and  pressed  against  the 
epiglottis.  The  food  is  then  forced  downward  into  the  (esophagus  by  the 
middle  and  inferior  constrictors,  after  which  the  parts  concerned  resume 
their  ordinary  position.  Pathological  and  surgical  operations,  in  which 
the  parts  involved  were  exposed,  have  given  favorable  opportunities  of 
observing  the  process  of  deglutition  in  man.  The  results  of  such  clin- 
ical investigation  confirm  what  one  might  expect  to  be  the  function  of 
the  parts  as  deduced  from  their  anatomy.  Thus,  in  the  cases  referred  to 
by  Berard,1  and  Beclard,2  the  palate  was  seen  to  be  elevated  while  the 
posterior  wall  of  the  pharynx  approached  it  in  deglutition.  Berard3 
mentions  the  case  of  a  lady  in  which,  through  complete  paralysis  of  the 
velum,  liquids  when  swallowed  returned  by  the  nose,  and  cites,  also, 
as  an  illustration  of  the  elevation  of  the  palate  in  deglutition,  the  experi- 
ment of  Debrou,  in  which  a  probe  being  introduced  along  the  floor  of 
the  nares  into  the  pharynx,  it  was  observed  that  every  time  the  patient 
swallowed  the  external  end  of  the  probe  was  depressed,  the  internal  end 
being  elevated  by  the  palate.  Numerous  cases,  among  others  those 
cited  by  Longet,4  in  which  the  epiglottis  has  been  destroyed  in  man, 
either  by  wounds  or  disease,  show  very  conclusively  that  in  swallowing 
liquids  at  least  the  epiglottis  is  indispensable  in  preventing  them  flowing 
into  the  larynx. 

It  is  true  that  the  glottis  is  closed  in  deglutition,  both  by  the  action 
of  the  constrictors  attached  to  the  thyroid  cartilages  and  by  the  intrinsic 
muscles  of  the  larynx,  but  this  does  not  explain  why  liquids  do  not 
flow  into  that  part  of  the  larynx  situated  above  the  glottis,  wdiich  they 
certainly  would  do  as  Berard  suggests,  unless  some  obstacle  was  inter- 
posed. It  is  easy  to  understand  why,  usually,  solid  food  can  be  swal- 
lowed without  difficulty,  even  though  the  epiglottis  be  deficient,  as  when 
the  larynx  is  elevated  in  deglutition  it  rises  up  under  the  base  of  the 
tongue,  and  so  is  pretty  well  covered.  The  food  being  moulded  into 
the  bolus,  and  covered  with  the  slimy,  viscid  saliva,  would  not  be  apt, 
then,  to  pass  into  the  larynx,  but  Avould  glide  over  the  base  of  the 
tongue  into  the  pharynx,  whereas  liquids  would  insinuate  themselves 
into  the  upper  part  of  the  larynx,  and  at  once  give  rise  to  a  fit  of 
coughing.  This,  indeed,  is  apt  to  take  place,  the  epiglottis  being 
absent,  if  a  small  fragment  of  solid  food,  a  crumb,  for  example,  be  swal- 
lowed incautiously.  Under  ordinary  circumstances,  the  food  being  pre- 
vented then  from  passing  into  the  posterior  nares  above  and  the  larynx 
below,  will  be  forced  into  the  oesophagus.  At  that  moment  the  third 
stage  of  deglutition  begins.  The  action  of  the  oesophagus  is  very  simple, 
consisting  in  the  contraction  of  its  circular  and  longitudinal  muscular 
fibres  from  above  downward,  by  which  action  the  food  is  forced  into  the 
stomach  (Fig.  45). 

1  Physiologie,  tome  ii.  p.  25.  -  Physiologic  Ilumaine,  p.  60. 

8  Op.  cit.,  pp.  zi,  25.  4  Physiologie,  18(51,  tome  i.  p.  115. 


DEGLUTITION, 


123 


A  peculiarity  about  the  muscular  fibres  of  the  oesophagus  is  in  the 
upper  portion  consisting  exclusively  of  striated  fibres,  whereas,  in  the 
lower  part  unstriated  fibres  predominate.  This  disposition  of  the  fibres 
is  interesting,  as  accounting,  probably,  for  the  fact  of  the  lower  third 
of  the  oesophagus'  remaining  contracted  for  a  short  time  after  the  food 
has  passed  into  the  stomach,  thereby  preventing  regurgitation.  This 
phenomenon  was  particularly  observed  first  in  animals  by  Magendie.1 

Fig.  45. 


Spleen 


s- Colon. 


Large  Intestine 


-Small  intestine. 
•  Colon. 


Digestive  apparatus  of  man.     (Milne  Edwards.) 

While,  as  has  been  stated,  the  first  period  of  deglutition  is  under  the 
control  of  the  will,  the  second  and  third  are  entirely  involuntary, 
depending,  as  we  shall  see  when  we  come  to  study  the  nervous  system, 
upon  an  impression  being  made  upon  the  mucous  membrane  of  the 
pharynx  and  oesophagus,  etc.,  which  sets  the  appropriate  nerves  and 
muscles  in  action.  Indeed,  without  solid  or  liquid  food  in  the  pharynx 
it  is  impossible  to  perform  the  second  act  of  deglutition  ;  apparently, 
this  is  done  sometimes  for  three  or  four  times  without  there  being  any- 
thing to  swallow,  but  there  is  really  always  present  under  such  circum- 
stances sufficient  saliva  to  produce  the  necessary  impression. 

It  is  hardly  necessary  to  call  attention  to  the  fact  that  solid  and 
liquid  foods  can  be  swallowed  in  all  positions.  It  is  a  common  feat 
among  jugglers  to  drink  a  bottle  of  wine  or  a  glass  of  beer  while  standing 
on  their  heads  or  hands. 


1  Memoires  sur  1'CEsophage,  a  l'lnstitut  de  France,  11  Oct.  1813. 


CHAPTER   VIII. 

GASTRIC  DIGESTION. 

The  stomach  is  a  muscular  membranous  sac  whose  walls  have,  on  an 
average,  a  thickness  of  a  little  more  than  a  line.  When  distended,  it 
measures  laterally  from  thirteen  to  fifteen  inches,  and  antero-posteriorly 
five  inches,  with  a  capacity,  according  to  Brinton,1  of  one  hundred  and 
seventy-five  inches,  or  about  five  pints.  The  capacity  of  the  stomach, 
however,  is  often  less  and  sometimes  even  much  greater,  varying  with 
the  age,  sex,  and  habit  of  the  individual.  It  is  held  in  position  in  the 
upper  part  of  the  abdominal  cavity  by  its  connection  with  the  oesophagus 
and  the  folds  of  the  peritoneum.  When  empty,  the  sides  of  the  stomach 
are  usually  in  contact,  and  the  whole  organ,  presents  a  flattened  appear- 
ance. When  distended  by  food,  however,  the  anterior  wall  of  the 
stomach  becomes  superior,  and  is  applied  to  the  diaphragm.  This  is 
due  to  the  ends  of  the  stomach  and  lesser  curvature  being  comparatively 
immovable.  As  the  food  enters  the  stomach  from  the  oesophagus,  it 
turns  to  the  left,  and,  passing  into  the  cardiac  end,  or  greater  pouch, 
thence  proceeds  along  the  greater  curvature  to  the  pyloric  end,  return- 
ing by  the  lesser  curvature  to  the  cardiac  portion,  to  begin  the  same 
course  over  again.  Each  of  these  revolutions  occupies  from  about  one 
to  three  minutes,  and  are  slowest  at  first,  becoming  more  rapid  as  diges- 
tion advances.  The  food  undergoes,  therefore,  a  sort  of  churning  action, 
passing  from  one  side  of  the  stomach  to  the  other.  As  the  circular 
muscular  fibres  surrounding  the  pyloric  orifice  offer  a  resistance  to  solid 
undigested  matter,  it  is  only  the  liquid,  pultaceous,  digested  food  which 
escapes  into  the  duodenum.  After  a  time,  however,  even  hard  foreign 
bodies,  like  stones,  coins,  etc.,  make  their  way  into  the  small  intestine. 

An  interesting  fact  connected  with  the  movements  of  the  stomach,  is 
a  noticeable  difference  between  the  contraction  of  the  pyloric  as  com- 
pared with  that  of  the  cardiac  end  of  the  stomach.  The  food  while  in 
the  cardiac  end  of  the  stomach  appears  to  be  subjected  to  a  simple 
pressure,  whereas  the  action  of  the  pyloric  portion  is  of  a  vigorous  ex- 
pulsive character.  Indeed,  when  digestion  is  at  its  height  the  cardiac 
portion  of  the  stomach  is  quite  distinctly  separated  from  the  pyloric 
portion  by  a  constricting  band.  The  organ  then  presents  an  hour-glass 
form,  of  which  two-fifths  consist  of  the  cardiac  portion.  It  is  worth 
mentioning  in  this  connection,  that  this  hour-glass  form  of  the  stomach, 
present  only  in  man  during  digestion,  is  the  form  presented  in  the 
manatee  (Fig.  46)  whether  digestion  is  going  on  or  not;  the  author2 

1  Cyclopaedia  of  Anatomy  and  Physiology.     Supplempnt,  p.  SOS.     London,  1837-1847. 
-  Proceedings  of  Academy  of  Natural  Sciences,  Philadelphia,  187G,  p.  45'J. 


FUNCTION    OF    THE    STOMACH. 


125 


having  found  in  the  dissection  of  several  individuals  the  stomach  always 
presenting  this  form,  whether  it  was  full  of  food  or  empty. 

After  the  food  has  been  digested  and  the  stomach  has  been  emptied 
of  its  contents,  which  processes  are  effected  within  a  period  of  from  two 
to  four  hours,  all  the  motions  just  described  cease,  and  do  not  recom- 
mence again   until  a  fresh  supply  of  food  is  taken.       The  peristaltic 


Fig.  4' 


Stomach  of  uianatc 


vermicular  motion  of  the  stomach  that  I  have  endeavored  to  describe, 
depends  upon  its  muscular  fibres,  assisted  by  the  diaphragm.  The 
muscular  coat  of  the  stomach,  which  averages  about  the^th  of  an  inch 
in  thickness,  consists  of  three  sets  of  fibres,  the  longitudinal,  circular, 
and  oblique,  which  are  disposed  from  without  inward,  in  the  order  just 
named — that  is,  the  longitudinal  fibres  are  external,  the  oblique  are 
internal,  while  the  circular  fibres  lie  between  the  other  two. 

These  three  sets  of  fibres  are,  however,  very  unequally  developed. 
Thus,  the  longitudinal  fibres  are  best  seen  in  the  lesser  curvature ;  the 
circular  fibres  are  rather  indistinct  to  the  left  of  the  cardiac  orifice,  and 
are  most  marked  at  the  pyloric,  forming  then  its  sphincter  muscle ; 
while  the  oblique  fibres  are  limited  to  the  cardiac  portion  of  the  stomach, 
passing  over  it  from  left  to  right.  It  is  at  the  point  where  these  oblique 
fibres  cease  that  the  stomach  becomes  constricted  in  digestion  into  the 
two  parts  already  described. 

Through  the  contraction  of  the  longitudinal  and  circular  fibres  the 
food  is  forced  along  toward  the  pylorus,  which,  through  its  sphincter 
muscle,  resists  at  first  all  but  thoroughly  digested  food.  The  cardiac 
orifice  is  guarded  by  the  fibres  in  that  situation,  as  well  as  by  the  con- 
traction of  the  lower  part  of  the  oesophagus  already  referred  to.  The 
movement  of  the  food  is  also  due,  no  doubt,  partly  to  the  pressure 
exerted  by  the  diaphragm  and  the  intestines.  The  natural  stimulus  to 
these  motions  of  the  stomach  during  digestion  is  the  presence  of  food. 
The  account  that  we  have  just  given  of  the  movements  that  the  stomach 
undergoes  during  digestion  in  man,  is  taken  entirely  from  the  experi- 


126 


CAST  RIC     IjH;  KS'I  I  ii.V 


ments  and  observations  of  Beaumont,1  to  whom  physiology  is  so  greatly 

indebted  for  much  that  is  positively  known  of  the  human  gastric  digestion. 

ks  what  I  have  to  Bay  of  the  secretion  of  the  gastric  juice  ;m<l  its 

effect  upon  food  in  the  living  human  body  is,  to  a  great  extent,  derived 
entirely  from  that  classical  work,  it  appears  to  me  proper  that  I  should 

narrate  the  main  facts  of  the  truly  celebrated  case  which  afforded 
Beaumont  the  opportunity  of  making  his  experiments  and  observations. 
Alexis  St.  Martin,2  a  voyageur  in  the  service  of  the  American  Fur 
Company,  a  man  about  eighteen  years  of  age,  of  good  constitution, 
robust  and  healthy,  was  accidentally  wounded  by  the  discharge  of  a 
musket  on  the  6th  of  June,  1*22.  The  charge,  consisting  of  powder 
and  duck  shot,  entered  the  left  side  posteriorly  and  obliquely,  blowing 
off  integument  and  muscles  of  the  size  of  a  man's  hand,  fracturing  the 
sixth  and  seventh  ribs,  lacerating  the  lower  portion  of  the  left  lobe  of 
the  lungs,  the  diaphragm,  and  perforating  the  stomach.  Dr.  Beaumont 
further  tells  us  that  he  saw  the  patient  within  half  an  hour  after  the 
accident,  and  then  describes  the  surgical  aspects  of  the  case  and  the 

Fig.  47. 


Ordinary  appearance  of  the  left  breast  and  s'uU-.  the  aperture  filled  with  the  valve  ; 

the  subject  in  an  erect  position.     (Beaumont.) 

treatment,  and  the  gradual  but  perfect  recovery  of  his  patient  so  far  as 
the  general  health  was  concerned.  The  perforation  through  the  walls 
of  the  stomach,  however,  remained  permanently  open,  having  resisted 
all  treatment.      This  perforation  (Fig.  47;  was  situated  three  inches  to 


«  Experiments  and  Observations  on  the  Gastric  Juice,  pp.  96,  97,  110,  111,  113.    Pittsburgh,  1833. 
-  Beaumont,  op.  cit.     Introduction. 


FUNCTION    OF    THE    STOMACH.  127 

the  left  of  the  cardiac  portion  of  the  stomach,  near  the  superior  termina- 
tion of  the  great  curvature,  and  measured  about  two  and  a  half  inches 
in  circumference.  The  opening  was  closed  under  ordinary  circum- 
stances by  a  movable  valve  formed  through  a  doubling  of  the  coats  of 
the  stomach,  which  had  been  formed  during  the  progress  of  the  case, 
and  which  effectually  prevented  the  escape  of  food.  This  valve  could 
be  easily  depressed,  when  the  interior  of  the  stomach  could  then  be 
examined. 

St.  Martin,  after  the  recovery  of  his  health,  performed  all  the  duties 
of  a  common  servant — chopping  wood,  carrying  burthens,  etc. — married 
and  had  several  children,  and  enjoyed  general  good  health  up  to  eighty 
years  of  age.  For  a  number  of  years,  off  and  on,  St.  Martin  was  under 
the  observation  of  Beaumont,  under  strictly  physiological  conditions. 
It  is  this  circumstance  which  makes  this  case  so  important  in  the  history 
of  the  physiology  of  digestion.  There  have  been  cases  of  gastric  fistula 
in  man,  both  before  and  since  that  of  St.  Martin,  but  either  such  cases 
were  complicated  with  pathological  conditions  or  the  circumstances  were 
such  as  to  make  constant,  detailed,  and  trustworthy  observation  for 
any  length  of  time,  such  as  that  given  by  Beaumont,  impossible. 
Interesting  cases  of  gastric  fistula,  the  result  of  wounds  or  gastrotomy, 
have  been,  however,  made  use  of  more  recently  for  purposes  of  physi- 
ological investigation,  by  Schmidt1  and  Richet,2  and  which  will  be 
referred  to  again. 

In  order  to  appreciate  the  immense  value  of  this  case  of  St.  Martin, 
it  should  be  mentioned  that  little  was  positively  known  of  gastric  di- 
gestion, as  it  takes  place  in  man,  before  the  observations  and  experi- 
ments of  Beaumont  were  made. 

Up  to  the  middle  of  the  eighteenth  century  it  was  still  a  subject  of 
discussion  whether  the  action  of  the  stomach  in  digestion  was  of  a 
chemical  or  mechanical  nature.  Among  those  who  favored  the  chemical 
theory  there  were  some  who  adhered  to  the  view  of  the  ancients,  who 
considered  that  digestion  consisted  in  a  kind  of  cooking,  while  others 
held  that  the  action  was  like  that  of  putrefaction,  or  again  of  fermenta- 
tion. On  the  other  hand,  of  those  who  advocated  the  mechanical  theory 
of  digestion,  some  exaggerated  greatly  the  triturating  force  of  the  walls 
of  the  stomach,  while  to  others  even  holding  this  view  objections  had 
presented  themselves,  like  that  of  the  walls  of  the  stomach  being  too 
thin  in  many  animals  to  exercise  any  great  mechanical  force:  while  in 
birds,  like  the  ostrich,  in  which,  though  the  walls  of  the  muscular  giz- 
zard are  extremely  thick  and  very  powerful,  digestion  was  still  known 
to  have  taken  place  even  when  the  walls  of  the  stomach  had  been  com- 
pletely separated  by  a  foreign  body,  like  an  impacted  nail,  and  which 
prevented  entirely  any  triturating  action,  as  in  the  case  mentioned 
by  Yalisneri,  and  referred  to  by  Milne  Edwards.3  In  this  connection 
it  may  be  mentioned  that  in  dissecting  an  ostrich  the  author  also  found 
the  walls  of  the  stomach  completely  separated,  the  impacted  body  in 
that  case  being  a  piece  of  hard  wood. 

1  Liebig's  Annalen,  1854,  xcii.  S.  43.  -  Comptes  Rendus,  tome  lxxxiv.  p.  I'iO.    Pari*.  1877. 

3  riivsiologie,  tome  ciuquieme,  p.  526. 


128  GASTRIC    DIGESTION. 

The  controversy  between  physiologists  about  the  chemical  and  me- 
chanical nature  of  digestion  was  brought  to  a  termination  by  the  dis- 
covery of  Reaumur,1  in  1752,  of  the  existence  of  a  gastric  juice  in  birds, 
and  of  the  demonstration  that  substances  were  softened  and  partly 
digested  in  the  stomach  of  those  animals,  apart  from  any  mechanical 
action  of  its  walls.  Familiar  with  the  fact  that  birds  of  prey  frequently 
vomit  up  their  food,  and  that  falconers  were  in  the  habit  of  making 
their  birds  vomit,  they  considering  such  action  to  be  salutary  in  its 
effects ;  it  occurred  to  Reaumur  to  take  advantage  of  this  circumstance 
with  reference  to  examining  the  contents  of  the  stomach  during 
digestion. 

After  showing  the  triturating  effect  of  the  muscular  gizzard  in  those 
birds  in  which  it  is  much  developed,  he  proceeded  to  experiment  with 
birds  in  which  the  gizzard  is  little  developed,  like  a  buzzard,  for  ex- 
ample, in  the  following  manner:  Meat  was  placed  in  a  tin  tube,  the 
openings  at  both  ends  being  covered  with  a  grating  which  would  allow 
any  fluid  to  pass  into  the  tube  and  mix  with  the  meat,  while  the  meat 
would  be  unaffected  by  the  mechanical  action  of  the  walls  of  the  stomach, 
the  walls  of  the  tin  tube  being  sufficiently  strong  to  resist  the  latter. 
Having  forced  the  tube  into  the  stomach  of  a,  buzzard,  several  hours 
afterward  the  meat  was  found  softened  and  partly  digested.  In  substi- 
tuting for  the  tube  with  the  meat  small  pieces  of  sponge,  Reaumur  was 
able  to  collect,  by  pressing  the  sponges  after  they  had  been  rejected,  a 
small  quantity  of  a  liquid  which  gave  an  acid  reaction,  and  which  was 
the  first  specimen  of  a  solvent  fluid  from  the  stomach  ever  obtained. 
Reaumur  also  performed  some  experiments  with  the  gastric  juice  so 
obtained,  but  they  were  not  satisfactory.  In  extending  his  experiments 
on  birds,  to  dogs  and  sheep,  Reaumur  got  pretty  much  the  same  results, 
and  concluded2  that  meat  can  be  digested  in  the  stomach,  not  only 
without  having  been  ground  up,  but  without  even  having  suffered  the 
slightest  rubbing.  This  operation  can  then  be  only  the  work  of  a  dis- 
solvant,  of  which  the  existence  is  well  demonstrated.  The  next  step  in 
advance  was  made  in  1777,  by  Edward  Stevens,  good  use  being  made 
of  a  man  who  for  years  had  been  accustomed  to  exhibit  his  habit  of 
swallowing  stones.  Stevens  tells  us  in  his  Be  Alimentorum  Oon- 
eotione*  that  he  used  a  hollow  silver  ball,  perforated  with  numerous 
holes,  and  divided  into  two  parts  by  a  septum.  In  one  compartment, 
for  example,  meat  was  placed,  in  the  other  bleak.  The  man  would 
then  swallow  the  silver  ball.  After  twenty  to  forty  hours  it  would 
be  passed  by  the  anus,  and  its  contents  would  be  found  partially  di- 
gested. Stevens  experimented  in  this  way  with  different  kinds  of 
food,  and  unless  the  food  was  very  hard,  the  silver  ball  was  usually 
found  empty  when  passed  by  the  anus,  showing  that  some  solvent  must 
have  passed  into  the  ball.  The  individual,  however,  leaving  Edinburgh, 
Avhere  the  observations  had  been  made,  Stevens  repeated  his  experi- 
ments upon  dogs,  making  use  of  ivory  balls,  which  were  filled  with 
different  kinds  of  food,  and  obtained  essentially  the  same  results. 

In  summing  up,  Stevens  concludes  that  his  experiments  prove  clearly 

1  Memoires  de  1' Academie  des  Sciences,  1752,  tome  lxix.  p.  461 

2  Op.  cit,  p.  471.  3  Thesaurus  Medicus,  Smellie  Tomus  iii.  p.  481. 


EXPERIMENTS    ON    DIGESTION.  129 

and  manifestly  that  digestion  cannot  be  accounted  for  by  heat,  tritura- 
tion, putrefaction,  or  even  fermentation  alone,  but  by  a  most  powerful 
humor  which  is  secreted  by  the  tunic  of  the  stomach  and  is  poured 
into  the  cavity  of  the  same. 

A  few  years  later  there  appeared  the  celebrated  work  of  Spallanzani, 
in  Avhich  the  observations  of  Reaumur  and  Stevens  were  repeated  and 
confirmed,  and  extended  in  a  series  of  experiments  made  upon  quite  a 
number  and  variety  of  animals,  including  several  interesting  observa- 
tions made  by  the  author  upon  himself,  some  of  Avhich  have  already 
been  alluded  to  in  speaking  of  the  subject  of  mastication.  Spallanzani1 
began  his  experiments  upon  himself  by  first  swallowing  little  linen  bags 
in  which  the  different  articles  of  food,  animal  or  vegetable,  were  sewn 
up.  These  were  usually  passed  by  the  anus  within  a  period  varying 
from  twenty-three  to  twenty-four  hours,  and  were  found  either  empty 
or  nearly  so,  the  contents  being  more  or  less  digested,  according  to  the 
kind  of  food  used  and  the  length  of  time  during  which  they  had  re- 
mained within  the  body.  Emboldened  by  his  success,  Spallanzani  tells 
us  he  ventured  then  to  swallow  little  wooden  tubes  five  lines  in  leno-th 
and  three  in  diameter,  the  sides  of  which  were  perforated  with  numerous 
little  holes  to  permit  the  free  ingress  of  the  juices  of  the  stomach. 
These  tubes  when  passed  by  the  anus,  though  very  fragile,  were  never 
broken  or  bruised,  which  they  would  have  been  had  they  been  subjected 
to  a  triturating  action,  while  the  meat  which  they  contained  being 
digested  when  passed  by  the  anus  showed  that  the  result  must  be  due 
to  the  solvent  action  of  the  gastric  juice  entering  the  tubes.  The 
necessity  of  first  masticating  the  food  before  swallowing  it  was  then 
demonstrated  :  and,  in  conclusion,  a  little  gastric  juice  was  obtained  bv 
vomiting,  and  the  effect  of  this  upon  boiled  beef  tried  outside  the  body, 
with  the  result  of  showing  that  the  beef  became  pultaceous,  and  that 
there  was  no  putrefaction.  Spallanzani  distinctly  recognized  a  most 
important  fact,  that  the  process  of  digestion,  beginning  in  the  stomach, 
is  completed  in  the  intestines. 

In  1824  Prout2  endeavored  to  show,  by  analysis,  that  the  acidity  of 
the  gastric  juice  in  animals  was  due  to  hydrochloric  acid. 

Shortly  afterward,  between  1825  and  1827  simultaneously,  Leuret 
and  Lassaigne,3  Tiedemann  and  Gmelin,4  made  a  detailed  and  extended 
series  of  observations  upon  digestion  ;  those  of  the  latter  being  the  most 
elaborate.  The  experiments  were  made  principally  upon  dogs,  cats, 
horses,  cows,  sheep,  birds,  reptiles,  and  fishes,  the  observations  on  man 
being  exceptional.  In  some  of  the  experiments  the  means  of  obtaining 
the  gastric  juice  were  the  same  as  those  used  by  Reaumur,  etc.,  already 
referred  to.  In  many  of  them,  however,  another  plan  was  adopted. 
The  animal  to  be  experimented  upon  after  fasting,  was  made  to  swallow 
stones,  nails,  etc.,  a  few  hours  afterward  the  animal  was  killed,  it  having 
been  ascertained  that  such  hard  substances  would  excite  the  stomach  to 
secrete  a  considerable  amount  of  gastric  juice — sufficient  in  quantity  to 

1  Fisica  Aniiuale  e  Vegetable,  tonio  secundo,  pp.  42,  41,  51,  52,  58,  64.     Venezia,  1782. 

2  Philosophical  Transactions,  1824. 

3  Recherches  pour  servir  a  1' llistoire  de  la  Digestion.    Paris,  1825. 

4  Recherches  sur  la  Digestion.    Paris,  183" 

9 


130  GASTRIC    DIGESTION. 

analyze  and  to  experiment  with.  Notwithstanding  the  number  and 
variety  of  the  animals  experimented  upon  by  these  physiologists,  their 
conclusions  were  not  entirely  satisfactory,  as  the  results  of  their  experi- 
ments and  observations  were  often  contradictory  and  inconsistent. 
While  the  composition  and  properties  of  the  gastric  juice  were,  to  a  cer- 
tain extent,  known,  great  difference  of  opinion  still  prevailed  as  to  what 
elements  it  owed  its  digestive  powers,  and  exactly  what  effect  it  had 
upon  different  kinds  of  food.  Further,  while  many  observations  were 
made,  and  some  definite  conclusion  drawn  as  regards  digestion  in 
animals,  little  or  nothing  was  added  by  Prout,  Leuret  and  Lassaigne, 
Tiedemann  and  Gmelin  to  the  knowledge  of  digestion  as  it  takes  place 
in  man,  already  gained  from  the  experiments  of  Stevens  and  Spallanzani. 

Leaving  this  little  historical  digression,  which  was  indispensable  in 
order  to  appreciate  the  value  of  the  observations  of  Beaumont,  let  us 
see  now  what  was  established  by  this  physiologist. 

Beaumont  was  the  first  to  observe  digestion  as  it  goes  on  in  the 
healthy  human  stomach,  to  describe  not  only  the  motion  of  the  latter, 
but  also  the  manner  in  which  the  gastric  juice  is  secreted,  its  effect  upon 
food,  the  changes  that  food  undergoes  in  the  stomach,  to  collect  the  normal 
gastric  juice  in  such  quantities  that  it  could  be  analyzed  and  studied  with 
reference  to  its  effect  upon  food  outside  the  body.  Indeed,  it  is  not  too 
much  to  say  that  with  the  exception  of  Schmidt's  case  in  Dorpat,  and 
Bichet's  in  Paris,  to  be  mentioned  again  shortly,  all  that  is  positively 
known  of  gastric  digestion  in  man  is  derived  from  the  case  of  St.  Martin. 
I  mention  this  particularly,  as  there  seems  to  be  a  widespread  impres- 
sion that  our  knowledge  of  gastric  digestion  in  man  is  derived  entirely 
from  gastric  fistula  made  upon  dogs,  it  being  taken  for  granted  that 
the  dog  can  be  compared  with  man  in  this  respect,  the  fact  of  the 
animal  being  a  carnivorous  one  being  altogether  lost  sight  of.  Curiously 
enough,  it  is  also  often  forgotten  that  it  was  the  case  of  St.  Martin 
that  suggested  to  Bassow,1  the  Bussian  naturalist,  the  experiment  of 
making  a  gastric  fistula  upon  a  dog. .  It  may  be  mentioned  in  this 
connection  that  Blondlot2  usually  gets  the  credit  of  having  done  this 
first,  no  doubt  from  his  having  popularized  this  very  important  experi- 
ment, and  from  his  numerous  observations  on  digestion.  The  manner 
of  performing  this  operation,  which  is  sufficiently  simple,  consists3 
essentially,  a  dog  being  used,  in  making  an  incision  about  two  inches 
long  in  the  median  line  into  the  abdominal  cavity,  beginning  at  about 
one  inch  below  the  ensiform  cartilage.  The  stomach  is  then  drawn  out 
of  the  abdominal  cavity,  and  a  slit  just  large  enough  to  admit  the  canula 
is  made  parallel  with  the  longitudinal  fibres.  The  canula,  preferably  of 
silver,  about  two  inches  long,  and  half  an  inch  in  diameter,  is  provided 
at  both  ends  with  a  rim  or  flange,  by  which  it  can  be  securely  ligated 
to  the  edge  of  the  opening  in  the  stomach  and  the  opening  in  the 
abdominal  walls.  The  wound  cicatrizing  around  the  canula,  a  perma- 
nent fistula  into  the  stomach  is  established.    The  animal  in  a  short  time- 

1  Bulletin  de  la  Societe  des  Naturalistes  de  Moscow,  1843.  tome  xvi.  p.  315. 

2  Traite  analytique  de  la  digestion,  1843. 

3  Bernard :  Physiologic  Experimental,  tome  ii.  p.  384.   Paris,  1856. 


MUCOUS    MEMBRANE    OF    STOMACH.  131 

Buffers  no  inconvenience  whatever,  and  will  serve  indefinitely  as  a  means 
of  obtaining  natural  gastric  juice. 

In  order  to  study  digestion  in  man  it  is  not  necessary,  however,  to 
make  a  gastric  fistula  in  a  dog,  as  Eberle1  showed  in  1834,  that  if  the 
mucous  membrane  of  the  stomach  be  macerated  in  water  slightly  acidu- 
lated a  liquid  is  obtained  which  will  act  upon  food  in  the  same  manner 
as  the  natural  gastric  juice,  and  which  is,  in  fact,  an  artificial  gastric 
juice.  Eberle  fell  into  the  error,  however,  of  supposing  that  he  could 
obtain  the  same  results  from  an  acidulated  infusion  made  of  any  mucous 
membrane  whatever. 

It  may  be  mentioned  in  this  connection  that,  as  the  opportunity  does 
not  always  present  itself  of  obtaining  the  mucous  membrane  of  the 
human  stomach  in  a  perfectly  fresh  condition,  that  of  the  pig  will  do 
equally  well,  as  shown  by  Kolliker2  and  others,  which  is  perfectly  intel- 
ligible when  it  is  remembered  that  its  mucous  membrane  is  almost 
identical  with  that  of  man.  Before  describing  the  phenomena  of  diges- 
tion in  man,  as  learned  from  the  observations  of  Beaumont,  Schmidt, 
Richet,  and  experiments  with  artificial  gastric  juice,  let  us  first  con- 
sider the  structure  of  the  mucous  membrane  of  the  stomach  which 
secretes  the  juice,  through  which  digestion  in  this  part  of  the  alimentary 
canal  is  effected. 

The  mucous  membrane  of  the  stomach,  in  the  living  healthy  subject, 
is  of  a  velvety,  pulpy  consistence,  with  an  average  thickness  of  about 
the  2*oth  °f  an  mcn^  and  in  color  of  a  pale  pink  or  reddish  appearance, 
which  rapidly  changes  after  death  into  a  brownish  hue.  The  mucous 
membrane  is  loosely  attached  to  the  submucous  coat  or  the  layer  of 
areolar  tissue  which  lies  between  the  mucous  coat  within  and  the  mus- 
cular coat  without.  It  is  through  the  looseness  of  this  attachment  that 
the  longitudinal  folds  into  which  the  membrane  is  usually  thrown  are 
due.  and  which  are  effaced  when  the  stomach  is  distended.  The  epithe- 
lium covering  the  mucous  membrane  of  the  stomach  is  of  the  columnar 
character,  and  presents  more  particularly  at  the  cardiac  orifice,  a 
marked  contrast  as  compared  with  the  pavement  epithelium  lining  the 
oesophagus. 

If  the  mucous  membrane  of  the  stomach  be  gently  washed  by  allow- 
ing a  small  stream  of  water  to  run  over  it  slowly,  which  will  carry  off 
the  adhering  mucus,  and  then  be  examined  with  a  simple  lens,  little 
polygonal  spaces  or.  depressions  will  be  noticed  in  its  surface,  varying 
in  size  from  the  y^-th  to  the  2-ortn  °f  an  mcn  m  diameter.  If  these 
depressions  or  alveoli  be  further  examined  with  the  microscope,  they 
will  be  seen  to  consist  of  a  number  of  small  round  apertures  of  about 
the  3-5-oth  to  -g-jyg-th  of  an  inch  in  diameter.  These  minute  apertures 
are  the  mouth-like  openings  of  the  gastric  follicles,  small  tubules  vary- 
ing in  length  from  the  ^th  to  the  gL-th  0f  an  inch,  and  which  are  im- 
bedded in  the  mucous  membrane,  the  blind  or  closed  ends  of  the  tubules 
looking  outwardly  toward  the  submucous  coat,  the  open  ends  inwardly 
toward  the  interior  of  the  stomach  (Fig.  48). 

The  gastric  tubules  of  the  ostrich,  or  the  water-cells  of   the  first 

1  Physiologie  der  Verdauung,  S.  80.     Wurzburg,  1834. 

2  Gewebelehre,  Funfte  Auflage,  S.  402. 


132 


GASTRIC    DIGESTION 


stomach  of  the  llama  (Fig.  -f'1)  give  an  excellent  idea  of  the  general 

disposition  of  the  gastric  glands  of  the  human  stomach.      It  need  hardly 


Fig.  48, 


Stomach  of  llama.     Water  cells  seen  from  outside. 


Vertical  transverse  section  of  the 
coats  of  a  pig's  stomach.  30  diam- 
eters, a.  Gastric  glands,  b.  Muscu- 
lar layer  of  the  mucous  membrane. 
e.  Submucous  or  areolar  coat.  d. 
Circular  muscular  layer,  e.  Longi- 
tudinal muscular  layer.  /.  Serous 
coat.     (After  Kollikeb.) 


be  mentioned  that  the  water-cells  of  the 
llama  do  not  contain  gastric  juice,  the  latter 
being  secreted  by  the  tubules  of  the  fourth 
stomach.  The  gastric  tubules  differ  con- 
siderably in  their  structure  and  form,  ac- 
cording to  the  part  of  the  stomach  examined. 
Thus,  in  the  pyloric  portion  of  the  stomach  the  tubules  (Fig.  50)  are 
lined,  to  a  certain  extent  at  least,  with  a  continuation  of  the  columnar 
epithelium  covering  the  inner  surface  of  the  stomach;  in  the  upper 
parts,  however,  of  these  tubules  the  lining  cells  become  shorter  and 
more  cubical  in  character,  and  correspond  according  to  Ebstein1  and 
Heidenhain2  in  their  function  with  the  central  cells  found  in  the  tubules 
found  in  the  cardiac  part  of  the  stomach.  The  pyloric  tubules,  while 
terminating  usually  in  a  branched  manner,  terminate  also  simply.  If 
the  middle  zone  of  the  stomach  be  now  examined,  both  simple  (Fig.  51) 
and  branched  tubules  (Fig.  52)  will  be  found  resembling  those  in  the 
pyloric  portion,  but  while  the  upper  portion  of  the  tubule  (Figs.  50,  51) 
is  lined  with  columnar  epithelium,  the  succeeding  part  or  neck  is  filled 
rather  than  lined  by  large  ovoidal  or  spheroidal  granular  cells  of  about 
the  12100th  of  an  inch  in  diameter,  the  so-called  ovoid  cells,  formerly, 
however,  known  as  peptic  cells.  Toward  the  bottom  or  fundus  of  the 
gland  these  peptic  or  ovoid  cells  (Fig.  51,  P)  do  not  form  a  continuous 
layer,  but  are  seen  scattered  here  and  there,  and  bulging  out  so  as  to 
give  the  tubule  a  varicose  appearance,  the  remaining  portion  of  the 
tubule,  except  the  narrow  passage-way  in  the  middle,  being  occupied  by 


i  Archiv  f.  Mic.  Anat.,  Band  vi.  S.  515,  1870. 

2  Hermann  :  Physiologie,  Funfter  Band,  S.  598.     Leipzig,  1880. 


GASTRIC     GLANDS. 


133 


finely  granular  polyhedral  angular  cells,  the  so-called  central  cells, 
similar,  as  just  mentioned,  to  those  found  in  the  pyloric  tubules.  In 
the  cardiac  portion  of  the  stomach,  more  particularly  around  the  cardiac 
orifice,   the  tubules   are  branched  in  character,  the  upper  part  of  the 

tubule    dividing    into    two    or 
Fig.  51.  three  branches,  and  there  usu- 

c  ally  subdividing  again.     These 

cardiac  tubules,  like  simple 
ones  found  in  the  middle  zone 
of  the  stomach,  contain  both 
ovoid  and  central  cells.  It 
will  be  observed  from  this  brief 
description  that  two  kinds  of 
glands  are  found  in  the  human 
and  canine  stomach,  differing; 
essentially  in  their  structure: 

Fin.  52. 


Gastric  glands  from  the  tlog's 
stomach.  M.  A  pyloric  or 
mucous  gland.  m.  Mouth. 
n.  Neck  tr.  A  deep  portion 
cut  transversely.      (After  Kb- 

STF.IN. I 


Gastric  glands  from  the 
stomach,  highly 
magnified.  1.  Neck  of  the 
gland.  2.  Fundus.  3. 
Transverse  section.  P. 
Peptic  or  ovoid  cells.  H. 
Central  cells.  C  Ends  of 
columnar  cells.  (After 
Hf.idenhain.) 


Gastric   gland  from  human   stomach.     1. 
Columnar  cells.    2.  Ovoid  cells.    (Kollikee.) 


pyloric  tubules,  simple  and  branched,  situated  in  the  pyloric  part  of 
the  stomach,  containing  columnar,  epithelial,  and  central  cells ;  cardiac 
tubules,  simple  and  branched,  situated  in  the  middle  and  cardiac  parts 
of  the  stomach,  containing  columnar,  epithelial,  and  central  cells,  and 
ovoid  cells  also. 

While  undoubtedly  such  a  distinction  as  that  just  described  exists 
between  the  gastric  glands  in  man,  the  exact  line  of  demarcation  is  not 
as  distinct  as  in  that  of  the  dog  ;  the  different  kind  of  glands  passing  in 


134  GASTRIC    DIGESTION. 

man  into  each  other  through  intermediate  forms.  Around  the  csecal 
ends  of  the  cardiac  tubules,  more  particularly,  are  usually  found  a  few 
involuntary  muscular  fibres,  the  effect  of  the  contraction  of  which  is  to 
force  out  their  contents.  The  stomach  is  a  highly  vascular  organ,  as 
one  would  suppose  from  the  large  size  of  the  arteries  supplying  it.  It 
is  not  necessary,  however,  to  describe  in  detail  its  vascular  supply,  and 
simply  mentioning,  also,  that  at  the  pyloric  portion  of  the  stomach  some 
rudimentary  villi  are  found,  and  that  scattered  all  through  the  organ 
solitary  glands  may  be  seen,  whose  minute  structure  will  be  considered 
elsewhere,  I  will  pass  on  to  the  manner  in  which  the  gastric  juice  was 
said  to  be  secreted  in  St.  Martin.  During  the  intervals  of  digestion  the 
stomach  is  empty,  its  mucous  membrane  being  simply  covered  with  a 
very  thin,  transparent,  viscid  mucus.  At  this  time  the  reaction  of  the 
membrane  is  either  faintly  alkaline  or  neutral.  With  the  introduction 
of  food  into  the  stomach,  the  membrane  at  once  changes  its  pale  ap- 
pearance, becoming  red  and  turgid  from  the  increased  amount  of  blood. 
Small  drops  of  gastric  juice  appear  as  small  pellucid  points  on  the  sur- 
face of  the  membrane,  which  has  now  an  acid  reaction,  and  gradually 
a  little  stream  of  gastric  juice  begins  to  flow  upon  the  food  in  the 
stomach.  Beaumont  showed  most  conclusively  that  food  is  the  natural 
stimulus  to  the  secretion  of  the  healthy  gastric  juice.  "Let  good  diges- 
tion wait  on  appetite,"  for  the  exciting  impression  of  food  is  diffused 
over  the  whole  secreting  surface,  and  the  maximum  effect  is  thereby 
obtained.  Local  stimulus,  however,  like  that  of  an  India-rubber  tube, 
will  excite  a  flow,  and  this  Beaumont  used  when  a  small  quantity  of 
gastric  juice — an  ounce  and  a  half,  for  example — was  required  unmixed 
with  mucus  or  food.  Everyone  knows  from  experience,  how  digestion 
is  influenced  by  the  nervous  system — a  bad  piece  of  news,  a  sudden 
shock,  stopping  digestion  entirely,  perhaps,  for  hours.  Beaumont  ob- 
served that  whenever  the  nervous  system  was  disturbed  or  depressed  by 
anger  or  fear,  by  undue  excitement  from  stimulating  liquors,  from  over- 
loading the  stomach,  etc.,  the  mucous  membrane  became  pale  and  moist 
or  red  and  dry,  and  the  secretions  vitiated,  diminished,  or  altogether 
suppressed.  It  was  also  noticed  that  when  St.  Martin's  stomach  was 
out  of  order  or  inflamed,  the  same  kind  of  morbid  condition  was  exhibited 
by  the  tongue,  the  condition  of  the  latter  being  relieved  by  placing  a 
little  magnesia  upon  the  surface  of  the  stomach,  thus  illustrating  the 
intimate  sympathy  existing  between  the  two  organs.1 

It  is  impossible  to  state  exactly  the  amount  of  gastric  juice  secreted 
by  a  man  during  the  twenty-four  hours.  Approximately  it  may  be  said 
to  amount  to  about  seven  kilogrammes  (fourteen  pounds)  daily.  This 
estimate  is  based  upon  the  amount  of  gastric  juice  absolutely  collected 
from  animals  whose  weight  was  compared  with  that  of  an  adult  man,2 
and  by  the  amount  of  gastric  juice  necessary  to  digest  a  known  quantity 
of  meat,  one  gramme  of  meat  (about  half  a  drachm)  requiring  13.5 
grammes  (about  one  fluidounce)  of  gastric  juice.3  It  must  be  remem- 
bered, however,  that  the  gastric  juice  is  being  reabsorbed  with  the  food 

i  Beaumont,  op   cit.,  pp.  103,  104,  105,  106,  107,  108,  109. 
-  Schmidt:  Liebig's  Annalen,  1854,  xcii.  S.  46. 
-'■  Dalton's  Physiology,  7th  ed.,  L882,  p.  162. 


GASTRIC    JUICE.  135 

as  it  is  being  secreted,  and  that,  therefore,  there  is  some  risk  of  counting 
the  same  gastric  juice,  or  the  elements  of  the  same,  over  again.  Obser- 
vations made  upon  dogs  by  Blondlot,1  may  be  mentioned  here  in  refer- 
ence to  the  influence  that  swallowing  food  has  upon  the  amount  of  the 
gastric  juice  secreted.  This  experimenter  noticed  that  alkalies  increase 
the  flow  of  the  gastric  juice  while  acids  diminish  it,  hence  the  importance 
of  the  alkaline  saliva  in  promoting  gastric  digestion.  But  the  mere 
effect  of  gustation,  apart  from  the  admixture  of  the  saliva  with  the  food, 
exerts  an  influence  on  the  flow  of  the  gastric  juice,  for  when  sugar,  even 
when  mixed  with  saliva,  was  passed  directly  into  the  stomach  of  the 
dog  through  the  fistulous  opening,  a  smaller  quantity  of  gastric  juice 
was  secreted  than  when  the  sugar  was  first  introduced  through  the 
mouth.  The  experiments  of  Kolliker,2  Goll,  and  Donders  with  the 
mucous  membrane  of  the  stomach  of  man  and  the  pig,  and  which  the 
author  has  had  opportunities  of  confirming,  show  pretty  conclusively 
that  the  true  gastric  juice  is  only  secreted  by  the  cardiac  tubules,  or 
those  tubules  which  contain  both  ovoid  and  central  cells ;  the  pyloric 
tubules,  containing  only  central  cells,  supplying  probably  pepsin ;  the 
columnar  epithelial  cells  lining  the  interior  of  the  stomach  and  more  or 
less  prolonged  into  the  cardiac  and  pyloric  tubules,  elaborating  mucus. 

Judging  from  what  has  been  learned  of  the  process  of  salivary  secre- 
tion, analogy  would  lead  us  to  suppose  that  the  gastric  juice  is  secreted 
in  an  essentially  similar  manner,  and  such  would  appear  to  be  the  case, 
as  shown  more  particularly  by  the  researches  of  Heidenhain.3  Thus,  if 
sections  of  the  gastric  glands  of  an  animal  be  examined  before  the 
taking  of  food,  the  so-called  central  cells  of  the  cardiac,  as  well  as 
those  of  the  pyloric  glands,  will  be  found  pale,  finely  granular,  and 
not  staining  readily  with  aniline  or  carmine.  With  the  beginning 
of  digestion,  however,  these  cells  become  swollen,  coarsely  granular, 
turbid,  and  stain  more  readily  with  the  above  reagents  ;  as  digestion 
continues,  the  coarse,  granular,  and  turbid  condition  and  disposition  to 
stain  increase,  while  at  the  same  time  the  cells  become  smaller  and 
shrunken.  The  only  conclusion  to  be  drawn  from  the  changes  in  the 
character  of  these  cells  is,  that  the  development  of  a  coarsely  granular, 
readily  stainable  material,  etc.,  during  digestion  constitutes  the  elabora- 
tion out  of  that  albuminous  principle  of  the  gastric  blood  of  either  pepsin 
itself,  or,  what  is  more  probable,  of  pepsinogen,  or  a  stage  in  the  forma- 
tion of  the  same — a  propepsin,  so  to  speak.  And  since  the  changes 
just  described  take  place  equally  in  the  centre  cells  of  the  pyloric,  as 
well  as  of  the  cardiac  portion  of  the  stomach,  it  follows,  as  held  by 
Heidenhain,4  that  the  former  as  well  as  the  latter  produce  pepsin,  and 
this  conclusion,  based  upon  histological  grounds,  is  confirmed  by  the 
physiological  fact  of  an  acid  infusion  of  the  pyloric  glands  possessing 
digestive  properties.  Inasmuch,  however,  as  the  ovoid  or  peptic  cells 
of  the  cardiac  portion  of  the  stomach  do  not  exhibit  during  digestion 
the  histological  changes  observed  in  the  central  cells  of  the  cardiac  and 
pyloric  glands,  only  swelling  up  and  projecting  somewhat  externally 
from  the  wall  of  the  gland,  and  from  the  fact  of  ovoid  cells  being  present 

1  up.  rit..  p.  219.  -  Loc.  cit. 

a  Hermann  :  Handbuch.  Fuufter  Band,  1880,  S.  141.  *  Ibid.,  S.  130. 


18b'  GASTRIC    DIGESTION. 

in  the  glands  of  the  stomach  of  the  frog  coincidently  with  the  presence 
of  acid,  the  pepsin-forming  cells  being  confined  almosl  entirely  to  the 
lower  part  of  the  oesophagus  in  that  animal,  it  would  seem  reasonable 
to  attribute,  with  Heidenhain,1  to  the  ovoid  cells  the  production  of  the 
acid  of  the  gastric  juice,  either  out  of  the  sodium  chloride  of  the  blood, 
or  ■  u ii<-  less  stable  chloride  compound.  If  such  be  the  case,  however, 
it  is  somewhat  difficult  to  understand  why,  after  injecting  ferrocyanide 
of  potassium  and  ferric  lactate  into  the  blood  of  an  animal,  as  in  the  ex- 
periment of  Bernard,2  the  production  of  Prussian  blue  should  be  limited 
to  the  surface  of  the  stomach,  since  if  the  ovoid  cells  of  the  glands 
actually  produce  the  acid  the  presence  of  which  is  necessary  for  the 
formation  of  the  salt,  the  Prussian  blue  should  be  visible  in  the  cells  of 
the  fundus  or  their  vicinity,  as  well  as  upon  the  surface  or  mouth  of  the 
gland,  unless  the  acid  is  expelled  from  the  gland  as  rapidly  as  produced, 
which  is  not  improbable. 

It  may  be  mentioned  in  this  connection,  that  the  acidity  of  the  long, 
tubular-like  gastric  glands  of  birds  is  also  restricted  to  the  mouths  of 
the  glands. 

Notwithstanding  what  has  just  been  said,  it  must  be  admitted  that 
the  physico-chemical  changes  upon  which  the  elaboration  of  the  gastric 
juice  depends,  are,  as  regards  many  points,  still  very  obscure. 

i  Op.  'it  .  S.  135,  148.  '-  Lif.uidesde  l'Organisme,  tome  ii.  p.  375.     Paris,  1859. 


CHAPTER    IX. 

GASTRIC    DIGESTION.— (Continued.) 

Composition  of  Gastric  Juice. 

The  first  to  attempt  to  analyze  the  gastric  juice  was  Scopoli,  an 
Italian  chemist,  in  the  last  century.  The  gastric  juice  examined  was 
obtained  by  Spallanzani  from  a  raven,  and,  according  to  Scopoli,1  con- 
sisted of  an  animal  matter,  earthy  salts,  and  what  would  now  be  called 
hydrochloric  acid.  The  gastric  juice  of  St.  Martin  was  examined  by  the 
late  Professor  Dunglison,  who,  in  a  letter  to  Beaumont,"  states  that  it 
contained  free  muriatic  and  acetic  acids,  phosphates,  and  muriates,  with 
bases  of  potassium,  sodium,  magnesium,  and  calcium,  and  an  animal 
matter  soluble  in  cold  water,  but  insoluble  in  hot ;  the  specific  gravity, 
according  to  Silliman,  being  1.005.  Numerous  analyses,  during  the  early 
part  of  this  century,  were  also  made  of  the  gastric  juice  of  different  kinds 
of  animals  by  Prout,  Leuret  and  Lassaigne,  Tiedemann  and  Gmelin,  and 
later  by  Bernard,  and  Barreswil,3  Blondlot,  and  others.  The  results  of 
these  analyses  essentially  agree  so  far  as  relates  to  the  presence  of  salts 
and  an  animal  matter.  The  main  difference  in  them  is  as  regards  the 
acid  that  gives  the  gastric  juice  its  decidedly  acid  reaction.  The  most 
minute  and  thorough  analysis  of  the  human  gastric  juice  yet  made  is 
that  of  Schmidt.  Schmidt  and  his  pupils  had  under  observation  for 
several  weeks  in  Dorpat  a  woman  who  had  a  fistulous  opening  in  the 
stomach,  and,  as  her  general  health  was  good,  there  is  no  reason  to 
suppose  that  her  gastric  juice  was  abnormal  in  any  respect.  Table 
XXXV.  gives  the  mean  of  two  distinct  analyses  made  of  the  woman's 
juice  by  Schmidt : 

Table  XXXV.4 — Composition  of  Human  Gastric  Juice 
holding  Saliva. 

Water 994.400 

Pepsin,  etc 3.195 

Hydrochloric  acid 0.200 

Calcium  chloride        ........  0.061 

Sodium  chloride         ........  1.464 

Potassium  chloride 0.-550 

Calcium       "| 

Magnesium     phosphate 0.125 

Ferrum         ) 

Loss 0.005 

1000.000 

i  Spallanzani,  op.  cit.  2  Op.  cit.,  pp   78,  81. 

3  Coinptes  Rendus,  1844,  tome  ix.  4  Annalen  der  Chemie,  L854,  Rami  xcii.  S.  46. 


138  GASTRIC    DIGESTION. 

Schmidt  gives  as  the  mean  of  the  two  analyses  the  number  994.404 
for  the  water,  and  1.465  for  the  sodium  chloride.  This  is  probably  a 
typographical  error,  as  the  other  numbers  are  those  given  in  the  table. 

The  loss,  which  is  fractional  in  the  mean  of  the  two  analyses,  is  not 
given  in  the  original  paper. 

It  will  be  seen  from  this  analysis  that  human  gastric  juice  consists  of 
water,  pepsin,  hydrochloric  acid,  chlorides,  and  phosphates.  Pepsin, 
the  organic  nitrogenized  principle  of  the  gastric  juice,  was  discovered 
and  named  by  Schwann,1  though  more  thoroughly  investigated  by 
Wasmann.  It  is  usually  prepared  at  the  present  day  by  making  an 
infusion  of  the  stomach,  filtering  and  precipitating  by  lead  acetate  ; 
sulphuretted  hydrogen  being  then  added  to  the  precipitate,  an  insoluble 
lead  oxide  is  formed,  and  the  pepsin  is  set  free.  This  is  further 
treated  with  absolute  alcohol,  and  then  appears  as  a  whitish  neutral 
powder.  When  pepsin  is  dissolved  in  slightly  acidulated  water  an 
artificial  gastric  juice  is  obtained  differing  but  little,  except  in  power, 
from  the  natural  secretion.  The  pepsin  obtained  directly  from  the 
gastric  juice  by  treating  with  alcohol  is  more  powerful  than  that  derived 
by  the  methods  just  referred  to.  In  the  amount  of  pepsin  given  in 
Table  XXXV.  it  should  be  mentioned  that  a  small  trace  of  ammonia  was 
reckoned  with  it,  which  was  probably  developed  during  the  analysis. 
At  the  present  day  there  is  still  some  question  among  physiologists  as 
to  whether  the  acidity  of  the  gastric  juice  in  animals  depends  upon 
hydrochloric  or  lactic  acid. 

What  interests  us  at  this  moment  is  as  to  the  acidity  of  the  human 
gastric  juice.  It  has  been  ascertained  that  it  is  immaterial  whether 
the  pepsin  be  acidulated  with  hydrochloric  or  lactic  acid  so  far  as  its 
digestive  action  is  concerned,  the  onty  difference  being  that  a  greater 
effect  is  obtained  with  the  hydrochloric  than  with  the  lactic  acid :  a 
priori,  then  we  might  expect  to  find  either  acid,  or  even  both,  according 
to  the  circumstances  under  which  the  individual  is  living  whose  gastric 
juice  is  analyzed.  As  a  matter  of  fact,  free  hydrochloric  acid  was 
obtained  with  great  readiness  by  the  late  Professor  Dunglison  from  the 
gastric  juice  of  St.  Martin,  and,  as  we  see  from  Table  XXXV.,  by 
Schmidt,  from  that  of  the  woman  in  Dorpat.  The  objection  is  often 
made  that  the  hydrochloric  acid  obtained  by  these  observers  was  due 
to  their  method  of  analysis :  its  presence  being  due  to  the  lactic  acid 
decomposing  the  alkaline  chlorides  at  a  certain  elevation  of  tempera- 
ture, it  being  assumed  that  lactic  acid  is  the  free  acid  of  the  gastric 
juice.  On  the  other  hand,  it  is  well  known  that  under  certain  con- 
ditions lactic  acid  is  generated  in  the  system  in  the  secretions  or  from 
the  food,  and  its  presence  in  the  gastric  juice  may,  therefore,  at  times 
be  accidental.  It  is  proper  to  state,  however,  that  the  late  Prof.  F.  G. 
Smith,2  in  examining  the  gastric  juice  of  St.  Martin,  in  1856,  found 
mostly  free  lactic  acid,  but  little  hydrochloric.  An  important  observa- 
tion, bearing  upon  this  question,  was  made  by  Prof.  Graham.3  Some 
fluid,  supposed  to  be  gastric  juice,  obtained  by  the  late  Dr.  Bence  Jones 

l  Muller's  Archiv,  1836,  S.  66 

"-  Philadelphia  Examiner,  Philadelphia,  1856,  p   393 

3  CarpeDter's  Physiology,  8th  ed.,  p.  156. 


ACTION    OF    G-ASTKIC    JUICE    UPON    FOOD.  139 

from  a  patient  affected  with  sarcina  ventricnli,  was  analyzed  by  the 
method  of  dialysis,  which  does  not  involve  heat,  and  gave  signs  of  con- 
taining both  hydrochloric  and  lactic  acids,  the  latter  being  comparatively 
small  in  quantity. 

The  question  of  the  acidity  of  the  human  gastric  juice  reduces  itself, 
therefore,  as  to  whether  it  depends  upon  hydrochloric  or  lactic  acid,  or 
both.  The  evidence  at  present  seems  to  us  to  favor  the  view  that 
hydrochloric  acid  is  the  acid  of  the  gastric  juice.  Practically,  however, 
so  far  as  digestion  is  concerned,  either  of  these  acids,  or  even  acetic  will 
do,  though  it  is  not  true  that  any  acid  will  replace  the  hydrochloric  or 
lactic ;  acids,  like  malic,  tartaric,  tannic,  etc.,  retarding  or  stopping 
digestion.  The  most  important  fact  in  gastric  digestion  is  that  the 
pepsin  should  be  acidulated  with  either  hydrochloric  or  lactic  acid. 
Pepsin  without  acid  will  not  digest,  and,  on  the  other  hand,  acidulated 
water  without  pepsin  is  equally  without  digestive  effect. 

Whether  the  acid  and  the  pepsin  are  united  in  the  gastric  juice,  acting 
as  one  substance,  or  whether  they  exist  there  independently,  has  not 
yet  been  positively  determined.  The  remaining  matters  entering  into 
the  composition  of  the  gastric  juice  are  unessential  in  digestion,  so  far 
as  is  at  present  known. 

Let  us  now  turn  to  a  consideration  of  the  action  of  the  gastric  juice 
upon  the  different  articles  of  food.  Our  knowledge  in  this  respect,  so 
far  as  the  living  man  is  concerned,  is  essentially  based  upon  the  obser- 
vations of  Beaumont,'  supplemented  by  those  of  Schmidt,  Richet,  etc. 
The  principal  effects  of  the  gastric  juice  upon  food,  as  observed  in  man, 
can,  however,  be  easily  demonstrated  with  a  gastric  juice  artificially 
prepared  in  the  following  manner  : 

The  dried  mucous  membrane  of  the  stomach  is  cut  up  into  small 
pieces  and  placed  in  suitable  test-tubes,  into  which  distilled  water  is  then 
poured.  To  this  infusion  of  the  mucous  membrane  there  should  then 
be  added  a  few  drops  of  hydrochloric  acid.  The  artificial  gastric  juice 
so  prepared  should  further  be  maintained  at  a  temperature  of  about 
100°  F.  Into  the  test-tubes  can  now  be  put  small  pieces  of  coagulated 
white  of  egg,  boiled  meat,  etc.,  and  which,  when  left  there  about  twelve 
hours,  will  be  found  digested.  A  little  stirring  from  time  to  time  will 
aid  the  process. 

In  order  to  show  the  necessity  of  the  combined  effects  of  the  pepsin 
and  the  acid,  it  is  well  to  have  at  the  same  time  one  test-tube  containing 
the  macerated  mucous  membrane  only,  and  another  with  acid,  but  with- 
out the  prepared  membrane.  The  food  in  these  two  test-tubes  will  be 
found  comparatively  unchanged,  that  in  the  tube  containing  the  hydro- 
chloric acid  having  become  only  syntonin.  Post-mortem  examinations 
made  upon  individuals  dying  during  digestion  also  offer  opportunities  of 
examining  the  effect  of  the  gastric  juice  upon  food,  which,  unfortunately, 
are  too  often  neglected.  At  one  time  it  was  supposed  that  the  gastric 
juice  acted  upon  all  kinds  of  food.  It  is  well  known  now,  however,  that 
its  action  is  limited  almost  entirely  to  those  foods  containing  nitrogenized 
principles,  such  as  meat,  milk,  eggs,  gelatin,  cheese,  bread  and  other 

1  Op.  .it.,  pp.  125,  126,  1'27,  148,  149,  200. 


1 40  GASTRIC     DIGESTION. 

vegetable  foods  containing  gluten;  the  starches,  sugars,  oils,  and  fats 
undergoing  little  it' any  change  in  the  stomach.  When  meat  is  subjected 
to  the  action  of  the  gastric  juice,  whether  obtained  from  a  fistula  in  the 
stomach  or  artificially  prepared,  it  will  be  observed  that  it  gradually 
becomes  softer,  changes  in  color,  and  breaks  down  into  a  grumous,  pul- 
taceous  mass.  Under  the  microscope  the  muscular  fibres,  though  broken 
up  into  small  pieces  and  retaining  but  little  tenacity,  are  readily  recog- 
nized through  their  characteristic  strise.  The  intermuscular  connective 
tissue,  sarcolemma,  has  disappeared,  however,  being  completely  dis- 
solved out.  Meat  is,  therefore,  not  actually  dissolved  in  the  stomach — 
it  is  rather  disintegrated  into  a  pultaceous  liquid,  which,  passing  easily 
into  the  small  intestine,  is  there  still  further  digested.  Beaumont,  in 
his  experiments  with  natural  gastric  juice,  usually  used  about  one  ounce 
of  gastric  juice  to  one  drachm  of  food.1 

It  is  a  matter  of  common  observation  that  raw  or  soft-boiled  eggs  are 
more  easily  digested  than  hard-boiled  ones  ;  and  experiments,  both  with 
the  natural  and  artificial  juice,  show  that  the  raw  white  of  egg  is  more 
quickly  broken  clown,  disintegrated,  and  the  pure  albumen  separated 
from  the  membranous  sacs,  than  when  the  cooked  egg  is  used.  Gelatin 
is  rapidly  dissolved  by  the  gastric  juice ;  and  casein,  as  in  milk,  is  first 
coagulated  by  it  and  then  digested  like  coagulated  albumen.  The  gastric- 
juice  not  only  acts  physically  upon  the  nitrogenized  articles  of  the  food, 
softening,  disintegrating  them,  etc.,  but  so  changes  the  molecular  ar- 
rangement of  the  chemical  principles  composing  them  that  they  cannot 
be  recognized  by  the  usual  tests  for  albumen,  such  as  heat,  nitric  acid,  etc. 

Thus  albumen  becomes  albuminose  or  albumen-peptone,  differing 
from  albumen  also  in  one  most  important  respect — that  it  can  be  ab- 
sorbed, whereas  albumen  when  injected  undigested  into  the  blood  will 
be  excreted  by  the  kidneys,  it  not  being  assimilated.2  Casein  is  changed 
during  gastric  digestion  into  casein-peptone,  fibrin  into  fibrin-peptone, 
etc.  Milk,  as  is  well  known  to  those  engaged  in  the  making  of  cheese, 
is  curdled  by  the  gastric  juice — that  is  to  say,  its  casein  is  precipitated. 
This  effect  is  not  due,  however,  as  might  be  supposed,  to  the  acid  present, 
as  gastric  juice  after  being  neutralized  is  still  efficacious  in  this  respect, 
but  probably  to  some  special  ferment,  since  the  neutralized  gastric  juice, 
after  boiling,  loses  this  property,  and  from  the  fact  that  the  effect  is 
largely  dependent  upon  temperature.  The  general  product  of  the 
digestion  of  the  albuminous  or  nitrogenized  principles  by  the  gastric 
juice  is  often  spoken  of  as  albuminose  or  peptone,  so  named  by  Mialhe3 
and  by  Lehman,4  respectively.  The  peptones  all  agree  in  being  soluble 
in  water  and  not  precipitated  by  heat,  acids,  or  alkalies,  and  eminently 
diffusible.  As  shown,  however,  by  both  these  chemists,  slight  differences 
exist  between  these  products  of  digestion,  according  to  the  particular 
kind  of  food  used,  and  hence  it  is  more  proper  to  speak  of  them  in  the 
way  just  indicated. 

Much  difference  of  opinion  still  prevails  among  physiologists  as  to 
the  changes  which  albuminous  substances  undergo    during   digestion. 

i  Op.  cit.,  p.  269. 

2  Bernard:  Liquides  de  l'Organisme,  tome  i.  p.  467.     Paris,  1859.    ■ 

3  Memoire  sur  la  digestion  et  l'aasimilation  de.-s  materies  albuminoides.     Paris,  1847. 

4  Lehrbuch  der  pbysiologiscben  chemie,  Band  ii.  S.  46. 


ACTION    OF    GASTRIC    JUICE     UPON    FOOD.  141 

According  to  Brucke,1  albuminous  substances  are  converted  in  the 
stomach  first  into  syntonin,  and  then  into  peptone,  a  simple  expression 
of  the  facts  we  have  just  demonstrated,  the  phenomenon  being  essentially, 
according  to  Hoppe-Seyler,2  one  of  hydration  in  the  presence  of  pepsin. 
Meissuer,3  however,  holds  that  albumen  is  only  imperfectly  digested  by 
gastric  juice,  becoming  peptone  and  parapeptone,  the  latter  being  an 
imperfect  form  of  peptone,  and  requiring  further  digestion  in  pancreatic 
juice  to  convert  it  into  peptones ;  while,  according  to  Kuhne,4  albu- 
minous substances  undergo  still  more  complex  changes  in  being  trans- 
formed into  peptone,  the  albumen  being  first  converted  into  two 
substances,  each  of  which  passes  through  a  series  of  intermediate  stages 
before  becoming  what  is  called  by  Kuhne  antipeptone  and  hemipeptone  ; 
the  one  series,  to  which  the  antipeptone  belongs,  being  acted  upon  more 
particularly  by  the  pepsin  of  the  gastric  juice  ;  the  other,  to  which  the 
hemipeptone  belongs,  by  the  gastric  and  pancreatic  juices  combined  ; 
the  hemipeptone,  through  the  influence  of  the  trypsin  of  the  pancreatic 
juice,  being  finally  converted  into  leucin,  tyrosin,  etc.  Until,  however, 
the  facts  upon  which  such  views  are  based  are  better  established  and  the 
contradictions  involved  are  reconciled,  it  will  be  impossible  to  say  which 
of  the  above  views,  if  any,  is  entitled  to  the  most  credit  as  representing 
the  actual  changes  through  which  albuminous  substances  pass  in  be- 
coming peptones. 

A  curious  fact  during  the  action  of  the  gastric  juice  upon  meat,  and 
not  yet  understood,  is  the  absence  of  putrefaction.  The  explanation 
usually  offered  of  this,  that  two  catalytic  actions  do  not  go  on  simul- 
taneously, is  simply  a  restatement  of  the  fact  to  be  explained,  catalysis 
being  simply  a  convenient  word  expressing  our  ignorance  of  the  phe- 
nomena. The  action  of  the  gastric  juice  upon  fats  appears  to  consist 
simply  in  dissolving  the  fat  vesicles  and  so  allowing  the  escape  of  their 
oily  contents.  When  fat  is  taken  into  the  stomach  as  oil  it  passes 
through  the  pylores  into  the  small  intestine  unchanged.  Glucose  or 
grape  sugar  does  not  appear  to  be  affected  by  the  gastric  juice,  and  it  is 
probable  that  this  kind  of  sugar  is  at  once  absorbed  as  soon  as  taken  into 
the  stomach.  Experiments  with  artificial  gastric  juice  upon  cane  sugar 
show,  however,  that  after  several  hours  it  is  converted  into  grape  sugar. 
This  effect  seems  to  depend  simply  on  the  acid  of  the  gastric  juice,  and 
as  the  change  takes  place  very  slowly,  it  is  not  likely  that  any  amount 
of  cane  sugar  is  converted  into  glucose  in  the  stomach. 

There  is  still  some  doubt  as  to  the  effect  of  gastric  juice  upon  starch 
in  the  stomach.  This  is  due  to  the  fact  that  the  saliva  will  continue  to 
transform  starch  into  sugar  after  the  food  has  passed  into  the  stomach, 
the  gastric  juice,  in  man  at  least,  not  interfering  with  this  action.  When 
starch  is  therefore  transformed  into  sugar  in  the  human  stomach  it  is 
probably  due  to  the  saliva  swallowed.  It  should  be  mentioned,  however, 
that,  according  to  the  late  Prof.  F.  G.  Smith,5  starch  was  converted  into 
sugar  when   introduced  directly  into  the  stomach  of  St.  Martin,  though 

1  Vurlesmigcn,  Ereter  Band,  S.  .'ill.    Wien,  1881. 

a  Physiol.  Cbemie,  II.  Theil,  S.  227.  Berlin,  1878. 

^  Zeits.  f.  Rat.  Med.,  vii.  1  ;  viii.  280  ;  x.  1  ;  xii.  Ifi  ;  xiv.  303. 

4  Verhand.   Nat.  Hist.  Verein.    Heidelberg,  1876. 

6  Op.  cit.,  p.  518. 


142  GASTRIC    DIGESTION. 

the  man  carefully  avoided  swallowing  his  saliva  during  the  period  of  the 
experiment.  The  effect  in  this  cast",  however,  was  probably  due  not  to 
the  gastric  juice,  but  to  the  gastric  mucus. 

Artificial  gastric  juice  out  of  the  body  has  no  effect  upon  starch  so 
far  as  the  formation  of  sugar  is  concerned  ;  it  will,  however,  dissolve  the 
cells  and  set  free  the  starch  when  the  substance  is  used  in  this  form.  It 
was  shown  by  Beaumont  that  bones  are,  to  a  certain  extent,  digested  by 
the  gastric  juice,  a  small  portion  being  dissolved.  As  the  calcium  phos- 
phate and  carbonate  are  so  indispensable  in  nutrition,  and  as  the  calcium 
Diphosphate  is  soluble  in  acids,  the  stomach  is  that  part  of  the  aliment- 
ary canal  where  one  would  naturally  look  for  the  solution  of  bone  in 
digestion. 

According  to  Beaumont,1  water,  alcohol,  and  other  fluids  seem  to  be 
unaffected  by  the  gastric  juice,  passing  either  into  the  intestine  or  being 
directly  absorbed  by  the  stomach. 

In  making  experiments  upon  digestion  with  natural  or  artificial  gas- 
tric juice,  it  will  be  found  that  in  order  to  insure  success  a  temperature 
of  about  100°  F.  should  be  constantly  maintained. 

From  a  great  number  of  experiments  performed  upon  St.  Martin 
Beaumont2  concluded  that  the  natural  temperature  of  the  human  stomach 
was  100°  Fahr.,  and  that  the  injection  of  food  into  the  stomach  did 
not  elevate  the  temperature.  The  importance  of  heat  in  digestion  will 
be  seen  when  this  function  is  contrasted  in  the  hot-  and  cold-blooded 
animals  ;  in  the  latter,  where  the  heat  of  the  body  is  about  that  of  the 
surrounding  air  during  winter  digestion  stops  altogether,  or  goes  on 
very  slowly ;  while  in  the  former,  the  temperature  being  independent 
of  external  conditions,  at  least  within  narrow  limits,  digestion  goes  on 
independent  of  change  in  the  season. 

In  reference  to  the  influence  of  exercise  upon  digestion,  Beaumont3 
observed  that  moderate  exercise  conduces  considerably  to  healthy  and 
rapid  digestion ;  severe  and  fatiguing  exercise,  on  the  contrary,  retards 
it.  This  is  readily  understood  when  it  is  remembered  that  exercise 
elevates  the  temperature  and  accelerates  the  circulation.  On  the  other 
hand,  if  too  much  blood  is  diverted  from  the  stomach  to  the  brain  or 
extremities  by  much  mental  or  physical  exercise  indigestion  ensues. 
No  rules,  however,  can  be  laid  down  absolutely  in  this  respect.  In 
some  individuals  there  is  an  uncontrollable  desire  to  sleep  after  eating, 
the  good  effects  of  which  are  so  evident  that  it  is  absurd  to  resist  the 
feeling,  whereas,  in  other  cases,  gentle  exercise  is  equally  imperatively 
demanded. 

It  is  a  matter  of  common  observation  that  animals,  as  a  general  rule, 
take  little  or  no  exercise  after  eating.  That  digestion  is  retarded,  and 
even  entirely  stopped,  by  too  much  exercise,  the  author  has  had  ample 
opportunities  of  observing  from  post-mortem  examination  made  both 
on  human  beings  and  animals  who  had  eaten  food  a  short  time  before 
death,  and  who  were  known  to  have  taken  a  considerable  amount  of, 
and   often  violent,  exercise  during  that  period.      Other   physiologists 

i  Op.  cit.,  p.  97.  2  Op.  cit.,  pp.  273,  276.  3  Ibid.,  p.  94. 


ACTION    OF    GASTRIC    JUICE    UPON    FOOD. 


143 


seem  to  have  had  the  same  experience.  Thus,  in  the  last  century,  as 
related  by  Saunders,1  Dr.  Harwood,  of  Cambridge,  procured  two  dogs, 
equally  well  fed ;  one  of  these  he  kept  quiet,  the  other  he  compelled  to 
take  constant  exercise  immediately  after  eating.  A  few  hours  after 
feeding  both  dogs  were  killed.  The  food  was  found  entirely  digested  in 
the  stomach  of  the  dog  that  had  been  kept  quiet,  while  in  that  of  the 
one  that  had  been  compelled  to  take  the  exercise  the  food  was  undigested. 


Table  XXXVI.2 — Digestion  of  Food  in  Stomach. 


Kind  of  food. 

Pig's  feet,  tripe     . 

Salmon,  trout 

Barley  soup  .... 

Milk' 

Potatoes,  roasted  ;  beans,  boiled 

Roast  turkey 

Soft  boiled  eggs    . 

Beefsteak,  broiled 

Pork,  raw      .... 

Hard  boiled  eggs . 

Mutton  soup 

Oyster  soup  .... 

Potatoes,  boiled    . 

Beef  and  vegetable  soup 

Duck,  roasted       .         .        '. 

Veal,  broiled 

Veal,  fried    .... 

Pork,  boiled 

Cabbage,  boiled    . 

Pork,  roasted 


Time. 

.  1  hour. 

.  1     " 

.  1  hour  30  min. 

.  2  hours. 

2     " 

.  2  hours  30  min. 

.  2     "       30     " 

.  2     "       30     " 

.  3  hours. 

.  3     " 

.  3  hours  30  min. 

.  3     "        30     " 

.  3     "       30     " 

.  3     "       30     " 

.  4  hours. 

.  4     " 

.  4     " 

.  4  hours  30  min. 

.  5  hours  15  min. 


It  will  be  observed  from  Table  XXXVI.,  taken  from  the  much  more 
extensive  one  of  Beaumont,  that  certain  articles  of  food  are  digested  in 
the  stomach  much  more  rapidly  than  others.  Thus,  pig's  feet,  tripe, 
are  digested  in  one  hour,  milk  and  roast  potatoes  in  two,  soft  boiled 
eggs  in  three  hours,  hard  boiled  in  three  and  a  half,'  roast  duck  in  four, 
while  roast  pork  requires  for  its  digestion  more  than  five  hours.  It 
must  not  be  supposed,  however,  that  because  certain  articles  of  food  are 
slowly  digested,  that  necessarily  they  will  give  rise  to  uneasiness  or 
inconvenience  in  the  stomach,  but  there  are  times  when  the  administra- 
tion of  food,  with  reference  to  its  rapid  digestion,  becomes  of  vital 
importance.  Thus,  in  certain  critical  periods  of  disease,  when  a  life 
hangs  upon  a  thread,  when  every  moment  that  vitality  can  be  prolonged 
is  invaluable,  the  judicious  administration  of  food  that  can  be  easily 
and  quickly  digested  and  absorbed  may  be  the  only  means  of  saving 
the  patient.  It  must  be  borne  in  mind  that  the  natural  stimulus  of  the 
gastric  juice  is  the  presence  of  food,  and  that  for  the  time  being  there 
is  a  limit  to  the  amount  of  this  secretion,  like  all  others.  Hence, 
whenever  there  have  been  great  prostration  of  strength  and  loss  of  tone, 
the  stomach,  enfeebled  like  the  rest  of  the  body,  can  digest  but  little ; 


1  A  Treatise  on  the  Structure,  Economy,  and  Diseases  of  the  Liver,  p.  '201. 

2  Beaumont,  op.  cit.,  p.  269. 


London,  1803. 


1-14  GASTRIC    DIGESTION. 

food,  under  such  circumstances,  should  be  given  cautiously,  both  in 
quantity  and  quality. 

In  concluding  the  subject  of  gastric  digestion  attention  should  be 
called  to  the  fad  that  the  coats  of  the  stomach  itself  are  unaffected  by 
the  action  of  the  gastric  juice  during  life,  but  are  digested  after  death. 
It  is  said  that  when  one  of  the  old  alchemists  announced  that  he  possessed 
a  universal  solvent,  the  question  was  at  once  asked  in  what  did  he  keep 
it.  Naturally  enough  it  was  asked  in  the  last  century  of  those  who  held 
that  the  gastric  juice  would  dissolve  organic  substances,  why  it  did  not 
act  upon  the  stomach  itself.  We  have  seen,  however,  that  the  gastric 
juice  does  not  digest  all  kinds  of  organic  food,  but  that  its  action  is 
limited  rather  to  particular  kinds  of  it,  it  having  no  action  upon  fat  and 
starch,  for  example.  The  answer  would  then  appear  to  be,  that  the 
stomach  is  lined  with  some  substance  that  the  gastric  juice  does  not  act 
upon  at  least  during  life,  it  being  well  known  that  tripe,  for  example, 
or  the  mucous  membrane  of  the  calf  will  be  digested  when  taken  as  food 
by  another  animal. 

John  Hunter1  showed,  in  1772,  and  others  since,  that  the  stomach, 
or  more  particularly  the  cardiac  part  of  it,  in  man  and  animals  dying 
suddenly,  was  digested  by  its  own  gastric  juice  after  death.  Hunter's 
explanation  of  the  phenomena  was  that  during  life  the  vital  principle 
protected  the  stomach  from  the  dissolving  influence  of  the  gastric  juice, 
but  that  after  death,  the  vital  principle'  being  no  longer  present,  the 
gastric  juice  produced  its  characteristic  effect.  This  so-called  explana- 
tion is  equivalent  to  saying  that  the  stomach  is  not  digested  during  life 
and  is  digested  after  death,  a  mere  restatement  of  the  fact  of  which  we 
wish  to  learn  the  cause,  not  an  explanation  of  it. 

Pavy2  argued  that  the  alkalinity  of  the  blood  in  the  stomach  during 
life  neutralized  the  acidity  of  the  gastric  juice  and  hence  protected  the 
stomach.  This  observer  endeavored  to  demonstrate  the  truth  of  his 
explanation  by  ligating  all  the  gastric  vessels  in  a  rabbit  and  so  depriv- 
ing the  stomach  of  its  alkaline  blood  and  then  subjecting  it  to  the  action 
of  its  acid  gastric  juice.  But  under  such  circumstances  the  stomach  is 
practically  dead,  and  we  know  that  a  dead  stomach  will  be  digested. 
Pavy's  so-called  explanation  is  only  a  demonstration  then  that  a  dead 
stomach  will  be  digested,  not  an  explanation  of  the  fact.  Further,  that 
this  is  not  the  true  explanation  is  shown  from  the  fact  that  sometimes 
the  alkaline  intestinal  secretion  will  act  upon  the  coats  of  the  intestine 
'permeated  with  alkaline  blood  in  the  same  manner  as  the  gastric  juice 
acts  upon  the  stomach. 

According  to  Profs.  Dalton3  and  Flint,4  it  is  impossible  for  the  gastric 
juice  to  act  upon  the  stomach  so  long  as  the  catalytic  changes  incident 
to  nutrition,  etc.,  are  going  on,  but  that  after  death  these  catalytic 
changes  having  ceased  then  the  gastric  juice  will  act.  Apart  from  it 
being  well  known,  however,  that  the  so-called  catalytic  changes  incident 
to  nutrition  going  on  in  the  living  frog's  legs  or  in  the  living  rabbit's 
ear,  do  not  prevent  these  parts  being  acted  upon  when  passed  into  the 

i  Phil.  Trans.,  London,  1772.  -  Phil.  Trans.,  London,  1863. 

3  Physiology,  2d  edit.,  1801,  p.  132.  4  Physiology,  vol.  ii.  p.  281. 


DIGESTION    OF    FOOD    IN    STOMACH.  145 

stomach  of  a  living  dog  in  which  a  fistulous  opening  has  been  made,  it 
appears  to  us  that  this  explanation  differs  only  from  Hunter's  in  using 
the  word  catalysis  instead  of  vital  spirit.  To  offer  as  an  explanation  of 
the  immunity  enjoyed  during  life  by  the  coats  of  the  stomach  from  the 
effects  of  the  gastric  juice,  the  antagonism  of  a  catalytic  action,  is,  like 
Hunter's,  only  a  restatement  of  the  fact  to  be  explained. 

Bernard1  taught  that  the  living  epithelium  of  the  stomach  protected 
it  from  the  gastric  juice,  assuming  that  the  epithelium  was  as  constantly 
renewed  as  destroyed.  According  to  Pavy,2  however,  the  mucous  mem- 
brane can  be  removed  in  a  living  animal,  and  the  coats  of  the  stomach, 
though  exposed,  are  yet  unaffected  by  the  gastric  juice.  This  experi- 
ment, however,  does  not  seem  t<>  apply  to  man.  for  pathological  facts, 
like  the  round  ulcer  of -the  stomach,  would  seem  to  show  that  in  the 
absence  of  the  epithelium  the  parts  beneath  are  affected  during  life 
by  a  kind  of  corrosion  due  to  the  gastric  juice.  A  confirmation  of  the 
view  that  the  epithelium  lining  of  the  stomach  gives  it  its  immunity 
from  digestion  during  life,  is  shown  by  the  fact  that  worms,  like  the 
thread-worm,  ascaris,  etc.,  whose  body  wall  is  covered  with  epithe- 
lium are  able  to  live  in  the  stomach,  bathed  at  times  in  gastric  juice. 
After  the  death  of  the  worm,  from  any  cause,  the  mouth  or  anus  being 
opened,  then  the  gastric  juice  is  able  to  penetrate  within  its  body  and 
will  then  act  upon  the  viscera  until  often  nothing  will  be  left  of  the 
worm  except  its  outer  body  wall,  which  will  float  about  in  the  stomach, 
unaffected  by  the  gastric  juice.  In  the  same  way,  if  the  epithelium  of 
the  stomach  be  loosened  from  the  parts  beneath,  it  will  be  found  undi- 
gested in  the  gastric  juice;  as  a  matter  of  fact,  it  is  not  digested  whether 
living  or  dead  any  more  than  the  skin  of  the  ascaris  is  digested.  There 
is  no  reason  for  assuming,  then,  that  during  life  it  is  rapidly  regenerated 
because  it  is  constantly  being  destroyed.  After  death  the  epithelium 
loosening  itself  from  the  coats  of  the  stomach,  the  latter  will  no  doubt 
be  attacked  by  the  gastric  juice  as  long  as  the  temperature  is  maintained 
at  100°  F.,  the  epithelium  itself  remaining  unaffected.  This  explana- 
tion has  at  least  one  advantage — that  it  does  not  call  upon  vital  spirits, 
catalysis,  or  similar  fetich  ideas,  to  explain  a  phenomenon  of  digestion, 
but  depends  simply  upon  the  chemico-physical  fact  as  to  whether  or  no 
epithelium  is  digested  in  gastric  juice. 

In  concluding  the  subject  of  gastric  digestion  it  may  not  be  superfluous 
to  notice  that  the  alimentary  canal  of  man,  as  a  whole,  is  intermediate 
in  character  between  that  of  the  carnivora  and  herbivora,  furnishing  an- 
other proof  in  addition  to  those  already  given,  that  the  natural  diet  of 
man  is  a  mixed  one.  The  food  of  an  herbivorous  animal  or  vegetable 
feeder  consisting  of  grass,  leaves,  roots,  etc.,  contains  comparatively 
little  nutriment,  and,  therefore,  a  great  quantity  of  it  must  be  eaten. 
This  necessarily  entails  a  long  and  capacious  alimentary  canal  with 
special  modifications  in  different  parts  of  it,  the  effect  of  which  is  that 
the  maximum  amount  of  nutriment  is  obtained  from  the  food.  Thus 
when  the  stomach  of  a  ruminating  animal,  like  the  llama  (Fig.  49),  or 
giraffe  (Fig.  82),  is  compared  with  that  of  man,  it  will  be  observed  that 

1  Physiologie  Experimentale,  tome  ii.  p.  401.     Paris,  1S56.  2  Op.  cit.,  p.  103. 

10 


146 


GASTRIC    DIGESTION. 


the  stomach  of  the  ruminant  is  subdivided  into  four  compartments  (Fig. 
53,  b,  c,  d,  e),  the  last  of  which,  the  abomasum,  communicating  with  the 

small    intestine,    corresponds    with 
FlG-  53-  that  of  man,  and  secretes  the  gastric 

juice.  Of  the  other  three  stomachs, 
the  rumen  (/>)  is  the  largest,  and 
together  with  the  reticulum  (c)  or 
honeycombed  stomach  (not  seen  in 
Fig.  4i>)  receives  the  food  after  it 
has  been  chewed  and  insalivated. 
After  a  few  moments,  however,  a 
bolus  of  food  wrill  be  regurgitated 
into  the  mouth  and  there  thoroughly 
masticated  and  insalivated.  The 
second  time,  however,  that  it  is  swal- 
lowed the  food  passes  directly  into 
the  third  stomach,  the  psalterium  (d) 
or  monyplies.  This  is  effected  by 
means  of  a  musculo-valvular  ar- 
rangement at  the  mouth  of  the 
oesophagus,  which  serves  both  to 
shut  off  the  cavity  of  the  rumen 
and  reticulum  and  to  divert  the 
bolus  of  food  directly  from  the  (esophagus  into  the  psalterium,  whence 
it  passes  into  the  abomasum  (e)  or  fourth  stomach  and  thence  into  the 
intestine.  By  this  arrangement  of  the  rumen,  etc.,  the  thorough  masti- 
cation and  insalivation  of  the  food  are  insured,  while  the  psalterium  or 
third  stomach  acts  as  a  filter  or  strainer,  its  mucous  membrane  being- 
raised  up  into  folds,  like  the  leaves  of  a  book,  permitting  only  finely 
divided  or  semi-li<piid  matter  to  pass  into  the  abomasum.  Were  not 
the  food  thus  thoroughly  digested  much  of  its  nutritive  value  would 
be  lost. 

The  stomach  of  a  meat  eater,  on  the  other  hand,  is  as  simple  as  that 
of  man,  while  its  intestines  are  not  as  long,  its  food  being  so  much  more 
nutritious  as  compared  with  that  of  the  vegetable  feeder. 

We  have  seen  why  a  strictly  meat  diet  should  be  avoided  in  man  as 
well  as  a  vegetable  one,  hence  his  alimentary  canal  will  not  be  as  simple 
as  that  of  the  one  nor  as  complicated  as  that  of  the  other,  but  interme- 
diate in  character  between  the  two.  ' 

The  further  illustration  of  this  subject  brings  us,  however,  to  a  con- 
sideration of  the  intestines,  to  which  let  us  now  turn. 


Compound  stomach  of  an  ox.  a.  (Esophagus 
b.  Rumen,  or  first  stomach.  c.  Reticulum,  0] 
second,  d.  Omasum,  or  third,  e.  Abomasus,  01 
fourth.    /.  Duodenum.     (From  Rymer  Jones.) 


CHAPTER   X 


INTESTINAL    DIGESTION.      INTESTINAL    JUICE.     PANCREATIC 
JUICE.    LIVER.    GLYCOGEN.    BILE.    FECES.    DEFECATION. 

We  have  seen  that  shortly  after  food  is  taken  into  the  stomach  it 
passes  in  small  quantities  through  the  pyloric  orifice  into  the  small 
intestine,  or  the  part  of  the  alimentary  canal  intervening  between  the 
stomach  and  the  ilio-csecal  valve.  The  small  intestine  is  a  cylindrical 
tube  and  in  situ  measures  on  an  average  from  fifteen  to  eighteen  feet, 
but  when  separated  from  the  mesentery  or  the  peritoneum,  which  holds 
it  in  position  in  the  abdominal  cavity,  it  will  be  found  to  be  a  little 
longer — about  twenty  feet.  It  has  a  diameter  of  about  one  and  a 
quarter  inches. 

The  small  intestine  is  composed,  in  addition  to  its  external  or  perito- 
neal coat,  of  two  others  :  of  a  mucous  membrane,  including  an  epi- 
thelial and  submucous  or  fibrous  coat  (Fig.  54,  4,  5),  and  of  a 
muscular  coat  lying  exteriorly  between  the  peritoneum  and  the 
mucous  membrane.  The  muscu- 
lar coat  consists  of  unstriped  Fig.  54- 
muscular  fibre,  arranged  in  two 
layers,  longitudinally  or  parallel 
with  the  long  axis  of  the  intestine, 
and  circularly  or  at  right  angles 
with  the  axis  (Fig.  54,  2,  3)  ;  the 
circular  fibres  being  better  devel- 
oped than  the  longitudinal  ones. 

It  is  through  the  .slow  and  grad- 
ual contraction  and  relaxation  of 
these  muscular  fibres,  the  so- 
called  peristaltic  or  vermicular 
movement,  that  the  food  is  pro- 
pelled along  the  intestine,  the 
contraction  of  the  circular  muscu- 
lar fibre  at  the  pyloric  orifice  pre- 
venting regurgitation  into  the 
stomach. 

Like  the  movements  of  the 
stomach,  the  natural  stimulus  to  the  vermicular  motion  of  the  intestine 
is  the  presence  of  food,  during  the  intervals  of  digestion  the  intestine 
being  at  rest.  The  peristaltic  or  vermicular  motion  of  the  intestine  can 
be  well  seen  by  opening  an  animal  in  full  digestion.  What  is  positively 
known,  however,  of  the  intestinal  movements  in  man  is  derived  from 
pathological  cases  where  the  abdominal  walls  were  so  thin  that  the 
motion  could,  to  a  certain  extent,  be  seen  and  felt,  or  from  cases  of 


Portion  of  the  duodenum,  viewed  from  without, 
natural  size.  1.  Thickness  of  the  duodenum.  2,  3. 
Longitudinal  and  transverse  layers  of  fibres  of  the 
muscular  coat.  4.  Fibrous  coat.  5.  Exterior  of  the 
mucous  membrane,  with  the  duodenal  glands  im- 
bedded.    (Leidy  ) 


148 


INTESTINAL    JUICE, 


intestinal  fistula  like  that  under  the  care  of  Busch,  which  will  be 
referred  to  again  shortly.  The  gradual  passage  of  the  food  through  the 
alimentary  canal  is  no  doubt,  as  suggested  by  Longet,1  facilitated  by 
the  gases,  nitrogen,  oxygen,  carburetted  hydrogen,  which  are  constantly 
found  there,  the  canal  being  kept  distended  and  its  walls  supported  in 
this  way. 

As  the  food  passes  into  the  small  intestine  it  becomes  incorporated 
with  the  bile,  the  pancreatic  and  intestinal  juices,  the  first  two  secretions 
pass  into  the  duodenum  from  the  liver  and  the  pancreas  respectively; 
the  last,  however,  is  secreted  by  glands  found  all  through  the  intestinal 
tract.  While  the  further  changes  that  the  food  undergoes  in  the  small 
intestine  are  due  to  the  simultaneous  effects  of  the  bile,  pancreatic  and 
intestinal  secretion,  it  is  better,  however,  to  study  the  effects  of  each  of 
these  secretions  separately  whenever  possible  in  order  to  ascertain  their 
relative  importance  in  digestion  ?  We  will  begin,  then,  with  the  intes- 
tinal juice. 

Intestinal  Juice. 


Fig.  5.->. 


The  succus  entericus,  as  it  is  also  called,  is  secreted  by  two  kinds  of 
glands,  the  glands  of  Brunner  or  Brunn  and  the  follicles  of  Lieberkuhn. 
The  former  are  confined  to  the  duodenum  ;  the  latter,  however,  are 
found  not  only  in  the  small  intestine  but  in  the  large  intestine  also. 

The  duodenal  or  glands  of  Brunner 
(Fig.  55)  are  of  the  racemose  type 
of  gland ;  they  average  about  the 
Y^th  of  an  inch  in  diameter  and  to 
the  naked  eye  appear  like  little 
round  bodies  in  the  submucous  tis- 
sue. The  excretory  duct,  which 
transmits  the  secretion  from  the 
grape-like  masses  of  which  the 
gland  consists,  pierces  the  mucous 
membrane  and  opens  into  the  cavity 
of  the  intestinal  canal. 

According  to  Hirst  and  Hei- 
denhain,2  the  cells  of  Brunner's 
glands  exhibit  essentially  the  same 
changes  during  periods  of  rest  and 
activity  as  those  of  the  pyloric  tubules  of  the  stomach,  being  large  and 
clear  during  the  period  intervening  between  meals  and  small  and  cloudy 
during  digestion,  the  secretion  being  elaborated  during  the  former  period 
and  poured  out  during  the  latter. 

The  reaction  of  the  secretion  is  alkaline.  According  to  Grutzner,3  it 
will  digest  fibrin  in  an  acid  solution,  and  Budge4  and  Krolow  state  that 
a  watery  extract  will  convert  starch  into  sugar.  Beyond  these  facts 
nothing  is  known  positively  of  the  properties  of  the  secretion  of  Brun- 
ner's glands. 


A  vertical  section  of  the  duodenum  highly  mag- 
nified. 1.  A  fold-like  villus.  2.  Epithelium  of  the 
mucous  membrane.  3.  Orifices  of  the  tubular 
glands,  4.  5.  Orifice  of  a  duodenal  racemose  glaud, 
C.  7.  Two  vesicles  of  the  latter,  more  highly  mag- 
nified, exhibiting  the  epithelial  cells  lining  their 
internal  surface.     (Leidy.) 


1  Physiologie,  1873,  tome  1,  p.  166. 
8  Pfluger's  Archiv,  Band  xii.  S.  288. 


-  Hermann  :  Physiologie,  Funfter  Baud,  S.  163. 
4  Hoppe-Seyler :  Phys.  Cheniie,  S.  270. 


INTESTINAL    JUICE.  149 

By  far,  however,  the  greatest  quantity  of  the  intestinal  juice  is  se- 
creted by  the  follicles  of  Lieberkiihn,  otherwise  known  as  the  simple 
tubular  glands  of  the  intestine.  These  glands  resemble  somewhat  the 
pyloric  tubules  of  the  stomach,  consisting  of  a  basement  membrane  lined 
with  a  single  layer  of  columnar  cells.  The  tubules  having  a  diameter 
of  about  -g-g-Q-th  of  an  inch,  extend  through  the  mucous  membrane,  which 
is  about  y^-th  of  an  inch  thick,  their  fluid  ends  look  toward  the  muscular 
coat,  their  mouths  opening  into  the  cavity  of  the  intestine.  The  secre- 
tion of  these  tubules  will  therefore  pass  into  the  interior  of  the  intestine. 
The  tubules  are  as  closely  packed  together  as  possible  and  are  only 
absent  in  that  part  of  the  duodenum  where  the  glands  of  Brunner  are 
found,  and  in  the  remaining  part  of  the  small  intestine,  the  so-called 
jejunum  and  ileum1  in  the  position  of  the  Peyer's  patches  and  solitary 
glands,  and  even  here  they  are  not  entirely  absent. 

From  the  immense  number  of  these  tubules  one  would  infer  that  a 
very  considerable  quantity  of  intestinal  juice  is  secreted.  The  exact 
amount  daily  poured  into  the  intestine  has  never  been  accurately  deter- 
mined ;  it  does  not  appear  to  be,  however,  as  much  as  we  would  have 
anticipated. 

The  reaction  of  the  intestinal  juice  is  alkaline,  but  as  it  is  very  doubtful 
whether  normal  intestinal  juice  has  ever  been  collected  in  any  animal 
or  man  it  is  not  worth  while  to  consider  in  detail  its  composition.  Prob- 
ably it  is  composed  of  water,  salts,  and  some  albuminous  principles.  It 
is  true  that  numerous  experiments  have  been  made  upon  animals  with 
the  object  of  obtaining  the  intestinal  juice,  of  determining  the  quantity 
secreted,  its  composition,  and  effects  upon  food,  etc.  These  experiments 
unfortunately,  however,  were  not  made  under  physiological  conditions, 
hence  the  results  obtained  are  of  little  value  as  illustrating  digestion  in 
the  animal  experimented  upon  and  practically  useless  in  their  applica- 
tion to  man.  Frerichs,2  for  example,  experimented  in  this  way.  A 
loop  of  the  small  intestine  of  a  living  cat  or  dog  was  withdrawn  from 
the  abdomen  during  the  interval  of  digestion.  The  loop  was  four  to 
eight  inches  in  length,  was  isolated  from  the  rest  of  the  intestine  by  a 
ligature.  It  was  opened  and  washed  and  then  replaced  in  the  abdomen. 
Some  hours  afterward  the  animal  was  killed  and  the  contents  of  this 
isolated  portion  of  the  intestine  examined.  It  was  found  to  contain  a 
fluid  which  was  assumed  to  be  intestinal  juice.  It  is  probable,  however, 
that  during  the  intervals  of  digestion  no  intestinal  juice  is  secreted,  the 
natural  stimulus  to  the  secretion  being  the  presence  of  food,  as  is  the 
case  in  the  secretion  of  the  gastric  and  pancreatic  secretions  and  the 
bile.  Further,  the  method  of  experimenting  made  use  of  by  Frerichs 
involves,  necessarily,  the  ligating  and  division  of  the  vasomotor  nerves 
of  the  intestine  with  the  consequent  changes  in  the  circulation  and 
nutrition  of  the  parts.  The  fluid  obtained  being,  therefore,  abnormal, 
it  is  not  necessary  to  describe  its  properties. 

1  The  distinction  between  jejunum  and  ileum  is  entirely  an  artificial  one,  there  being  no  difference 
structurally  between  the  two.  The  small  intestine  naturally  divides  itself  into  duodenum  and  ileum, 
distinguished  by  the  former  containing  the  glands  of  Brunner,  the  latter  the  patches  of  Peyer.  More 
than  three  hundred  years  ago  Vesalius  observed  (De  corporis  hnmani  fabrira  Libri  septein,  p.  600.  Basil, 
1543)  "Qua  propter  quis  jejunum  habendus  sir  finis,  aut  quod  ilei  principium,  non  statuo."  The  namo 
jejunum  being  therefore  a.  meaningless  one,  ought  long  since  to  have  fallen  into  disuse. 

-  Wagner  :  Physiologic,  1846,  Band  iii.  S.  581. 


150  INTESTINAL    JUICE. 

Bidder  and  Schmidt1  adopted  a  different  plan  from  that  of  Frerichs. 
These  investigators  cut  off  the  bile  ami  the  pancreatic  juice  from  the 
intestine  by  ligating  the  bile  and  pancreatic  ducts  and  then  introduced 
food  with  the  object  of  studying  the  effects  of  the  intestinal  juice  upon 
it.  It  is  questionable,  however,  after  such  an  operation,  whether  diges- 
tion is  normal,  and  even  if  it  were,  the  results  of  feeding  cats  and  dogs 
operated  upon  in  this  way  upon  vegetable  articles  of  food,  like  starch, 
etc.,  could  hardly  be  expected  to  throw  much  light  upon  intestinal 
digestion  as  it  takes  place  in  man. 

Colin's2  experiments  not  differing  essentially  in  principle  from  that 
of  Frerichs's,  it  would  be  superfluous  to  describe  in  detail  bis  results, 
or  those  obtained  by  the  method  of  Thiry.3  The  latter  consisted  in 
cutting  a  piece  out  of  the  intestine,  and  after  joining  the  lower  end  of 
the  upper  part  of  the  intestine  to  the  upper  end  of  the  lower,  of  attaching 
the  isolated  cut  out  portion,  its  nerves  and  vessels  being  undisturbed, 
by  its  open  end,  to  the  fistulous  opening  in  the  abdominal  walls,  the 
other  end  being  closed. 

Were  our  knowledge  of  the  properties  of  the  intestinal  juice  in  man 
dependent  upon  the  experiments  that  have  been  made  upon  animals, 
we  would  know  positively  next  to  nothing  about  it.  Fortunately,  how- 
ever, for  physiology,  there  occurred  some  years  ago  a  case  of  intestinal 
fistula  in  a  woman  which  proved  to  be  for  intestinal  digestion,  what 
St.  Martin's  case  was  for  gastric  digestion.  It  is  true  that  the  obser- 
vations of  Busch,  who  had  charge  of  the  case,  are  not  by  any  means  as 
extended  or  complete  as  those  of  Beaumont ;  nevertheless,  they  are 
invaluable  to  us,  as  what  is  known  of  the  action  of  the  intestinal  juice 
during  digestion  in  man  is  almost  entirely  based  upon  them. 

Busch4  tells  us  that  a  woman,  thirty-one  years  of  age,  in  the  sixth 
month  of  her  fourth  pregnancy,  being  tossed  by  a  bull,  was  wounded  in 
the  abdomen.  The  wound  was  situated  between  the  umbilicus  and 
pubes,  and  consisted  of  two  contiguous  openings  communicating  with 
the  intestinal  canal.  It  is  probable  that  these  two  openings  were  in 
the  upper  third  of  the  small  intestine. 

Notwithstanding  her  ravenous  appetite  the  patient  became  very  much 
emaciated  in  consequence  of  her  food  passing  out  of  the  upper  of  the 
two  openings  just  referred  to.  It  occurred  to  Busch,  however,  that  the 
life  of  the  woman  might  be  saved  by  introducing  cooked  food  into  the 
lower  opening,  or  that  communicating  with  the  lower  portion  of  the 
intestine.  This  plan  of  treatment  proved  successful.  The  nutrition 
of  the  patient  rapidly  improved.  The  opening,  however,  not  uniting, 
the  woman  was  made  the  subject  of  the  observations  contained  in  the 
paper  just  referred  to. 

It  will  be  observed  that  from  the  peculiar  conditions  of  the  case,  food 
introduced  by  the  mouth,  unless  absorbed  by  the  stomach,  wTould  pass 
on  into  the  upper  portion  of  the  intestine,  and  so  out  of  the  body  by  the 
upper  of  the  two  openings,  having  been  modified  in  its  course  by  the 
saliva,  gastric,  intestinal,  and  pancreatic  juices  and  the  bile;  whereas, 

l  Die  Verdamingssafte,  1852,  S.  271.  -  Physiologie  Comparee,  1854,  p.  648. 

3  Wiener  Sitzberichte,  1864,  p.  77.  4  Virchow's  Archiv,  1858,  Band  xiv.  S.  140. 


INTESTINAL    JUICE.  151 

food  introduced  into  the  lower  of  the  two  openings  would  be  modified 
by  the  intestinal  juice  only,  as  it  passed  along  the  small  intestine,  and 
if  not  digested  or  absorbed  would  pass  out  by  the  anus  unchanged. 
The  conditions  of  the  experiment  were,  therefore,  perfectly  physio- 
logical. 

The  intestinal  juice  was  secreted  in  response  to  the  natural  stimulus 
of  the  food,  while  its  effect  upon  the  different  kinds  of  food  could  be 
studied,  cither  mixed  or  unmixed  with  the  gastric,  pancreatic  juices, 
etc.  Necessarily  the  quantity  of  intestinal  juice  obtained  at  any  one 
time,  by  the  introduction  of  sponges,  etc.,  was  not  sufficient  to  admit 
of  detailed  analysis;  the  reaction  was  determined,  however,  to  be 
alkaline.  The  general  results  of  Busch's1  observations  and  experiments 
upon  the  intestinal  juice  may  be  summed  up  as  follows : 

Starch,  both  raw  and  hydrated,  was  invariably  converted  by  it  into 
glucose ;  cane  sugar,  however,  was  not  changed  into  glucose,  appearing 
in  the  feces  as  cane  sugar.  The  intestinal  juice  digested  more  or  less 
cooked  meat  and  coagulated  albumen,  but  had  little  or  no  effect  upon 
fat ;  the  latter  when  introduced  into  the  lower  opening  of  the  intestine 
is  always  found  in  the  feces  as  fat  unchanged. 

In  the  case  of  intestinal  fistula  lately  observed  by  Demant,2  starch 
was  converted  into  glucose,  but  albuminous  substances  did  not  appear 
to  be  transformed  into  albuminose.  No  effect  was  observed  upon 
neutral  fats,  though  oily  matters  containing  free  acid  were  emulsified. 
The  results  of  the  observations  of  Demant  confirm  in  the  main  those  of 
Busch.  It  must  be  remembered,  however,  that  the  fistula  in  the  former 
case  was  situated  much  lower  than  in  the  latter,  and  that  the  experi- 
ments upon  the  different  kinds  of  foods  were  performed  outside  of  the 
body  after  the  intestinal  juice  had  been  drawn  from  the  fistula.  The 
observations  of  Busch  were,  therefore,  made  under  more  strictly  physio- 
logical conditions  than  those  of  Demant,  and  deserve  greater  confidence. 

o    -  ... 

It  will  be  seen,  therefore,  that  the  action  of  the  intestinal  juice  in 
digestion  is  of  a  supplementary  character,  reinforcing  the  effects  of  the 
saliva  upon  starch,  and  of  the  gastric  juice  upon  the  albuminoids,  it 
having  no  effect,  however,  upon  cane  sugar  or  fat. 

Before  turning  to  the  consideration  of  the  remaining  digestive  secre- 
tions,  attention  should  be  called  to  a  peculiar  disposition  of  the  mucous 
membrane  of  the  intestine,  which,  to  a  certain  extent,  retards  the 
passage  of  the  food  and  exposes  it  longer  to  the  digestive  fluids  and  to 
a  greater  absorbing  surface.  I  refer  to  the  villi  and  the  valvular  con- 
niventes.  On  opening  the  small  intestine  and  gently  washing  it,  one 
will  observe  that  instead  of  it  being  smooth,  it  presents  a  velvety  ap- 
pearance. This  is  due  to  the  mucous  membrane  (Fig.  56)  being  raised 
up  into  millions  of  little  cones  or  cylinders,  the  villi,  which  project  in- 
wardly into  the  cavity  of  the  intestine.  As  these  little  structures  are 
intimately  connected  with  the  subject  of  absorption,  our  account  of  their 
anatomy  will  be  deferred  until  the  next  chapter,  merely  mentioning 
them  here  as  offering  a  certain  amount  of  resistance  to  the  passage  of 

1  Op.  cit.,  S.  186.  2  Virchow's  Arehiv,  1879,  Band  lxxv   S.  419. 


152 


INTESTINAL    JUICE. 


food,  just  as  any  roughened  surface  offers  resistance  as  compared  with  a 
smooth  one  to  a  substance  passing  over  it. 


Pig.  56. 


WW 

nr1 


Portions  of  the  mucous  membrane  from  the  ileum,  moderately  magnified,  exhibiting  the  villi  on  its 
free  surface,  and  between  them  the  orifices  of  the  tubular  glands.  1.  Portion  of  an  agmiuated  gland. 
2.  A  solitary  gland.     3.   Fibrous  tissue.     (Leidy.) 

While  the  villi  are  found  all  through  the  small  intestine,  the  valvule 
conniventes,  which  have  the  same  function  in  this  respect,  are  restricted 
to  a  certain  portion  of  it,  being  absent  in  the  upper  half  of  the  duode- 
num and  in  the  lower  third  of  the  ileum.  The  valvulae  conniventes 
(Fig.  57)  are   duplicatures  of  the  mucous  membrane  extending  trans- 

Fig.  57. 


Portion  of  small  intestine  laid  open  to  show  valvulfe  conniventes.     (Brinton.) 

versely  across  the  intestine  at  right  angles  to  its  long  axis,  and  occu- 
pying usually  one-third  or  a  half  of  the  circumference,  and  sometimes 
extending  all  around  the  tube.  The  folds  are  widest  in  the  middle, 
measuring  often  from  one-quarter  to  one-half  of  an  inch.  On  either 
side  of  the  middle  line  they  thin  away  until  they  are  lost  in  that  part 
of  the  mucous  membrane  attached  to  the  muscular  coat.  Inasmuch  as 
there  can  be  counted  usually  over  800  of  these  folds,  it  can  be  readily 
understood  how  the  extent  of  the  mucous  membrane  is  increased  by 
them.  Naturally  the  food  will  takes  a  longer  time  to  pass  over  and 
between  these  barriers,  so  to  speak,  than  over  a  plane  surface,  and  this 
is  of  advantage  in  digestion  and  absorption,  as  the  food  will  be  more 
thoroughly  incorporated  with  the  secretions  and  have  a  better  chance  of 
being  absorbed. 

It  is  often  stated  that  the  valvulae  conniventes  are  only  found  in  the 
intestine  of  man,  this  is  erroneous;  they  are  present,  as  Bischoff  has 
shown,  in  the  gorilla,  and  the  author  in  the  chimpanzee  ;*  they  are 


1  Proceedings  Acad.  Nat.  Sciences,  Philadelphia,  1S80,  p. 


16G. 


PANCREATIC    JUICE. 


153 


also  found  in  the  ox,  llama,  camel,  elephant,  in  the  ornithorhynchus, 
and  are  well  developed  in  the  shark,  giving  rise  in  the  latter  animal  to 
the  so-called  spiral  valve. 

Merely  mentioning  that  the  solitary  glands  and  patches  of  Peyer 
will  he  described  when  the  subject  of  the  blood  is  considered,  let  us  pass 
on  now  to  the  consideration  of  the  pancreatic  juice  and  the  bile,  and  of 
the  role  that  these  secretions  play  in  digestion. 


Pancreatic  Juice. 


The  pancreas,  in  its  general  structure,  resembles  so  closely  the  parotid 
and  submaxillary  glands,  that  it  was  known  to  the  older  anatomists  as 
the  abdominal  salivary  gland  (Fig.  58).     It  is  situated  in  the  upper  and 

Fig.  58. 


View  of  the  pancreas  ami  surrounding  organs.  l-5th.  I.  The  tinder  surface  of  the  liver.  17.  Gall- 
bladder. /.  The  common  bile-duet.  «.  The  stomach,  d.  Duodenum.  /;.  Head  of  the  pancreas,  t.  Tail, 
and  i,  body  of  that  gland.     Pancreatic  duct  (e)  and  its  branches,    r.  The  spleen,    v.  The  hilus     c,  c.  The 

crura  of  the  diaphragm.     (Qtain.) 

posterior  part  of  the  abdominal  cavity,  behind  the  stomach  and  between 
the  duodenum  and  the  spleen.  It  is  about  seven  inches  long,  and  an  inch 
and  a  half  broad,  and  from  half  an  inch  to  an  inch  thick.  It  usually 
weighs  about  three  to  four  ounces,  and  in  its  minute  structure  is  of  the 
racemose  type.  Its  duct  in  man  passes  into  the  duodenum  by  a  com- 
mon orifice  with  the  ductus  choledochus,  three  or  four  inches  below  the 
pylores.  Not  unfrequently  there  is  also  a  supplementary  pancreatic 
duct  opening  into  the  duodenum  a  little  above  the  main  duct. 

The  secretion  of  the  pancreas,  or  the  pancreatic  juice,  has  never  been 
obtained  from  man.  Probably  it  is  very  much  like  that  of  the  pan- 
creatic gland  of  the  dog,  which,  according  to  Bernard,1  consists  of  water, 
an  organic  substance  (pancreatin),  and  salts.  With  the  exception  of 
what  has  been  learned  from  pathological  observations,  nothing  is  known 
of  the  effect  of  the  pancreatic  juice  upon  food  during  digestion  in  man, 

1  Physiologie  Experimental,  tome  ii.  p.  237.     Paris,  1856. 


154  PANCREATIC    JUICE. 

and  such  observations  would  be  inconclusive  unless  viewed  by  the  light 
of  experiments  upon  animals  and  comparative  anatomy. 

The  first  physiologist,  so  far  as  known  to  the  author,  who  attempted 
to  obtain  the  natural  pancreatic  juice  from  a  living  animal,  was  Reg- 
nerus  de  Graaf,1  who,  in  1662,  opened  the  intestine  of  a  dog  and  intro- 
duced a  duck's  quill  into  the  orifice  of  the  pancreatic  duct.  According 
to  Bernard,2  however,  the  fluid  obtained  by  de  Graaf  was  not  pancreatic 
juice,  being  acid  in  reaction,  whereas  the  normal  pancreatic  juice,  ac 
cording  to  Bernard,  is  alkaline.  Majendie3  repeated  de  Graaf 's  experi- 
ment, but  with  not  much  success.  Leuret4  and  Lassaigne,  in  1824,  and 
Tiedemann  and  Gmelin,5  in  1827,  obtained  what  they  supposed  to  be 
the  natural  pancreatic  juice  from  the  horse  and  dog,  but  nothing  was 
learned  of  its  physiological  properties  from  their  experiments.  Little 
or  nothing  was  known  of  the  natural  pancreatic  juice  up  to  the  year 
1846,  when  Bernard  obtained  the  pancreatic  juice  of  the  dog,  and  in- 
vestigated its  properties. 

Bernard's  method6  of  obtaining  the  pancreatic  juice  consisted  in  open- 
ing the  abdomen  of  a  living  dog  and  inserting  a  canula  into  the  principal 
pancreatic  duct.  Bernard  showed  that  during  the  intervals  of  digestion 
no  pancreatic  juice  is  secreted,  and  that  the  organ  is  of  a  pale  color. 
The  animal  experimented  upon  should,  therefore,  be  fed  moderately  an 
hour  or  so  before  the  operation.  The  pancreas  then  becomes  rose 
colored,  full  of  blood,  and  secretes  a  viscid  alkaline  juice,  which  flows 
into  the  duodenum,  even  before  the  digested  food  gets  there  from  the 
stomach.  In  experimenting  with  the  pancreatic  juice  thus  obtained, 
Bernard  showed  that  it  was  important  to  study  its  properties  as  soon 
as  possible,  for,  unlike  the  gastric  juice,  it  soon  decomposes.  Another 
difference  between  a  pancreatic  and  gastric  fistula  consists  in  the  im- 
possibility of  maintaining  permanently  the  former,  for  even  if  the  canula 
remains  in  place  a  few  days  the  pancreatic  juice  changes  entirely  its 
character,  becoming,  according  to  Bernard,  decidedly  abnormal.  This 
change  takes  place  usually  in  a  few  hours,  and  so  sensitive  is  the  pan- 
creas, that  sometimes  the  secretion  is  abnormal,  even  when  first  drawn.7 

Apart  from  the  impropriety  of  assuming  that  the  pancreatic  juice  of 
man  and  the  dog  are  necessarily  identical,  one  might  reasonably  doubt 
even  whether  the  secretion  obtained  by  Bernard's  method  always  really 
represents  the  normal  pancreatic  juice  in  the  dog.  the  pancreas  being  so 
readily  inflamed  and  irritated  by  the  operation.  It  is  probable,  however, 
that  the  secretion  obtained  by  Bernard  was  normal,  and  that  his  con- 
clusions in  reference  to  the  properties  of  the  secretion  and  functions  of 
the  pancreas  generally  are  in  the  main  correct,  as  they  accord  pretty 
well  with  what  the  facts  of  comparative  anatomy  and  pathology,  and 
the  results  of  experiments  with  artificial  pancreatic  juice  teach  us  of  the 
functions  of  the  gland. 

It  is  well  known  that  in  the  rabbit  the  pancreatic  duct  opens  sepa- 
rately into  the  intestine  twelve  inches  below  the  bile-duct,  instead  of  by 

i  Opera  Omnia,  1678,  p.  292.  2  Op.  cit,  p.  176. 

3  Physiologic,  p.  307.   Paris,  1816.  4  Op.  cit  ,  p.  102. 

5  Op.  cit.,  p.  27.  ''»  Op.  cit.,  p.  100. 

7  According  to  the  later  observations  of  Berstein,  it  appears,  however,  that  a  permanent  pancreatic 
fistula  can  be  maintained.     Lndwiar's  Arbeiten,  I860. 


PANCREATIC    JUICE.  155 

an  opening  common  to  it  and  the  bile-duct,  as  is  the  case  in  man  or  the 
dog;  Bernard1  tells  us  that  after  feeding  a  rabbit  with  fat  he  noticed 
that  it  was  only  below  the  entrance  of  the  pancreatic  duct  into  the 
intestine  that  the  lymphatics  of  the  small  intestine  or  lacteals  contained 
any  fat.  This  observation  not  only  suggested  to  Bernard  the  idea  that 
the  pancreatic  juice  emulsified  the  fat — that  is,  reduced  it  to  a  fine  state 
of  subdivision,  and  so  rendered  it  absorbable — but  was  also  the  starting- 
point  of  his  researches  upon  the  functions  of  the  pancreas  generally. 
While  it  is  true  that  in  the  rabbit,  as  a  general  rule,  emulsified  fat  is 
only  found  in  the  lymphatics  below  the  entrance  of  the  pancreatic  duct, 
this  is  not  invariably  so,  as  according  to  Bidder  and  Schmidt,2  and  our 
own  observations,  emulsified  fat  is  at  times  found  in  the  lymphatics 
above  this  point.  While  the  rabbit  is  a  convenient  animal  for  making 
Bernard's  experiment,  it  may  be  mentioned  in  this  connection  that  the 
beaver,  though  a  rarer  animal,  presents  even  a  more  favorable  disposi- 
tion for  making  the  observation  than  the  rabbit,  the  pancreatic  duct 
in  this  rodent  opening  eighteen  inches  below  the  bile-duct.  Having 
examined  several  beavers  in  full  digestion,  the  author  noticed  also  that 
in  some  cases,  as  in  the  rabbit,  the  lymphatics  contained  chyle,  both 
above  and  below  the  entrance  to  the  pancreatic  duct.  Even  if  it  were 
true  that  fat  never  is  emulsified  in  the  rabbit,  except  by  the  pan- 
creatic juice,  it  would  not  prove  that  the  pancreas  is  indispensable 
in  the  digestion  of  fat  either  in  man  or  animal.  Fat,  as  such,  not  being 
the  natural  food  of  the  rabbit,  there  is  no  necessary  connection  betwreen 
it  and  its  pancreatic  juice ;  while  in  many  fish,  whose  food  contains  fat, 
the  pancreas  is  absent.  In  birds,  also,  the  fat  is  usually  absorbed  by 
the  mesenteric  bloodvessels  in  general,  and  not  by  the  lymphatics  of  the 
small  intestine. 

Eberle,3  however,  showed,  in  1834,  that  an  artificial  pancreatic  juice, 
prepared  by  making  an  infusion  of  the  pancreas,  would  emulsify  oil 
when  mixed  and  agitated  with  it,  and  Bernard,4  apparently  without 
knowing  of  Eberle's  views,  proved  that  the  pancreatic  juice  of  the  dog, 
obtained  by  a  fistula,  would  do  the  same,  about  two  parts  of  the  pan- 
creatic juice  of  the  dog,  by  weight,  emulsifying  one  part  of  oleaginous 
matter. 

These  experiments  with  the  artificial  and  natural  pancreatic  juice  and 
the  facts  of  comparative  anatomy  just  referred  to,  show  conclusively  that 
while  the  pancreatic  juice  emulsifies  fats  and  so  promotes  their  absorp- 
tion, the  pancreatic  secretion  is  not  indispensable,  fat  being  digested 
and  absorbed  even  in  the  absence  of  the  pancreas.  The  digestion  and 
absorption  of  fat  must,  therefore,  be  affected  by  other  secretions  as  well 
as  by  the  pancreatic  juice.  Let  us  see  whether  pathology  throws  any 
light  upon  this  question. 

In  a  number  of  cases  reported  by  pathologists  in  which  there  was 
disease  of  the  pancreas  in  human  beings,  it  was  observed  that  a  fatty 
diarrhoea  was  present  during  life,  and  such  is  the  case  also  to  a  certain 

1  Op.  cit.,  p.  179.  2  Die  Verdauungssafte,  S.  55.     Leipzig:,  1852. 

:;  Die  Verdauung,  S.  251.     Wurzburg,  1834  *  0]).  cit.  p.  257. 


156  PANCREATIC    JUICE. 

extent  in  animals  in  which  the  pancreas  has  been  destroyed,  as  shown 
by  Bernard1  and  others. 

*  Such  cases  and  experiments  are  often  offered  as  proofs  of  the  influence 
exerted  by  the  pancreas  in  promoting  the  digestion  and  absorption  of 
fats.  It  is  interesting  in. this  connection,  however,  that  Brunner,2  who 
was  the  first,  so  far  as  the  author  is  aware,  to  destroy  the  gland  in  a 
living  animal,  states  in  his  work  on  the  pancreas  that  he  succeeded  in 
keeping  a  dog  alive  three  months  after  the  pancreas  had  been  extir- 
pated, and  that  yet  he  found  the  feces  normal.  Further,  it  is  well 
known  also  that  often  in  cases  of  fatty  diarrhoea  the  pancreas  has  been 
found  after  death  healthy,  the  liver  being  the  diseased  organ,  and  that 
occasionally  both  pancreas  and  liver  are  affected  at  the  same  time.3 
Indeed,  so  often  is  the  liver  affected  in  such  cases  that  fatty  diarrhoea 
is  regarded  as  much  a  symptom  of  hepatic  as  of  pancreatic  disease.  The 
conclusion  from  such  cases  would  seem  to  be  that  the  bile  emulsifies  the 
fats  to  some  extent  at  least  as  well  as  the  pancreatic  juice.  And  this 
is  in  accordance  with  the  fact  already  mentioned,  of  finding  emulsified 
fat  occasionally  in  the  lymphatics  of  the  rabbit  above  the  entrance  of  the 
pancreatic  duct.  In  the  case  of  the  intestinal  fistula  observed  by  Busch, 
it  will  be  remembered  that  the  food  that  was  taken  in  the  mouth  passed 
out  of  the  upper  of  the  two  openings  of  which  the  wound  consisted. 
According  to  Busch,4  when  fat  was  taken  in  by  the  mouth  it  passed  out 
of  the  upper  opening  in  the  state  of  a  fine  emulsion.  This  change  in  the 
fat  must  then  be  due  in  man  to  either  the  pancreatic  juice,  bile,  or  the 
intestinal  juice.  But  we  have  seen,  according  to  Busch,  that  fat  intro- 
duced into  the  intestine  through  the  lower  opening  of  the  wound  ap- 
peared in  the  feces  unchanged.  The  intestinal  juice,  or  at  least  that 
part  of  it  secreted  by  the  follicles  of  Lieberkiihn,  cannot  be  supposed  to 
emulsify  the  fat.  This  function,  then,  must  be  performed  by  either  the 
pancreatic  juice  or  the  bile,  or  both,  unless  the  secretion  of  Brunner's 
glands  is  hereafter  shown  to  exert  such  an  influence. 

An  important  observation  made  by  Bernard5  was  that  the  alkaline 
pancreatic  juice  out  of  the  body,  when  mixed  with  a  neutral  fat,  decom- 
posed the  latter  into  glycerin  and  a  fatty  acid,  the  phenomenon  being 
evidently  one  of  hydration  in  presence  of  a  ferment  as  follows  : 

Stearin.  Water.  Stearic  acid.  Glycerin. 

C57Hm06    +     3(H20)     =    3(C18H3602)     +     C3H803 

If  this  change  takes  place  in  the  human  intestine,  which  is  very  prob- 
able, it  will  account  for  the  presence  of  the  palmitates  and  oleates  found 
in  the  blood  and  feces,  as  soap — that  is,  a  fatty  acid  combined  with 
alkali. 

It  is  admitted  by  all  physiologists  that  the  pancreatic  juice  transforms 
starch  instantaneously  into  glucose,  one  part  of  pancreatic  juice  by 
weight  being  required  for  the  conversion  of  4.5  parts  of  starch.  This 
function  of  the  pancreatic  juice  was  first  demonstrated  in  1844  by  Val- 
entin,6 who  experimented  with  an  artificial  pancreatic  juice  prepared 
by  making  a  watery  infusion  of  the  gland.      Bernard7  showed  that  the 

1  Op.  (it.,  p.  276.  2  Experiments,  nova  circa  Pancreas,  p.  12.     Amst.,  1073. 

■'■  Miine  Edwards:  Physiologic,  tome  vii.  p   7(3.     Longet :  I'hysiologie,  tome  i.  p.  291. 
*  Op.  cit..  S.  175  6  Op.  cit.,  p.  257. 

6  Lehrbuch  der  Physiologic,  S.  356.     Braunschweig,  1817.  7  Op.  cit.,  S.  329. 


PANCREATIC    JUICE.  157 

natural  pancreatic  juice  had  the  same  effect  in  a  very  marked  degree. 
Since  at  least  nearly  one-half  of  the  food  of  man  consists  of  starch,  this 
function  of  the  pancreatic  juice  is  a  most  important  one. 

We  have  seen  that  cane  sugar  is  very  slowly  converted  into  glucose 
in  the  stomach,  but  in  such  small  quantities  that  we  must  look  for  its 
further  digestion  in  the  small  intestine.  The  case  reported  by  Busch1 
shows  that  the  transformation  of  cane  sugar  into  glucose  in  the  intestine 
is  due  to  the  pancreatic  juice,  for  the  bile  has  no  such  effect,  nor  the 
intestinal  juice,  while  when  cane  sugar  was  introduced  into  the  mouth 
glucose  appeared  at  the  upper  opening  of  the  wound;  when  cane  sugar 
was  introduced  into  the  intestine  by  the  lower  opening  of  the  wound  it 
appeared  unchanged  in  the  feces.  Cane  sugar  is,  however,  converted 
into  glucose  by  artificial  intestinal  juice.  In  addition  to  the  effects  of 
the  pancreatic  juice  upon  the  kinds  of  food  already  referred  to,  it  has 
also  the  property  of  assisting  the  digestion  of  albuminous  substances, 
about  one  part  by  weight  of  pancreatic  juice  digesting  eight  of  albumin- 
ous substances.  This  effect  of  the  pancreatic  juice  was  first  demon- 
strated by  Eberle2  in  1834,  with  an  acidulated  infusion  of  the  tissue  of 
the  pancreas.  Afterward  Bernard,3  in  his  investigations  of  the  pan- 
creas, called  attention  again  particularly  to  this  fact. 

While  the  albuminous  substances  are  converted  into  peptones  by  the 
pancreatic  juice  it  appears  that  no  intermediate  stage  like  sytonin  is 
formed,  as  we  saw  was  the  case  in  the  digestion  of  albumen  by  gastric 
juice,  and,  further,  that  this  action  of  the  pancreatic  juice  is  rather  of  a 
secondary  character,  as  a  considerable  portion  of  the  albumen  is  only 
converted  into  leucin  and  tyrosin. 

Inasmuch  as  the  pancreatic  juice  effects  important  changes  in  the 
fats,  starches,  sugar,  and  albuminoids,  it  might  be  supposed  from  the 
fact  of  the  albuminous  substances  of  the  pancreatic  juice  possessing 
such  different  properties  that  it  was  a  compound  rather  than  a  simple 
substance.  Chemists  have  shown  pretty  conclusively  that  such  is  the 
case,  that  the  organic  matter  consists  of  three  principles,  pancreatin 
converting  starch  into  glucose,  trypsin  transforming  albumen  into  albu- 
minose,  leucin.  tyrosin,  etc.,  and  a  third  substance,  as  yet  unnamed 
and  not  as  well  understood  as  the  other  two,  decomposing  the  fats  into 
glycerin  and  fatty  acids. 

As  regards  the  formation  of  leucin  and  tyrosin  by  the  action  of  the 
pancreatic  juice,  it  should  be  mentioned  that  a  far  greater  quantity  of 
these  substances  is  formed  outside  of  the  body  in  digestion  with  pan- 
creatic juice  than  within  it. 

It  has  been  learned  from  the  researches  of  Heidenhain4  more  particu- 
larly, that  each  cell  of  the  pancreas  of  a  dog,  for  example,  after  a  period 
of  about  thirty  hours'  fasting  consists  of  two  zones,  an  outer  zone,  which 
is  either  homogeneous  or  delicately  striated  and  readily  staining  with 
carmine,  and  a  large  inner  zone  finely  granulated  and  staining  with 
difficulty;  the  nucleus,  situated  partly  in  the  outer  zone  and  partly  in 
the  inner  one,  is  irregular  in  form.     If  the  cell  be  examined,  however, 

i  Op   cit.,  S.  170,  185.  -  Op.  cit.,  S.  235.  3  Op.  cit.,  p.  333. 

4  Pfluger'a  Archiv,  1875,  Band  x.  S.  557.     Hermann:  Physiologic,  Funfter  Baud,  S.  174,  182. 


158  PANCREATIC    JUICE. 

during  a  period  of  activity — six  hours,  for  example,  after  food  has  been 
taken— the  outer  zone  of  the  cell  will  be  found  to  be  the  longest,  the 
inner  zone  in  some  instances  having  disappeared  altogether,  and  the 
whole  cell  will  be  seen  to  have  become  smaller  and  staining  readily 
throughout  almost  its  whole  extent,  through  the  small  size  of  the  inner 
zone,  and  the  nucleus  regular  in  outline. 

The  natural  inference  to  be  drawn  from  these  observations  is,  that 
during  secretion  the  inner  zone  furnishes  either  the  secretion  or  the 
materials  of  the  same,  and  consequently  diminishes  in  extent  in  propor- 
tion to  the  activity  of  the  process,  while  the  outer  zone  enlarges  through 
assimilation  of  materials  brought  to  the  cell  by  the  blood  and  that  the 
materials  of  the  inner  zone  are  elaborated  at  the  expense  of  that  of  the 
outer  one.  That  such  is  actually  the  case  appears  to  have  been  shown 
by  the  observations  of  Kuhne  and  Lea,1  made  upon  the  pancreas  of 
the  living  rabbit,  in  which  the  changes  just  described  were  observed  as 
they  took  place  (Fig.  59,  A,  B). 

Fig.  59. 


A  portion  of  the  pancreas  of  the  rabbit,  A  at  rest.  B  in  a  state  of  activity,  a.  The  inner  granular  zone, 
which  in  A  is  larger,  and  more  closely  studded  with  granules,  than  in  B,  in  which  the  granules  are  fewer 
and  coarser.  &.  The  outer  transparent  zone,  small  in  A,  larger  in  B,  and  in  the  latter  marked  with  faint 
striae,  c  The  lumen,  very  obvious  in  B,  but  indistinct  in  A.  d.  An  indentation  at  the  junction  of  two 
cells,  seen  in  B,  but  not  occurring  in  A.     (Kuhne  and  Sheridan  Lea.) 

The  fact  that  a  glycerin  extract  made  out  of  a  pancreas  taken  out  of 
the  body  while  still  warm  has  no  digestive  effect,  whereas  the  same 
glycerin  extract  made  out  of  a  pancreas  kept  for  twenty-four  hours 
will  digest  fibrin,  shows  that  the  pancreas  contains  at  the  moment  that 
it  is  taken  out  of  the  body  but  little  of  its  albuminous  ferment,  but  that 
it  does  contain  a  substance  readily  convertible  into  such,  particularly  in 
the  presence  of  acid,  which  Heidenhain  has  called  zymogen.  If  such 
be  the  case,  it  would  appear  then  that  the  trypsin,  the  active  albuminous 
ferment  of  the  pancreatic  juice,  is  developed  out  of  the  zymogen2  stored 
up  in  the  inner  zone  of  the  cell,  and  that  the  latter  is  elaborated  out  of 
the  materials  of  the  outer  zone. 

As  to  whether  the  remaining  pancreatic  ferments  are  produced  in 
the  same  way  has  not  yet  been  shown.     It  may  be  mentioned3  that  the 

»  Verhandl.  Nat.  Hist.  Med.  Verien,  Band  i.     Heidelberg,  1877. 

2  Heidenhain  :  Hermann's  Physiologie,  Funfter  Band,  S.  188. 

3  Pfluger's  Archiv,  Band  xiv.  S.  465. 


BILE.  159 

pressure  under  which  the  pancreatic  juice  is  secreted  is  about  IT  milli- 
metres of  mercury. 

In  concluding  our  account  of  the  pancreas,  its  absence  in  many  kinds 
of  fish,  in  all  invertebrates  except  perhaps  the  cephalopoda,  appears  to 
show  that  the  pancreatic  secretion  cannot  be  as  indispensable  in  diges- 
tion and  absorption  as  is  often  supposed. 

The  Bile. 

That  the  bile  plays  an  important  part  in  digestion  would  be  naturally 
inferred,  as  suggested  by  Haller,1  from  the  fact  that  it  is  poured  into 
the  beginning  of  the  intestine ;  whereas,  if  it  were  purely  excrementi- 
tious  in  character,  it  would  be  eliminated  rather  at  the  end  of  it,  in  the 
vicinity  of  the  rectum,  for  example,  or  at  least  separated  from  the  blood 
without  mixing  with  the  food. 

It  has  been  shown  also  by  Schwann.  Schellbach,  Bidder  and  Schmidt, 
Arnold,  Kuhne,  and  others,2  that  if  the  bile  is  diverted  from  the  ali- 
mentary canal  by  a  biliary  fistula  sooner  or  later  the  animal  dies.  The 
exceptions  to  this  statement  are  only  apparent,  for  in  those  cases  where 
animals  have  lived  for  any  length  of  time  with  a  biliary  fistula  the  bile 
was  licked  up  and  swallowed  or  else  double  the  amount  of  food  was 
eaten  to  compensate  for  the  amount  of  bile  lost.  Further,  it  has  been 
well  established,  by  those  who  have  experimentally  investigated  the  sub- 
ject, that  the  flow  of  bile  is  greatest  during  digestion.  This  was  shown, 
for  example,  by  Prof.  Flint's  observations  upon  a  dog  with  a  biliary 
fistula. 

Table  XXXVII.3 — Flow  of  Bile  during  Digestion. 


Time. 

Amount. 

Time. 

Amount. 

Immediately 

after 

feeding 

8.1  grs. 

12  hours  after 

feedii 

'g     ■ 

.     5.7  grs. 

1  hour 

after  feedi 

ug     .     . 

20.5    " 

14     " 

" 

.     5.0    " 

2  hours 

,     << 

u 

35.7   " 

16     " 

a 

.     8.6    " 

4     " 

it 

it 

38.9    " 

18     " 

" 

.     9.9   " 

6     " 

n 

a 

22.2    " 

20     " 

" 

.     4.7    " 

8     " 

" 

it 

:;;;.5  " 

22     "          " 

u 

.     7.5    " 

10     " 

" 

it 

24.4   " 

If  the  bile  were  purely  excrementitious  in  character,  why  should  its 
flow  into  the  intestine  be  intermittent,  or  the  amount  be  connected  with 
digestion.'  A  significant  fact  in  reference  to  the  use  of  the  bile  in  diges- 
tion  is  that  in  starvation  the  gall-bladder  is  usually  found  distended  with 
bile.  If  the  flow  of  the  bile  has  no  connection  with  digestion,  there  would 
be  no  reason  for  this  retention.  On  the  other  hand,  it  is  well  known  that 
if  the  bile  is  indefinitely  retained,  either  in  animals  or  man,  death  takes 
place ;  showing  that  the  bile  contains  some  excrementitious  material 
which,  under  ordinary  circumstances,  is  eliminated  from  the  economy. 

That  the  bile  is  of  use,  and  yet  of  no  use,  is  confirmed  by  the  fact 
already  alluded  to.4  that  in  the  doris,  one  of  the  mollusca,  there  are  two 
hepatic  ducts,  one  of  which  conveys  part  of  the  hepatic  secretion  into 
the  intestine,  the  other  carries  the  remainder  directly  out  of  the  body. 

1  Elements  Physiologiae,  tomuBsextus,  p.  615.     Lausanne,  1757. 

-  Funke  :  Physiologic,  Erster  Band,  S.  199.    Longet :  Physiology,  tome  premier,  p.  2G9. 

3  Flint  :  Physiology,  voi.  ii.  p.  375.  4  Introduction,  p.  37. 


160  BILE. 

Assuming  that  the  bile  has  some  use  in  digestion,  let  us  see  now  what 
is  known  of  its  effect  upon  food. 

When  bile  is  mixed  with  the  acid  peptones,  the  result  of  stomach 
digestion,  a  precipitate  is  formed,  but  inasmuch  as  this  precipitate  is 
almost  instantly  redissolved  by  the  alkaline  intestinal  and  pancreatic 
juice  the  significance  of  this  fact  is  not  very  apparent.  Bile  has  no 
effect  upon  cane  sugar,  while  the  conversion  of  starch  into  sugar  by  the 
bile  is  not  constant,  being  rather  due  to  the  mucus  that  the  bile  may 
contain;  this  effect  of  the  bile  is,  therefore,  insignificant. 

There  remains  only,  then,  the  consideration  of  the  effect  of  bile  upon 
the  fats.  For  a  long  time  it  has  been  known  that  bile  can  be  used  to 
take  out  grease  spots  in  clothing,  etc.,  the  bile  having  the  property  of 
dissolving  the  acid  fat.  Many  physiologists  at  the  present  clay  hold, 
and  with  great  probability,  that  the  effect  of  bile  upon  the  fatty  articles 
of  food  within  the  intestine  is  the  same  as  that  just  mentioned  and 
made  use  of  by  scourers  and  others. 

Bile  also,  to  some  extent,  emulsifies  fat,  though  much  less  perfectly 
than  the  pancreatic  juice. 

It  has  been  shown  by  Wistinghausen  and  Hoffmann1  that  membranes, 
when  moistened  with  bile,  greatly  facilitate  the  passage  through  them  of 
fat ;  whereas,  when  the  membranes  are  moistened  with  water,  the  passage 
of  the  fat  was  entirely  retarded.  We  shall  see  the  importance  of  this 
observation  when  Ave  come  to  study  the  absorption  of  fat  by  the  villi. 

Admitting  that  one  important  use  of  the  bile  is  the  dissolving  and 
emulsifying  of  fat,  and  thereby  facilitating  its  absorption,  we  have  an 
explanation  of  those  cases  of  fatty  diarrhoea  observed  in  men  where  the 
liver  is  diseased,  and  where  the  bile  is  either  not  secreted  or  its  flow 
obstructed,  and  to  which  we  have  already  called  attention  in  speaking 
of  the  function  of  the  pancreas. 

The  experiments  upon  animals  made  by  Brodie,  Majendie,  Mayo, 
Hawkins,  Tiedemann  and  Gmelin,  Leuret  and  Lassaigne,  Bidder  and 
Schmidt,  etc.,  with  a  view  of  determining  whether  the  amount  of  fat 
absorbed  by  the  lacteals  is  diminished  when  the  bile  is  diverted  from 
the  intestines,  are  somewhat  discordant.2  The  general  conclusion,  how- 
ever, from  the  observations  of  these  experimenters,  seems  to  be  that 
there  is  less  fat  absorbed  when  the  bile  is  cut  off  from  the  intestine, 
than  under  the  normal  conditions.  Indeed,  according  to  Leuret  and 
Lassaigne,3  while  a  thousand  parts  of  chyle  in  a  healthy  dog  contain 
thirty-two  parts  of  fat,  there  are  found  only  two  parts  of  fat  in  the  chyle 
of  a  dog  in  which  the  bile  has  been  eliminated  by  a  fistula.  Bidder 
and  Schmidt4  give  as  the  result  of  their  experiments  very  much  the 
same  proportion. 

The  facts  of  pathology  and  experiment  then  agree  in  showing  that 
an  important  function  of  the  bile  is  to  assist  the  pancreatic  juice  in  pre- 
paring the  fatty  parts  of  the  food  for  absorption. 

It  was  noticed  by  Saunders5  that  the  bile  prevents  the  putrefaction 
of  the  food  in  the  intestine.     Since  then  the  majority  of  experimenters 

1  MilDe  Edwards  :  Physiologie,  tome  v.  p.  2'23. 

2  Berard  :  Physiologie,  tome  ii.  p.  364.     Longet :  Physiologie,  tome  i.  p.  274. 

3  Recherches  sur  la  Digestion.  4  Die  Verdauungssafte,  p.  227. 
6  Diseases  of  the  Liver,  pp.  136,  155,  167,  208.     London,  1803. 


FUNCTIONS    OF     BILE. 


161 


have  noticed  that  in  animals,  when  the  bile  is  prevented  from  passing 
into  the  intestine,  either  by  ligating  the  ductus  communis  or  making  a 
biliary  fistula,  the  food  becomes  putrid,  exhaling  a  very  disagreeable 
and  offensive  odor,  while  the  gases  of  the  intestine  are  greatly  increased 
in  quantity. 

According  to  Tiedemann  and  Gmelin,  Eberle,  Schiff,  and  other 
physiologists,  the  bile  exercises  a  stimulating  effect  upon  the  intestine, 
exciting  the  peristaltic  action  and  increasing  the  secretion  of  the  intes- 
tinal juices.  The  want  of  such  stimulus  explains,  according  to  those 
who  hold  the  ancient  and  plausible  view  of  the  bile  being  a  natural 
purgative,  the  character  of  the  stools  in  persons  affected  with   jaundice. 

Fig.  60. 


Gall  bladder 


Large  intestine 


~Spleen. 


-Small  intestine. 
"Colon. 


Rectum. 


Digestive  apparatus  of  man.     iMilsk  Edwards.] 


the  feces  in  such  cases  being  passed  at  long  intervals  and  in  a  hard 
condition,  through  the  want  of  peristaltic  action  and  the  softening  effect 
of  mixture  with  the  secretions. 

The  antiseptic  and  stimulating  action  of  the  bile  does  not  appear  to 
be,  however,  as  indispensable  as  the  changes  it  produces  in  the  fats. 

In  connection  with  the  uses  of  the  bile  in  digestion,  a  few  words  about 
the  gall-bladder  do  not  appear  superfluous.  That  the  gall-bladder 
(Fig.  60)  is  simply  a  receptacle  for  the  bile  seems  to  be  shown  from  the 
facts  that  it  is  occasionally  absent  in  man  without  the  secretion  of 
bile  being  suppressed,  and  that  when  the  cystic  duct  is  either  obliterated 

ll 


162 


GALL-BLAl)l»Ki;. 


or  obstructed,  no  bile  is  found  in  the  gall-bladder,  only  mucus  then 
being  present.  In  the  intervals  of  digestion  the  muscular  fibres  of  the 
duodenum  appear  to  constrict  the  orifice  of  the  ductus  communis  to 
such  an  extent  as  to  prevent  the  flow  of  the  bile  into  the  intestine ;  the 
bile  then  necessarily  flows  back  into  the  gall-bladder.  This  can  be 
shown  in  the  cadaver  by  simply  compressing  the  liver,  the  effect  of 
which  is  that  the  bile  flows  into  the  hepatic  duct,  and  thence  back  to 
the  gall-bladder. 

While  it  cannot  be  said  that  there  is  any  invariable  rule  as  regards 
the  presence  of  or  absence  of  the  gall-bladder  even  in  closely  allied 
animals,1  it  being  found,  for  example,  in  the  hog,  while  absent  in  the 
peccary,  being  present  in  the  antelope  though  not  in  the  deer,  some- 
times absent  and  sometimes  present  even  in  the  same  animal,  as  in  the 
giraffe ;  nevertheless,  in  the  carnivora,  it  may  be  stated,  without  excep- 
tion, that  the  gall-bladder  is  always  present.  The  significance  of  this 
latter  fact  is  obvious,  when  it  is  remembered  that  while  a  herbivorous 
animal,  like  the  cow  or  deer,  eats  continuously,  a  carnivorous  one,  like 
the  lion  or  tiger,  only  obtains  its  food  at  intervals,  and  in  large  quan- 
tities, hence  the  need  of  a  supply  of  bile  already  formed  to  assist  the 
digestion  of  the  food.2 

The  disposition  of  the  gall-bladder  in  the  python  further  illustrates 

its  use  as  a  receptacle.  In  this 
serpent  the  gall-bladder  is  situated 
some  distance  from  the  liver.  Were 
it  connected  with  it,  the  prey,  when 
introduced  into  the  stomach,  would 
compress  the  gall-bladder  and 
force  the  bile  into  the  intestine 
before  the  food  arrived  there,  and 
the  effect  of  the  bile  upon  the 
food  would  be  lost.  The  position 
of  the  gall-bladder,  however,  is 
such  that  when  the  food  about 
reaches  the  duodenum  compres- 
sion is  exerted,  and  the  bile  passes 
into  the  intestine  at  the  proper 
moment.  As  Owen3  well  observes, 
"this  fact  in  comparative  anatomy 
is  significant  of  the  share  taken  by 
the  biliary  secretion  in  the  act  of 
chylification." 

The  amount  of  bile  secreted  in 
a  given  period  of  time  in  man  can 
only  be  approximately  estimated 
from  experiments  made  upon  ani- 
mals with  biliary  fistula.  Assum- 
ing that  the  amount  of  bile  secreted  by  the  carnivora  and  man 
proportionally  to  the  weight  to  be  about  the  same,  there  would  be  from 


Portions  of  the  liver  of  the  hog,  exhibiting  the 
lohular  structure.  The  large  vessel  is  a  branch  of 
the  portal  vein,  the  outlines  of  the  lobules  being 
seen  through  its  transparent  wall.  The  orifices, 
large  and  small,  seen  in  the  portal  vein,  are  fine 
branches  sent  between  the  lobules.  The  two  ves- 
sels lying  to  the  right  of  the  portal  vein  are 
branches  of  the  hepatic  artery  and  duct.    (Leidy.) 


i  Milne  Edwards  :  Physiologie,  tome  vi.  p.  455.  ~  Cuvier 

3  Comparative  Anatomy  of  Veitebrates,  vol.  i.  p.  452. 


Anatomie  Coniparee,  tome  iv.  p.  37. 


STEUCTURE    OF    THE    LIVER, 


163 


about  two  and  a  half  to  three  pounds  of  bile  secreted  in  twenty-four 
hours  by  a  man  weighing  140  pounds. 

The  bile  being  secreted  by  the  liver,  let  us  now  consider  the  structure 
of  the  latter.  The  liver  is  the  most  constantly  present  gland  in  the 
animal  kingdom,  and  is  the  largest  gland  in  the  human  body,  weighing 
on  an  average  3  kil.  (50  ozs.).  If  the  surface  of  the  liver  be  examined, 
it  will  be  seen  to  be  far  from  homogeneous,  consisting,  in  fact,  of  a  great 
number  of  little  masses,  the  hepatic  lobules,  varying  in  diameter  from 
one  to  two  mm.  (-^th  to  y^tli  of  an  inch).  The  lobules  are  better  seen, 
however,  in  the  liver  of  the  pig  (Fig.  61)  than  in  that  of  man,  and  are 
especially  well  marked  in  the  liver  of  the  South  American  capromys. 
If  now  one  of  the  hepatic  lobules,  or  acini,  be  examined  microscopi- 
cally, it  in  turn  will  be  found  to  be  made  up  of  still  smaller  nucleated 
polyhedral  masses,  the  hepatic  cells  (Fig.  62),  varying  in  diameter  from 
the  ^y-th  and  -g^th  of  a  mm.  (-^th  to  tne  Tjrtn  °f  an  mcn)- 


Fig.  62. 


Fig.  63. 


Transverse  section  of  part  of  a  lobule  from  thejrab- 
bit's  liver,  a,  a,  a.  Nucleated  glandular  cells,  b,  b,  b. 
Capillary  bile-ducts  passing  between  the  adjacent  cells. 
c,  c,  c.  Sections  of  capillary  bloodvessels.    (Genth.) 


Ramification  of  portal  vein  of  liver,     a.   Twig  ot 
portal   vein.       6,  b.    Interlobular    veins,      c.    Acini. 

(Dai/ton.) 


Just  as  the  liver  is  made  up  of  lobules,  so  each  lobule  is  made  up  of 
cells,  and  as  it  is  through  the  agency  of  the  cells  that  the  bile  is  elabo- 
rated out  of  the  blood,  the  manner  in  which  the  latter  traverses  the  liver 
must  be  next  studied. 

The  liver  is  supplied  with  blood  by  the  portal  vein  and  hepatic  artery. 
The  portal  vein,  accompanied  by  the  hepatic  artery,  entering  the  liver 
at  the  transverse  fissure,  and  dividing  and  subdividing  into  numerous 
branches,  ramifies  as  the  interlobular  veins  (Fig.  63)  between  the  lobules 
and  anastomoses  freely  around  them.  From  these  peripheral  inter- 
lobular veins  arise  still  smaller  ones,  the  intralobular  veins  (Figs.  64,  65), 
which,  passing  into  the  lobule  from  its  margin  in  a  radiating  manner, 
unite  in  the  centre  as  the  central  vein  (Fig.  64).  The  latter 
passing  directly  through  the  lobule,  terminates  in  the  sublobular  vein, 
on    which    the    lobule    rests.       The    various    sublobular    veins    (Fig. 


164 


STRUCTURE    O F    T HE    LIVE  R  . 


66),  in  turn  uniting  together,  constitute  the  hepatic  vein.  The  latter 
terminates  in  the  ascending  vena  cava,  and  leaves  the  liver  at  right 
angles  to  which   the  portal   vein   enters.      That    the  portal    and  hepatic 


Pig.  64. 


Cross-section  of  a  lobule  of  the  human  liver,  in  which  the  capillary  network  between  the  portal  and 
hepatic  veins  has  been  fully  injected.  60  diameters.  1.  Section  of  the  intralobular  or  central  vein. 
2.  Its  smaller  branches  collecting  blood  from  the  capillary  network.  3.  Interlobular  or  peripheric 
branches  of  the  vena  ports  with  their  small  ramifications  passing  inward  toward  the  capillary  network 
in  the  substance  of  the  lobule.     (Sappey.) 


Fig.  65. 


Lobule  of  liver,  showing  distribution  of  bloodvessels  ;  magnified  22  diameters,  a,  a.  Interlobular  veins. 
b.  Intralobular  vein.  c,c,c.  Lobular  capillary  plexus,  d,  d.  Twigs  of  interlobular  vein  passing  to  ad ja- 
cent^lobules.     (Dalton.) 

veins  are  essentially  the  proximal  and  distal  parts  of  one  and  the  same 
vein,  is  shown  not  only  in  the  injection  of  either  of  them  equally  well 
through  the  other,  but  also  in  the  manner  in  which  the  vascular  system 


STRUCTURE    OF    THE    LIVER.  165 

and  the  liver  develop.  In  the  embryo,  as  we  shall  see  hereafter,  at  an 
early  period  the  continuity  of  the  portal  and  the  hepatic  veins  is  quite 
evident,  it  not  being  until  later  that  the  connection  between  the  two  is 
obscured  by  the  liver,  which  grows  parasitic-like  around  the  vessels 
which  later  supply  it  with  blood.  The  latter,  capillary  vessels,  consti- 
tute then  what  we  have  just  described  in  the  adult  as  the  interlobular, 
intralobular,  central,  and  sublobular  veins,  while  that  part  of  the  vein 
which  enters  the  liver  is  known  as  the  portal  vein,  that  part  leaving  it 
the  hepatic. 

The  hepatic  artery,  after  entering  the  liver,  like  the  portal  vein, 
ramifies  between  and  within  the  lobules,  but  unlike  the  portal  vein  does 
not  pass  through  the  lobules,  but  terminates  within  them  in  the  intra- 
lobular capillaries.  That  such  is  the  case,  is  shown  by  the  injection  of 
the  hepatic  vein  through  the  hepatic  artery.  Further,  that  the  liver 
cells  elaborate  bile  both  out  of  the  blood  brought  to  them  by  the  hepatic 

Fig.  66. 


.'*-.-:  'it''.'  ■ 

Injected  twig  of  a  sublobular  vein  passing  into  the  hepatic  lobules  About  30  diameters.  1.  Small  sub- 
lobular vein.  2.  Central  veins  passing  into  the  base  of  the  lobules.  3.  Their  smaller  subdivisions.  4. 
Capillary  network  of  communication  with  the  extreme  ramifications  of  the  vena  porta-.     (Sappey.  ) 

artery,  as  well  as  by  the  portal  vein,  is  shown  by  the  fact  that  the  bile 
is  still  secreted,  even  if  diminished,  if  the  latter  be  ligated,1  and  that 
the  bile  is  secreted  even  in  cases  where  the  portal  vein  has  been  found 
obliterated  after  death,2  or  passing  into  the  vena  cava.3 

Pathological  as  well  as  experimental  considerations  show  that  the 
liver  cells  are  the  active  agents  in  the  elaboration  of  the  bile.  Thus  in 
certain  diseased  conditions  of  the  liver,  noticeable  more  particularly  in 
the  liver  of  animals,  the  cells,  or  the  interspaces  between  them,  are  found 
filled  with  bile,4  while  if  a  substance  like  that  of  sulpho-indigotate  of 
sodium,  indigo  carmine  of  the  arts,  be  injected  into  the  circulation  of  a 

1  (lie  Comptes  Rendus,  tome  xliii.  p.  463.     Paris,  1856.  "  Andral  :  Ibid.,  p.  467. 

■>  Abernethy:    Phil.  Trans.,  p.  59.     London,  1793.     Lawrence:    Med.   Chir.   Trans.,  vol.  v.  p.   174. 
London,  1814. 
4  Stiles:  Bulletin  of  the  Xew  York  Academy  of  Medicine,  1868,  vol.  iii.  p.  350. 


166  DEVELOPMENT    OF    THE    LIVER. 

very  young  mammal,  a  sucking  pig,  for  example,1  the  liver  cells,  or 
the  interspaces  between  them,  according  to  the  length  of"  time  elapsing 
between  the  performing  of  the  experiment  and  the  killing  of  the  animal, 
will  be  seen  to  contain  the  salt  of  sodium  injected.  Since  the  bile 
does  not  exist  as  such   in  the  blood,  it  follows  that  the  liver  cells  not 

only  eliminate  from  the  blood  the 
Fig.  67.  principles  of  which  the  bile  consists, 

but   also  elaborate   the   same    into 
bile. 

The  bile  having  been  elaborated 
by  the  liver  cells  out  of  the  blood 
flowing  within  the  vessels  situated 
Diagram  showing  how  a  few  hepatic  ceiis  may     at  the  angles  formed  by  the  junction 

orma  hollow  tube.  1.  Large  cell;  viewed  from  0f  three  01'  more  Cells,  paSSCS  thence 
this  side  the  tubes  would  appear  to  be  the  breadth  ^  ^  interspaces  between  the 
of  a  single  cell,     2.  Two  cells  the  diameter  of  the  ..      /T-,.        nfTN       l    ,      .  .  . 

tube.  3.  Passage-way  for  the  bile,  (leh.v.)  cells  (Fig.  67),  and  since  these  inter- 
spaces open  into  the  minute  biliary 
ducts  (Fig.  62,  b,  6),  they  may  be  regarded  as  the  beginnings  of  the 
latter.  The  bile-ducts  begin  then  simply  as  intercellular  passages,  pos- 
sessing no  proper  walls  distinct  from  the  cells  bounding  them. 

At  the  margin  of  the  lobule,  however,  a  basement  membrane  becomes 
more  evident,  and  the  cells  covering  it  present  rather  a  columnar  shape 
as  compared  with  the  polyhedral  form  of  the  true  hepatic  cells.  The 
cellular  passages  or  interspaces  having  now  become  true  walled  ducts, 
with  a  diameter  of  the  y^g-th  of  a  mm.  (go^jth  of  an  inch),  ramify 
between  the  lobules,  and  are  here  seen  to  consist  distinctly  of  basement 
membrane  lined  with  columnar  epithelium,  while  the  larger  ducts,  in 
addition  to  the  basement  membrane,  possess  abundant  elastic  tissue, 
and  a  certain  amount  of  plain  muscular  tissue. 

In  addition  to  the  mucous  glands  opening  into  the  ducts,  large  race- 
mose csecal-like  glands  are  present  often  in  such  great  numbers  as 
almost  to  conceal  the  parent  tube  from  which  they  spring.  The  use 
of  these  glands  is  not  known. 

That  the  bile-ducts  begin  as  just  described,  is  further  confirmed  by 
the  manner  in  which  the  liver  develops,  and  by  its  structure  in  the  lower 
animals. 

The  liver,  as  we  shall  see  when  we  come  to  study  the  development  of 
the  organs  of  the  body,  first  appears  as  a  bud  or  diverticulum  (Fig. 
68,  L)  of  that  part  of  the  intestine  which  afterward  in  the  adult 
becomes  the  duodenum  and,  like  the  latter,  consists  of  two  layers,  an 
external  intestinal  fibrous  (i),  and  an  internal  intestinal  glandular  (//). 

In  the  former  are  developed  the  capillary  vessels,  which,  as  we  have 
seen,  connect  the  portal  and  the  hepatic  veins;  in  the  latter,  the  hepatic 
cells.  Very  soon  the  primitive  sac-like  diverticulum  of  the  intestine 
subdivides  into  the  two  primitive  lobes  (Fig.  69,  L,  L),  while  through 
the  narrowing  of  that  part  of  the  sac  opening  into  the  intestine  (Bd) 
a  duct  is  formed,  the  primitive  bile-duct,  a  diverticulum  from  the  latter 
constituting  the  future  gall-bladder.     It  is  evident  that  in  this  early 

i  Choezonsczewsky  :  Virchow's  Archiv,  1860,  Band  xxxv.  S.  153. 


DEVELOPMENT    OF    THE    LIVER. 


167 


embryonic  condition  of  the  liver  the  intestinal  glandular  layer  (g)  lining 
the  sac  constitutes  the  secreting  portion  of  the  gland,  and  the  interior 
of  the  sac  (bd),  the  beginning  of  the  bile-duct,  since  the  cavity  of  the 


yHHUi 


Development  of  the  liver. 

Fro.  69. 

X_-_  „ — _     L 


•' 


4\° 


Development  of  the  liver. 

Fig.  70. 


V  V 


HH 


.*•  hi 


TM^T^TTJT 


Development  of  the  liver. 


former  (bd)  is  continuous  with  that  of  the  latter  (Bd),  while  the  intes- 
tinal fibrous  wall  (i)  of  the  sac  supports  the  bloodvessels  (Fig.  70,  P) 
supplying  the  blood,  out  of  which  the  glandular  cells  (Gf)  lining  the  sac 
will  elaborate  the  bile.     The  latter  passes  thence  by  the  duct  (Bd)  into 


168  STRUCTURE    0E    LIVER    IN    LOWER    ANIMALS. 

the  intestine  (I).  The  structure  of  the  liver  al  this  stage  is  therefore 
similar  to  that  of  any  other  true  gland,  the  simplest  expression  of  which 
is  a  basement  membrane  separating  blood  on  one  side  from  cells  on  the 
other,  the  latter  elaborating  out  of  the  former  the  secretion  or  excretion 
characteristic  of  the  gland. 

Such  a  disposition  obtains  in  all  glands,  however  complicated  the 
structure  of  the  gland  may  be,  whether  it  be  follicular,  tubular,  race- 
mose, the  cells  are  always,  without  exception,  separated  from  the  blood 
by  a  membrane,  while  the  spaces  between  the  cells  ami  into  which  the 
secretion  exudes,  constitute  the  beginning  of  the  duct;  further,  just  as 
the  lobes  L  L  are  formed  through  the  subdivision  of  the  primitive  sac-like 
diverticulum  of  the  intestine  (X),  so  are  the  lobules  (IT)  formed  through 
the  subdivision  of  the  lobes  (Fig.  70)  and  as  the  lobes  are  defined  by 
the  fibrous  wall  (i),  so  are  the  lobules,  the  fibrous  wall  of  the  embryonic 
sac  corresponding  to  Glisson's  capsule  in  the  adult,  which  dipping  down 
between  the  lobules  with  the  interlobular  veins  and  the  hepatic  cells 
becomes  thinner  and  thinner,  and  finally  disappears,  or  becomes  so 
fused  with  either  the  walls  of  the  cells  or  of  the  vessels,  as  to  be  in- 
distinguishable from  the  latter. 

That  the  structure  of  the  liver  in  the  adult  is  essentially  the  same  as 
in  the  embryo,  consisting  of  bloodvessels,  in  whose  meshes  (Fig.  65) 
lie  cylinders  of  basement  membrane,  containing  secreting  cells,  or  in 
the  deeper  parts  simply  of  cylinders  of  cells  (Fig.  62),  the  spaces  be- 
tween the  latter  (Fig.  67,  Fig.  69,  bd)  constituting  the  beginnings  of 
the  bile-ducts,  is  still  further  shown  by  the  facts  of  comparative  anat- 
omy. For  as  is  well  known,  the  transitory  changes  through  which  the 
liver  of  the  higher  animals  passes  is  more  or  less  permanently  retained 
in  those  of  the  lower  ones.  Thus,  in  the  amphioxus  the  lowest  of  ver- 
tebrates, the  liver  consists  of  a  simple  sac-like  diverticulum  of  the  in- 
testine, corresponding  to  the  first  stage  in  the  development  of  the  liver 
of  the  higher  vertebrates.  Passing  to  the  lowest  of  fishes,  the  mars 
ipo-branchise,  of  which  the  myxine  is  an  example,  we  find  the  liver  a 
little  more  complex  than  in  the  amphioxus,  consisting  of  two  lobes 
with  lobules,  the  lobes,  however,  remaining  quite  distinct  throughout 
life,  whereas  in  the  higher  vertebrates  on  the  other  hand  tliey  coalesce 
more  or  less  completely  at  an  early  period,  constituting  in  the  adult  one 
organ. 

The  racemose-like  subdivided  condition  of  the  embryonic  liver,  which, 
as  we  have  just  seen,  is  a  transitory  one  in  the  liver  of  the  higher  ver- 
tebrates, is  permanently  retained  as  such  in  the  liver  of  many  inverte- 
brates ;  the  liver,  for  example,  in  the  slug  (Limax)  and  snail  (Helix) 
among  the  mollusca,  consisting  of  lobes  divided  into  lobules,  each  lobule 
consisting  of  creca  composed  of  basement  membrane  lined  with  mucous 
secreting  cells.  Essentially  the  same  structure  obtains  in  the  liver  of 
the  lamp  shells  or  brachiopoda  (Terebratulima),  consisting  in  these 
animals  of  numerous  caeca  lined  with  cells  easily  separable  from  each 
other,  and  over  which  the  visceral  bloodvessels  ramify. 

The  same  type  of  structure  is  seen  in  the  liver  of  the  Crustacea,  con- 
sisting in  our  common  crayfish  (Astacus)  of  two  lobes,  one  in  each  side 
of  the  intestine,  and  united  by  an  isthmus,  each  lobe  consisting  of  long 


STRUCTURE    OF    LIVER    IN     LOWER     ANIMALS, 


169 


Fig.  71. 


conical  caeca  massed  together,  the  latter  (Fig.  71)  consisting  of  basement 
membrane,  supporting  numerous  secreting  cells,  on  the  inner  surface. 
The  same  disposition  essentially  obtains  in  the  liver  of  the  corrupedia, 
being  well  seen  in  the  common  barnacle  (Balanus).  It  is  needless  further  to 
multiply  examples,  since  wherever  the  liver  exists 
in  such  ;i  condition  that  its  minute  structure  can 
be  readily  made  out,  it  will  invariably  be  found  to 
consist  of  caeca  more  or  less  aggregated  together, 
consisting  of  basement  membrane  lined  with 
cells  between  and  around  which  the  bloodves- 
sels ramify,  the  spaces  between  the  cells  con- 
stituting the  beginning  of  the  bile-ducts.  A 
priori,  therefore,  we  should  expect  to  find  the 
minute  structure  of  the  liver  essentially,  the 
same  as  that  of  the  lower  animals,  and  such 
we  have  found  to  be  the  case  as  studied  in  its 
minute  structure,  and  in  its  development. 

It  is  held,  however,  by  many  physiologists 
that  the  glands  which  in  the  invertebrates  we 
have  described  as  being  biliary  in  function,  are 
not  really  such,  the  secretion  elaborated  by  them 
not  containing  the  characteristic  bile  acids. 
Even  admitting  that  this  is  the  case  on  the 
supposition  that  the  transitory  stages  through 
which  the  higher  animals  pass  are  permanently 
retained  in  the  lower,  one  might  expect  to  find 
the  bile  in  the  latter  not  corresponding  exactly 
in  composition  with  that  of  the  former,  but 
rather  with  a  transitory  stage  in  the  develop- 
ment of  the  same.  Further,  the  fact  of  the 
biliary  tubules  in  insects  secreting  urea,  uric- 
acid,  etc.,  so  far  from  being  inconsistent  with 
the  view  of  the  tubules  being  biliary  in  function 
is  confirmatory  of  it,  since,  as  we  shall  see 
hereafter,  there  are  good  reasons  for  supposing 
that  urea,  to  a  certain  extent,  at  least,  is  produced  in  the  liver  of  verte- 
brates. 

The  bile  as  obtained  by  Jacobsen1  from  a  case  of  biliary  fistula  was 
clear  greenish,  brownish-yellow,  neutral  in  reaction,  and  of  a  specific 
gravity  of  1.002;  when  mixed  however  with  mucus,  as  is  the  case 
when  taken  from  the  gall-bladder,  the  bile  is  more  or  less  ropy  in  con- 
sistence, with  an  alkaline  or  neutral  reaction,  having  a  faint  odor,  a  bit- 
ter taste  and  a  specific  gravity  of  about  1.020,  and  bright  golden-red  in 
color,  as  is  the  case  also  in  the  bile  of  the  omnivora  and  carnivora,  that 
of  the  herbivora  being,  on  the  contrary,  of  a  golden  or  bright  green,  the 
difference  being  due,  as  we  shall  see,  to  the  relative  amount  in  which 
the  bile  pigments  bilirubin  and  biliverdin  are  present.  It  is  oxidation 
of  the  latter  which  gives  rise  to  the  changes  in  color  which  the  bile 
exhibits  after  exposure. 


One  of  the  hepatic  cieca  of  As- 
tacus  affirms  (crayfish),  highly 
magnified,  showing  the  prog- 
ress of  development  of  the 
secreting  cells,  from  the  blind 
extremity  to  the  mouth  of  the 
follicle  :  specimens  of  these,  in 
their  successive  stages,  are 
shown  separately  at  a,  6,  c,  d, 
e.     (Leidv.) 


'  Jahresber.  der  Thier  Chemie,  iii.  S.  193,  1873.     Hermann  :  Physiologie,  Funfter  Band.  S.  119. 


170  COMPOSITION    OF    THE    BILE. 

The  bile  when  shaken  up  with  air  or  water  foams  up  into  a  frothy 
mixture.  Tliis  property  is  due  to  the  presence  of  the  biliary  salts.  The 
bile  is  also  dichroic — that  is,  it  presents  two  different  colors  according 
to  its  mass,  when  examined  with  transmitted  lighl  :  thus,  while  a  layer 
of  ox  bile  two  or  three  centimetres  thick  is  green,  that  of  five  or  six  cen- 
timetres appears  red.  The  bile  is  also  fluorescent ;  thus,  if  green  bile 
be  viewed  by  the  violet  or  blue  rays  of  the  spectrum,  it  becomes  faintly 
luminous,  with  a  yellow,  greenish  tint. 

The  bile,  chemically,  is  a  highly  complex  fluid,  consisting  of  water, 
biliary  salts,  mucus,  pigment,  cholesterin,  fats,  and  inorganic  salts,  the 
water  and  solids  being  in  100  parts  in  the  proportion  of  about  86  to  14, 
as  may  be  seen  more  in  detail  from  Table  XXXVIII.,  giving  the 
analyses  of  Frerichs  and  Gorup  Besanez1  of  human  bile  obtained  from 
the  gall-bladder. 

Table  XXXVIII. — Composition  of  the  Bile. 

Frericlis.  Gorup  Besanez. 


In  100  parts.                                   Man,  Man,  Man,  Man,  Woman,             Boy, 

set.  18.  set.  22.  sat.  49.  set.  68.  set.  28.  set.  12. 

Water      ....  86.00  85.92  82.27  90.87  89.81  82.81 

Solids      ....  14.00  14.08  17.73          9.13  10.19  17.19 


5.65 


Biliary  acids  with  alkali 

7.22 

9.14 

10.79 

7.37 

Fat 

0,32 

0.92 

4.73 

'  3.09 

Cholesterin 

0.16 

0.26 

Mucus  and  pigment 

2.66 

2.98 

2.21 

1.76 

1.45 

Inorganic  salts 

0.65 

0.77 

1.08 

0.63 

14.80 
2.39 


Of  the  different  principles  which  constitute  the  bile,  most  of  them,  as 
the  water,  cholesterin,  fat,  and  inorganic  salts,  preexist  as  such  in  the 
blood,  and  are  simply  eliminated  from  the  latter  by  the  liver  cells  ;  the 
biliary  salts  and  the  biliary  pigment,  however,  are  not  found  in  the  blood, 
but  are  elaborated  by  the  liver  cells  out  of  the  principles  brought  to  them 
by  the  blood.  The  presence  of  the  biliary  acids,  then,  in  the  urine,  for 
example,  is  a  proof  that  the  bile  has  been  secreted,  but  has  been  pre- 
vented by  some  obstruction  from  passing  into  the  duodenum  and  being 
reabsorbed.  A  jaundice  from  mere  obstruction  in  which,  however,  the 
bile  has  been  secreted,  can  be  then  distinguished  from  one  in  which  no 
bile  has  been  secreted  by  the  presence  or  absence  of  the  biliary  acids  in 
the  urine ;  the  color  of  the  skin  in  the  latter  case  being  probably  due 
to  the  diffusion  into  the  tissues  of  the  broken-down  hsemoglobin  of  the 
red  blood-corpuscles,  and  which  we  shall  see  is  almost  identical,  if  not 
absolutely  so,  in  chemical  composition  with  the  biliary  pigment. 

The  biliary  salts  do  not  consist,  as  one  would  suppose  from  their 
name,  of  simply  inorganic  salts,  such  as  are  ordinarily  found  in  the 
secretions,  but  of  soda,  united  with  glycocholic  and  taurocholic  acids, 
the  organic  nitrogenized  acids  so  characteristic  of  the  bile,  and  upon 
which,  to  a  great  extent,  the  properties  of  the  latter  depend 

The  biliary  salts,  the  sodium  taurocholate,  C26H44NS07Na,  and  the 
sodium  gylcocholate,  C26H42N06Na,  may  be  obtained  from  the  bile  in  the 

1   Lehrbucb  dor  Physiologischen  Chemie,  S.  519.     Braunschweig,  1878. 


BILIARY     SALTS    AND    ACIDS.  171 

following  manner :  The  bile  having  been  mixed  with  animal  charcoal 
to  decolorize  it,  is  evaporated  to  dryness,  and  then  treated  with  alcohol. 
The  alcohol  having  been  distilled  off,  the  dry  residue  is  then  further 
treated  with  absolute  alcohol ;  anhydrous  ether,  after  filtering,  is 
added  to  the  filtrate  until  the  precipitate  formed  ceases  to  be  thrown 
down.  After  standing  some  hours  the  precipitate  crystallizes  as  the 
resinous  matter  of  the  bile,  also  known  as  bilin,  and  which  contains 
both  sodium  taurocholate  and  glycocholate,  if  both  biliary  acids  be 
present  in  the  bile,  and  which  can  be  separated  from  each  other  by 
making  an  aqueous  solution  of  the  bilin,  adding  neutral  lead  acetate 
and  then  filtering.  The  filtered  solution  will  contain  the  sodium  tauro- 
cholate alone,  the  sodium  glycocholate  being  decomposed  and  precipi- 
tated as  an  insoluble  lead  glycocholate. 

Fig.  72. 


Sodium  glycueholate  from  ox-bile,  alter  two  daye'  crystallization.  At  the  lower  part  ot  the  figure 
the  crystals  are  melting  into  drops,  from  the  evaporation  of  the  ether  and  absorption  of  moisture. 
(Dalton.) 

The  biliary  acids  themselves  may  then  be  separated  from  their 
respective  salts  by  means  of  dilute  sulphuric  acid  or  lead  acetate  and 
sulphydric  acid.  The  relation  existing,  chemically,  between  these  two 
acids,  is  shown  in  the  formula: 

Taurocholic  acid.  filycocholic  acid. 

C26H,5NSO,    —     H.,0— S     =     C26H43N06 

by  which  it  is  seen  that,  in  deducting  water  and  sulphur,  taurocholic 
becomes  glycocholic  acid.  As  a  general  rule,  both  the  biliary  salts  are 
present  in  human  bile,  though  the  proportion  in  which  they  exist  may 
vary  considerably.  Thus,  in  the  case  of  biliary  fistula  observed  by 
Jacobsen,  already  referred  to,  the  sodium  taurocholate  was  present  only 
in  small  quantity  or  absent  altogether.  Usually,  in  the  bile  of  the 
herbivora  the  sodium  glycocholate  preponderates,  in  that  of  the  carni- 
vora  the  taurocholate.  In  the  bile  of  the  cat  and  dog,  however,  the 
sodium  taurocholate  alone  is  found. 


172  pettenkofer's  test   for   bile. 

Both  the  biliary  salts  crystallize  in  hemispherical  or  star-shaped 
masses  of  fine  radiating  needles  (Fig.  72)  which,  while  soluble  in 
alcohol  and  water,  are  insoluble  in  ether.  The  two  salts  are  distin- 
guished from  each  other,  as  just  mentioned  in  speaking  of  the  manner 
of  obtaining  them,  in  that  the  sodium  taurocholate  is  not  precipitated 
by  the  neutral  lead  acetate,  Pb(C2H302)2  3A<p  but  only  by  the  tribasic 
lead  acetate,  Pb(C2H302)2PbO.  It  is  an  interesting  fact  that  the  biliary 
salts,  like  glucose,  lactose,  and  glycogen,  exert  a  right-handed  rotation 
on  polarized  light,  all  other  substances  in  the  animal  body,  so  far  as  is 
known,  having  the  opposite  effect  when  examined  by  polarized  light. 
The  play  of  colors  from  cherry-red  to  purple  or  violet  ensuing  when 
cane  sugar  and  sulphuric  acid  are  added  to  bile,  or  to  a  solution  con- 
taining the  biliary  salts  or  acids,  and  which  is  due  to  the  decomposition 
of  the  latter,  or  to  the  cholalic  acid  entering  into  their  formation, 
furnishes  a  very  simple  but  reliable  test  for  bile.  This  test,  commonly 
known  as  Pettenkofer's,  is  applied  as  follows  :  One  part  of  cane  sugar 
being  dissolved  in  four  parts  of  water,  one  drop  of  the  solution  is  added 
to  every  cubic  centimetre  of  the  solution  to  be  examined.  To  this 
mixture  a  few  drops  of  sulphuric  acid  are  slowly  added,  the  tempera- 
ture of  the  mixture  not  being  allowed  to  rise  above  70°  Cent.  If  bile 
acids  be  present  in  proportions  of  1  to  500  in  a  solution  treated  this 
way,  a  cherry-red  color  first  appears,  which  rapidly  changes  to  violet, 
and  then  to  a  deep  red  purple.  Inasmuch,  however,  as  there  are  other 
substances,  such  as  albuminous  matters,  amylic  alcohol,  olein,  morphine, 
codeine,  etc.,  which  present  this  same  play  of  colors  when  treated  with 
cane  sugar  and  sulphuric  acid,  it  is  necessary  to  point  out  the  precau- 
tions which  must  be  taken  in  applying  Pettenkofer's  test  for  bile,  in 
order  to  exclude  these  sources  of  error.  With  the  exception  of  the 
morphine,  which  is  unlikely  to  occur  in  an  extract  of  the  animal  fluid, 
especially  in  the  proportions  just  referred  to,  this  can  be  accomplished 
if  the  suspected  liquid  be  first  evaporated  to  dryness,  the  dry  residue 
extracted  wTith  absolute  alcohol  and  decolorized,  if  necessary,  with 
animal  charcoal,  then  precipitated  with  ether,  and  the  precipitate  dis- 
solved in  water.  Spectrum  analysis  of  Pettenkofer's  test  can  also  be 
used  in  distinguishing  bile  from  the  substances  just  referred  to,  and 
which  give  the  same  reactions. 

Pettenkofer's  test,  when  carefully  applied,  is  an  extremely  delicate 
one,  since  a  solution  of  sodium  glycocholate  in  the  proportion  of  1  to 
2000,  and  sodium  taurocholate  of  1  to  3000  of  water  respectively,  can 
be  recognized  by  it,  as  shown  in  the  following  formula  : 

Taurocholic  acid.  Water.  Cholalic  acid.  Taurin. 

C24H45NS07     +     H20     =     C24H4n05     +     C,H7NS03 

Glycocholic  acid.  Water.  Cholalic  acid.  Glycin. 

C26H43N06     +     H20     =     C24H40O5     +     C2H5N02 

Glycocholic  acid,  when  boiled  with  dilute  sulphuric  or  hydrochloric 
acid,  caustic  potash,  or  baryta  water,  becomes  cholalic  acid  and  glycin, 
and  in  a  similar  manner  taurocholic  acid  can  be  shown  to  consist  of  the 
same  acid  and  taurin.      While  cholalic  acid  is  a  non-nitrogenized  acid, 


GMELIX'S    TEST     FOR    BILE.  173 

as  may  be  seen  in  both  the  above  instances,  it  is  associated  with  a  nitro- 
genous body,  in  the  first  case  with  glycin  (amido-acetic  acid),  and  in  the 
second  with  taurin  (amidoistheonic  acid).  The  reaction  given  in  the 
above  formula  is  as  interesting  from  a  pathological  as  from  a  purely 
chemical  point  of  view,  since,  in  all  probability,  as  shown  by  Hoppe- 
Seyler,1  the  decomposition  of  glycocholic  and  taurocholic  acids  into 
cholalic  acid,  glycin,  and  taurin  takes  place  in  the  intestines,  the  acid 
passing  out  of  the  body  in  the  feces,  the  ammonium  compounds,  the 
glycin  and  taurin,  being  reabsorbed.  The  view  of  the  biliary  acids 
being  decomposed  in  the  intestine  and  partially  absorbed,  or  entirely  so 
undecomposed,  is  confirmed  by  several  facts.  Thus,  in  experimenting 
with  a  dog,  whose  bile  usually  furnished  in  five  days  :2,i'74  grammes 
(34  grains)  of  sulphur,  Bidder  and  Schmidt2  found  in  the  feces  during 
that  period  0.384  of  a  gramme  (4.0  grains),  of  which  about  0.154 
gramme  (1.5  grain)  could  have  been  derived  from  the  bile,  the  remain- 
ing sulphur  being  obtained  from  the  hair  in  the  feces.  That  is,  only  a 
fractional  part  of  the  sulphur  originally  present  in  the  bile  was  found 
in  the  feces,  whereas  had  not  the  taurocholic  acid  been  decomposed  and 
partly  absorbed  all  of  the  sulphur  would  have  been  found  there.  On 
the  other  hand,  that  the  biliary  acids  may  be  absorbed  undecomposed 
is  shown  by  the  observations  of  Taffeiner,3  who  found  the  biliary  salts 
in  chyle  from  the  thoracic  duct.  Further,  the  experiments  of  Schiff,* 
in  which  it  was  shown  that  the  amount  of  bile  evacuated  through  a 
biliary  fistula  was  about  one-third  of  that  normally  poured  into  the 
intestine,  would  lead  one  naturally  to  suppose  that  the  bile  is  ordinarily 
absorbed  in  part,  at  least,  soon  after  it  has  passed  into  the  latter. 

The  color  of  the  bile,  as  we  have  already  mentioned,  depends  upon 
the  proportion  in  which  the  bile  pigments,  bilirubin  and  biliverdin,  are 
present.  Bilirubin,  C16H1SX2<  )3,  the  red  or  orange-red  coloring  matter 
of  the  bile,  can  be  obtained  from  gall-stones  by  extraction,  is  crystalliz- 
able,  readily  soluble  in  alkaline  liquids  and  chloroform,  less  so  in  alcohol 
and  ether,  but  entirely  insoluble  in  pure  water.  If  to  a  solution  of 
bilirubin,  spread  out  on  the  surface  of  a  porcelain  plate,  for  example, 
a  drop  of  nitroso-nitric  acid  be  added,  a  characteristic  play  of  colors — 
green,  blue,  violet,  red,  and,  finally,  yellow — will  be  observed  at  the 
circumference  of  the  drop  of  acid  as  it  diffuses  itself  through  the  solu- 
tion, and  which  is  due  to  the  successive  oxidation  of  the  bilirubin. 
This  reaction  is  an  exceedingly  delicate  one,  the  play  of  colors  being 
evident  in  solutions  of  bilirubin  containing  only  1  part  in  70,000,  and 
is,  therefore,  utilized  as  Gmelin's  test  in  determining  the  presence  of 
the  coloring  matter  of  the  bile.  That  bilirubin,  though  not  identical,  is 
at  least  the  modified  coloring  matter  of  the  red  blood- corpuscles  or 
haemoglobin,  appears  to  be  shown  from  the  fact  of  its  being  found  in 
old  blood  extravasations,  on  account  of  its  similarity  in  color  and 
chemical  composition  with  that  of  the  latter,  and  that  if  the  blood 
freshly  drawn,  and  alternately  frozen   and   thawed,  be   reinjected   into 

1  Virchow'a  Archiv.  Band  xxv.  S.  1S1  ;  xxvi.  S.  519. 

2  Die  VerdauuDg-isafte,  S.  217.     Leipzig,  1852. 

;;  Sitzungsberichte,  Band  lxxvii.  S.  286.    Wien,  1878. 
4  Pfluger's  Archiv,  1870,   S.  598. 


174 


CIIOLESTEUIN  , 


the  circulation,  bilirubin  is  found  in  the  urine.  Bilirubin,  when  oxi- 
dized, loses  its  red  color,  becoming  green,  us  in  the  first  stage  of 
Gmelin's  test,  and  is  then  transformed  into  biliverdin,  the  green  colored 
pigment  of  the  bile,  the  process  being  apparently  one  of  hydration  as 
well  as  of  oxidation,  as  shown  by  the  following  formula: 


Bilirubin.  Water. 

C16H18N203    +     H20    + 


o 


Biliverdin. 

C16H20NA 


Biliverdin  crystallizes  somewhat  imperfectly  from  an  evaporated 
solution  in  glacial  acetic  acid,  is  insoluble  in  water,  ether,  and  chloro- 
form, but  is  readily  soluble  in  alkaline  solutions  and  alcohol.  It  fre- 
quently constitutes  an  ingredient  of  human  gall-stones.  Its  presence 
can  not  only  be  determined  by  Gmelin's  test,  but  by  means  of  spectrum 
analysis. 

Both  bilirubin  and  biliverdin  pass  as  the  coloring  matter  of  the  bile 
into  the  alimentary  canal,  in  the  lower  part  of  which,  as  we  shall  see 
presently,  they  give  the  feces  their  characteristic  color,  and  as  such 
pass  out  of  the  body. 

Cholesterin,  C26H440,  so  called  on  account  of  its  having  been  first 
obtained  as  a  solid  deposit  from  the  bile,  is  a  constant  ingredient  of  that 
fluid,  though  occurring  only  in  the  proportion  of  one  per  cent.  It  is  a 
non-nitrogenous,  crystallizable  body,  appearing  as  thin,  colorless,  trans- 
parent, rhomboida!  plates  (Fig  73)  when  deposited  from  its  ethereal  or 


Fio   73. 


r1      UJ I     i 


Cholesterin,  from  an  encysted  tumor.     (Dalton.) 

alcoholic  solution.  It  is  insoluble  in  water,  but  soluble  in  a  solution  of 
the  biliary  salts,  oily  liquids,  and  chloroform,  as  well  as  in  ether  and 
boiling  alcohol. 

Cholesterin  is  found  in  the  blood,  spleen,  crystalline  lens,  brain,  spinal 
cord,  and  nerves,  as  also  in  other  parts  of  the  body.  It  differs,  therefore, 
from  the  biliary  salts  and  pigment  in  not,  like  them,  being  elaborated  in 
the  liver,  but  as  preexisting  in  the  tissues,  and  being  simply  separated 
from  the  blood  by  that  organ  and  eliminated  from  the  system  as  part  of 


ORIGIN     OF    THE    BILE.  175 

the  bile,   passing  out  of  the  body  in  the  feces   as  cholesterin,  or,  ac- 
cording to  Flint,1  as  stercorin,  a  modified  form  of  the  same. 

Of  the  remaining  principles  entering  usually  into  the  composition  of 
the  bile  a  few  words  will  suffice.  According  to  Jacobsen,  the  bile 
obtained  from  the  biliary  fistula  already  referred  to,  contained,  in  addi- 
tion to  biliary  salts,  pigment  and  cholesterin  ;  fractional  quantities  of 
free  fat,  lecithin,  and  sodium  palmitate  and  stearate.  Of  the  mineral 
salts  present,  sodium  and  potassium  chloride,  sodium  and  calcium  phos- 
phate, and  sodium  carbonate,  the  sodium  chloride  and  sodium  phosphate 
were  most  abundant,  the  former  being  in  the  proportion  of  5.4  parts,  the 
latter  1.3  per  thousand. 

We  have  seen  that  the  bile  is  both  a  secretion  and  an  excretion — that 
is,  that  it  contains  some  principle  which  fulfils  some  function,  in  all 
probability  that  of  promoting  digestion  and  absorption,  and  some  prin- 
ciple which,  if  retained  within  the  system,  proves  excrementitious,  and 
that  the  biliary  salts  are,  to  a  great  extent,  reabsorbed,  while  the  pig- 
ment and  cholesterin  pass  out  of  the  body  in  the  feces  either  as  such 
or  more  or  less  modified.  The  natural  conclusion  from  these  facts  seems 
to  be  that  the  quality  of  the  bile  as  a  secretion  is  due  to  its  biliary  salts, 
and  as  an  excretion  to  its  biliary  pigment  and  the  cholesterin. 

From  what  has  been  said  of  the  manner  in  which  the  saliva,  gastric 
and  pancreatic  juices  are  secreted,  it  might  be  supposed  that  the  bile  is 
elaborated  by  the  liver  cells  in  a  somewhat  similar  manner  out  of  mate- 
rials brought  to  them  by  the  blood.  That  such  is  the  case,  appears 
from  the  fact  already  mentioned  of  the  bile  not  preexisting  as  such 
in  the  blood,  and  further  of  it  not  accumulating!;  in  the  blood  during  the 
short  period  which  some  animals,  frogs,  for  example,  live  after  extirpa- 
tion of  the  liver. 

That  the  bile  is  not  a  mere  filtrate  from  the  blood  is  shown,  as  in 
the  case  of  the  secretion  of  the  saliva,  from  the  pressure  under  which 
it  is  secreted  (in  the  dog  220  mm.  (8.8  in.)  sodium  carbonate  solution") 
being  greater  than  that  of  the  blood  supplying  the  liver,  and  that 
chemical  action  is  going  on  during  secretion  is  equally  evident  from 
the  amount  of  heat  developed  and  carbonic  acid  produced. 

That  there  is  some  genetic  connection  between  the  luemoalobin  of 
the  blood,  and  the  bilirubin  and  biliverdin  of  the  bile,  after  what  has 
been  said  of  the  latter  substances  there  can  be  little  doubt,  and  that 
the  cholesterin,  taurin,  and  glycin  of  the  tissues  as  well  as  such  amounts 
of  the  latter  substances  as  are  reabsorbed  from  the  intestine  may  be 
carried  to  the  liver  cells  and  elaborated  synthetically  into  bile,  the  lat- 
ter to  a  certain  extent,  therefore,  being  made  over  again  out  of  the 
same  elements,  appears  probable.  It  must  be  admitted,  nevertheless, 
that  the  materials  out  of,  and  the  manner  in  which  the  bile  is  exactly 
secreted  or  excreted  is  still  of  a  very  speculative  nature. 

The  function  of  the  liver,  as  might  be  supposed  from  its  size  and 
constant  presence  in  the  animal  kingdom,  is  not  however  limited  to  the 
secreting  or  excreting  of  bile,  for,  as  we  shall  see,  it  exercises  an  impor- 

•  Physiology,  1867,  vol.  ii.  p.  299. 

2  Heidenhain  :  Hermann's  Physiologie,  Funfter  Band,  S.  269. 


176  GLYCOGEN. 

t.int  influence  certainly  in  the  embryo,  and  very  probably  also  in  the 
adult,  in  the  elaboration  of  the  red  blood-corpuscles.  Further,  the 
liver  cells  have  the  power  of  developing,  storing  up,  and  transforming 
a  substance  glycogen;  so  called,  from  the  resemblance  to  and  readiness 
with  which  it  becomes  sugar,  and  the  origin  and  use  of  winch  may  be 
considered  as  appropriately  here  as  elsewhere,  though  it  should  be  men- 
tioned thai  glycogen  is  found  in  the  brain,  muscles,  placenta,  and  other 
parts  of  the  body  as  well  as  in  the  liver. 

Glycogen.  C6H10O5,  a  white  pulverulent  mass,  is  isomeric  with  starch 
and  dextrin.  It  differs  however,  physically  from  the  latter  in  that  its 
solution  is  opalescent,  while  that  of  dextrin  is  clear,  and  that  the  ad- 
dition of  iodine  gives  to  the  solution  of  glycogen  a  deep  brownish-red 
color,  but  to  that  of  dextrin  a  rosy  red,  and  to  starch  the  characteristic 
blue.  Glvcogen  is  soluble  in  both  hot  and  cold  water,  but  insoluble  in 
ether  and  alcohol,  and  is  one  of  the  few  substances  in  the  animal  body 
that  deviate  the  plane  of  polarization  to  the  right.  Glycogen  in  solu- 
tion, like  other  starchy  bodies,  is  readily  converted  into  glucose  when 
boiled,  for  example,  with  a  dilute  mineral  acid,  or  brought  in  contact  at 
the  temperature  of  the  body  with  saliva,  pancreatic  or  intestinal  juice, 
or  serum.  Glycogen  becomes  glucose  also,  if  simply  allowed  to  remain 
in  the  liver  after  death,  or  if  brought  in  contact  with  its  tissue  after 
removal  from  the  body,  the  albuminous  principles  of  the  liver  very 
probably  assisting  as  ferments  in  the  development,  though  the  phenom- 
enon is  essentially  one  of  hydration  as  shown  by  the  formula  : 

Glycogen.  Water.  Glucose. 

C6H10O5    +     H20    -     C6HrA 

Glycogen  can  be  readily  obtained  in  the  following  manner.  Imme- 
diately after  death,  the  liver  of  a  well  fed  animal  is  taken  out  of  the 
body  and  cut  up  into  small  pieces,  and  coagulated  with  boiling  water. 
A  concentrated  decoction  is  then  made  of  the  liver  tissue  thoroughly 
ground  up,  and  decolorized  with  animal  charcoal.  Strong  alcohol 
being  now  added,  the  glycogen  will  be  precipitated  as  a  white  powder; 
but  this  is  impure,  being  mixed  with  a  small  quantity  of  glucose, 
biliary  salts,  and  albuminous  matter.  The  latter  can  be  removed, 
however,  by  washing  with  alcohol,  and  boiling  with  potassium  hydrate. 
The  residue  being  filtered  and  dissolved  in  water,  and  any  albuminous 
principles  still  present  being  removed  with  acetic  acid,  the  glycogen  is 
reprecipitated  with  alcohol,  and  then  dried,  when  it  can  be  kept  for  a 
long  time,  it  retaining  its  properties  indefinitely.  The  quantity  of  gly- 
cogen in  the  liver  varies,  as  a  general  rule,  between  seven  and  seventeen 
per  cent. — that  is  to  say,  assuming  that  the  liver  in  man  weighs  about 
fifty  ounces,  the  amount  of  the  glycogen  present  wTould  be  from  three  to 
eight  ounces,  the  amount  depending,  however,  upon  the  length  of  time 
elapsing  since  the  taking  of  food,  and  the  character  of  the  latter,  in- 
creasing with  digestion  and  diminishing  with  fasting,  and  disappearing 
altogether  if  no  food  be  taken  for  four  or  five  days,  being  more  abun- 
dant on  a  vegetable  than  on  an  animal  diet,  and  particularly  abundant 
if  the  food  consists  largely  of  carbohydrate  matter.  When  the  chemical 
composition  of  glucose  and  glycogen  is  compared,  and  when  it  is  remem- 


ORIGIN    OF    GLYCOGEN".  177 

bered  that  all  of  the  starch  and  sugar  of  the  food  is  transformed  into 
glucose  during  digestion,  the  above  becomes  intelligible,  on  the  suppo- 
sition that  the  glucose  carried  by  the  portal  vein  to  the  liver  during 
absorption  is  converted  by  and  stored  up  in  the  liver  cells  as  glycogen, 
the  transformation  of  the  glucose  into  glycogen  being  one  of  dehy- 
dration, as  shown  by  the  formula  : 

Glucose.  Water.  Glycogen. 

C6H1206    -    H20    =     C6ff10O5 

The  fact  of  glycogen  being  developed  on  an  animal  diet  as  well 
as  on  a  vegetable  one,  though  in  less  amount,  so  far  from  being 
an  objection  to  the  origin  of  glycogen,  as  just  offered,  is  a  confir- 
mation of  it,  since  it  is  readily  conceivable  how  nitrogenized  matter 
may,  like  glycin,  split  up  in  the  economy  into  glucose  and  urea,  as 
shown  by  the  formula  : 

Glycin.  Urea.  Glucose. 

4(C2H5N02)     =     2CON2H4  C6H1206 

the  glucose  becoming  then  glycogen,  as  in  the  former  case,  where  it 
was  derived  from  vegetable  matter,  and  the  urea  being  eliminated  by 
the  kidneys.  That  such  a  transformation  of  nitrogenized  matter 
actually  takes  place  in  the  system,  at  least  under  certain  conditions, 
appears  from  the  fact  that  in  certain  cases  of  diabetes,1  when  the  food 
contained  no  carbohydrate  matter,  the  glucose  increased  pari  passu  with 
the  urea.  The  above,  to  a  certain  extent  theoretical  considerations, 
are  confirmed  by  experimental  ones.  Thus  it  has  been  shown  by 
Bernard,2  Pavy,3  Doch.4  Tscherinow,5  and  others  that  the  amount  of 
glycogen  in  the  liver  is  notably  increased  within  a  few  hours  after  the 
taking  of  starchy  or  saccharine  articles  of  food,  and  that  while  gly- 
cogen is  developed  on  an  animal  diet,  the  amount  produced  is  far  less 
than  on  a  vegetable  one. 

There  appears  to  be  no  doubt,  therefore,  that  the  carbohydrate  princi- 
ples of  the  food,  and  to  some  extent  the  nitrogenized  ones  also,  trans- 
formed into  glucose,  together  with  the  glucose  from  the  glycin  of  the 
glycocholic  acid,  are  conveyed  in  the  blood  of  the  portal  vein  to  the 
liver,  and  that  the  glucose  so  derived  is,  probably  by  dehydration,  con- 
verted into  glycogen,  and,  for  the  time  being,  at  least,  is  stored  up  as 
such  in  the  liver  cells.  That  the  glycogen  remains,  however,  only 
temporarily  in  the  liver,  appears  from  the  fact,  as  shown  first  by  Ber- 
nard,6 that  in  a  fasting  animal,  or  in  one  that  has  been  fed  on  an 
exclusively  meat  diet,  that  the  liver  and  the  blood  of  the  hepatic  vein 
contain  glucose,  though  there  is  not  the  slightest  trace  of  it  in  that  of 
the  portal  vein,  the  glycogen  stored  up  in  the  liver  during  the  intervals 
of  digestion  being  gradually  converted  into  glucose,  and  conveyer!  away 
by  the  hepatic  veins  into  the  general  circulation. 

That  the  transformation  of  glycogen  into  glucose  is  merely  a  question 
of  time,  is  shown  by  the  fact  that  a  decoction  made  out  of  a  liver  taken 

1  Singer:  Med.  Chir.  Trans.,  xliii.  p.  S27. 

-  Physiologic  Experimentale,  p.  159.    Paris,  1855. 

:s  Nature  and  Treatment  of  Diabetes.     London.  1862. 

4  ('tinker's  Arcliiv.  1872,  Band  v.  S.  571. 

■•  Virchow's  Archiv,  18G9.  Band  xlvii.  S.  102.  •'•  Op.  ,-it..  p.  204. 

12 


178  GLYCOGEN. 

out  of  the  body  of  a  fasting  animal,  is  clear,  whereas  if  it  is  made  out 
of  one  taken  from  an  animal  fed  within  a  few  hours,  it  is  decidedly 
opalescent  through  the  glycogen  it  contains  not  as  yet  having  been 
transformed  into  glucose. 

It  is  denied  by  some  experimenters  that  the  liver  actually  contains 
glucose  during  life.  Inasmuch,  however,  as  glucose  can  be  demon- 
strated in  the  liver  within  twenty  seconds  after  the  death  of  the  animal 
from  which  it  has  been  taken,  it  can  hardly  be  doubted  that  such  is  the 
case.  While  there  may  be  a  difference  of  opinion  as  to  whether  the 
liver  contains  glucose  during  life,  there  is  no  difference  of  opinion  as  to 
its  containing  glucose  after  death.  Indeed,  if  all  the  blood  be  washed 
out  of  the  liver  by  forcing  water  through  the  portal  vein,  the  liquid,  as 
it  escapes  by  the  hepatic  vein,  will  be  found  to  contain  glucose,  and  this 
even  after  upward  of  half  an  hour  after  repeated  injections.  And  then, 
when  the  presence  of  glucose  can  no  longer  be  demonstrated,  if  the 
liver  be  put  aside  in  a  warm  place  for  a  few  hours,  glucose  can  again  be 
obtained,  it  being  a  long  time  before  its  glycogen,  the  source  of  the  glu- 
cose, is  exhausted. 

As  to  what  becomes  of  the  glucose  thus  constantly  poured  into  the 
general  circulation  from  the  liver,  there  can  be  no  doubt  of  it  being 
ultimately  transformed,  probably  through  oxidation,  into  carbonic  acid 
and  water.  Just  how  and  where  this  final  change  is  brought  about,  is 
still  not  exactly  known,  but  in  all  probability  the  change  is  effected  in 
the  tissues,  since,  as  we  shall  see,  the  venous  blood  contains  less  glucose 
and  more  carbonic  acid  than  the  arterial. 

In  conclusion,  it  may  be  pointed  out  that  the  transformation  of  glu- 
cose into  glycogen,  and  of  glycogen  into  glucose  in  the  animal,  finds  an 
analogy  in  the  vegetable,  since,  as  is  well  known,  the  starch  in  the  leaves 
of  a  plant  having  been  converted  into  sugar,  passes  down  to  the  roots, 
where  not  infrequently  it  is  reconverted  into  starch. 

While  for  convenience'  sake  we  have  studied  separately  the  different 
effects  cf  the  intestinal,  pancreatic,  and  biliary  secretions,  it  must  not 
be  forgotten  that  the  action  of  these  secretions  in  digestion  is  simulta- 
neous,  and  in  their  actions  are,  to  a  certain  extent,  supplementary  to 
those  produced  by  the  saliva  and  gastric  juice.  Whenever,  therefore, 
the  opportunity  presents  itself  of  opening  the  alimentary  canal  of  a 
human  being  who  has  died  in  full  digestion,  it  will  be  well  to  take 
advantage  of  it,  Avith  reference  to  the  examination  of  the  changes  which 
the  food  undergoes,  through  its  successive  admixture  with  the  saliva  and 
the  gastric  juice,  and  its  further  modifications  due  to  the  simultaneous 
action  of  the  intestinal  secretions.  Essentially  the  same  result  can  be 
obtained,  experimentally,  so  far  as  the  digestion  of  meat  or  vegetable 
food  is  concerned,  by  killing  dogs  or  rabbits  respectively,  at  different 
periods  after  feeding,  and  examining  the  contents  of  the  stomach  or 
intestine  microscopically. 

Figs.  74,  75,  and  76  give  an  excellent  idea  of  the  general  appearance 
exhibited  by  meat  and  fat,  according  to  the  part  of  the  alimentary  canal 
of  the  dog  examined,  from  which  the  specimen  was  taken.  Thus  (Fig. 
74)  in  the  grayish  grumous  acid  fluid  of  the  stomach  are  seen  under 
the  microscope  more  or  less  disintegrated  muscular  fibres,  fat  vesicles, 


CONTENTS    OF     SMALL    INTESTINE 


170 


and  a  few  oil  globules.  In  the  duodenum  (Fig.  75)  the  muscular  fibres 
are  pale,  broken  up,  further  disintegrated,  though  still  recognizable  by 
their   stripe.     The    fat    vesicles   become    shrivelled,   the    oil   drops    are 


Fig.  74. 


Fig.  75. 


i      h 

§ 


•^w         itflil 


From  duodenum  of  dog,  during  digestion  of  meat. 

Contents  of  stomach  during  digestion  of  meat,  from  a.  Fat   vesicle,    with    its  contents  diminishing.     The 

the  dog.    a.  Fat  vesicle,  filled  with  opaque,  solid,  granu-  vesicle  is  beginning  to  shrivel  and  the  fat  breaking  up. 

lar  fat      6.  6.  ISits  of  partially  disintegrated  muscular         6,  6.  Disintegrated  muscular  fibre      c,  c.  Oil  globules. 

fibre      e.  Oil  globules.  (Dalton.)  ^Dalton.) 

increased  in  number,  and  the  fat  is,  to  a  great  extent,  liquefied  and 
emulsified.  In  the  middle  and  lower  parts  of  the  small  intestine  (Fig. 
76)  the  meat  is  seen  to  be  entirely  broken  down,  a  considerable  quantity 
of  granular  debris  is  present,  the  fat  vesicles  are  found  empty,  while 

Fig.  76. 


From  las!  quarter  of  small  intestine,     a,  a.  Fat  vesicle,  quite  empty  and  shrivelled,    i  Dalton.) 

the  emulsified  fat  has  almost  disappeared,  having  been  taken  up  by  the 
absorbents. 

The  chemical  changes  produced  in  the  food  by  digestion,  are  of  the 


180  THE     LARGE    INTESTINE. 

same  continuous  character.  The  starches  gradually  become  glucose,  the 
albuminous  substances  are  converted  into  albuminose,  leucin,  and  tyrosin, 
while  the  fats  are  emulsified,  and  probably,  to  a  certain  extent,  also 
saponified.  Thus,  during  intestinal  digestion  we  find  the  alimentary 
canal  containing  a  mixture  consisting  of  albuminose,  glucose,  and 
emulsified  and  saponified  fat,  substances  which  we  will  see  are  readily 
absorbed  by  the  bloodvessels  and  lymphatics,  and  various  indigestible 
principles.  The  latter,  together  with  such  of  the  above  substances  as 
escape  absorption,  pass  into  the  large  intestine.  To  the  consideration 
of  this  part  of  the  alimentary  canal  let  us  now  turn. 

The  Larue  Intestine. 

This  portion  of  the  intestinal  canal  is  so  called  on  account  of  its 
relatively  large  size.  Usually  it  is  found  to  measure  from  four  to  six 
feet  in  length,  and  from  one  and  two-thirds  to  two  and  two-thirds  inches 
in  diameter.1  The  general  direction  of  the  large  intestine  beginning 
with  the  caecum,  is  from  the  right  iliac  fossa  upward,  then  transversely 
across  to  the  left  side  of  the  body  ;  thence  downward  into  the  left  iliac 
fossa,  finally  terminating  as  the  rectum.  The  small  intestine  is  thus 
surrounded  by  the  large  intestine,  the  latter  being  disposed  in  the  form 
of  a  horseshoe. 

The  large  intestine,  like  the  small,  consists  essentially  of  two  coats,  a 

mucous,  including  the  submucous,  and  a  muscular.   In  addition,  the  large 

intestine  is,  to  a  great  extent,  covered  with  peritoneum,  which  serves  to 

maintain  it  in  position,  and  to  connect  it  with 

Fig.  77.  certain   of   the  abdominal  and   pelvic  viscera. 

While  the  villi   and  valvulse    conniventes  are 

absent  in   the  large  intestine,  throughout  the 

whole  extent  of  its  mucous  membrane  there  are 

found  tubular  and  solitary  glads  which  do  not 

differ  essentially  in  their  minute  structure  from 

those    of    the    small   intestine.       The  tubular 

glands  (Fig.    77)   of  the  large  intestine  are, 

however,    more    numerous,    longer    and    more 

Section   of  the    mucous    mem-  '  '  p 

braneof  the  colon.  i.  Free  sur-  closely  set  together  than  tliose  of  the  latter,  and 
face  exhibiting  the  orifices  of  the  often  are  subdivided  at  their  csecal  extremities, 
tubular  glands,  2.    3.  Fibrous    According  to  some  physiologists,2  in  addition 

tissue       moderately      magnified.  9  i         i  i  i  p  i     • 

(Lbjdy.)  to  the  solitary  glands,  there  are  also  found  in 

the  large  intestine  glands  which  differ  from 
these  in  that  they  are  supposed  to  open  into  the  intestine  by  an  aper- 
ture said  to  be  plainly  visible  to  the  naked  eye.  These  glands  are  the 
so-called  utricular  glands  (Fig.  78).  They  do  not  differ  from  the  ordi- 
nary solitary  glands,  being  really  closed  follicles,  the  so-called  aperture 
or  opening  (Fig.  78,/)  being  only  a  depression  in  that  part  of  the  mucous 
membrane  situated  over  the  gland  and  separating  it  from  the  interior 
of  the  intestine.3 

1  Cyclopaedia  of  Anatomy  and  Physiology,  v.  p.  362. 

-  Milne  Edwards:   Physiologic,  IXHO,  tome  vi.  p.  408. 

3  Sappey  :  Anatomie,  1879,  tome  iv.  p.  257.  Kolliker:  Gewebelehre,  1867,  8.  422.  Hyrtl  :  Anatomic, 
1880,  Funfzehnte  Auf.  S.  089.  Henle  :  Anatomie,  1873,  Zweiter  Band,  S.  193.  Quain's  Anatomy,  1878, 
vol.  ii.  p.  3. 


THE    LARGE    INTESTINE, 


181 


The  mucous  membrane  of  the  large  intestine  is  paler,  thicker,  and 
more  closely  adherent  to  the  underlying  parts  than  that  of  the  small 
intestine.     The  muscular  coat  of  the  large  intestine  differs  considerably 


Fig.  78. 


Fig.  79. 


m  / 


Section  of  large  intestine  showing  utricular  gland. 
/.  Depression  in  mucous  membrane,  a.  Tubular 
glands.  b.  Muscularis  mucosa;.  r.  Submucous 
coat.     d.  e.  Muscular  coats.     (Kollikf.r.) 


View  of  the  ileo-colic  valve  from  the  large 
intestine  (after  Santorini).  %  The  figure  shows 
the  lowest  part  of  the  ileum,  i,  joining  the 
caecum,  c,  and  the  ascending  colon,  o,  which 
have  been  opened  anteriorily,  so  as  to  display 
the  ileo-colic  valve  ;  a,  the  lower,  and  e,  the 
upper  segment  of  the  valve,  p.  Vermiform 
appendix. 


in  certain  points  from  that  of  the 

small  intestine.     Thus,  in  the  colon 

more  particularly,  the  longitudinal 

fibres  are  fathered  together  in  three 

well-marked  bands,  one  of  which  is 

anterior,   while  the   other   two  are 

latero  posteriorly  situated.  Thelarge 

intestine  is  divided  by  anatomists  into  three  portions,  the  caecum,  colon, 

and  rectum,  these  differing  in  their  size,  shape,  and  the  character  of 

their  mucous  and  muscular  coats. 

The  most  important  part,  physiologically,  of  the  c*cum  or  caput  coli, 
the  widest  portion  of  the  large  intestine,  is  the  ileo-crecal  valve,  by  means 
of  which  the  contents  of  the  ileum,  after  they  have  passed  into  the 
large  intestine,  are  prevented  from  returning  into  the  small  intestine. 
The  small  intestine  opens  into  the  large  intestine  by  a  slit-like  aperture 
(Fig.  79,  a  e)  which  lies  nearly  transverse  to  the  direction  of  the  latter. 
This  aperture  is  bounded  above  and  below  by  two  semilunar  folds  or 
valves  which  project  inward  toward  the  cfecum  and  colon.  At  each 
end  of  the  aperture  the  two  valves  or  folds  run  into  each  other  and  are 
then  prolonged  at  each  side  as  a  ridge  or  frcenum,  which  gradually  fades 
away.  That  portion  of  the  valve  which  looks  toward  the  ilium  is 
covered  with  villi,  and  in  other  respects  resembles  the  mucous  membrane 
of  the  small  intestine,  while  that  upon  the  opposite  side  of  the  valve  is 
destitute  of  villi,  and  its  mucous  membrane  is  like  that  of  the  large 
intestine.  Each  segment  of  the  valve  is  covered  with  mucous  mem- 
brane, and  consists  of  submucous  tissue  and  muscular  fibres,  derived 
from  the  circular  muscular  fibres  of  both  the  ilium  and  large  intestine. 


182 


CAECUM    AND    STOMACH 


The  longitudinal  muscular  fibres  of*  the  ileum,  however,  run  con- 
tinuously into  those  of  the  large  intestine,  taking  no  part  in  the  forma- 
tion of  the  valve,  but  are  stretched  across  it.  The  effect  of  distention 
of  the  caecum  by  its  contents  is  that  the  fraena  being  put  on  the  stretch, 
the  edges  of  the  valves  are  brought  in  apposition,  closing  the  ileo-caecal 
aperture  so  completely  that  all  reflux  from  the  large  intestine  into  the 
ileum  is  prevented,  but  at  the  same  time  no  hindrance  is  offered  to  the 
passage  of  the  contents  of  the  ileum  into  the  large  intestine.  An  inter- 
esting feature  about  the  caecum  is  its  vermiform  appendix  (Fig.  80,  V), 

Fig.  80 


Caecum  of  capybara.     (From  nature.) 

a  worm-like  tube,  beginning  at  its  lower  end  and  terminating  in  a  blind 
extremity,  attaining  usually  about  a  length  of  from  three  to  six  inches, 
and  having  a  diameter  about  the  size  of  a  quill. 

The  vermiform  appendix,  so  far  as  is 
Fig.  81.  known,  has  no  use  in  man,  but  is  a  very 

interesting  structure  as  representing  in 
man,  in  a  rudimentary  condition,  that 
which  is  well  developed  and  performs 
important  functions  in  many  animals. 
Thus  in  the  horse,  tapir,  elephant,  rabbit, 
and  beaver  the  caecum  is  very  large ; 
in  the  capybara  (hydrochoerus),  a  species 
of  rodent,  the  caecum  (Fig.  80)  measured 
twenty-six  inches  in  length,  while  in  a 
koala  (phascolarctos),  a  small  marsupial, 
also  examined  by  the  author,  it  attained 
a  length  of  fifty  inches.  Now,  by  com- 
paring the  crecum  in  the  capybara  with 
the  vermiform  appendix  in  man,  it  will  be  found  that  the  latter  corre- 
sponds to  the  blind  part  of  the  caecum,  V,  in  the  capybara,  while  the 
caecum,  or  caput  coli,  in  man  is  homologous  with  that  part  of  the  caecum 
in  the  capybara  communicating  with  the  large  intestine,  I.     In  other 


Stomach   of  capybara.     (From  nature.) 


CECUM     AND    STOMACH, 


183 


words,  the  caecuni  in  the  animals  just  mentioned  is  equal  in  man  to  the 
vermiform  appendix  and  caecum.  Further,  it  will  be  observed  that  the 
caecum  of  the  capybara  (Fig.  80)  is  much  longer  than  the  stomach  of 
that  animal  (Fig.  81),  the  latter  measuring  only  ten  inches,  while  it  is 
needless  to  state  that  just  the  reverse  relation  obtains  as  regards  the  same 
parts  in  man.  The  significance  of  this  contrast  is  evident  enough  when 
the  digestion  of  food  in  man  and  the  capybara  is  considered.  In  the 
first  instance,  as  we  have  seen,  the  action  of  the  stomach  is  very  impor- 
tant ;  in  the  latter  instance  it  is  but  relatively  so,  the  imperfect  diges- 
tion of  food  in  the  stomach  of  the  capybara  being  completed  in  its  caecum. 
In  the  same  manner  the  caecum  in  the  tapir,  horse,  and  elephant,  etc., 
supplements  the  imperfect  digestive  action  of  the  stomach  in  these 
animals.  On  the  other  hand,  in  the  giraffe,  in  which  there  are  four 
well-developed  stomachs,  B,  C,  D,  E,  (Fig.  82)  the  caecum,  Y,  (Fig.  83) 
is  relatively  small.      In  a  word,  there  is  an  inverse  ratio,  both  anatomi- 


Fig.  82. 


Stomach  of  giraffe.     (From  nature 


(Esophagus.     B.  Rumen.     C.  Reticulum.     I).  Psalterium. 
B.  Abomasum. 


cally  and  physiologically,  between  the  stomach  and  the  caecum  :  when 
the  one  is  large  and  active,  the  other  is  small  and  inactive,  and  vice 
versa.  The  conclusion  must  not,  however,  be  drawn  that  the  caecum 
in  these  animals  secretes  a  gastric,  or  any  other  digestive  juice.  The 
caecum  rather  appears  to  be  a  receptacle  where  the  fluids  absorbed  by 
the  food  in  its  rapid  passage  through  the  alimentery  canal  have  time 
to  produce  their  digestive  effects. 

The  acid  reaction  often  noticed  in  the  caecum  of  animals,  and  some- 


184 


RECTUM. 


times  in  man,  is  not  due  to  acid  secretion,  but  to  a  kind  of  lactic  or 
butyric  acid  fermentation  set  up  in  the  food,  tlie  normal  reaction  of 
the  secretion  of  the  caecum  being  alkaline.  That  the  vermiform  ap- 
pendix in  man  is  a  rudimentary  organ  is  confirmed  by  the  fact  that  it 
is  relatively  longer  in  the  embryo  than  the  adult.  It  is  worthy  of  note 
that  the  vermiform  appendix  is  found  as  in  man  in  all  four  anthropoid 
apes,  the  gorilla,  chimpanzee,  orang,  and  gibbon  ;  and  more  remarkable 
still  that  it  is  present  in  a  marsupial,  the  wombat  (Phascolomys). 

In  addition  to  what  has  already  been  said  of  the  colon,  an  important 
feature  is  its  sigmoid  flexure,  so  called  from  the  S-like  curve  the  colon 
makes  just  before  passing  into  the  rectum.  This  curvature,  as  we  shall 
see,  is  the  position  where  the  feces  are  temporarily  retained. 

The  large  intestine  terminates  in  the  rectum,  which,  while  straight  in 
animals  in  which  it  was  originally  described,  is  far  from  being  such  in 
man.  In  fact,  the  rectum  in  man  first  passes  obliquely  downward  from 
left  to  right,  from  opposite  the  left  sacro-iliac  articulation  to  the  middle 


Fig.  88. 


Caecum,  etc.,  of  giraffe.     V.  Caecum.     I.  Small  intestine.     C.  Colon. 

line  of  the  sacrum.  It  then  curves  forward  back  of  the  prostate  in  the 
male,  and  the  vagina  in  the  female,  and  finally  passes  backward  and 
downward,  terminating  in  the  anus.  The  anus  is  a  dilatable  orifice,  lined 
with  mucous  membrane  and  covered  with  skin,  the  skin  and  mucous 
membrane  becoming  continuous  with  each  other.  The  margin  of  the 
anus  and  lower  part  of  the  rectum  are  embraced  by  the  external  and  in- 
ternal sphincter  muscles,  the  levators  ani  and  coccygei.  These  muscles 
serve  to  support  the  bowel,  and  to  close  its  anal  orifice.  The  internal 
sphincter  muscle  consists  of  the  circular  fibres  only  greatly  developed. 
It  is  situated  an  inch  above  the  anus,  extending  over  about  half  an  inch 
of  the  intestine,  and  is  two  lines  thick. 

The  rectum,  about  eight  inches  in  length,  is  not  sacculated  like  the 
rest  of  the  large  intestine,  the  longitudinal  muscular  fibres  being  scat- 
tered over  its  surface.  While  the  upper  part  of  the  rectum  is  narrow, 
at  the  lower  part  it  is  dilated  into  a  kind  of  reservoir  just  above  the 


FECES.  185 

anus.  The  mucous  membrane  of  the  rectum  is  more  vascular,  thicker, 
and  redder  than  that  of  the  colon,  and  moves  more  freely  over  the 
muscular  coat.  It  is  thrown  into  numerous  folds,  most  of  which  are 
however  effaced  when  the  rectum  is  distended. 

The  Contents  of  the  Laroe  Intestine. — While  there  is  no 
reason  to  suppose  that  anything  like  true  digestion  takes  place  in  the 
large  intestine  of  man,  various  important  changes  are  effected  there  by 
which  the  undigested  residue  of  the  food  is  gradually  transformed  into 
the  feces,  the  most  marked  changes  being  in  the  consistence,  color,  and 
odor  of  the  contents  of  the  large  intestine,  and  which  are  gradually 
developed  in  the  undigested  food  as  it  passes  from  the  csecum  through 
the  colon  into  the  rectum.  As  the  undigested  food  passes  through  the 
large  intestine  its  liquid  portions  are  being  constantly  absorbed,  the 
feces  therefore  have  a  much  firmer  consistence  than  the  contents  of  the 
ileum.  The  large  intestine  is  therefore  physiologically  important,  as 
presenting  an  extensive  absorbing,  if  not  a  digestive  surface.  The 
absorbing  power  of  the  rectum  is  well  known.  Indeed,  life  can  be  sus- 
tained for  months  by  giving  nutritious  enemata. 

The  color  of  the  feces  is  of  a  dark  yellowish-brown,  and  appears  to 
be  due  to  modified  bile  pigment,  which  is  precipitated  when  the  acid 
contents  of  the  stomach  or  the  chyme  mix  with  the  bile  in  the 
duodenum.  As  the  soda  of  the  bile,  on  which  the  solubility  of  the  bile 
pigment  depends,  is  soon  neutralized  by  the  acid  gastric  juice,  the  bile 
pigment  is  thus  set  free,  and  is  so  modified  as  it  passes  through  the 
alimentary  canal  that  ultimately  it  does  not  respond  to  the  usual  tests. 
It  is  well  known  that  when  the  bile  is  deficient  or  absent,  the  stools 
become  lighter  or  clay-colored.  The  color  of  the  feces  varies  also 
according  to  the  diet. 

While  the  cause  of  the  odor  of  the  feces  cannot  be  said  to  be  exactly 
understood,  there  can  be  no  doubt  that  it  is  due  to  a  great  extent  to 
the  imperfect  oxidation  of  the  food,  to  the  presence  of  skatol  (C9H0N) 
and  indol  (C8H.N),  nitrogenous  substances  developed  during  pancreatic 
digestion,  to  the  decomposition  of  the  bile,  and  to  the  secretion  of  the 
glands  of  the  colon  and  rectum. 

The  reaction  of  the  feces  is  variable,  sometimes  acid,  often  alkaline 
or  neutral,  depending  chiefly  upon  the  kind  of  food  eaten. 

The  entire  quantity  of  feces  passed  in  twenty-four  hours  varies  from 
four  to  seven  ounces ;  as  might  be  expected,  there  being  a  greater  amount 
of  feces  on  a  vegetable  than  on  an  animal  diet,  the  former  containing  a 
greater  quantity  of  indigestible  matter  than  the  latter.  When  the  con- 
tents of  the  large  intestine  are  examined  microscopically,  there  will  be 
found  a  number  of  undigested  substances  derived  from  the  vegetable  and 
animal  foods.  Among  other  matters,  the  spiral  vessels  of  vegetables, 
the  cortex  of  grains,  hard  vegetable  seeds,  structures  generally  consist- 
ing largely  of  cellulose,  muscular  tissue  in  various  stages  of  disintegra- 
tion, tendinous  and  elastic  structure,  the  organic  constituents  of  bone. 

The  feces  have  been  examined  chemically  by  Berzelius,  Simon,  Mar- 
cet,  Wehsarg,  Ihrung,1  and  others.      The  human  feces,  on  an  average. 

1  Milne  Edwards  :   Physiologie,  tunic  vii.  p    143, 


186  DEFECATION. 

may  be  said  to  consist  of  seventy -five  parts  of  water  to  twenty-five  of 
solid  residue.  In  the  latter  there  have  been  found  among  other  sub- 
stances the  ammonium-magnesium  phosphate,  the  magnesium  phosphate, 
the  calcium  phosphate,  and  a  small  quantity  of  iron,  fatty  acids,  occa- 
sionally cystin,  excretin1  and  excretoleic  acid,  and  stercorin  ;2  this  latter 
substance,  as  has  already  been  mentioned,  is  according  to  Flint  modi- 
fied cholesterin.  In  the  large  intestine  there  is  found  carburetted  hydro- 
gen gas  as  well  as  nitrogen,  hydrogen,  and  carbonic  acid,  which  are 
also  present  in  the  small  intestine  and  stomach.  Oxygen  gas  is, 
however,  found  only  in  the  stomach. 

Defecation. 

In  health  the  feces  are  usually  discharged  once  in  twenty-four  hours. 
This  rule,  however,  is  far  from  being  invariable,  being  modified  by 
individual  peculiarities. 

Indeed,  there  are  well  authenticated  cases  of  the  act  of  defecation 
not  having  been  performed  during  a  period  of  eight  years,  and  even 
longer,  the  unabsorbed  food  apparently  having  been  either  rejected  by 
the  mouth,  or  eliminated  by  the  skin  or  kidneys.  On  the  other  hand, 
there  seems  to  be  no  reason  to  doubt  that  there  have  been  also  cases  in 
which  the  bowels  were  evacuated  as  often  as  twelve  times  daily,  and  that 
for  thirty  years,  and  yet  without  the  health  being  affected.3 

The  feces  are  gradually  passed  through  the  contraction  of  the  mus- 
cular fibres  of  the  large  intestine  into  the  sigmoid  flexure  of  the  colon, 
where  they  accumulate,  and  are  retained  for  some  time.  It  is  probably 
the  descent  of  the  feces  from  the  sigmoid  flexure  of  the  colon,  which 
is  the  immediate  cause  of  the  desire  to  defecate,  the  action  being,  to  a 
certain  extent  as  we  shall  see,  under  the  control  of  the  will.  It  is  often 
thought  that  the  feces  accumulate  in  the  rectum ;  the  lower  part  of  the 
rectum,  however,  in  health  is  almost  always  empty.  In  old  persons,  or 
in  those  of  a  constipated  habit  the  feces  are  often  found  there. 

In  the  act  of  defecation,  the  feces  first  pass  from  the  sigmoid  flexure 
of  the  colon  into  the  upper  constricted  part  of  the  rectum,  then  into 
the  lower  portion,  the  sphincter  muscle  at  first  resisting,  then  giving 
away,  through  the  inhibition  (due  to  the  stimulus  of  the  feces)  of  the 
nervous  centres  controlling  the  sphincter  ani,  and  the  fecal  mass  leaves 
the  body.  The  action  is  assisted  by  the  levator  ani,  which  favors  the 
relaxation  of  the  external  sphincter,  and  by  the  compression  of  the 
viscera  through  the  action  of  the  diaphragm  and  the  abdominal  muscles. 
When  the  glottis  is  closed  a  point  of  support  is  further  given  to  the 
latter  muscles. 

Resume  of  Digestion. 

In  concluding  the  subject  of  digestion,  it  does  not  appear  to  be  super- 
fluous to  give  a  brief  resume  of  the  different  processes  of  which  we 
have  given  a  somewhat  detailed  account. 

l  Marcet:  Phil.  Trans.,  1854.  2  Flint  :  Physiology,  vol.  ii.  p.  3'J9  ;  vol.  iii.  p.  291. 

3  Dunglison  :  Human  Physiology,  8th  ed.  vol.  i.  p.  191  Philadelphia,  1856.  Chapman  :  Lectures  on 
the  Diseases  of  Thoracic  and  Abdominal  Viscera,  p.  294.     Philadelphia,  1844. 


RESUME   OF    DIGESTION.  187 

The  food,  after  having  been  taken  into  the  mouth,  is  masticated,  and 
through  the  action  of  the  tongue  and  cheeks  having  been  collected  into 
a  bolus,  is  then  swallowed.  The  saliva  poured  into  the  mouth  acts 
mechanically,  aiding  mastication  and  deglutition :  and  chemically,  in 
converting  some  of  the  starch  into  glucose. 

The  albuminous  substances  of  the  food  are  converted  into  albuminose 
or  peptones  by  the  gastric  juice,  which  has  also  the  effect  of  dissolving, 
to  some  extent,  the  walls  of  the  fat  vesicles,  the  fat  itself  thus  set  free, 
however,  being  unaffected  by  this  secretion.  That  part  of  the  starch 
which  has  escaped  conversion  into  glucose  by  the  saliva  either  in  the 
mouth  or  stomach,  passes  together  with  the  cane  sugar  unchanged  into 
the  small  intestine. 

While  the  effect  of  the  intestinal  juice  is  limited  to  supplementing 
the  action  of  the  saliva  upon  starch,  and  that  of  the  gastric  juice  upon 
albuminoids,  the  pancreatic  juice  not  only  acts  upon  both  these  kinds  of 
food,  converting  the  starch  into  glucose,  and  the  albumen  into  albumi- 
nose, leucin,  tyrosin,  etc.,  but  also  converts  cane  sugar  into  glucose,  and 
emulsifies  and  saponifies  the  fats.  The  bile  assists  in  the  emulsifying  of 
fats,  and  promotes  their  absorption,  it  further  retards  putrefaction,  and 
in  stimulating  the  peristaltic  action  of  the  intestine  acts  as  a  natural 
purgative. 

The  conversion  of  starch  into  glucose,  of  albumen  into  albuminose, 
etc.,  appears  to  consist  in  a  hydration  of  these  substances,  brought 
about  by  the  presence  of  ptyalin,  pepsin,  etc.,  entering  into  the  compo- 
sition of  the  saliva,  gastric  juice,  etc.,  respectively.  These  organic 
principles,  to  which  the  action  of  the  alimentary  secretions  to  a  large 
extent  is  due,  are  elaborated  out  of  the  blood,  and  stored  up  during  the 
intervals  of  digestion  by  the  cells  of  which  the  glands  consist.  The 
ptyalin,  pepsin,  trypsin,  pancreatin,  etc.,  poured  out  at  the  moment  of 
secretion,  differ  somewhat  from  the  principles  actually  present  in  the 
gland  during  the  intervals  of  digestion,  being  developed  out  of  the  latter 
at  the  moment  of  secretion.  That  the  phenomenon  of  secretion  is  not 
one  of  mere  filtration,  is  shown  by  the  pressure  exerted  by  the  secre- 
tion, and  that  chemical  action  is  going  on  is  made  evident  through  the 
heat  and  carbonic  acid  developed. 

The  contents  of  the  large  intestine  consist  essentially  of  the  undi- 
gested  part  of  the  food  (amounting  to  about  one-fifth),  decomposed  bile, 
and  of  such  digested  principles  as  have  not  been  absorbed.  As  these 
pass  through  the  large  intestine  they  gradually  assume  the  consistence, 
color,  odor,  etc.,  of  the  feces.  The  latter  accumulating  in  the  sigmoid 
flexure  of  the  colon,  pass  into  the  rectum  and  thence  out  of  the  body, 
their  expulsion  constituting  the  act  of  defecation. 


CHAPTER   XI. 

ABSORPTION. 

While  the  digested  food  in  the  alimentary  canal  may  be  said  to  be 
inside  of  the  body,  using  the  word  in  its  ordinary  acceptation,  physio- 
logically it  is  still  outside  of  it,  for  if  the  food  simply  remained  in  the 
alimentary  canal  it  would  be  of  no  use  for  nutritive  purposes.  Indeed, 
unless  the  digested  food  gets  into  the  blood,  and  is  so  carried  to  all  parts 
of  the  organism,  and  repairs  the  waste  of  its  tissues,  and  supplies  the 
material  for  force,  it  might  as  well  not  be  taken  into  the  system  at  all. 
The  process  by  which  the  digested  food  passes  from  the  interior  of  the 
alimentary  canal  into  the  blood,  either  directly  or  indirectly,  is  known 
as  absorption. 

It  is  not  to  be  understood,  however,  that  absorption  is  by  any  means 
limited  to  the  alimentary  canal,  or  that  the  substances  of  which  food 
consists  are  the  only  ones  that  can  be  absorbed.  We  shall  soon  see  that 
oxygen  is  absorbed  by  the  blood  as  it  circulates  through  the  lungs,  that 
the  skin  will  take  up  various  substances,  and  that  effusions  found  under 
certain  circumstances  in  the  cavities  of  the  pleura,  pericardium,  peri- 
toneum, etc.,  can  be  absorbed  by  these  serous  surfaces.  Inasmuch,  how- 
ever, as  we  have  just  seen  how  the  food  is  digested,  naturally  our  study 
of  absorption  will  begin  with  the  consideration  of  the  process  as  it  goes 
on  in  the  alimentary  canal. 

That  the  ancients  were  well  aware  that  the  human  body  absorbs,  is 
evident  from  their  writings.  Thus  Hippocrates,1  for  example,  speaks  of 
"the  veins  of  the  stomach  and  intestine  attracting  the  clearest  and  most 
fluid  parts  of  the  solid  and  liquid  food."  Nothing,  however,  appears 
to  have  been  known  at  that  period  of  the  lymphatic  system.  It  is  true, 
that  in  the  writings  of  Galen  there  are  preserved  vague  illusions,  like 
those  of  Erasistratus,2  "to  arteries  in  the  mesentery,"  "full  of  milk," 
and  of  Hierophilus3  to  "particular  veins  ending  in  certain  glands,"  but 
the  context  shows  that  these  old  anatomists  regarded  the  vessels  alluded 
to,  which  were,  no  doubt,  lymphatics,  as  nutrient,  and  not  as  absorbent 
in  their  function.  Indeed,  at  that  period  the  use  of  the  arteries  even 
was  unknown,  they  being  considered  as  air-keepers,  as  their  etymology 
implies,  rather  than  carriers  of  blood. 

As  the  venous  blood  from  the  capillaries  of  the  stomach  and  intes- 
tine is  conveyed  from  the  gastric  and  mesenteric  veins  by  the  portal 
vein  to  the  liver,  and  thence  by  means  of  the  hepatic  vein  and  inferior 
vena  cava  to  the  heart  (Fig.  84),  a  route  evidently  exists  by  which  the 
digested  food  in  the  alimentary  canal  can  get  into  the  general  circula- 

1  Opera  Omnia,  p.  lilt.     Lndg-.  Bat  a  v.,  1665, 

2  Galenus  0]  era  Omnia,  tomus  i.  Cap.  5,  |>.  61.     Venetiis,  1556.  :i  Ibid.,  Cap.  19,  p.  141. 


LACTEALS,    THORACIC    DUCT,    ETC. 


189 


tion.  The  ancients  were  right,  therefore,  in  considering  the  veins  as  a 
means  of  absorption,  although  at  the  same  time  they  knew  almost 
nothing  of  the  course  of  the  circulation.  The  first  part  of  the  lym- 
phatic system  discovered  was  the  thoracic  duct  in  the  horse,  described 
by  Eustachius,1  the  Roman  anatomist,  in  1563.  Eustachius,  while 
showing  that  the  duct  terminated  in  the  subclavian  vein,  failed,  how- 
ever,  to  show  where  it  commenced,  and,  therefore,  did  not  learn  its 
functional  importance.     Indeed,  the  discovery  itself  was  forgotten,  and 


Fig.  84. 


Fig.  85. 


View  of  the  principal  branches  of  the  vena  porta;. 
%,  1.  Lower  surface  of  the  right  lolie  of  the  liver. 
2.  Stomach.  3.  Spleen  4.  Pancreas.  5.  Duodenum. 
6.  Ascending  colon.  7.  Small  intestine.  8  Descend- 
ing colon,  a.  Vena  porta;  dividing  in  the  transverse 
fissure  of  the  liver,  b.  Splenic  vein.  c.  Bight  gastro- 
epiploic, d.  Inferior  mesenteric,  e.  Superior  mesen-  clavian  veins,  d.  Point  of  opening  of  thoracic 
teric  vein.    /.  Superior  mesenteric  artery.    (Quain.)      duct  into  left  subclavian.     (Dalton.) 


Lacteals,  thoracic   duct,  etc.     o.    Intestine.     6. 
Vena  cava  inferior.      c,  c.  Right   and   left  sub- 


its  significance  was  not  appreciated  till  the  following  century.  The 
history  of  the  lymphatic  system  really  begins  with  Gasparis  Aselli's 
discovery,  in  1(322,  in  the  dissecting  amphitheatre  at  Pavia,  of  the 
lacteals  of  the  small  intestine  in  the  dog.  Aselli  tells  us  in  his  work2 
on  the  lacteals  that,  on  opening  a  dog  to  show  some  friends  the  recurrent 
laryngeal  nerves,  he  was  surprised  to  find  in  the  mesentery  in  addition  to 


Opusc.  Anat.,  Antig  13,  i  .  280.     Li .di.  Batav  ,  1707. 

De  Lactibus  Sine  Lacteis  Venis,  Cap.  i\.     Mediolani,  MDCXXVII. 


190  ABSORPTION. 

the  arteries  and  veins,  delicate,  white  lines,  which,  at  first,  he  thought 
were  nerves.  On  pricking  one  of  them,  however,  and  seeing  a  whitish, 
milk-like  fluid  escape,  he  exclaimed,  like  Archimedes  of  old,  "•Eureka!" 
for  he  felt  he  had  made  a  great  discovery.  Wishing  to  confirm  his  dis- 
covery, Aselli,  on  the  following  day,  opened  a  second  dog,  but  was  dis- 
appointed in  not  finding  the  white  vessels  seen  on  the  previous  occasion, 
and  began  to  feel  that  he  had  been  too  hasty  in  announcing  the  dis- 
covery of  a  new  set  of  vessels.  On  reflection,  however,  it  occurred  to 
Aselli  that  the  first  dog  had  been  well  fed  before  being  opened,  whereas, 
the  second  one  had  been  deprived  of  food  for  some  time,  and  that,  per- 
haps, the  absence  of  the  white  vessels  was  due  to  this  cause.  A  third 
dog  was  well  fed,  and  then  opened,  when  the  white  vessels  were  again 
seen.  Aselli 's  method  of  experimentation  shows  how  well  he  appre- 
ciated the  importance  in  repeating  an  experiment  or  confirming  an 
observation,  of  the  conditions  being  the  same  in  both  cases. 

Aselli  further  extended  his  observations  to  other  animals,  and  found 
the  lacteals  in  cats,  lambs,  pigs,  cows,  and  the  horse.  It  was  not,  how- 
ever, until  1628,  two  years  after  Aselli's  death,  that  the  lacteals  were 
demonstrated  in  man.  For  this  observation  science  is  indebted  to 
Peiresc,1  Senator  from  Aix,  who,  wishing  to  know  whether  Aselli's 
discovery  could  be  extended  to  man,  permitted  the  body  of  a  criminal  who 
had  been  executed  to  be  opened,  when  the  lacteals  were  found  (Fig.  85), 
the  anatomists  interested  in  the  post-mortem  examination  having  at- 
tended to  the  feeding  of  the  criminal  before  execution. 

Aselli  supposed  that  the  lacteals  which  he  had  discovered  in  the 
mesentery  carried  the  chyle  to  the  liver.  This  error  was  corrected  by 
Pecquet,2  a  Frenchman,  who  showed,  in  1G49,  that  in  the  dog,  and 
afterward  in  the  horse,  ox,  pig,  etc.,  the  mesenteric  lymphatics,  or 
lacteals,  terminated  in  a  reservoir,  the  receptaculum  chyli,  now  often 
called  in  honor  of  its  discoverer  the  reservoir  of  Pecquet ;  and  further, 
that  this  receptaculum  was  the  beginning  of  the  thoracic  duct.  The 
functional  significance  of  the  forgotten  discovery  of  Eustachius  became 
then  for  the  first  time  apparent,  for  it  was  shown  that  the  lymphatics 
of  the  small  intestine  and  thoracic  duct  offered  a  route  by  which  the 
digested  food  could  be  carried  from  the  alimentary  canal  to  the  blood 
in  the  subclavian  vein,  and  thence  to  the  heart.  Two  years  after  the 
important  discovery  of  the  receptaculum  chyli — that  is,  in  1651 — lym- 
phatics were  demonstrated  in  the  liver  and  other  parts  of  the  body  by 
Rudbeck,3  and  their  course  and  connection  with  each  other  and  the 
mesenteric  lymphatics  made  out.  These  vessels  were,  however,  called- 
by  the  Swedish  anatomist  aquifermous,  or  serous  vessels. 

A  few  months  after  Rudbeck 's  discovery,  they  were  again  described 
by  Bartholinus,4  Professor  of  Anatomy  at  Copenhagen,  who  designated 
them  lymphatics,  the  name  they  now  bear.  Bartholinus  appears  also 
the  first,  so  far  as  the  author  has  been  able  to  learn,  to  have  seen  the 

1  Milne  Edwards  :  Physiologie,  tome  v.   p.  450.     Paris,  1859.     Berard  :  Pbysiologie,  tome  ii.  p.  565. 
Paris,  1849. 
'-  Joannis  Pecquet!  :   Diepasi  Experimenta  Nova  Anatomica,  Cap  v.  and  vi.     Amst.,  1661. 

3  Olai  Rudbeck  :   Nova  Exerritatio  Anatomica  exhibens  ductos  hepaticos  aquosos  vasa  glandularum 
serosa.     Clericus  <fc  Mangetus,  Bibliotbeca  Anatomica,  tomus  ii.  p.  629.     Geneva?,  1699 

4  Thomae  Bartboliinv  :  Auatomia  de  Lacteis  Tlioracis  et  vases  Lymphaticis.     Hagas  Com,  1666. 


LYMPHATIC    SYSTEM.  191 

reservoir  of  Pecquet  in  man,  which  he  figures,1  the  thoracic  duct  having 
been  discovered  by  Van  Home,  in  1G52.2  Jolyffe,3  a  student  of  medi- 
cine at  Cambridge,  England,  seems  also  to  have  discovered  the  lym- 
phatics independently  of  both  Rudbeck  and  Bartholinus.  While  Jolyffe, 
however,  did  not  publish  anything  in  reference  to  the  lymphatics,  he 
nevertheless  made  preparations  of  them,  which  Glisson4  states  to  have 
seen  in  1652. 

In  the  following  century  the  lymphatic  system  was  studied  in  man 
and  animals  by  many  anatomists,  especially  by  William5  and  John 
Hunter,6  Hewson,7  Monro,8  Cruikshank,9  the  great  work  of  Mascagni10 
appearing  also  about  this  period. 

During  the  present  century  the  lymphatic  system  has  been  most 
carefully  investigated  by  the  best  anatomists  and  physiologists  of  the 
day.     Let  us  consider  now  briefly  its  structure  and  uses. 

The  lymphatic  system  in  general  consists  of  vessels  which,  beginning 
in  the  skin,  mucous  membrane,  glands,  etc.,  converge  toward  each  other 
and  gradually  uniting  with  larger  and  larger  trunks  finally  terminate  in 
the  subclavian  veins  as  the  right  and  left  thoracic  ducts.  The  lymph 
from  the  right  side  of  the  head  and  that  from  the  upper  extremity 
passes  into  the  blood  of  the  right  subclavian  vein,  while  that  from  the 
rest  of  the  body,  including  the  lymph  and  chyle  from  the  small  intes- 
tine, is  conveyed  into  the  blood  of  the  left  subclavian  vein  by  the 
left  thoracic  duct. 

The  lymphatics,  in  their  general  structure,  resemble  very  closely  the 
veins,  consisting,  like  these  vessels,  of  three  coats,  an  external  one, 
composed  essentially  of  white  fibrous  tissue ;  a  middle  muscular  elastic 
coat,  the  elastic  muscular  fibres  being  arranged  circularly,  and  an  internal 
epithelial  layer  constituting  the  internal  coat.  The  lymphatics  also  con- 
tain valves,  consisting  usually  of  two  semilunar  folds.  The  lymphatics 
originate  as  plexuses,  or  as  continuations  of  the  interlacunar  spaces  of 
the  tissues.  These  spaces  are  usually  lined  with  a  continuation  of 
the  internal  epithelial  coat  of  the  lymphatics. 

Here  and  there,  along  the  course  of  the  lymphatics,  solid  bodies  may 
be  seen  varying  in  size  between  a  hemp  seed  and  an  almond,  which 
apparently  surround  the  vessels,  and  through  which  the  contents  must 
pass  in  their  way  to  the  thoracic  ducts.  These  bodies  are  the  lymphatic 
glands,  and  are  more  evident  in  certain  parts  of  the  body  than  in  others, 
being  well  developed,  for  example,  in  the  cervical,  axillary,  and  inguinal 
regions.  The  minute  structure  and  uses  of  these  glands  will  be  described 
when  the  elaboration  of  the  blood  is  considered.  The  lymphatics  not 
only  connect  the  interstices  of  the  tissues  with  the  blood,  beginning  in 
the  one  and  ending  in   the  other,  but  they  also  communicate  with  the 

1  Compare  Sprsngel,  Hist,  de  la  medicine,  tome  quatriene,  p.  212. 

-  Hyrtl  :  Lehrbuch  der  Anatomie,  1870,  S.  43.  3  Sprengel,  op.  cit.,  p.  210. 

4  Francisci  Glissonii  :   Anatomia  Hepatis,  p.  30S.     Clericus  &  Mangetus,  Bibliotlieca  Anat.,  tome  ii. 
Gen.  1699. 
6  Medical  Commentaries,  William  Hunter.     London,  1777. 

6  Works  of  John  Hunter,  Palmer's  edition,  vol.  1. 

7  Phil.  Trans.,  1767  and  1768,  and  Lymphatic  System  in  the  Human  Subject  and  in  other  Animals,  by 
William  Hewson.    London,  1774. 

•  Alex.  Monro  :  Anatomy,  p.  310.     Edinburgh,  1782. 

v  The  Anatomy  of  the  Absorbing  Vessels  of  the  Human  Body.    By  William  Cruikshank.    Lond.  1786. 
'"  Vasorun)  Lymphaticorum  Corporis  Human i.     Paulo  Mascagni,  Senis,  1787. 


192  A  BSORPTION". 

serous  cavities.  Indeed,  the  scions  cavities,  like  the  peritoneum,  pleura, 
etc.,  can  be  regarded  morphologically,  as  dilated  lymphatic  sacs  lying1 
between  the  viscera,  these  inter-organic  spaces  representing  on  a  large 
scale  the  minute  inter-lacunar  spaces,  which  we  have  just  seen  often 
constitute  the  beginning  of  a  lymphatic. 

Lymphatics  are  found  very  generally  throughout  the  system.  Accord- 
ing to  Sappey,2  however,  they  have  never  been  demonstrated  in  teeth, 
hair,  nails,  etc.  Possibly,  though,  future  researches  may  show  that 
lymphatics  exist  even  in  such  situations. 

It  is  only  within  recent  years  that  the  fluid  contained  in  the  lymph- 
atics, or  lymph,  has  been  satisfactorily  studied.  The  lymph  obtained 
by  experiments  made  upon  animals  in  the  beginning  of  this  century  by 
Muller,3  Magendie,4  Collard  de  Martigny,5  etc.,  was  in  too  small  quanti- 
ties to  admit  of  thorough  analysis,  while  the  observations  of  Marchand, 
Colberg;6  and  Nasse,7  were  unsatisfactory,  as  the  human  lymph  collected 
in  these  cases  was  probably  abnormal.  While  it  had  been  tried  before, 
it  was  only  in  1853  that  Colin8  succeeded  in  making  a  fistula  in  the 
thoracic  duct  of  the  horse,  and  showed  by  this  method  of  investigation 
that  large  quantities  of  normal  lymph  could  be  obtained  in  a  short  space 
of  time.  Colin  afterward  extended  his  observations,  experimenting  in 
the  same  way  on  other  animals,  and  his  method  is  the  one  now  employed 
by  physiologists  in  the  investigation  of  the  lymph. 

Lymph  is  a  transparent,  yellowish,  alkaline  liquid;  the  opaline  appear- 
ance that  it  sometimes  exhibits  is  due  to  small  particles  of  fat,  while  the 
rosy  tint  that  is  often  observed  in  it  is  caused  by  the  red  corpuscles 
that  have  passed  into  it  from  the  blood.  When  examined  under  the 
microscope,  lymph  is  seen  to  consist  of  a  liquor,  and  small  bodies  float- 
ing in  it,  the  lymph  corpuscles  or  globules.  These  measure  on  an  aver- 
age about  2  ^  0 th  of  an  inch  ;  they  are  homogeneous  or  granular  in 
appearance,  and  are  undistinguishable,  as  we  shall  see  from  the  white- 
corpuscles  of  the  blood.  When  we  come  to  study  the  red  blood-cor- 
puscles in  man  and  animals,  one  of  the  most  striking  facts  to  be  noted 
will  be  the  great  difference  in  their  size.  As  regards  the  lymph  or 
white  corpuscles,  however,  it  has  been  shown  by  Gulliver9  and  others 
that  their  average  diameter  bears  no  relation  to  that  of  the  red  corpuscle, 
being  as  large,  for  example,  in  the  musk  deer,  where  the  red  corpuscle 
is  small,  as  in  man  where  it  is  large.  Further,  the  white  corpuscle  in 
birds  is  usually  smaller  than  that  of  mammals,  whereas  the  red  cor- 
puscle of  birds  is  larger  that  of  the  mammal,  while  in  the  frog  both 
the  white  corpuscle  and  the  red  are  larger  than  those  of  the  mammal. 

Like  the  blood,  the  lymph  coagulates  when  drawn  from  the  living 
body.  This  is  due  in  both  cases  to  the  fibrin  which  these  fluids  contain. 
The  lymph  clot,  however,  is  less  solid  than  that  of  the  blood,  and  little 
or  no  serum  exudes  from  it.  The  clot  consists  not  only  of  fibrin,  but  of 
the  lymph  corpuscles  that  the  lymph  carries. 

1  The  Lymphatic  System,  p.  222.     Recklinghausen:  Strieker's  Histology.     New  York,  1872. 

2  Anatomie,  tome  deuxieme,  p.  791. 

3  Annales  des  Sciences,  1834,  tome  i.  p.  340.     4  Precis  de  Physiologie,  tome  ii.  p.  192.     Paris,  1836. 
6  Journ.  de  Phys.  de  Magendie,  1828,  tome  viii.  p.  152. 

«  Muller's  Archiv,  1838,  p.  139.  ^  Zeits.  fur  Phys.  von  Treviranus,  1832. 

*  Phys.  Camp.,  1856,  tome  ii.  p.  100,  IJ  The  Works  of  William  Hewson,  p.  244.     Loudon,  1 840. 


LYMPH    AND    CHYLE.  193 

Chemically,  the  liquor  of  the  lymph  differs,  as  we  shall  see,  from  the 
liquor  of  the  blood  quantitatively,  rather  than  qualitatively,  both  these 
fluids  consisting  essentially  of  water,  albumen,  fibrin,  and  salts.  Usually 
the  lymph  (Table  XXXIX.)  contains  as  much  fibrin  as  the  blood,  but 
less  albumen.  There  is  more  water  in  the  lymph  than  in  the  blood, 
but  the  amount  of  salts  in  both  liquids  is  about  the  same.  From  the 
fact  of  these  two  liquids,  the  liquors  of  the  lymph  and  blood,  being  alike 
in  their  chemical  composition,1  one  may  naturally  infer  that  the  lymph 
is  nothing  but  that  part  of  the  blood  which  has  escaped,  leaked  out,  so 
to  speak,  from  the  vascular  system  into  the  surrounding  tissues,  and 
afterward  is  soaked  up  by  the  lymphatics. 

Table  XXXIX. — Composition  of  Lymph  and  Chyle. 

Water 

Solid  residue 

Fibrin 

Albumen  ....... 

Fat 

Extractives        ...... 

Salts 


Lymph.2 

Chyle.3 

939.87 

904.8 

60.13 

95.2 

0.56 

42.75 

70.8 

3.82 

9  2 

5.70 

10.8 

7  30 

4.4 

It  has  already  been  mentioned  that  the  red  corpuscles  often  found  in 
the  lvmph  are  really  red  blood-corpuscles  that  have  escaped  from  the 
capillaries.  While  it  is  possible  that  some  of  the  lymph  corpuscles  may 
also  be  only  white  blood-corpuscles  that  have  passed  from  the  blood  with 
the  red  ones  into  the  lymph,  the  lymph  corpuscles  in  general  appear  to 
originate  in  an  entirely  different  manner,  there  being  good  reasons  for 
supposing  that  they  are  produced  in  the  lymphatic  glands,  spleen,  etc. 
The  consideration  of  the  origin  of  the  lymph,  or  white  corpuscles,  and 
their  relation  to  the  red  ones  and  the  glands  just  mentioned,  we  will, 
however,  defer  until  the  blood  is  studied,  and  pass  on  to  the  considera- 
tion of  the  quantity  of  the  lymph,  and  the  causes  of  its  flow  through 
the  system. 

Naturally,  from  the  conditions  of  the  case,  the  amount  of  lymph  can 
be  estimated  only  apnroximately.  In  making  a  fistula  of  the  thoracic 
duct,  the  circulation  must  be  interfered  with  to  a  certain  extent,  and 
this  circumstance  will  be  a  source  of  error  in  deducting  the  amount  of 
lymph  in  the  body  from  that  poured  out  through  the  fistula.  Though 
the  exact  amount  of  lymph  cannot  be  estimated,  it  is  safe  to  say  that 
the  amount  is  probably  underestimated,  rather  than  exaggerated.  Colin1 
obtained  from  the  horse  about  a  pound  of  lymph  in  an  hour,  and  as 
much  as  four  pounds,  and  even  more,  from  the  ox  in  the  same  period  of 
time.  Dalton5  estimated  that  in  twenty-four  hours  there  are  between 
three  and  a  half  to  four  pounds,  or  2000  grammes,  of  lymph  produced 
in  a  man  of  average  weight.  Various  causes  have  been  assigned  by 
physiologists  for  the  flow  of  the  lymph.      Of  these  some,  no  doubt,  are 

1  The  lymph,  according  to  the  investigations  of  Ludwig  (Arbeiten,  1871,  S.  121)  and  his  pupils,  con- 
tains, like  the  blood,  alsj  gases,  carbonic  acid  and  nitrogen  being  most  commonly  found. 

2  Gubler  and  Sulvenne  :  Gaz.  Med.  de  Paris,  1854.  p.  454.  :;  Recs     Phil.  Trans..  1842,  p.  81. 
<  Physiologie  Comparee,  tome  ii.  p.  100.  s  Physiology,  1882,  p.  323. 

13 


194 


ABSORPTION, 


Fig.  80. 


more  important  than  others.  Let  us  consider  them  briefly.  One  of  the 
principal  causes  of  the  flow  of  the  lymph  is  undoubtedly  the  vis  a  tergo 
resulting  from  the  constant  passing  of  the  serum  of 
the  blood  into  the  lymphatic  system,  and  as  the  lymph, 
on  account  of  the  valves  (Fig.  86)  in  the  vessels,  must 
How  always  from  the  periphery  or  the  radicles  of  the 
system,  toward  the  great  trunks  and  bloodvessels,  each 
successive  addition  of  serum  to  the  lymphatic  system 
will  act  as  a  force  propelling  forward  the  lymph  already 
there. 

From  the  fact  that  the  lymphatics  contain  unstriped 
muscular  fibre,  it  is  probable  that  these  vessels  at 
times  contract  upon  their  contents.  This  action,  how- 
ever, wrould  appear  to  be  slight,  inasmuch  as  the 
rhythmical  contractions  of  the  lymphatics  in  mammals 
are  rarely  observed.  It  should  be  mentioned  in  this 
connection,  however,  that  frogs,  toads,  lizards,  etc., 
the  lymphatics  of  which  are  unprovided  with  valves, 
possess  the  so-called  lymphatic  hearts.  The  latter  are 
dilated  portions  of  the  lymphatics,  exhibiting  contrac- 
tility, and  which  pulsate  regularly. 

The  influence  of  muscular  contractions  upon  the 
flow  of  the  lymph  must  not  be  forgotten,  for  pressure 
upon  the  lymphatics  from  this  source  will  have  the 
same  effect  as  we  shall  see  it  has  in  accelerating  the 
flow  of  blood  in  the  veins. 

From  the  disposition  of  the  terminal  portion  of  the 
lymphatic  system  in  the  thoracic  cavity,  it  might  natu- 
rally be  inferred  that  during  inspiration,  inasmuch  as 
all  the  parts  are  dilated,  that  the  flow  of  lymph  into  the  thoracic  ducts 
would  be  increased,  and  that,  during  expiration,  as  all  of  the  parts  are 
contracted,  the  lymph  will  then  flow  onward  into  the  left  subclavian 
vein,  regurgitation  being  impossible  through  the  presence  of  valves. 
Experiment  has  shown  that  such  is  in  fact  the  case.  With  each  inspi- 
ration the  thoracic  ducts  become  dilated  through  the  increased  flow  of 
lymph,  at  that  moment  the  lymph  flows  freely  from  the  right  thoracic 
duct  into  the  right  subclavian  vein.  With  each  expiration  the  lymph 
is  expelled  with  increased  force  from  the  left  thoracic  duct  into  the  left 
subclavian  vein,  and  when  a  fistula  is  made  in  that  situation  the  lymph 
issues  as  an  intermittent  jet. 

Of  the  different  causes  just  given  for  the  flow  of  the  lymph,  it  would 
appear  that  the  vis  a  tergo  and  the  respiratory  movements  are  the  most 
important,  the  contractility  of  the  vessels  and  the  pressure  of  surround- 
ing parts  being  of  secondary  importance. 

Up  to  this  moment,  in  speaking  of  the  lymphatic  system,  we  have 
only  alluded  incidentally  to  the  lymphatics  of  the  small  intestine,  or  the 
lacteals.  As  these  vessels  have  a  special  interest  for  us  in  connection 
with  the  absorption  of  the  digested  food,  let  us  study  them  now  a  little 
more  in  detail. 

The  lacteals,  or  lymphatics  of  the  small  intestine,  begin  in  the  villi,. 


Valves  of  the  lymph- 
atics. (Sappey.) 


STRUCTURE     OF    VILLI, 


195 


which  structures  we  only  alluded  to  in  speaking  of  the  alimentary  canal, 
reserving  for  the  present  moment  their  more  detailed  consideration.  The 
villi  are  small  processes  of  the  mucous  membrane  of  the  small  intestine, 
measuring  on  an  average  about  the  one-thirty-sixth  of  an  inch  in  length, 
and  about  the  one-seventy-second  of  an  inch  in  breadth.  They  are 
usually  conical,  and  flattened  in  form,  though  sometimes  cylindrical,  or 
terminating  in  an  enlarged  or  clubbed-like  extremity.  The  villi  are 
largest  and  most  numerous  in  the  duodenum  and  the  so-called  jejunum. 
They  are  closely  set  upon  the  inner  surface  of  the  intestine  over  the 
valvule  conniventes,  as  well  as  between  the  same,  and  give  rise  to  the 
characteristic  velvety  appearance  of  the  mucous  membrane  in  this 
situation. 

It  has  been  estimated  that  in  the  upper  part  of  the  small  intestine 
there  are  fifty  to  ninety  villi  to  the  square  line,  their  total  number 
amounting  to  about  four  millions.  The  villi  can  be  well  seen  by 
examining  a  piece  of  intestine  under  water  with  a  simple  lens,  the 
mucus  having  been  first  removed  by  gentle  washing.  When  studied 
with  the  microscope  the  villus  is  seen  to  consist  of  a  prolongation  of  the 
epithelial  layer  of  the  mucous  membrane  of  the  intestine,  enclosing  a 
network  of  bloodvessels,  the  beginning  of  the  lymphatics,  or  the  lacteals, 
and  some  plain  muscular  fibres.      These  structures  are  held  together 


Fro.  87. 


Fig. 


Villus  of  man  with  lacteal  and  bloodvessels 
injected.     (Teichmaxn.) 


"W^^vQi^m 


Villus  of  man  showing  lacteal  surrounded 
by  epithelial  cells.     (Frey.) 


and  supported  by  lymphoid  or  retiform  tissue,  which,  at  the  surface,  is 

condensed  into  a  basement  membrane,  upon  which  the  epithelial  cells  rest. 

Up  to  this  time  it  is  doubtful  if  nerves  have  been  demonstrated  in 


19(> 


ABSORPTI  O X 


the  villi.  It  is  very  probable,  however,  that  they  are  present.  Each 
villi  usually  receives  one  arterial  twig,  which,  after  penetrating  it,  breaks 
up  into  capillaries  situated  just  beneath  the  basement  membrane.  The 
blood  is  returned  usually  by  one  vein.  The  lymphatic,  or  the  lacteal, 
begins  in  the  centre  of  the  villus,  usually  as  a  single  vessel  (Fig.  87), 
with  a  closed  and  somewhat  expanded  extremity.  Its  calibre  is  con- 
siderably larger  than  that  of  the  capillary  bloodvessels  surrounding  it. 

The  lacteal  within  the  villus,  like  the  lymphatics  elsewhere,  is  sur- 
rounded by  a  delicate  layer  of  flattened  epithelioid  cells  (Fig.  88).  These 
are  connected  with  the  cells  of  the  basement  membrane  through  those 
of  the  lymphoid  or  connective  tissue  lying  between  (Fig.  89). 

The  columnar  epithelial  cells  which  cover  the  villi,  and  also  the 
surface  of  the  mucous  membrane,  and  which  are  prolonged  into  the 
tubular  glands,  present  a  granular  appearance  with  an  oval  nucleus. 
They  terminate  toward  the  basement  membrane  in  a  tapering  manner, 
and  measure  about  the  iQQQih  of  an  inch  (^-th  of  a  mm.)  in  length. 


Flu.  Si). 


Fig.  90. 


Diagrammatic  representation  of  the  origin 
of  the  lacteals  in  a  villus,  according  to  Funke. 
e.  Central  lacteal,  d.  Connective-tissue  corpus- 
cles with  the  communicating  branches,  c.  Co- 
lumnar epithelial  cells,  the  attached  extremities 
of _which  are  directly  contiguous  with  the  con- 
nective-tissue corpuscles.     (Carpenter.) 


Origin  of  the  lacteals,  according  to  Letzerich.  The 
cells  marked  a,  are  cup  or  goblet  cells,  and  are  seen 
to  be  intercalated  amongst  the  columnar  epithelial 
cells,  and  to  communicate  with  a  delicate  plexus,  b, 
that  opens  at  various  points  into  the  central  lacteal, 
c, /.  d.  Layer  of  clear  connective  tissue,  e.  Con- 
nective tissue  with  numerous  nuclei.     (Carpenter.) 


Their  free  end,  or  the  surface  looking  toward  the  interior  of  the  intes- 
tine, consists  of  a  layer  of  a  highly  refractory  substance,  with  vertical 
stride  running  through  it.  These  stripe  have  been  regarded  by  Kolliker1 
and  Funke2  as  minute  canals ;  Henle,3  however,  considers  them  to  be 
solid  rods.  Some  of  these  columnar  cells  usually  contain  mucus,  and 
swell  up  upon  the  addition  of  water  into  the  so-called  goblet  cells  (Fig. 
DO),  which  are  regarded  by  Letzerich4  as  the  true  beginning  of  the 
absorbent  system. 

The  lymphatic  or  lacteal,  after  emerging  from  the  villus,  passes  into 


i  Gewebelehre,  S.  409.     Leipzig.  1807. 

3  Anatomie,  Eingeweidelehre,  S.    177.     Braunschweig,  1873. 

*  Virchow's  Arcliiv,  Baud  xxxix.  S.  435. 


-  Physio'.ogie,  S.  222.     Leipzig,  1876. 


CHYLE.  197 

the  lymphatics  of  the  intestine.  These  are  usually  described  as  consist- 
ing of  two  sets,  the  deep  and  superficial.  The  latter  pass  in  the  mesen- 
tery to  the  lymphatic  glands.  The  lymphatics  coming  from  the  latter, 
as  we  have  seen,  converge  toward  the  receptaculum  chyli. 

During  the  intervals  of  digestion  the  lymphatics  of  the  small  intes- 
tine, or  the  lacteals,  contain  lymph,  undistinguishable  from  that  of  the 
lymphatics  of  the  rest  of  the  body.  During  digestion  and  absorption, 
however,  and  more  especially  when  fatty  articles  have  constituted  part 
of  the  food,  the  epithelial  cells  of  the  villi,  and  the  lymphatics  of  the 
small  intestine,  are  then  filled  with  the  chyle.  The  chyle  is  a  coagulable, 
alkaline,  opaque,  whitish,  milky-like  fluid,  hence  the  name  of  the  lacteals 
given  to  the  lymphatics  of  the  small  intestine,  in  which  it  is  found. 

The  chyle  (Table  XXXIX.),  however,  is  only  the  lymph  with  the 
products  of  digestion  added  to  it,  and  as  the  lacteals  absorb  principally 
the  fat,  the  essential  difference  between  the  chyle  and  the  lymph  is 
that  the  former  contains  a  great  quantity  of  fat,  the  latter  usually  only 
a  trace.  In  reference  to  any  analysis  of  the  chyle,  it  must  not  be  for- 
gotten that  its  composition  will  differ  according  to  whether  the  portion 
examined  has  been  taken  from  the  lacteals  or  the  thoracic  duct.  Indeed, 
chyle  drawn  from  the  thoracic  duct  is  not  pure  chyle,  but  chyle  mixed 
with  the  lymph  which  has  been  brought  from  the  extremities  to  the 
receptaculum  chyli,  and  thence  passed  into  the  thoracic  duct. 

The  chyle  of  the  thoracic  duct  will  contain,  therefore,  less  fat  and 
other  solid  constituents,  being  diluted  with  the  lymph  mixed  with  it. 
Further,  the  amount  of  fat  in  the  chyle  will  be  variable,  depending 
upon  the  diet  of  the  man  or  animal  examined.  Thus,  the  chyle  of  a 
carnivorous  animal  will  contain  more  fat  than  that  of  a  herbivorous  one, 
the  food  of  the  former  being  richer  in  fat  than  that  of  the  latter.  At 
one  time  it  was  supposed  that  the  lacteals  absorbed  exclusively  the  fatty 
substances,  but  it  is  now  known  that  they  also  take  up,  at  least  in  small 
quantities,  albuminoid  and  saccharine  substances,  salts  and  water. 

Of  the  amount  of  the  chyle  poured  into  the  thoracic  duct,  it  is  impos- 
sible to  give  even  an  approximate  estimate. 

When  examined  microscopically,  the  milky  appearance  of  the  chyle 
is  seen  to  be  due  to  an  immense  number  of  very  minute  fatty  granules, 
which  constitute  the  so-called  molecular  base  of  the  chyle,  and  which 
measure  on  an  average  from  the  !  2  o  o  o ^a  °^  an  *ncn  ^°  ^ne  1 2  5  0  0 *n  °f 
an  inch  in  diameter.  These  granules  appear  to  be  coated  with  albumen, 
which  probably  prevents  their  running  together  and  coalescing.  The 
so-called  chyle  corpuscles  found  in  greater  or  less  number  in  the  chyle, 
do  not  differ  from  those  of  the  lymph  or  blood,  and  will  be  considered 
again  when  the  latter  fluid  is  studied. 

What  has  been  already  stated  in  reference  to  the  supposed  causes  of 
the  flow  of  the  lymph  will  apply  equally  well  to  that  of  the  chyle ;  but 
there  are  eertain  conditions,  in  addition  to  those  already  mentioned, 
which  appear  to  influence  favorably  the  flow  of  the  chyle,  and  so  deserve 
a  passing  notice.  It  will  be  remembered  that,  in  speaking  of  the 
structure  of  the  villi,  allusion  was  made  to  the  plain  muscular  fibre  that 
they  contain.  These  muscular  fibres  are  dispersed  longitudinally 
around   the   lacteal,   and    their    contraction  will   obviously  retract  the 


198 


ABSORPTION. 


Fig.  91. 


villus.  The  effect  of  the  action  of  these  muscular  fibres  will  then  be 
to  force  the  contents  of  the  lacteal  out  of  the  villus  into  the  superficial 
lymphatics.  These  muscular  fibres  have  probably,  then,  some  im- 
portance in  aiding  the  flow  of  the  chyle  toward  the  thoracic  duct. 

It  wrill  be  remembered  that  the  thoracic  duct,  in  passing  to  the  left 
side  to  terminate  in  the  subclavian  vein,  passes  behind  the  aorta. 
Haller1  called  attention  to   this   fact   as  an  important  one,   the  great 

physiologist  considering  that  the 
contractions  of  the  aorta  in  com- 
pressing the  duct  would  favor  the 
flow  of  the  chyle  and  lymph  toward 
the  subclavian  vein.  Recently,  Prof. 
Draper2  has  further  suggested  that 
the  flowT  of  blood  in  the  subclavian 
vein  exerts  a  suction  force  upon  the 
contents  of  the  thoracic  duct,  basing 
his  view  upon  the  hydraulic  princi- 
ple of  Venturi,  that,  if  into  a  tube 
(Fig.  91)  through  which  a  current 
of  water  is  steadily  flowing  another 
tube  opens,  its  more  distant  end 
being  in  communication  with  a  reser- 
voir of  water,  a  current  will  be  like- 
wise established,  and  the  reservoir 
be  emptied  of  its  contents.  The 
anatomical  disposition  of  the  parts,  together  with  the  fact  that  the  flow 
of  the  chyle  ceases  with  the  flow  of  the  blood,  appear  to  show  the  close 
dependence  of  the  movement  of  the  one  on  that  of  the  other.  It  will 
be  remembered  that,  up  to  the  time  that  the  lymphatics  were  discovered, 
absorption  was  considered  to  be  effected  by  the  veins  only.  After  the 
discovery  of  the  lymphatics,  however,  physiologists  fell  into  the  opposite 
error  of  attributing  absorption  solely  to  the  lymphatics,  denying  that 
the  veins  took  any  share  in  this  process.  Indeed,  it  was  not  until  the 
present  century  that  it  was  experimentally  demonstrated  that  the  veins 
as  well  as  the  lymphatics  absorb.  Apart,  however,  from  any  experi- 
mental evidence,  the  facts  of  comparative  anatomy  alone  might  have 
shown  that  of  the  two  sets  of  vessels,  so  far  as  the  absorption  of  the 
digested  food  is  concerned,  the  veins  play  a  more  important  part  than 
the  lymphatics.  Thus  it  is  well  known3  that  in  the  amphioxus,  the 
lowest  of  the  vertebrata,  and  in  all  the  invertebrata,  the  lymphatic  system 
is  absent.  In  these  animals,  therefore,  absorption  is  carried  on  solely  by 
veins.  Further,  while  the  lymphatic  system  is  present  in  fishes, 
batrachia,  reptiles,  and  birds,  it  is  only  in  the  mammalia  that  it 
acquires  the  functional  importance  that  we  have  ascribed  to  it. 

Indeed,  according  to  Bernard,4  the  name  lacteal  cannot  be  properly 
applied  to  the  lymphatics  of  the  small  intestine  in  the  oviparous  verte- 


Principle  of  Venturi.  (Draper.) 


1  Elementa  Physiologic,  tomus  vii.  p.  237.  -  Physiology,  1878,  p.  79. 

3  Owen  :  Comp.  Anat.  of  Vertebrates,  vol.  i    p.  455  ;  vol.  ii    p.  180  ;  vol.  iii.  p.  504      Milne  Edwards: 
Physiologie,  tome  iv.  p.  462.     Gegenbaur  Vergleichende  Anatomie,  S.  857.     Leipzig,  1870. 

4  Physiologie  Experimentale,  tome  ii.  p.  312. 


VENOUS    ABSORPTION.  199 

brates,  since  these  lymphatics  contain  always,  even  during  digestion, 
with  few  exceptions,  a  clear,  transparent  lymph  instead  of  chyle,  an 
opaque,  whitish  fluid,  the  fat  in  these  animals  being  taken  up,  not  by 
the  so-called  lacteals,  but  by  the  portal  vein,  the  greater  part  of  it  being 
thence  carried  to  the  renal  veins  (Jacobsen's  system),  and  so  to  the 
vena  cava. 

Inasmuch  as  absorption  is  carried  on  by  the  veins  in  the  lower  ani- 
mals, we  would  naturally  infer  that  these  vessels  must  be  of  great 
importance  in  this  respect  in  man  and  the  mammalia,  That  such  is  the 
case  can  be  readily  demonstrated  experimentally.  Magendie1  appears 
to  have  been  the  first  to  show  conclusively  by  experiment  that  absorp- 
tion takes  place  by  the  bloodvessels. 

Of  his  many  remarkable  and  accurate  experiments,  the  following 
may  be  mentioned :  In  one  experiment,  the  abdomen  of  a  dog  that  had 
been  well  fed  some  hours  previously  was  opened,  and  a  loop  of  the  in- 
testine drawn  out.  Ligatures  were  placed  around  this  loop  at  a  distance 
of  about  fifteen  inches  apart,  The  lymphatics  arising  from  this  portion 
of  the  intestine  being  all  ligated  in  two  places,  were  divided  between 
the  ligatures.  Of  the  five  mesenteric  arteries  and  veins  passing  into 
the  general  vascular  system,  four  were  divided  and  ligated  so  that  the 
loop  of  the  intestine  remained  in  connection  with  the  rest  of  the  system 
by  only  a  single  vein  and  artery,  even  the  cellular  coat  of  which  was 
dissected  off,  so  as  to  remove  all  doubt  of  there  being  a  trace  of  a  lym- 
phatic left.  Some  upas  was  then  introduced  into  the  loop  of  the  intes- 
tine prepared  in  the  above  manner,  which  was  then  replaced  in  the 
abdomen,  and  in  a  few  minutes  the  characteristic  symptoms  of  poisoning 
appeared,  showing  that  the  upas  had  been  absorbed  by  the  vein. 

In  another  experiment,  where  the  poison  was  introduced  into  the 
foot,  the  only  connection  between  the  limb  and  the  rest  of  the  body 
was  through  two  quills,  introduced  into  the  divided  femoral  bloodvessels, 
the  rest  of  the  parts  having  been  dissected  off.  In  this  case,  also,  the 
only  possible  means  by  which  the  poison  could  pass  into  the  general 
system  and  make  its  effects  evident  was  through  the  circulating  blood. 

The  experiments  of  Magendie  were  immediately  fully  confirmed  by 
Tiedemann  and  (linelm,2  who  showed,  in  an  elaborate  series  of  experi- 
ments, that  different  kinds  of  foods,  odorous  and  coloring  matters, 
saline  and  metallic  substances  were  absorbed  by  the  radicles  of  the 
portal  vein  as  well  as  by  the  lymphatics  of  the  small  intestine. 

Segalas3  modified  the  experiments  of  Magendie,  and  further  con- 
firmed them  by  demonstrating  that  a  poison  like  mix  vomica,  when 
introduced  into  the  alimentary  canal,  fails  to  produce  its  characteristic 
effects  so  long  as  the  circulation  of  the  blood  is  interrupted,  or  when 
the  blood  carrying  the  poison  from  the  intestine  is  allowed  to  escape 
from  the  vein  and  not  pass  into  the  general  circulation. 

Magendie's  experiments  were  also  fully  repeated  and  confirmed  in 
this  city  by  Drs.   Harlan,  Lawrence,  and  Coates,  the  committee  ap- 

1  Journal  de  Physiologie,  p.  18      Paris,  1821. 

2  Recherches  sur  la  route  qui  preunent  diverses  substances  pour  passer  d'Estomac  et  du  Canal  intestinal 
dans  le  Sang.    Paris,  1821. 

3  Journal  de  Physiologie,  tome  ii.  p.  117.     Paris,  1822. 


200  ABSORPTION. 

pointed  by  the   Academy  of  Medicine  of    Philadelphia   to  investigate 
the  subject.1 

A  convenient  method  of  demonstrating  venous  absorption  is  to  open 
the  abdomen  of  a  frog,  withdraw  a  loop  of  the  intestine,  and  ligate  it 

Fig.   92. 


c 

aa.  Intestine,    b.  Point  of  ligature  of  mesenteric  vein.    c.  Opening  in  intestine  for  introduction  of  poison. 

d.  Opening  in  mesenteric  vein  behind  the  ligature.     (Dalton.) 

in  two  places,  cut  away  all  the  mesentery,  leaving  only  a  single  artery 
and  vein,  and  introduce  a  solution  of  ferrocyanide  of  potassium  into 
the  intestine  by  an  opening  made  in  the  latter,  replace  the  loop  within 
the  abdomen,  and,  after  a  few  minutes,  open  one  of  the  veins  of  the 
foot.  On  testing  the  blood  for  the  ferrocyanide  of  potassium  by  adding 
tincture  of  the  chloride  of  iron,  the  presence  of  the  salt  introduced 
into  the  intestine  will  become  at  once  evident,  through  the  formation  of 
Prussian  blue,  the  latter  being  best  demonstrated  by  adding  the  per- 
chloride  of  iron  to  the  serum,  the  blood  having  been  allowed  to  stand, 
or  to  a  clear  extract  of  the  blood  made  by  boiling  the  latter  with  a 
little  sodium  sulphate  and  filtering. 

It  is  obvious  that  the  only  means  by  which  the  salt  of  potassium 
could  pass  from  the  intestine  into  the  general  circulation,  and  thence 
into  the  blood  of  the  extremities,  was  by  means  of  the  vein  left  in  the 
mesentery.  The  above  experiment  is  essentially  the  same  as  that  per- 
formed by  Panizza2  upon  the  horse. 

We  have  seen  that  while  the  principal  function  of  the  lymphatics  of 
the  small  intestine  is  to  absorb  fat,  nevertheless  they  can  and  do  take 
up  albuminose,  glucose,  and  water ;  on  the  other  hand,  the  mesenteric 
veins,  in  addition  to  absorbing  these  latter  substances,  take  up  also,  at 
times,  considerable  quantities  of  fat.  Briefly,  then,  the  functions  of  the 
lymphatic  and  venous  absorbents  are  essentially  the  same ;  as  a  rule, 
however,  the  fats  pass  into  the  blood  by  the  one  route,  the  remaining 
alimentary  substances  by  the  other. 

i  Phila.  Journal  of  the  Med.  and  Phys.  Sciences,  1821,  vol.  iii.  p.  273,  am!  1822,  vol.  v.  p.  327. 
2  I)e  l'absorption  veineuse.     Paris,  1843. 


ABSORPTION     BY     STOMACH    AND    RECTUM.  201 

As  digestion  is  only  completed  in  the  small  intestine,  Ave  considered 
it  most  appropriate  to  begin  the  study  of  absorption  there.  It  must  not 
be  supposed,  however,  that  nothing  is  absorbed  by  the  stomach.  On 
the  contrary,  there  can  be  little  doubt  that  water  and  other  liquids 
are  very  rapidly  taken  into  the  blood  there,  and  also  albuminose  and 
whatever  glucose  may  be  present.  Experiments  made  upon  animals 
where  the  pylorus  has  been  tied,  and  water  introduced  into  the  stomach, 
showed  that  in  a  very  short  time  the  liquid  is  absorbed  by  that  viscus. 

The  difference  of  opinion  prevailing  among  experimenters  in  refer- 
ence to  the  absorbing  power  of  the  stomach  is  due,  no  doubt,  to  the 
fact  that  this  differs  very  considerably  in  animals.  Thus,  water  is 
absorbed  very  slowly  by  the  stomach  in  the  horse,  arid  in  small  quanti- 
ties, though  very  rapidly,  and  in  considerable  quantity,  in  the  dog  and 
rabbit.1  So  far  as  man  is  concerned,  the  case  of  Busch,2  already 
referred  to,  showed  conclusively  the  absorbing  powers  of  the  human 
stomach,  almost  all  the  sugar  eaten  being  absorbed  in  this  part  of  the 
alimentary  canal,  as  well  as  a  considerable  quantity  of  the  albumen. 

It  is  well  known  to  physicians  that  human  beings  can  be  kept  alive 
for  months  by  enemata,  the  rectum  absorbing  very  rapidly ;  its  capacity 
for  taking  up  water,  for  example,  is  probably  as  great  as  that  of  the 
stomach.  We  have  seen,  also,  that  the  rest  of  the  large  intestine 
absorbs  to  a  large  extent. 

As  the  digested  food  ordinarily,  however,  is  absorbed  before  it  reaches 
this  part  of  the  alimentary  canal,  further  reference  to  absorption  in  this 
respect  is  not  necessary. 

That  the  mucous  membrane  of  the  mouth  is  capable,  also,  of  absorb- 
ing is  shown  from  the  effects  observed  when  tobacco-juice  is  retained, 
even  for  a  short  time,  in  the  mouth.  Food,  however,  remains  for  such 
a  short  time  in  the  mouth,  that  little  chance  is  offered  for  its  absorption 
in  this  part  of  the  alimentary  canal. 

Absorption  by  the  skin  and  by  serous  cavities,  and  the  influence  of 
the  nervous  system  and  the  circulation  upon  this  function,  can  be  more 
conveniently  treated  when  these  subjects  are  especially  considered.  We 
will  pass  on,  therefore,  to  the  study  of  the  causes  of  absorption. 

l   Colin,  op.  cit..  tome  ii.  p.  20.  2  Op.  fit.,  p.  140. 


C  IIAPTEK  XII. 

OSMOSIS. 

We  have  seen  that  during  absorption  the  digested  food  passes  from 
the  interior  of  the  alimentary  canal  into  the  veins  and  lymphatics.  The 
investigation  of  the  causes  of  the  phenomena  of  absorption  resolves 
itself,  therefore,  into  the  determination  of  the  conditions  on  which 
depend  the  passage  of  the  liquid  or  semi-liquid  albuminose,  glucose, 
etc.,  and  emulsified  fat  through  the  epithelium  of  the  alimentary  canal 
and  the  wall  of  the  capillary  or  lymphatic  into  the  blood  or  lymph. 

In  physical  science  the  diffusion  of  liquids  into  each  other  when  sepa- 
rated by  a  membrane  is  known  as  osmosis.  Let  us  consider,  briefly, 
what  is  understood  by  the  term  osmosis,  and  see  whether  the  facts  of 
absorption  that  we  have  described  can  be  explained  by  this  principle. 

The  name  of  Dutrochet  is  invariably  associated  with  any  discussion 
of  the  phenomena  of  osmosis.  The  history  of  the  subject  teaches  us, 
however,  that  the  discovery  of  this  important  physical  principle,  like 
that  of  all  others,  was  not  a  sudden,  but  a  gradual  one.  Many  of  the 
phenomena  had  been  observed,  and  numerous  experiments  bearing  upon 
the  subject  had  been  performed  and  recorded  before  the  time  of  the 
distinguished  French  physiologist.  The  merit  of  Dutrochet  consisted  in 
not  only  devising  and  performing  new  experiments,  but  of  generalizing 
the  facts  of  osmosis,  and  applying  them  to  the  explanation  of  absorption 
in  living  beings. 

The  first  recorded  experiment,  so  far  as  I  have  been  able  to  learn, 
bearing  upon  the  subject  of  osmosis,  was  performed  as  long  ago  as  1748 
by  the  Abbe  Nollet,1  who,  in  investigating  the  causes  of  the  boiling  of 
liquids,  showed  that  when  a  vial  of  alcohol  covered  with  a  bladder 
was  immersed  in  water  the  bladder  became  convex,  the  water  diffusing 
through  the  membrane  into  the  alcohol,  whereas,  if  the  vial  was  filled 
with  water,  and  immersed  in  alcohol,  the  bladder  became  concave,  the 
water  diffusing  through  the  membrane  from  the  vial  into  the  alcohol. 

Nollet  further  showed  that,  while  water  passed  readily  through  the 
bladder,  alcohol  only  did  so  with  difficulty  and  under  pressure.  In  1802 
Parrot2  observed  that  an  egg,  from  which  the  shell  had  been  removed, 
would  absorb  water,  the  liquid  traversing  the  egg  membrane.  The  fact, 
however,  was  only  noted,  no  further  application  being  made  of  it. 
Equally  unfruitful  were  the  observations  of  Soemmering3  and  Van 
Mons,4  who,  about  1812,  called  attention  to  the  fact  that  spirituous 
liquors  became  more  condensed  through  the  evaporation  of  their  water, 

1  Memoires  de  l'Academie  des  Sciences,  p.  101.     Paris,  1748. 

2  Bulletin  scient.  de  l'Acad.  de  Petersburg,  1840,  t.  vii.  p.  346. 

3  Gilbert's  Annalen  der  Physik,  1819,  t.  lxi.  p.  104. 

4  Annales  gen.  des  sciences  phya.,  t.  i.  p.  70.     Bruxelles,  1810. 


EN  DOS  MO  METER.  203 

the  vessels  containing  them  are  closed  by  membranous  stoppers,  the 
water  passing  through  the  membranes. 

Porrett,1  in  1816,  noted  that  a  galvanic  current  influenced  the  passage 
of  water  through  a  membranous  septum,  the  fluid  accumulating  around 
the  negative  pole. 

The  observations  just  mentioned  have  for  us  now  but  little  more  than 
an  historical  interest,  but  the  experiments  of  Lebkuchner,2  in  1813,  and 
Magendie,3  in  1820,  are  very  important  still,  as  being  the  first  in  which 
it  was  positively  demonstrated  that  various  solutions  would  pass  readily 
through  membranes  into  the  blood  of  the  living  animal.  Lebkuchner 
showed  that  potassium  ferrocyanide  placed  upon  the  jugular  vein  of  a 
living  rabbit  in  a  few  minutes  passed  into  the  blood,  and  could  be  detected 
in  the  blood  of  the  jugular  vein  of  the  opposite  side  when  tested  for  by 
adding  sulphate  of  iron.  Magendie  dissected  out  the  jugular  vein  of  a 
dog,  and  placing  it  upon  a  card,  poured  upon  it  a  solution  of  nux 
vomica,  taking  the  precaution  of  not  letting  the  poison  touch  anything 
but  the  card  and  vein,  and  observed  in  a  few  minutes  the  symptoms  of 
poisoning. 

Important  observations  and  experiments  bearing  upon  the  subject  of 
osmosis,  were  further  made  in  1822,  by  Fischer,4  of  Breslau.  This 
experimenter  not  only  constructed  what  is  now  called  an  endosmometer, 
but  showed  that  when  the  tube  of  the  apparatus  closed  by  animal  mem- 
brane, and  filled  with  a  saline  solution,  was  plunged  into  pure  water,  the 
water  passed  through  the  membrane  into  the  saline  solution,  while  the 
latter  passed  in  the  reverse  direction  through  the  membrane  into  the 
water.  Fischer  also  noted  some  of  the  conditions  influencing  these 
currents,  observing  that  they  continued  until  the  liquids  were  of  the 
same  density,  and  that  they  Avere  active  according  to  the  thinness  of  the 
membrane  used.  Notwithstanding  the  value  of  the  observations  and 
experiment  referred  to  in  the  above  historical  resume,  they  do  not  appear 
to  have  received  from  physiologists  the  attention  they  merited,  and  would 
not  have  assumed  their  present  importance  had  it  not  been  for  the  later 
investigations  of  Dutrochet.5 

This  able  investigator  described  thoroughly  the  passage  of  liquids 
through  animal  membranes  :  he  showed  the  influence  of  different  liquids 
used,  measured  the  force  of  the  currents,  constructed  the  endos- 
mometer, and  called  particular  attention  to  the  currents,  naming  them 
endosmotic  and  exosmotic,  according  as  they  passed  into  the  tube  from 
the  surrounding  liquid,  or  in  the  reverse  direction,  and  applied  the  facts 
to  the  explanation  of  physiological  phenomena.  Since  then  the  subject 
of  osmosis  has  been  most  thoroughly  investigated  by  Graham. b  This 
physicist  discards  the  terms  endosmosis  and  exosmosis,  considering  that 
there  is  but  one  current,  the  inward  one,  and  designating  it  by  the  term 
osmotic,  and  the  whole  phenomena  as  osmosis. 

According  to  Graham,  the  molecules  of  the  salt  in  the  outward  cur- 
rent travel  by  diffusion  through  the  porous  membrane.     "  It  is  not  the 

1  Annals  of  Philosophy,  1816,  vol.  viii.  p.  74. 

-  Archiv  General  de  Sledeeine,  t.  vii.  p.  439.     Paris,  1825. 

3  Journal  de  Phvs.,  tome  i.  p.  1.     Paris,  1821. 

*  Gilbert's  Annalen  der  Physik,  1822,  Band  lxxii.  S.  301. 

5  Memoires  pour  servir  a  la  llistoire  Anatomiques  et  Phyaiologiques  ies  Animaux,  tome  i.   Paris,  1837. 

«  Osmotic  Force,  Phil.  Trans.,  1854,  p.  178. 


204 


OSMO 


whole  saline  Liquid  winch  moves  outward,  but  merely  the  molecule-  of 
salt,  their  water  of  solution  being  passed,  the  inward  current  of  water, 
on  the  other  hand,  appearing  to  be  a  true,  sensible  stream."  According 
to  this  view,  the  only  true  current  in  the  endosmometer  (  Fig.  93)  is  that 

of  the  water  from  the  jar  (A)  through  the 
Fig.  93.  membrane  (C)  into  the  bulbous  tube  (B) 

containing  the  yellow  saline,  consisting  of 
a  solution  of  potassium  bichromate,  the 
apparent  outward  movement  from  the  jar 
(B)  into  the  water  in  A,  being  due  to  the 
diffusion  of  the  molecules  of  the  salt.  So 
far,  however,  as  the  physiologist  is  con- 
cerned, the  important  fact  in  this  experi- 
ment is,  that  there  is  an  exchange  going  on, 
the  water  passing  one  why.  the  -alt  the 
other.  A  more  delicate  and  interesting 
way  of  illustrating  osmosis  is  to  replace 
the  jar  of  the  last  experiment  with  an  egg 
prepared  in  the  following  way :  At  one  end 
of  the  egg  the  shell  is  removed  in  such  a 
way  as  to  leave  the  lining  membrane  of  the 
egg  intact:  at  the  other  end,  shell  and 
membrane  are  both  perforated  sufficiently 
to  permit  the  passing  of  a  glass  tube  into 
the  egg;  the  tube  is  beld  securely  to  the 
egg  by  sealing  wax.  The  a%'^  is  then 
placed  in  a  wine-glass  of  water,  and  the 
level  of  the  water  noted.  Shortly  after- 
ward the  yellow  of  the  ^^  will  be  Been 
rising  in  the  tube,  and  the  level  of  the 
i  mm  water  falling  in  the  wine-glass.     The  water 

of  the  glass  gradually  passes  through   the 
egg,   distending   if-   ;ind   forcing  the  content-  of  the 


membrane  of 

d'^  upward. 


the 

On  the  other  hand,  the  salts  of  the  i-^^ — the  chlorides, 
phosphates,  sulphates — will  be  found  to  have  diffused  away  from  the 
rest  of  the  egg  into  the  water  of  the  glass,  as  can  be  readily  shown  by 
appropriate  tests.  Thus,  if  a  i'ttw  drops  of  silver  nitrate  be  added  to 
the  water,  at  once  argentic  ehloride  will  he  formed  and  precipitated, 
showing  that  the  sodium  chloride  ha-  passed  into  the  water. 

An  important  fact  to  be  noted,  the  physiological  significance  of  winch 
will  be  appreciated  shortly,  is  that  little  or  no  albumen  is  found  in  the 
water,  scarcely  a  trace  of  it,  if  any,  passing  through  the  egg  membrane, 
particularly  if  the  water  be  distilled.1  In  this  experiment  also,  as  well 
as  in  the  preceding  one.  the  substances  on  either  side  of  the  membrane 
(in  the  case  of  the  egg,  most  of  them  at  least]  diffused  into  each  other. 
Thi-.  as  we  shall  see  in   a   moment,  depends  not  only  on  the  membrane 


apart  Hialbe     Cbimii  appliqol  a  is  physiologie,  err.,  p.  130.     B«  lard     Qaa    ties  Bopitaux,  1851, 
I    324 


CAPILLARY    ATTRACTION.  205 

being  capable  of  imbibing  both  liquids,  but  also  that  the  latter  were 
miscible  with  each  other.  If  a  membranous  septum,  however,  be  used, 
which  will  imbibe  only  one  of  the  liquids,  that  one  alone  will  traverse 
the  septum,  will  increase  the  volume  of  the  other  liquid  if  it  is  miscible 
with  it,  but  there  will  be  no  exchange. 

A  convenient  way  of  illustrating  this,  and  also  of  showing  thai  a 
liquid  septum  will  act  in  this  respect  in  the  same  way  as  a  membranous 
one,  is  to  place  in  a  vial  some  chloroform,  and  then  pour  gently  on  the 
chloroform  water,  and  on  the  top  of  the  water  sulphuric  ether,  the 
water  serving  as  the  septum.  In  a  short  time  it  will  be  found  that  the 
ether  has  passed  through  the  wrater  and  has  mixed  with  the  chloro- 
form, so  that  instead  of  the  vial  containing  three  layers,  ether,  water, 
and  chloroform,  it  contains  only  two — water  on  top,  and  a  mixture  of 
chloroform  and  ether  below.  The  chloroform  having  no  affinity  for  the 
water,  will  not  pass  through  it:  the  ether,  on  the  other  hand,  will  not 
only  pass  through  the  water,  but.  being  miscible  with  the  chloroform, 
will  diffuse  into  it,  and  so  give  rise  to  the  result  just  described.  Osmosis 
further  will  take  place,  semi-liquid  substances  being  used  as  septa. 
Thus,  if  sulphuric  acid  and  litmus  water  be  separated  by  boiled  gelatin, 
the   acid  will  make  its   way  through    the   gelatin,   and  will   color  the 

•  ©  © 

litmus.  The  litmus,  however,  having  but  little  affinity  for  the  gelatin, 
diffuses  but  slightly  into  the  gelatin,  so  that  but  little  of  the  septum  is 
colored. 

Having  given  several  illustrations  of  osmosis,  let  us  consider  now  the 

©   © 

causes  of  the  same.  The  phenomenon  of  osmosis  depends  essentially 
upon  two  conditions  :  first,  that  the  membranous  septum  is  capable  of 
imbibing  the  liquids  which  it  separates :  second,  that  the  liquids  are 
miscible.  It  will  be  remembered  that  in  speaking  of  the  organic  proxi- 
mate principles,  allusion  was  made,  among  their  other  properties,  to  that 
of  their  taking  or  giving  up  of  water.  The  swelling  up  of  a  tendon  or 
muscle  when  immersed  in  water,  and  the  giving  up  of  the  same  when 
desiccated,  are  common  examples  of  the  imbibition  by  organic  tissues  of 
liquids.  Every  organic  tissue  and.  indeed,  all  substances,  however  solid 
they  may  appear,  are  more  or  less  porous,  at  least  in  the  sense  that  the 
particles  of  which  a  body  consist  are  separated  to  a  greater  or  less 
extent  from  each  other.  It  is  through  the  presence  of  the  interspaces, 
between  the  particles  of  which  a  tissue  consists,  that  imbibition  is  possi- 
ble, that  the  tissue  is  capable  of  taking  up  a  liquid,  retaining  it  for  some 
time,  and  finally  giving  it  up  again. 

1  «  ©  ©  I  © 

The  passage  of  a  liquid  into  the  interspaces  or  interstices  of  a  tissue 
is,  however,  an  example  of  capillarity,  the  particles  of  which  the 
tissues  consists  bearing  to  the  liquid  passing  through  the  spaces  between 
them  the  same  relation  that  the  walls  of  a  capillary  tube  bear  to  the 
liquid  moving  within  them.  The  ascent  of  the  oil  in  the  wick  of  a 
lamp  is  a  familiar  example  of  capillary  action. 

Imbibition,  the  first  condition  of  osmosis,  depending  as  it  does  upon 
capillarity,  necessitates,  for  its  understanding,  a  brief  consideration  of 
this  principle.  Capillary  attraction,  so  called  on  account  of  its  being 
usually  observed   in   tubes  of  very  fine  hair-like  or  capillary  diameter, 


206 


OSMOSIS. 


can  be  best  understood  if  we  confine  our  attention  for  the  moment  to 
one  or  two  elementary  physical  facts. 

It  is  well  known  that  if  a  drop  of  mercury  be  placed  upon  a 
perfectly  clean  plate  of  glass  it  rolls  off'  and  falls  to  the  ground,  its 
globular  form  being  preserved,  the  particles  of  the  mercury  being  held 
together  through  the  force  of  cohesion,  and  its  falling  from  the  glass 
being  due  to  the  want  of  any  adhesion  between  the  two  substances.  On 
the  other  hand,  if  a  drop  of  water  be  placed  on  a  similar  plate  or  glass, 
the  water  becomes  flattened,  adhering  to  the  surface,  and  when  the  glass 
is  tilted  the  water  runs  to  the  edge,  leaving  a  wet  line,  but  does  not 
fall  to  the  ground,  sticking  to  the  plate  in  spite  of  gravity,  the  water 
being  retained  by  the  glass  through  the  force  of  adhesion.  If  the  plate 
be  first  greased,  then  the  drop  of  water  will  behave  like  the  drop 
of  mercury,  and  for  the  same  reason,  the  water  not  adhering  to  grease 
falls  like  mercury  to  the  ground.  There  are,  therefore,  two  forces,  that 
of  cohesion  and  adhesion.  Through  the  first  the  particles  of  a  sub- 
stance are  held  together  or  cohere ;  through  the  second,  the  particles  of 
one  substance  are  attracted  by  those  of  a  dissimilar  one,  or  adhere. 

Let  us  modify  the  preceding  experiment  by  partially  immersing  a 
clean  glass  plate  in  a  vessel  of  water.  It  will  now  be  noticed  that  the 
surface  of  the  liquid  in  contact  with  the  glass  is  slightly  elevated,  and 
that  this  elevation  gradually  diminishes  until  the  level  of  the  remain- 
ing liquid  is  reached.    (Fig.  94.)    It  is  very  evident  from  what  has  just 


Fig.  94. 


Fig.  95. 


been  said  of  adhesion  and  cohesion,  that  the  different  elevation  of  the 
water  will  be  due  to  the  relative  strength  of  these  two  forces,  the  eleva- 
tion of  the  liquid  being  highest  where  the  liquid  is  in  contact  with  the 
glass,  adhesion  being  there  at  a  maximum,  cohesion  at  a  minimum, 
and  that  the  elevation  will  gradually  diminish,  the  force  of  cohesion 
increasing,  that  of  adhesion  at  the  same  time  diminishing.  Suppose, 
now,  that  we  immerse  a  second  plate  of  glass  in  the  water  parallel  to 
the  first,  the  water  will  be  most  elevated  where  the  liquid  comes  in 
contact  with  the  glass,  the  elevation  diminishes  as  the  distance  from  the 
second  plate  is  increased,  and  the  general  surface  of  the  water  will  be 
indicated  by  the  curve  (Fig.  95),  the  lowest  point  of  the  water  being 
equidistant  from  the  two  glass  plates.  As  the  two  glass  plates  are 
approximated,  naturally  the  elevation  of  the  water  will  be  increased 
(Fig.  96),  since  the  quantity  of  water  being  continually  diminished,  the 


MISCIBILITY    OF    LIQUIDS.  207 

force  of  adhesion  at  the  same  time  increases  in  proportion  to  the  rela- 
tively greater  surface  of  glass  exposed.     In  a  word,  the  elevation  of  the 
liquid  is  inversely  as  the  distance  of  the 
plates.  Fig.  96. 

If  we  now  immerse  two  more  plates  of 
glass  parallel  to  each  other,  and  perpen- 
dicular to  the  first  two,  we  shall  have  a 
four-sided  glass  arrangement,  to  the  inside 
of  which  the  water  will  adhere.  The 
transition  from  such  an  apparatus  to  a 
capillary  tube  is,  either  theoretically  or 
practically,  a  simple  one,  the  conditions 
being  in  the  latter  essentially  such  as  we 
have  described. 

Modern1  theory  deduces,  then,  the  form  and  elevation  of  the  liquid 
in  capillary  tubes  as  the  resultant  of  the  forces  of  adhesion,  cohesion, 
and,  of  course,  gravity.  Inasmuch  as  these  conditions  are  all  present 
in  the  phenomena  of  imbibition,  we  are  justified,  as  already  observed, 
in  regarding  this  an  example  of  capillary  action,  the  adjacent  par- 
ticles of  a  body  being  comparable  to  the  plates  of  glass,  or  the  side  of 
a  tube,  the  interspaces  between  them  to  the  space  between  the  plates,  or 
within  the  tube,  and  the  water  to  the  liquid  imbibed. 

In  order  that  an  osmosis  should  take  place,  it  is  evident  that  the 
membranous  septum  must  be  not  only  capable  of  imbibing  the  liquids 
through  capillary  action,  but  further,  that  the  liquids  separated  by  the 
septum  must  be  miscible,  otherwise,  though  the  liquids  might  get  into 
the  septum,  they  would  not  diffuse  into  one  another,  and  there  would 
be  no  current.  This  brings  us,  therefore,  to  the  consideration  of  the 
second  condition  of  osmosis,  the  diffusion  of  liquids. 

It  is  a  familiar  fact  that,  if  a  drop  of  water  rolling  over  a  surface, 
upon  which  it  can  preserve  its  globular  form,  comes  in  contact  with  a 
drop  of  mercury,  or  of  oil,  the  drops  do  not  run  into  each  other  or  fuse, 
the  particles  of  the  drop  of  water  having  a  greater  affinity  for  each 
other  than  for  the  particles  of  the  drop  of  mercury  or  of  oil,  and  vice 
versa.  On  the  other  hand,  if  the  drop  of  water  meets  with  a  drop  of 
alcohol,  the  two  do  run  into  each  other,  losing  their  identity,  the  par- 
ticles of  the  water  having  a  greater  affinity  for  those  of  the  alcohol  than 
they  have  for  each  other.  A  simple  illustration  of  the  diffusion  of 
liquids  is  to  place  in  a  small  vial  a  solution  of  copper  sulphate  and  im- 
merse the  vial  containing  the  solution  into  a  vase  of  water.  Soon  the 
surrounding  water  will  assume  a  blue  color  through  the  diffusion  into 
water  of  the  copper. 

The  dissolving  of  a  substance  in  a  menstruum  is  an  illustration  of  the 
same  principle,  the  molecules  of  the  dissolving  liquid  having  a  greater 
affinity  for  the  particles  of  the  substance  to  be  dissolved  than  these  have 
for  each  other.  The  solution  of  a  substance,  however,  depends  not 
only  upon  the  affinities,  chemical  or  physical,  existing  between  the  par- 

1  La  Place  :  Mecaniipie  celeste  snpp.  au  liviv  x.  Euvres  t.  iv.  p.  389.  Gauss  :  Comment  Soc.  scient. 
Gott.,  vii.  p.  39,  1829-1832.  Canot:  Physics,  trans!,  by  Atkinson,  p.  98  Loudon,  1870.  W'eisbach  : 
mechanics,  transl.  by  Coxe,  vol.  i.  p.  762.  SVv.  V..rk.  1872.  Maxwell:  Theory  of  11. at,  p.  2>n.  >,V\v 
York,  1877. 


208  osmosis. 

tides  of  the  substance  and  those  of  its  menstruum,  but  also  upon  the 
fact  that  when  the  cohesive  force  holding  together  these  particles  ceases 
to  act  the  particles  become  separated,  repel  each  other,  they  acting  then 
like  the  particles  of  a  gas.  Thus,  if  ice  be  dissolved  by  sulphuric  acid, 
the  latter  will  diffuse  equally  through  the  water,  whatever  the  volume  of 
the  latter  may  be.  The  diffusion  of  liquids  depends,  therefore,  upon 
the  affinities  existing  between  the  particles  of  which  the  liquids  consist 
and  a  repelling  force  of  the  same. 

Many  interesting  and  important  facts  in  reference  to  the  diffusion  of 
liquids  have  been  established,  more  particularly  by  the  researches  of 
Graham.1  It  is  not  essential,  however,  that  we  should  dwell  upon  these, 
merely  indicating  that  the  diff'usibilitv  of  liquids  differs  very  much, 
according  to  their  density,  composition,  the  character  of  the  septum, 
temperature,  etc. 

On  account,  however,  of  its  important  application  to  physiology  it 
is  necessary,  before  leaving  the  subject  of  diffusion,  to  call  attention 
to  the  distinction  made  by  Graham  between  what  this  physicist  calls 
crystalloids  and  colloids,  and  which  can  be  well  illustrated  by  the  fol- 
lowing simple  experiment :  If  a  piece  of  potassium  bichromate,  or  a  little 
of  the  same  substance  in  powder,  be  placed  in  the  centre  of  a  mass  of 
boiled  starch,  in  a  few  hours  the  whole  of  the  starch  will  be  seen  colored, 
the  potash  having  diffused  through  it.  On  the  other  hand,  if  a  piece 
of  caramel  be  similarly  placed  on  a  mass  of  boiled  starch,  it  will  remain 
where  placed,  not  diffusing  at  all.  Substances  which  diffuse  readily,  like 
the  salts  of  potassium,  are  termed  crystalloids,  while  those  that  do  not  do 
so  are  called  colloids.  Thus,  in  the  experiment  with  the  egg,  the  sodium 
chloride,  being  a  crystalloid,  diffuses  through  the  egg  membrane,  while 
the  albumen,  being  a  colloid,  remains  within  the  egg.  The  method  of 
dialysis  of  Graham,  so  useful  as  an  instrument  of  analysis,  is  based 
upon  this  distinction  of  crystalloids  :  thus,  if  a  fluid,  consisting  of  a  mix- 
ture of  organic  matter  and  arsenic,  be  placed  in  an  endosmometer,  in 
the  course  of  twenty-four  hours,  perhaps,  three-fourths  of  the  arsenic 
will  diffuse  through  the  membrane  into  the  surrounding  water,  the 
organic  matters  remaining  within  the  jar.  The  application  of  the  facts 
of  capillarity  and  diffusion  in  the  explanation  of  osmosis,  as  illustrated 
by  the  above  experiments,  is  so  evident,  that  it  may  appear  superfluous 
to  dwell  further  upon  the  subject.  We  will,  therefore,  merely  call 
attention  to  the  most  important  conditions. 

In  all  the  experiments  which  have  just  been  described  it  is  perfectly 
clear  that  the  first  condition  of  osmosis  is  that  the  liquid  shall  wet  the 
membrane,  or,  in  other  words,  that  the  membrane  is  capable  of  imbi- 
bition. This,  we  have  seen,  is  due  to  capillary  force.  The  second 
condition  is,  that  the  liquids  having  been  imbibed  by  the  membrane  are 
miscible,  or  will  diffuse,  otherwise  they  would  get  no  further  than  the 
interstices  of  the  membrane,  and  there  would  be  no  currents.  The 
modifications  of  the  phenomena,  according  to  whether  the  septum  is 
solid,  liquid,  or  semi-solid,  as  to  whether  the  current  is  cndosmotic  or 

i  Phil.  Trans.,  1850 


CONDITIONS    FAVORING    ABSORPTION.  209 

exosmotic,  of  the  relative  force  of  the  two,  etc.,  can  be  shown  to  depend 
upon  these  two  conditions. 

Having  gone  over  this  preliminary  ground,  let  us  now  see  whether 
the  established  facts  of  capillarity  and  diffusion,  and  the  theorv  of 
osmosis  deduced  from  them,  can  be  applied  to  the  explanation  of 
absorption,  as  it  takes  place  in  the  living  body. 

During  absorption  from  the  alimentary  canal  we  have  seen  the 
digested  food  in  a  liquid  or  semi-liquid  state  pass  through  the  epithe- 
lium, and  the  wall  of  a  capillary  or  lymphatic  into  the  blood  or  lymph. 
The  epithelium  and  capillary  wall  in  the  living  body  are  comparable, 
therefore,  to  the  septum  of  the  endosmometer,  the  liquids  in  the  intes- 
tinal canal  and  the  blood  and  lymph  corresponding  to  the  fluids  sepa- 
rated by  the  septum  in  that  instrument. 

The  action  of  a  hydragogue  cathartic,  such  as  magnesium  sulphate, 
is  also  an  illustration  of  osmosis,  since  the  salt  passes  from  the  interior 
of  the  alimentary  canal  through  the  epithelial  layer  of  the  intestine  and 
wall  of  the  capillary  into  the  blood,  and  the  watery  part  of  the  blood, 
together  with  some  albumen  (the  latter  effect  being  due,  probably,  to 
the  presence  of  the  saline),  passes  into  the  interior  of  the  alimentary 
canal.  The  osmosis  can  be  experimentally  imitated  by  placing  the 
solution  of  the  magnesium  sulphate  within  the  jar  of  the  endosmometer 
and  the  serum  of  the  blood  within  the  bulbous  tube,  the  serum  passing 
through  the  membrane  into  the  magnesium  sulphate,  and  the  latter 
passing  into  the  serum  and  increasing  its  volume. 

Supposing  that  the  jar  represents  the  alimentary  canal,  and  the  bul- 
bous tube  the  bloodvessel,  the  osmosis  going  on  in  the  experiment  is 
essentially  the  same  as  that  in  the  living  body  after  the  administration 
of  a  hvdragoffue  cathartic. 

The  only  essential  difference  between  the  osmosis  that  takes  place 
during  absorption  and  after  the  administration  of  a  saline  and  in  an 
endosmometer  is  that  the  conditions  which  favor  osmosis  are  realized  in 
a  way  and  to  an  extent  in  the  living  body  that  cannot  be  imitated  for  a 
moment,  even  in  the  most  delicate  experiments.  Thus,  it  has  been 
found  that  the  activity  of  osmotic  currents  is  in  proportion  to  the 
extent  and  thinness  of  the  membrane.  When  we  come  to  study  the 
capillary  system  we  shall  see  that  the  extent  of  absorbing  surface  exposed 
by  it  is  enormous,  and  that  the  walls  of  the  capillaries  are  extremely 
delicate,  measuring,  on  an  average,  perhaps  from  the  12Q((()th  to  the 
•? 5  o  o  o th  °f  an  incn  m  diameter. 

One  can  readily  imagine  how  favorable  such  a  thin  septum  would  be 
in  the  production  of  osmosis.  It  can  be  shown,  also,  as  might  have 
been  supposed,  that  an  endosmotic  current  is  favored  by  having  little 
or  no  pressure  to  overcome,  such  a  current  ceasing  and  beginning 
again,  according  as  dense  substances,  like  mercury,  are  added  to  or 
taken  away  from  the  fluid  within  the  tube  of  the  endosmometer.  Now 
in  the  living  body  the  pressure  of  the  blood,  even  in  the  largest  arteries, 
seldom  exceeds  six  inches  of  mercury,  and  this  pressure  is  very  much 
reduced  as  the  blood  flows  into  the  capillary  and  venous  system,  so  that 
a  current  flowinn;  from  the  intestine  toward  the  blood  meets  with  no 
very  great  resistance. 

14 


210 


OSMOSIS. 


An  important,  though  not  indispensable,  condition  favoring  the  endos- 
motic  current  is  the  density  of  the  solution  in  the  bulbous  tube  of  the 
endosmometer,  the  flow  being  usually  greater  according  to  the  density  of 
the  solution.  We  find  this  to  be  the  case,  also,  in  absorption  from  the 
intestinal  cavity,  the  endosmotic  current  being  active  in  proportion  to 
the  amount  of  albumen  and  salts  in  the  blood.  Hence  the  activity 
of  absorption  after  the  administration  of  hydragogue  cathartics,  such 
drugs  diminishing  the  watery  constituents  of  the  blood,  and  so  increasing- 
its  density,  while,  at  the  same  time,  they  diminish  pressure.  Again, 
osmotic  currents  are  more  active  if  the  liquids  are  kept  in  movement. 
Thus,  when  osmosis  has  ceased,  it  can  often  be  made  to  commence 
again  by  simply  stirring  the  liquids.  It  is  evident  from  this  how  great 
and  favorable  are  the  influences  exerted  by  the  circulation  of  the  blood 
and  lymph  in  promoting  osmosis  and  absorption. 

The  importance  of  the  movement  of  the  liquids,  or  of  one  of  them,  in 
favoring  osmosis  is  shown  by  the  simple  apparatus  represented  in  Fig. 
97.     A  jar  (B),  furnished  with  two  stopcocks,  is  filled  with  a  colored 

Fig.  97. 


fluid,  litmus  water,  for  example.  To  both  stopcocks  are  fitted  equal 
portions  of  intestine  (D  and  C),  which  are  immersed  in  the  vases  of 
water  E  and  A.  Into  the  piece  of  intestine  C  is  fitted  a  siphon  (G) 
of  smaller  diameter  than  that  of  the  intestine,  a  siphon  (F)  of  as  large 
diameter  being  inserted  into  the  piece  of  intestine  D.  Both  siphons  (F 
and  G)  pass  into  the  vases  H  and  I.  The  stopcocks  of  the  reservoir  (B) 
being  opened,  the  colored  fluid  will  flow  into  the  two  pieces  of  intestine, 
but  inasmuch  as  the  small  size  of  the  siphon  G  will  offer  an  obstacle 
to  the  flow  of  the  colored  liquid  through  it  into  the  vase  I,  the  piece 
of  the  intestine  G  will  become  distended,  and  there  will  be  an  exos- 
mosis  from  it  of  the  colored  fluid  into  the  water  of  the  vase  A.  On 
the  other  hand,  the  colored  fluid  passing  readily  through  the  siphon  F, 
on  account  of  its  large  size,  the  piece  of  intestine  D  will  become  flaccid, 
and  there  will  be  a  rapid  flow  of  the  water  of  the  vase  E,  through  the 
intestine  D,  into  the  colored  fluid  flowing  through  it,  or  an  endosmosis. 


RESUME    OF    ABSORPTION.  211 

Finally,  an  increase  of  temperature  promotes  osmosis ;  the  high  tem- 
perature of  the  living  body  is,  therefore,  another  favorable  condition  in 
producing  this  phenomenon.  It  is  very  probable,  also,  that  electrical 
action  may  influence  the  production  of  osmotic  currents  in  the  living 
body,  as  we  have  seen  to  be  the  case  in  the  experiments  of  Porrett. 
At  present,  however,  no  definite  statement  can  be  made  as  to  the 
influence  electricity  may  exert  upon  absorption. 

It  will  be  remembered  that,  in  the  experiment  with  the  egg,  attention 
was  called  to  the  fact  that  no  albumen  passed  through  the  membrane 
from  the  egg  into  the  water  of  the  glass.  So  it  is  with  the  albumen  of 
the  blood,  the  flow  of  the  contents  of  the  intestine  being  toward  the 
albumen  of  the  blood,  as  the  flow  of  the  water  is  toward  the  albumen 
of  the  egg.  Indeed,  albumen  is  one  of  the  most  powerful  of  endosmotic 
substances.  On  the  other  hand,  albuminose  is  readily  absorbed  by  the 
bloodvessels  ;  the  significance  of  the  conversion  of  albumen  into  albumi- 
nose by  the  gastric  juice  becomes  now  very  evident. 

The  theory  of  absorption  that  we  have  just  sketched  is  that  almost 
universally  accepted  by  physiologists,  at  least  so  far  as  concerns  the 
absorption  of  albuminose,  glucose,  salts,  water,  etc. 

There  are,  however,  still  differences  of  opinion  as  to  whether  the 
absorption  of  fats  can  be  explained  in  this  way.  It  seems  to  us  that 
the  want  of  success  in  demonstrating  the  passage  of  fats  through  mem- 
branes out  of  the  body  has  often  been  due  to  the  fact  that  the  proper 
conditions  for  the  success  of  the  experiment  were  not  realized. 

It  will  be  remembered  that,  during  digestion,  the  fat  is  emulsified, 
and  becomes  mixed  with  the  bile,  alkaline  fluids,  etc.,  and  that,  during 
absorption,  this  modified  fat  passes  into  an  alkaline  fluid,  the  lymph.  It 
is  essential,  therefore,  that  these  conditions  should  be  fulfilled  if  we 
wish  to  demonstrate  the  osmosis  of  fat  out  of  the  body.  First,  then, 
we  must  make  an  emulsion  of  fat,  for  example,  by  adding  pancreatin 
to  olive  oil,  and  then  make  this  distinctly  alkaline  by  adding  bile  or  a 
sodium  salt.  Place  the  alkaline  emulsified  fat  in  the  jar  of  the  endos- 
mometer,  making  the  water  of  the  bulbous  tube  distinctly  alkaline  also, 
so  as  to  resemble  the  alkaline  lymph.  If  the  water  in  the  reservoir  be 
examined  some  hours  afterward,  the  fat  will  be  found  floating  in  drops 
upon  the  surface,  it  having  osmosed  through  the  membrane. 

Resume. — We  have  seen  that,  as  fast  as  the  food  is  digested,  it  is 
absorbed,  the  albuminose,  glucose,  salts,  and  water  being  taken  up  by 
the  radicles  of  the  portal  vein,  the  fats  by  the  lymphatics  of  the  small 
intestine,  or  the  lacteals,  often  a  small  quantity  of  albuminose,  etc. , 
passing  into  the  lymphatics,  the  portal  vein  taking  up,  also,  occasionally, 
some  fat,  and  that  the  absorption  of  food  is  an  illustration  of  osmosis,  the 
latter  depending  upon  capillary  attraction  and  the  diffusion  of  liquids. 
Whichever  of  the  two  routes  is  taken  by  the  digested  food  in  absorp- 
tion, the  essential  fact  is  that  it  gets  into  the  blood  sooner  or  later, 
and  thence  is  carried  by  the  circulation  to  all  parts  of  the  economy, 
repairing  the  waste  of  the  tissues  and  supplying  the  fuel  for  the  main- 
tenance of  the  heat  of  the  body  and  development  of  force. 

The  composition  and  circulation  of  the  blood  will  be,  naturally,  then, 
the  next  subject  for  our  consideration.    To  these,  then,  let  us  now  turn. 


CHAPTER    XIII. 

THE  BLOOD. 

From  time  immemorial  the  blood  lias  been  recognized  as  the  most 
important  fluid  in  the  human  body,  as  well  as  in  that  of  animals — in- 
deed, as  indispensable  to  life.  Daily  observation  continually  shows  that 
its  loss  prostrates  the  body  and  enfeebles  its  powers,  and,  with  excessive 
hemorrhage,  that  life  itself  ebbs  away, 

"  For  the  life  of  the  flesh  is  in  the  blood." 

This  is  readily  understood  when  it  is  known  that  the  blood  circu- 
lating- through  the  economv  is  the  source  of  the  animal  heat,  and  carries 
to  the  tissues,  and  the  cells  composing  them,  material  for  their  growth, 
renewal,  and  repair,  and,  at  the  same  time,  removes  from  them  that 
which  has  become  effete  and  worn  out  in  producing  the  phenomena  of 
life. 

This  "  peculiar  juice,"  as  the  Mephistopheles  of  Goethe  calls  it, 
represents,  therefore,  the  life  of  the  day,  of  the  past,  and  of  the  morrow. 
Let  us  consider  first  its  physical  characteristics. 

The  blood  is  an  alkaline  fluid,  with  a  specific  gravity,  when  defibri- 
nated,  according  to  Becquerel  and  Rodier,1  of  from  1.05;")  to  1.063. 
The  opacity  of  the  blood  is  due  to  the  fact  that  it  is  not  a  homogeneous 
liquid,  being  composed,  as  we  shall  see  presently,  of  two  elements — cor- 
puscles and  liquor  sanguinis,  or  plasma ;  these,  differing  in  their  refractive 
power,  offer  an  obstacle  to  the  transmission  of  light,  which  is  lost 
in  its  passage  from  the  air  through  the  liquor  and  corpuscles.  The 
hlood  has  a  saltish  taste,  and  a  faint  but  distinct  odor.  This  becomes 
more  apparent  when  a  few  drops  of  sulphuric  acid  are  added  to  the 
specimen  examined.  It  may  be  mentioned,  in  this  connection,  that 
the  importance  of  the  odor  of  the  blood,  as  made  use  of  in  criminal 
cases,  and  often  insisted  upon  by  medico-legal  writers,  has  been  grossly 
exaggerated. 

The  temperature  of  the  blood  in  man,  so  far  as  is  known,  varies  from 
80°  to  100°  Fahr.,  but  it  is  very  probable  that,  in  certain  parts  of  the 
body,  it  is  several  degrees  higher.  Bernard  found  that  in  dogs  and  sheep 
the  temperature  in  the  aorta  ranged  from  99°  to  105°,  and  reached 
even  107°  in  the  hepatic  vein.  According  to  the  same  authority,  the 
blood  is  hotter  in  the  right  than  in  the  left  side  of  the  heart ;  the 
temperature  is  higher  in  the  arteries  than  in  the  veins,  with  the 
exception,  however,  of  the  blood  in  the  portal  vein,  which  is  warmer 
than  that  in  the  aorta  independently  of  digestion.2  The  sudden  rise  of 
temperature  often  observed  in  man  just  before  death,  due,  perhaps,  to 
the  loss  of  vascular  tonicity,  would  seem  to  show  that  the  temperature 

1  Traite  de  Chemie  Pathologique,  p.  95.     Paris,  1854. 

2  Sur  los  Liquides  de  l'Organisme,  tome  i.,  3d,  4th,  5th  lecons. 


QUANTITY    OF    BLOOD    IN    HUMAN    BODY.  213 

of  the  blood  in  the  deeper  vessels  in  man  is  as  high  as  that  observed 
by  Bernard  in  the  animal  just  mentioned. 

One  of  the  most  striking  features  of  the  blood  is  its  color,  red  or 
scarlet  in  the  arteries,  blue  or  black  in  the  veins.  As  first  demonstrated 
by  Lower,1  this  difference  is  due  to  the  venous  blood  absorbing  air  as  it 
passes  through  the  lungs.  When  we  come  to  study  the  circulation  and 
respiration,  we  shall  see  that,  as  the  red  blood  passes  through  the 
capillaries  it  loses  oxygen  and  gains  carbonic  acid,  becoming  blue,  while 
it  turns  again  into  red  blood  in  the  lungs  with  the  fresh  absorption  of 
oxygen.  The  blood  of  the  pulmonary  artery,  however,  is  blue,  while 
that  of  the  pulmonary  vein  is  red.  The  blood  in  the  veins  coming  from 
glands,  during  secretion,  as  shown  by  Bernard,2  is  also  red,  and  this  is 
the  case  also  in  the  veins  when  the  sympathetic  is  cut.  The  explana- 
tion in  these  cases  seems  to  be  that  the  increased  supply  of  arterial 
blood  to  the  parts  carries  an  excess  of  oxygen  to  the  veins  sufficient  to 
maintain  the  red  color  of  the  blood  flowing  into  them. 

The  brightness  in  color  of  the  blood  depends,  to  a  certain  extent, 
upon  the  form  of  the  corpuscles ;  it  is  bright  w hen  they  are  flattened 
and  hollowed,  containing  oxygen,  and  dark  when  they  are  distended 
and  round,  containing  carbonic  acid,  the  reflection  of  the  light  depend- 
ing on  the  form  of  the  corpuscles. 

Numerous  experiments  have  been  made  from  time  to  time  to  deter- 
mine, if  possible,  the  quantity  of  blood  in  the  human  body.  Among 
others  may  be  mentioned  those  of  Valentin,  Blake,  Lehmann,  and 
Weber.  Valentin's  method3  consisted  in  injecting  into  the  circulation 
of  an  animal  a  given  quantity  of  a  saline  solution  and  then  drawing 
some  blood,  estimating  by  evaporation  the  proportion  of  the  w7aterto  the 
blood,  and  then  comparing  the  excess  of  water  with  that  of  a  quantity 
of  blood  drawn  previously.  Suppose  that  the  excess  of  water  in  the 
specimen  drawn  after  the  saline  injection  wras  one  part  of  water  to  ten 
of  blood,  and  that  five  ounces  of  water  had  been  injected,  then  the  quan- 
tity of  blood  would  be  fifty  ounces. 

Blake4  experimented  by  injecting  sulphate  of  aluminium  and  then 
ascertaining  the  amount  of  the  sulphate  in  a  given  quantity  of  blood 
drawn,  arguing  that  the  wdiole  quantity  of  the  sulphate  injected  was  to 
that  in  the  specimen  drawn  as  the  whole  quantity  of  blood  in  the 
body  was  to  that  drawn. 

The  observations  of  Lehmann5  and  Weber  were  made  upon  twTo  crim- 
inals who  were  first  wreighed  and  then  decapitated.  The  blood  remain- 
ing in  the  vessels  after  decapitation  was  calculated  by  injecting  water 
into  the  vessels  of  the  head  and  trunk  until  that  which  passed  out  by 
the  veins  exhibited  only  a  pale  yellowish  color.  This  was  evaporated 
and  the  dry  residue  was  assumed  to  represent  a  certain  quantity  of 
blood,  the  ratio  of  blood  to  its  residue  having  been  previously  ascer- 
tained. The  amount  of  blood  lost  by  decapitation  was  a  little  over 
twelve  pounds,  and  that  estimated  by  the  above  method  as  remaining 

i  Tractatus  de  Corde  item  de  Motu  et  Colore  Sanguinis,  p.  180.     Amstelodarui,  1669. 

-  Op  cit.,  pp.  268,  299. 

:  Repertorium  fur  Anat.  und  Phys.,  1837,  Band  ii.  S.  281. 

*  Philadelphia  Medical  Examiner,  August,  1841'. 

5  Lehrtrach  der  Phys.  Chemie,  L852,  tome  ii.  S.  234. 


214  THE    BLOOD. 

in  the  vessels  as  a  little  over  four  pounds,  making  for  the  whole  hody 
16.59  pounds. 

Table  XL.1 — Amount  of  Blood  in  the  Body. 

12  lbs.  of  blood  lost  in  execution. 

4    "    of  blood  collected  by  washing. 
16    "    of  blood  in  criminal  weighing  128  lbs.,  or 

1    "    of  blood  to  8  of  body  weight. 

The  weight  of  one  of  the  criminals  was  132.7  pounds  ;  this  would  give 
a  ratio  of  about  one  pound  of  blood  to  every  eight  of  body,  which  is 
about  what  physiologists  generally  assume.  It  must  be  remembered, 
however,  that  this  is  only  an  approximation,  for  the  amount  of  blood 
left  in  the  body  after  decapitation  cannot  be  accurately  determined  by 
the  method  just  mentioned.  Further,  the  amount  of  blood  in  the  body 
is  notably  increased  during  digestion.  Bernard2  has  shown  that  an 
animal  like  the  rabbit,  for  example,  during  digestion  can  lose  twice  as 
much  blood  as  when  fasting.  Burdach3  refers  to  a  case  reported  by 
Wrisberg  of  a  woman  losing  over  twenty-one  pounds  of  blood  after  de- 
capitation. Facts  like  these  show  the  importance  of  taking  into  con- 
sideration the  state  of  the  system  in  determining  the  quantity  of  blood. 
In  a  general  way  this  may  be  stated  in  an  adult  healthy  man  to  amount 
to  sixteen  or  twenty  pounds  and  is  distributed,  according  to  Ranke,4  in 
round  numbers  as  follows  : 

\  vascular  system.  J  skeletal  muscles. 

',  liver.  I  remaining  organs. 

When  the  blood  is  examined  under  the  microscope,  for  example,  cir- 
culating in  the  web  of  a  living  frog's  foot,  it  will  be  seen  to  consist,  as 
already  mentioned,  of  two  distinct  portions,  a  transparent  colorless 
liquid,  the  liquor  sanguinis  or  plasma,  and  of  minute  bodies  or  corpus- 
cles, the  blood  globules  or  blood  cells.  These  corpuscles,  which  float  in 
the  liquid  part  of  the  blood,  are  of  two  kinds,  the  white  and  the  red. 
The  latter,  discovered  by  Leuwenhoek5  in  1673,  are  far  more  numerous 
than  the  former  and  give  to  the  blood  its  red  color,  they  being  carriers 
of  oxygen. 

Let  us  study  the  red  corpuscles  first  and  then  the  white,  reserving 
for  the  present  the  consideration  of  the  plasma. 

When  blood  is  examined  under  the  microscope  the  corpuscles  will  be 
observed  in  different  positions,  some  on  their  edges  or  sides,  others  lying 
flat  (Fig.  98).  It  can  be  seen  that  they  are  circular,  flattened  disks, 
about  four  times  as  broad  as  thick  and  biconcave  in  form.  From  this 
latter  circumstance  they  are  thinnest  in  the  centre.  Therefore,  when  a 
corpuscle  is  viewed  under  the  microscope  from  the  flat  side,  if  the  edges 
are  in  focus  the  centre  will  appear  dark,  simulating  a  nucleus  (Fig.  99) ; 
wdiereas,  when  the  centre  is  in  focus  and  is  light  the  edges  will  appear 
dark  (Fig.  100).  In  reality,  however,  there  is  neither  a  nucleus  nor  a 
membranous  cell-wall,  the  red  corpuscle  being  a  homogeneous  structure- 

1  Lehniann,  op.  cit.  2  Op.  cit.,  tome  i.  p.  419. 

3  Traite  de  Physiologie  traduit,   par  Jourdain,  tome  vi.  p.  116.     Paris,  1837. 

*  Phvsiologie,  1871,  S.  373.  5  philos.  Transactions,  p.  23.     London,  1674. 


RED    CORPUSCLES. 


215 


Fig.  98. 


less  mass  of  living  matter,  soft,  transparent,  elastic,  and  of  a  pale  amber 
color.     The  red  color  of  the  blood  is  due  to  the  immense  number  of  the 
corpuscles.     Vierordt1  estimates 
that  a  cubic  millimetre  in  the 
male  contains  5,000,000,  in  the 
female  4,500,000. 

The  method  we  make  use  of 
in  counting  the  blood  corpus- 
cles is  essentially  that  of  Malas- 
sez  and  Potain2  and  Gowers.3 
It  consists  in  sucking  up  into  a 
graduated  tube  (Fig.  101,  A)  one 
cubic  millimetre  (^g-th  of  an 
inch)  of  blood  and  then  a  five  per 
cent,  solution  of  sodium  chloride 
from  a  jar  into  the  tube  until 
the  blood  and  the  solution  are 
drawn  into  and  fill  the  dilated 
portion  (Fig.  101,  B)  of  the 
tube.  This  dilated  portion  hav- 
ing a  capacity  of  100  milli- 
metres, the  blood  will  then  be 
diluted  100  times.  One  milli- 
metre of  this  mixture  will,  there- 
fore, contain  the  y^nj-th  of  a 
millimetre  of  blood  and  the 
of  a  millimetre  of  the 
or  the 
md  salr  s 


Human  blood  as  seen  on  the  warm  stage  Magnified 
about  1200  diameters,  c,  c.  Crenate  red  corpuscles,  p. 
A  finely  granular,  g.  A  coarsely  granular  pale  corpus- 
cle. Both  exhibit  two  or  three  vacuoles.  In  g  a  nu- 
cleus also  is  visible.     (Quain.) 


1     tl 

10  0  ll 

mixture  y^-jyth  of  ywo  tn 
mixture  of  blood 


1 0 1 0  0  th  of  a  millimetre  of  blood.     This 
olution  is  then  forced  out  on  an  object  glass 


Fig.  99. 


Fig.  100. 


Red  globules  of  the  blood,  seen  a  little  beyond 
the  focus  of  the  microscope.     (Dalton.) 


The  same,  seen  a  little  within  the  focus. 
(Dalton.) 


l  Physiologie,  S.  9.     Tubingen,  1871. 

-  Aii  hiv  de  Physiologie,  p.  ;!:>.     Paris,  1876. 


S  Lancet,  1877,  p.  797. 


211) 


THE     BLOOD. 


(Fig.  102,  C)  which  under  the  microscope  is  seen  to  be  divided  into  ten 
squares,  each  of  which  when  covered  by  the  compressorium  (Fig.  102,  D) 


Fig.  L01. 


Fig.  102. 


Graduated  moist  chamber  with  compressorium. 


has  a  capacity  of  the  yg-g-th  "^  a  millimetre.  Each 
square  will  then  contain  the  y^-g-th  of  a  millimetre  of 
the  mixture,  and  consequently  will  contain  the  y^tl! 


of 


-1— th 

1  o  o  U1 

Further, 


or 


tht 


4-n-n-th  of  a  millimetre  of  blood. 


ioo  oo; 

it  will  be   noticed  that  each  square  (Z>)  is 

subdivided  into  twenty  smaller  squares,  the  object  of 
which  is  to  facilitate  the  counting  of  the  corpuscles. 
Suppose  now,  for  example,  that  twenty-five  corpuscles 
could  be  counted  on  each  of  the  small  squares,  then  the 
large  square  would  contain  500  corpuscles;  but  as  the 
large  square  contains  only  the  10oootn  °^ a  uiillimetre 
of  blood,  it  follows  that  one  cubic  millimetre  (^g-th 
of  an  inch)  will  contain  500  x  10,000,  or  5,000,000 
corpuscles. 

The  division  of  the  object  glass  into  ten  squares  is 
to  enable  one  to  make  ten  independent  observations, 
so  as  to  obtain  an  average  result.  A  cubic  inch  of 
blood  will  contain,  therefore,  over  70,000,000,000 
red  blood  -  corpuscles,  or,  according  to  Huxley,1 
more  than  eighty  times  the  number  of  people 
upon  the  globe,  or  on  the  supposition  that  the 
blood  of  the  whole  body  amounts  to  sixteen  pounds 
or  112,000  grains,  and  that  one  cubic  inch  of  blood  weighs  168  grains, 
the  whole  blood  will   contain  over  forty  trillion  red  corpuscles. 


112(HMI 

168 


=  607  X  70,000,000,000  =  40,000,000,000,000  corpuscles. 


The  specific  gravity  of  the  corpuscles  is  a  little  higher  than  that  of 
the  liquor  sanguinis,  being  about  1.085.  On  observing  the  corpuscles 
in  blood  removed  from  the  body,  it  will  be  noticed  that  soon  a  number 
of  them  run  together,  forming  a  chain-like  rouleaux  of  coin  (Fig.  98). 


Elementary  Physiology,  London,  3  1  id.,  p.  78. 


RED     CORPUSCLES. 


217 


This  is  due,  according  to  Robin,1  to  an  exudation  from  the  corpuscles 
themselves  which  causes  them  to  adhere  to  each  other.  Shortly  after 
the  blood  is  drawn  the  corpuscles  will  exhibit  also  small  prominences  on 
their  surfaces,  giving  them  a  raspberry-like  appearance,  and  as  they 
become  dry  they  shrivel  up  and  their  edges  become  crenated  (Fig.  98). 
The  shape  of  the  corpuscles,  however,  can  be  restored  even  after  the 
lapse  of  months  and  years  by  treating  them  with  a  fluid  of  the  density 
of  serum  (1.028).  This  fact  is  important,  from  a  medico-legal  point 
of  view,  in  reference  to  determining  whether  a  stain  upon  clothing  or 
floors,  etc.,  is  blood. 

The  corpuscles  swell  up  and  dissolve  when  pure  water  is  added  to 
them,  and  acetic  acid  and  other  acids  have  the  same  effect. 

Under  the  influence  of  alkalies  the  corpuscles  instantly  swell  up, 
appear  to  burst,  and  then  entirely  disappear.  The  effect  of  heat  is  to 
produce  in  them  bud-like  processes.  In  studying  the  effects  of  such 
reagents  as  those  just  mentioned,  as  well  as  others,  the  apparatus  repre- 
sented in  Fig.  103,  which  is  to  be  placed  on  the  stage  of  the  micro- 

Fig.  103. 


Strieker's  warm  stage. 

s*cope,  will  be  found  useful.  It  consists  of  a  brass  box  opening  laterally 
by  two  tubes,  with  a  solid  rod-like  projection  in  the  middle,  and  per- 
forated in  the  centre.  The  central  aperture  can  be  converted  int<>  a 
chamber  by  cementing  to  its  lower  opening  a  cover  glass.  Surround- 
ing this  central  chamber  is  coiled  the  bulb  of  a  thermometer,  whose 
registering  surface  is  attached  externally  to  the  side  of  the  box. 

1  Journal  de  la  Phy-iolosie,  tonic  i.  p.  "295.     Paris,  1858. 


218  THE    BLOOD. 

By  connecting  one  of  the  lateral  apertures  opposite  the  projecting 
rod  of  the  box  with  the  reservoir  of  hot  water  and  the  other  with  a 
waste  pipe  a  constant  flow  of  hot  water  through  the  brass  box  is  insured, 
and  the  temperature  of  the  central  chamber  regulated  as  desired  by  the 
thermometer. 

By  screwing  on  to  the  rod-like  projection  of  the  brass  box  a  rod  of 
the  same  metal  and  heating  its  free  end  by  a  spirit  lamp,  the  tempera- 
ture can  also  be  elevated  as  required. 

If  it  is  desired  to  study  the  action  of  water  upon  the  blood  corpuscles, 
for  example,  the  apparatus  is  used  in  the  following  way  :  A  drop  of 
water  is  placed  on  the  floor  of  the  chamber,  and  a  drop  of  blood,  usually 
diluted  with  salt  solution,  upon  a  cover-glass ;  the  latter  is  then  placed 
inverted  over  the  chamber,  the  edges  of  which  have  been  previously 
oiled  or  surrounded  with  a  ring  of  putty,  so  as  to  make  the  chamber 
air-tight.  By  allowing  the  hot  water  to  flow  through  the  brass  box,  or 
heating  the  end  of  the  rod  by  the  spirit  lamp,  the  drop  of  water  on  the 
floor  of  the  chamber  is  made  to  evaporate,  and,  condensing  on  the  under 
surface  of  the  cover-glass,  gradually  affects  the  blood-corpuscle  it  meets 
there. 

The  effects  of  heat  simply  upon  the  blood  corpuscles  can  be  studied 
by  placing  the  blood  to  be  examined  upon  a  cover-glass,  and  dropping 
this  upon  another  glass  of  the  same  size,  the  edges  of  which  have  been 
previously  smeared  with  oil,  and  then  placing  the  two  glasses  with  the 
blood  and  oil  so  inclosed  over  the  opening  of  the  chamber.  Further, 
by  means  of  the  tubes  which  open  into  the  chamber,  a  current  of  gas 
can  be  made  to  pass  through  the  latter,  and  its  effects  studied  upon  the 
blood  placed  upon  a  cover-glass  and  inverted  over  the  chamber,  in  the 
manner  just  described  in  studying  the  effect  of  water. 

The  effect  of  electricity  upon  the  corpuscle  is  to  convert  it  temporarily 
into  rosette-,  mulberry-,  and  finally  horsechestnut-shaped  forms.  To 
demonstrate  this  effect,  we  usually  make  use  of  the  electrical  microscopic 
stage,  placing  the  drop  of  blood  upon  the  slide  in  such  a  position  that 
when  covered  it  spreads  out  between  the  two  poles  of  tinfoil,  Avhich  are 
about  six  millimetres  apart  and  connected  either  with  a  Leyden  jar 
having  a  surface  of  500  square  centimetres,  or  by  a  Du  Bois-Reymond 
induetorium  fed  by  a  single  Bunsen  cell,  according  to  the  kind  of 
electricity  to  be  used. 

According  to  the  high  authority  of  Gulliver,1  the  average  diameter 
of  the  red  blood-corpuscle  is  the  ^Vo^1  of  an  inch,  with  an  average 
thickness  of  about  the  T^Foth  of  an  inch.  The  diameter,  however, 
varies  as  much  as  from  the  ygVo^1  to  tne  40^0^  °f  an  incn-  The 
importance  of  remembering  these  variations  will  be  seen  presently. 

1  In  Works  of  William  Hewsou,  Sydenham  edition,  p.  237.     London,  184'i. 


DIAMETERS    OF    RED    BLOOD-CORPUSCLES. 


219 


Table  XLI.1 — Blood  Corpuscles. 
Mammals. 


Animal. 

Manatee  . 

Elephant 

Ant-eater 

Sloth 

Whale      . 

Camel 

Man 

Orang 

Chimpanzee 

Dog. 

Opossum  . 

Rabbit     . 

Black  Rat 

Mouse 

Bmwn  Bat 

Cray  Squirrel 

Ox   . 

Cat  . 

Sheep 

Goat 

Pigmy  Musk  Deer 

( >strich     . 
Owl . 
Swan 
Pigeon 

Turtle 
Viper 
Lizard 


Birds 


Reptiles. 


Diameter. 

1 

of  an  inch. 

2700" 

1 

U                  ,i 

^745 

1 

a            a 

27(39 

1 

a            it 

2865 

1 

a            t. 

3099 

1 

it            a 

3123 

1 

" 

3200 

1 

tt 

3383 

1 

a            a 

34lT 

1 

it             a 

3542 

1 

a            (i 

3557 

1 

it 

3607 

1 

a             ,t 

3754 

1 

a             . . 

3814 

1 

a            it 

3911 

1 

a            t. 

4000 

1 

a            a 

4267 
1 

4404 

1 

a            t. 

5300 

1 

a 

6366 

1 

a            it 

12325 

1 

a            a 

1649 

1 

n            a 

17(33 

1 

n            t. 

1806 

1 

a            t . 

1973 

1 

a            a 

12.il 

1 

a 

1274 

1 

it             a 

[555 

1  Drawn  up  principally  from  table  of  Gulliver,  op.  cit  ,  p.  237,  and  observations  of  author. 


220  THE    BLOOD. 


Amphibia. 

\iiimal.  Diameter. 

A.mphiuma      ......  of  an  inch. 

1  363 


Proteus    . 

Siren 

Menopoma 


i 

40(1 
1 

42U 
1 


Pushes. 


i 

20(1(1 

Perch L 

20 
1 

2134 


Pike 


Lamprey 


While  there  is  not  always  a  proportional  relation  between  the  size  of 
the  blood  corpuscle  and  that  of  the  animal — that  of  the  ox,  for  ex- 
ample, being  smaller  than  that  of  man  or  the  dog  (Table  XLI.) — Milne 
Edwards1  has  shown  by  a  comparison  of  the  size  of  the  blood  corpuscle 
in  the  five  classes  of  vertebrates,  that  there  does  exist  a  most  remarkable 
connection  between  the  size  of  the  corpuscle  and  the  degree  of  nervo- 
muscular  power  of  the  animal ;  the  corpuscles  being  small  in  the  most 
highly  developed  and  active  vertebrates,  and  large  in  those  least  so.  It 
will  be  seen  also,  more  particularly,  that  the  size  of  the  corpuscle  is 
most  intimately  related  to  the  activity  of  the  respiration,  the  corpuscle 
being  smallest  in  those  animals  whose  respiration  is  the  most  active,  and 
largest  in  those  in  which  this  function  is  slow.  This  might  be  expected, 
as  a  large  number  of  small  corpuscles  offer  a  larger  absorbing  surface 
to  the  oxygen,  the  respiratory  element,  than  a  small  number  of  large 
ones.  As  we  proceed  we  shall  see  that  muscular  is  largely  dependent 
upon  respiratory  activity.  Hence,  if  the  above  view  be  correct,  we 
should  expect  to  find  the  blood  corpuscles  smallest  in  the  active  verte- 
brates and  largest  in  the  sluggish  ones. 

On  comparing  the  size  of  the  blood  corpuscles  in  the  mammalia 
with  those  of  the  reptilia  or  batrac'hia  (Table  XLI.),  we  find  such  to  be 
the  case.  Of  course,  if  this  comparison  be  carried  out  to  extreme 
detail,  there  will  be  found  exceptions  to  the  rule,  for  no  doubt  other 
conditions  beside  those  of  respiration  influence  the  size  of  the  corpuscles, 
possibly  the  character  of  the  food,  etc.;  but  that  the  connection  just 
referred  to  is  something  more  than  mere  coincidence  seems  to  be  fully 
justified  by  Milne  Edwards's  elaborate  survey  of  the  facts. 

It  will  be  seen  from  Table  XLI.  that  there  are  a  few  mammals  in 
which  the  blood  corpuscles  are  larger  than  those  of  man,  and  that  the 
blood  corpuscle  of  the  pigmy  deer  (Tragulus)  is  the  smallest  known, 
while  those  of  a  batrachian,  the  amphiuma,  are  the  largest. 

The  exact  size  of  the  red  blood-corpuscle  in  man  is  not  only  of 
interest  physiologically,  but  also  from  a  medico-legal  point  of  view. 
Attention  has  already  been  called  to  the  fact  that  there  is  a  consider- 
able variation  in  the  size  of  the  human  corpuscles,  and  hence  it  is  often 
impossible  to  say  positively  whether  a  given  corpuscle  came  from  a 
human  being's  blood  or  that  of  an  ape,  dog,  rabbit,  rat,  mouse,  or  ox, 

1  Physiologie,  tome  i.  p.  57. 


RE])    BLOOD-CORPUSCLES    OF     VERTEBRATES 


221 


for  the  average  diameter  of  the  corpuscles  in  these  animals  is  within  the 
limits  of  the  variations  that  have  been  mentioned  as  occurring  in  man. 

When  a  large  quantity  of  human  blood  is  examined,  probably  ninety- 
five  corpuscles  out  of  every  hundred  will  exhibit  the  same  diameter,  but 
in  a  medico-legal  investigation  the  amount  of  blood  put  at  the  disposal 
of  the  expert  is  often  exceedingly  small — an  old  blood-stain,  a  single 
drop,  perhaps,  and  possibly  the  variable  corpuscles  contained  in  this  very 
drop.  Now,  as  the  size  of  the  corpuscle  in  the  dog  or  the  ox  varies  as 
well  as  that  of  man,  if  the  size  of  the  corpuscle  in  the  suspected  fluid  is 
only  taken  into  consideration,  the  blood  of  a  dog  might  be  determined 
to  be  that  of  a  man,  and  vice  versa.  In  fact,  it  is  impossible  to  say 
beyond  the  shadow  of  a  doubt  that  a  given  drop  of  liquid  is  human 
blood  and  not  that  of  the  animals  referred  to  above,  for  the  small  size 
of  the  variable  human  corpuscle  might  lead  the  examiner  to  think  the 
human  blood  had  come  from  a  dog  or  a  mouse,  while  from  the  variable 
large  corpuscles  in  the  blood  of  these  animals  there  might  be  a  suspicion 
that  their  blood  was  human. 

With  the  exception  of  the  camel  and  llama,  in  which  the  red  blood- 
corpuscles  are  oval,  the  form  of  these  bodies  in  the  mammalia  thus  far 
examined  is  circular,  which  adds  to  the  difficulty  of  distinguishing  the 


Fig.  104. 


Typical  char 


blood  of  the  domestic  mammals  from  that  of  man.  On  looking  at  Fiji. 
104,  it  will  be  seen  that  the  red  blood-corpuscles  in  birds,  reptiles, 
batrachia.  and  fishes  differ  from  those  of  man  and  the  mammalia  gener- 


222  THE    BLOOD. 

ally  in  being  oval  in  form  and  in  exhibiting  a  well-marked  nucleus,  and 
in  being  much  larger. 

The  only  partial  exceptions  to  the  above  statement  are  offered  by  the 
oval  corpuscles  of  the  dromedary  and  llama;  but,  as  will  be  seen  from 
Fie  104,  they  are  not  nucleated.  At  the  other  end  of  the  vertebrate 
series  we  find  a  further  exception,  in  the  nearly  circular  corpuscles  of 
the  lamprey,  but  these  are  nucleated.  There  can  be  no  difficulty, 
therefore,  in  distinguishing  the  blood  corpuscles  of  the  birds,  reptiles, 
etc.,  from  those  of  mammals.  The  oval  form,  and  the  presence  of  a 
nucleus,  especially,  are  sufficient  to  decide  positively  that  the  blood 
containing  such  corpuscles  is  not  mammalian.  Such  knowledge  has 
been  of  advantage  more  than  once  in  assisting  in  the  detection  of  murder. 

The  most  important  use  of  the  red  blood-corpuscles  is  undoubtedly  as 
carriers  of  oxygen.  Blood  will  absorb  ten  to  thirteen  times  as  much 
oxygen  as  water,  and  this  property  depends  upon  the  corpuscles.  In 
addition  to  the  facts  already  referred  to  of  the  connection  between  the 
respiratory  power  and  the  corpuscles,  it  may  be  mentioned  that  the 
number  of  corpuscles  is  greater  in  the  active  carnivora  than  in  the  more 
sluggish  herbivora,  and  that  in  man  in  those  individuals  whose  nervo- 
muscular  energies  are  most  developed  we  find  the  greatest  number  of 
corpuscles,  whereas  in  the  ansemic  the  number  falls  below  the  standard. 

Vital  activity  of  all  kinds,  respiratory,  nervo-muscular,  etc.,  necessi- 
tates a  constant  and  free  supply  of  oxygen,  and  this  want  is  preemi- 
nently filled  by  the  circulating  blood  carrying  the  red  corpuscles  laden 
with  the  indispensable  element.  Even  apparent  exceptions,  like  the 
absence  of  the  red  corpuscles  in  insects  offers,  are  really  no  exceptions 
to  the  above  statement  of  the  importance  of  oxygen,  for  in  those  animals 
which  exhibit  such  remarkable  nervo-muscular  power  the  oxygen  is  car- 
ried directly  to  the  tissues  by  the  tracheal  system  or  tubes  permeating 
their  entire  bodies,  and  hence  there  is  no  necessity  for  red  blood- 
corpuscles. 

In  the  remaining  vertebrata  the  amount  of  carbonic  acid  and  heat 
produced  and  nervo-muscular  power  put  forth  are  about  what  might  be 
expected  from  the  character  of  their  blood  and  the  corpuscular  elements 
contained  in  it. 

In  concluding  this  sketch  of  the  red  blood-corpuscles,  it  is  proper 
that  I  should  give,  if  possible,  an  account  of  their  origin,  for  there  is 
no  doubt  that  the  life  of  the  blood  corpuscles  is  of  limited  duration. 
Abundant  evidence  of  their  disintegration  is  to  be  seen  in  different  parts 
of  the  economy,  in  the  spleen  and  in  the  liver  for  example,  in  the  form 
of  blood  crystals,  and,  as  we  have  seen,  in  speaking  of  the  coloring 
matter  of  the  bile,  that  the  bilirubin  is  polymeric  with  the  coloring 
matter  of  the  blood  or  hgematin,  it  is  probable  that  the  bilirubin  is  de- 
veloped out  of  the  corpuscles  disintegrated  in  the  liver.  According  to 
some  physiologists,  the  origin  of  the  red  corpuscles  is  entirely  unknown, 
while  it  is  held  by  others  that  they  are  developed  in  some  way  out  of 
the  white  corpuscles  of  the  blood.  To  appreciate  the  facts  brought  for- 
ward in  favor  of  the  view  that  the  red  corpuscles  are  modified  white 
ones,  it  will  be  first  necessary  to  describe  the  latter,  which  up  to  this 
time  have  been  only  incidentally  alluded  to. 

To  the  consideration  of  the  white  corpuscles  let  us  now  turn. 


CHAPTER   XIV. 


THE  BLOOD.— (Cbntinued.) 

The  white  corpuscles  discovered  by  Hewson1  about  1770.  as  their 
name  implies,  are  of  a  grayish,  whitish  color,  of  a  round  form,  and  con- 
sist of  a  mass  of  protoplasm  containing  granules.  A  cell  wall  cannot 
be  said  to  exist.  Chemically  the  white  corpuscles  are  composed  of 
albuminous  substances,  lecithin,  glycogen,  salts.2 

When  the  blood  is  maintained  at  the  temperature  of  the  body  the 
form  of  the  white  corpuscle  is  seen  to  be  constantly  changing,  alternately 
protruding  and  retracting  its  body  substance  in  an  amoebiform  manner 
(Fig.   105).     By  adding  finely  powdered   indigo  to  serum  containing 

Fig.  105. 


Various  forme  assumed  by  the  white  corpuscles  of  the  blood.  The  upper  row  represents  the  white 
corpuscles  of  man;  the  lower  row,  white  coipiuc!es  from  the  newt,  showing  changes  effected  in  fifteen 
minutes      (Carpenter.) 

white  corpuscles  the  manner  in  which  they  feed  can  be  observed,  the 
indigo  being  drawn  into  the  body  of  the  corpuscle  by  the  retraction  of  its 
amoeba-like  arms  and  then  gradually  absorbed  and  assimilated.  Under 
the  influence  of  acetic  acid  the  body  of  the  corpuscle  clears  up  and  three 
or  more  nuclei  appear.  Whether  these  nuclei  preexist  and  the  acid 
only  makes  them  apparent,  or  whether  their  appearance  is  due  to  a  kind 
of  coagulation,  has  not  yet  been  positively  determined.  By  the  con- 
tinued action  of  water  and  acetic  acid,  and  more  readily  by  alkalies,  the 
white  corpuscles  are  dissolved  and  disappear. 

The  white  corpuscle  is  larger  than  the  red  one,  measuring  on  an 
average  the  2  ^0  0 th  of  an  inch.  The  white  corpuscles  are  far  less  numer- 
ous than  the  red  ones,  being  found  usually  in  the  proportion  of  one  white 
corpuscle  to  between  300  ami  500  red  ones.  This  proportion  as  we  learn, 
however,  from  the  observations  of  Hirst,3  varies  according  to  the  state 

1  Works,  p.  282.  -  Hoppc-Seyler :  l"ntei>uchungen,  Band  iv.  S.  441. 

a  Muller's  Archiv,  1856,  p.  174. 


224 


THE     liLOOD, 


of  digestion :   thus  before  breakfast  the  proportion  being  about  1  to  1800, 

one  hour  after  breakfast  it  was  1  to  700.  before  dinner  1  to  1500  after 
dinner,  1  o'clock,  1  to  400,  two  hours  later  1  to  1475,  after  supper,  8 
P.  M.,  1  to  550,  at  midnight  about  1  to  1200.  The  white  corpuscles 
differ  also  in  many  other  respects  from  the  red  ones  :  thus  in  the  manner 
in  which  they  are  affected  by  various  reagents,  and  in  the  way  in  which 
they  adhere  to  the  walls  of  the  vessels  in  which  they  are  circulating 
(Fig.  106),  the  red  corpuscles  keeping  in  the  middle  of  the  stream.     The 

white  corpuscles  further  are  found 
Fig.  106.  in    lymph,    chyle,    pus,    and    other 

fluids  as  well  as  in  the  blood;  the 
more  general  name  of  leucocytes  is 
often,  therefore,  given  to  them. 

It  is  well  known  that  the  leuco- 
cytes are  most  numerous  in  the 
splenic  vein,  and  that  in  diseases  of 
the  spleen,  liver,  and  lymphatic 
glands,  the  white  corpuscles  may 
increase  in  number  to  such  an  ex- 
tent as  to  form  a  half  or  a  third  of 
the  corpuscular  part  of  the  blood, 
hence  the  light  color  of  the  blood  in 
such  circumstances,  and  the  name 
of  the  disease — leucocythemia. 

The  number  of  the  white  corpus- 
cles increases  in  pregnancy,  and  are 
more  numerous  in  children  than  in 
adults.  The  proportion  of  the  white 
corpuscles  to  the  red  is  far  higher 
in  the  embryo  vertebrate  than  in  the  adult ;  according  to  Gulliver,1  in 
the  very  early  stages  of  embryonic  life  the  white  corpuscles  are  even 
in  excess.  Further,  in  examining  the  blood  of  the  amphioxus,  the  sim- 
plest of  vertebrates,  and  that  of  the  invertebrata  (with  but  few  exceptions) 
one  cannot  but  be  impressed  with  the  likeness  of  their  corpuscles  to  the 
white  ones  of  the  vertebrates  rather  than  to  the  red.  Let  us  see  whether 
these  facts  have  any  significance  in  throwing  light  upon  the  origin  of 
the  red  and  white  corpuscles. 

One  of  the  most  profound  truths  in  the  whole  range  of  biology  is  that 
the  transitory  stages  through  which  the  higher  animals  pass  are  perma- 
nently retained  in  the  lower  ones.  Ample  evidence  of  the  truth  of  this 
assertion  will  be  given  in  the  consideration  of  the  phenomena  of  repro- 
duction, and  it  will  be  found  then  that  the  blood  does  not  offer  any 
exception.  If  the  red  corpuscles  are  then  modified  white  ones  more 
highly  developed,  we  should  expect  to  find  white  corpuscles  in  the  lower 
animals  and  in  the  embryonic  forms  of  the  higher,  and  that  gradually 
the  white  ones  should  give  way  to  the  red  as  development  advances. 
This  we  have  seen  is  the  case.  Again,  the  white  corpuscles  are  identical 
with  those  of  the  lymph  and  chyle,  and  as  was  pointed  out  it  has  long 
been  a  matter  of  comment  that  in  the  upper  part  of  the  thoracic  duct 


A  small  venous  trunk,  a,  from  the  web  of  the 
frog's  foot.  6,  b.  Cells  of  pavement-epithelium, 
containing  nuclei,  d.  White  corpuscles,  e.  Red 
■corpuscles      (Carpenter.) 


1  Carpenter's  Physiology,  p.  234.    London,  1881. 


WHITE    CORPUSCLES.  225 

its  fluid  becomes  of  a  reddish  hue,  due  probably  to  the  gradual  develop- 
ment of  the  red  blood-corpuscles.  Again,  the  immense  number  of 
white  corpuscles  in  the  disease  leucocythemia,  just  referred  to,  may  be 
accounted  for  on  the  supposition  that  the  abnormal  conditions  are  such 
as  to  interfere  with  the  normal  transformation  of  the  white  corpuscles 
into  the  red.  Another  significant  fact  is  that  transitional  forms  between 
the  red  and  the  white  corpuscles  are  often  met  with  in  the  blood.  These 
facts  of  comparative  anatomy,  embryology,  and  pathology,  have  a 
significance  if  this  view  of  the  transformation  of  the  white  corpuscles 
into  the  red  be  correct,  otherwise  they  are  meaningless.  It  must  be 
admitted,  however,  that  the  exact  manner  in  which  the  red  corpuscle  is 
developed  from  the  white  has  not  been  definitely  made  out,  although, 
according  to  Kuss,1  both  Kolliker  and  Recklinghausen  have  seen  the 
transformation  of  white  globules  into  red  even  outside  the  organism  in 
blood  kept  at  the  temperature  of  the  living  organism  in  contact  with  a 
moist  atmosphere.  If  it  be  admitted  that  the  red  corpuscle  is  developed 
from  the  white,  the  next  question  that  will  naturally  be  asked  is,  Where 
does  the  white  corpuscle  come  from  ?  In  examining  the  blood  corpuscles 
at  different  periods  of  embryonic  life  it  will  be  found  that  some  have  a 
different  origin  from  others.  The  first  blood  corpuscles  are  almost 
indistinguishable  from  the  cells  of  the  body  of  the  embryo  generally. 
When  we  come  to  study  the  development  of  the  vascular  system  we  shall 
see  that  in  the  pellucid  area  of  the  embryo  of  the  cells  forming  the  meso- 
blastic  layer  some  soften  down  and  liquefy,  while  others  remain  floating 
in  the  liquor  so  produced.  The  latter  are  the  first  blood-cells  or  corpus- 
cles ;  they  are  round,  nucleated,  and  colorless,  and  reproduce  themselves 
by  fission.  (Fig.  107.) 

Fig.  107. 

/0-*k  J' a 


;\ 


Reproduction  of  first  blood  corpuscles,  in  embryo,  by  fission.     (Kirkes.  I 

With  the  development  of  the  liver  and  spleen  white  corpuscles  appear 
in  the  blood  ;  the  latter  as  they  pass  through  the  liver  become  colored, 
gradually  they  lose  their  granular  appearance  and  become  nucleated 
red  blood-corpuscles,  often  oval  shaped,  which  form,  as  we  have  seen,  is 
retained  through  life  in  the  oviparous  vertebrates,  but  in  the  mammalia. 
with  the  exception  of  the  camel  tribe,  is  only  transitory.  Gradually  the 
number  of  the  white  corpuscles  diminishes,  the  red  unnucleated  bicon- 
cave corpuscles  simultaneously  increasing,  the  latter  being  wanting  at 
the  first  month  of  intrauterine  life,  and  at  the  third  month  constituting 
only  about  one-fourth  of  the  corpuscles.     With  the  development  of  the 

1  Physiology,  translated  by  Dr.  Amory,  p.  122.    Boston,  1875. 
15 


226  THE    BLOOIt. 

embryo  the  white  corpuscles  .still  further  diminish,  until,  finally,  the 
circular,  biconcave,  unnucleated  red  corpuscles  predominate  in  the  pro- 
portion already  mentioned.  Possibly  the  red  corpuscles  reproduce 
themselves  also,  to  a  certain  extent,  fissiparously — that  is,  by  a  process 
of  division  in  the  adult  as  well  as  in  the  embryonic  condition.1;.,      j'yj 

In  certain  cases  after  excessive  hemorrhage  the  corpuscles  may  pos- 
sibly be  regenerated  in  this  manner ;  for  it  is  well  known  that  many 
vegetable  organisms  reproduce  themselves  fissiparously  in  vast  numbers, 
even  in  a  night,  far  more  rapidly  than  would  be  necessary  in  the  case  of 
the  corpuscles,  some  days  elapsing  before  their  normal  number  is  restored. 
Whatever  future  investigation  may  determines  as  to  the  origin  of  the 
red  and  white  corpuscles  or  their  relation  to  each  other,  there  can  be 
no  doubt  that  in  the  adult  the  materials  of  which  they  are  composed  are 
derived  from  the  food.  This  is  well  seen  in  the  beneficial  effect  of  giving 
iron  in  chlorosis,  where  the  number  of  the  red  corpuscles  is  diminished, 
and  which,  after  the  use  of  iron,  is  soon  restored  to  the  normal  standard. 
The  corpuscles  of  the  blood,  however,  do  not  exist  as  such  in  the  food, 
but,  like  the  other  elements  of  the  blood,  must  be  elaborated  from  it. 

While  it  must  be  admitted  that  the  exact  manner  in  which  the  blood 
is  elaborated  is  not  yet  understood,  nevertheless  the  general  features  of 
the  process  can  to  a  certain  extent,  at  least,  be  indicated.  Thus  a 
greater  part  of  the  water  found  in  the  blood  is  derived  from  that  present 
in  the  solid  and  liquid  food,  a  small  quantity  probably  being  due  to  the 
combustion  of  hydrogen.  The  blood-albumen  is  modified  albuminose, 
as  this  is  modified  food-albumen.  The  fibrin  can  be  regarded  as  an 
effete  product  undergoing  retrograde  metamorphosis.  The  oieates  and 
margarates  probably  result  from  the  saponification  of  the  fatty  food  by 

the  pancreatic  juice,  while  the  iron  and 
•""^  ]08  saline  principles   are   evidently  derived 

^|§§       u  ,  from  the  food. 

•' '„■■  '■-'. '•;  ,.'/-;        \  We    have   seen  that  there  are  many 

facts  which,  when  taken  together,  go  to 
show  that  the  red  corpuscles  are  modified 
white  ones.  It  remains  for  us  now  to 
consider  whether  any  definite  locality 
can  be  assigned  for  the  production  of  the 
/  ^/fRWS  '■'  *"  '  '  '  white  corpuscles,  and  to  ascertain,  if  pos- 
'■SK\tll^^g0^      sible'  what  are  the  elements  of  the  food 

out  of  which  they  are  developed, 
simple  lymphatic  giarid.   a  The  cap-         It  has  already  been   mentioned    that 
sale  with  sections  of  lymphatics,   d,  d.     t]ie  ^^g  corpuscles  are  not  confined  to 

Coursing  through   it.     b.   Lacunar  and  in-        .1        1  1         i     i      •  i        p  i    •         ii  i 

telecommunicating  passages,  permeated  by       the  bl°od>  bel"g  als0  foUnd   ln   tlie  b'mph, 

the  lymph,  and  forming  the  superficial     chyle,  etc.      They  are  also  found  in  the 
lymph-path  of  F.ey.   c.  Nucleus  or  me-     solitary    and    lymphatic  glands,  in    the 

dullary  portion  of  the  gland,  in  the  centre  i  •         ,i  i  c    ,  1 

of  which  the  section  of  a  bloodvessel  may       Spleen,    in    the    red    maiTOW    of    the    Can- 
be  seen.    The  path  pursued  by  the  lymph       CellouS     tissue    of    bones.        Let     US     now 

through  the  medullary  portion  constitutes     examine  the  minute  structure  of  these 

the  deep  or  secondary  lymph-path  of  Frey.       so.ca]led       kndg    an(l     gee    whether    the 

(Carpenter.  )  o 

facts  of  comparative  anatomy,  pathology, 
and  experiment  throw  any  light  upon  their  relation  to  the  white  cor- 
puscles found  in  them. 


STRUCTURE   OF  SOLITARY   AND    LYMPHATIC    GLANDS. 


227 


The  solitary  glands,  as  we  have  already  rfbticed,  are  distributed  all 
through  the  alimentary  canal ;  the  Peyer's  patches,  which  consist  of  a 
number  of  solitary  glands  united  together,  are,  however,  limited  to  the 
so-called  jejunum  and  ileum.  When  a  section  of  one  of  these  solitary 
or  simple  lymphatic  glands  is  examined  microscopically  (Fig.  108)  it  is 
seen  to  consist  of  a  capsule  of  connective  tissue  from  which  pass  inwardly 
strands  forming  a  meshwork,  in  the  interior  of  which  is  contained  the 
so-called  adenoid  or  cytogenous  tissue.  These  strands  of  connective 
tissue  serve  to  support' the  capillary  bloodvessels.  In  the  meshes  are 
found  lymph  corpuscles  and  sometimes  molecular  granules  and  small 
oil  globules.  Imagine  a  number  of  these  solitary  glands  held  together 
by  a  capsule  of  connective  tissue,  and  we  have  a  lymphatic  gland  (Fig. 
109).  The  meshes  in  the  lymphatic  gland  are,  however,  much  closer 
in  the  centre  than  at  the  sides,  hence  the  distinction  of  the  medullary 
and  cortical  parts  (Fig.  110).     Further  the  meshes  are  only  incom- 


Fig.  109. 


Fig.  110. 


d  *  J 

Section  of  lymphatic  gland,  showing  a,  a,  the  fibrous 
tissue  which  forms  its  exterior.  6,  h.  Superficial  vasa 
inferentia.  c,  c.  Larger  alveoli,  near  the  surface,  d,  d. 
Smaller  alveoli  of  the  interior,  e,  e.  Fibrous  walls  of 
the  alveoli.     (Carpenter.) 


Longitudinal  section  through  tne  hilum  of  a 
mesenteric  gland  from  the  ox,  showing  the 
commencement  of  the  efferent  lymphatic  vessels 
injected  from  a  puncture  of  the  glandular  sub- 
stance, a.  Plexus  of  efferent  vessels  b.  Lymph 
paths.  c.  Medullary  cords.  d.  Trabecular. 
(Kolliker.) 


pletely  filled  by  the  pulp,  free  spaces  being  left  between  the  pulp  and 
the  strands.  These  spaces  communicate  on  the  one  hand  with  the 
lymphatic  vessels  entering  the  gland,  and  on  the  other  with  the  lymph- 
atics leaving  it  at  the  hilus.  The  afferent  and  efferent  lymphatic  vessels 
and  these  spaces  can  be  injected.  Probably  this  is  the  explanation 
of  the  gland  appearing  after  injection  as  a  mass  of  vessels,  a  rete  mirabile 
between  and  continuous  with  the  lymphatics  passing  in  and  out  of  it. 
The  pulp  consists  principally  of  lymph  corpuscles,  these  being  most 
numerous  in  the  medullary  parts  of  the  gland  where  the  bloodvessels 
are  also  freely  distributed. 

The  lymph  or  chyle  passes  from  the  afferent  vessels  into  the  spaces 
left  between  the  pulp  and  the  strands,  and  comes  in  contact  with  the 
lymph  corpuscles  and  the  blood,  more  particularly  in  the  medullary 
parts  of  the  gland  ;  after  circulating  through  these  spaces  the  lymph  or 
chyle  passes  out  of  the  gland  at  the  hilus  by  the  efferent  lymphatic 
vessels,  and  so  passes  on  to  the  thoracic  duct. 


228  THE    BLOOD. 

The  researches  of  Klein,1  von  Recklinghausen,2  and  others,  have 
.shown  that  the  walls  of  the  serous  sacs,  like  the  peritoneum,  pleura, 
etc.,  consist,  to  a  considerable  extent,  of  the  adenoid  or  cytogenous 
tissue  just  mentioned,  which  enters  into  the  formation  of  the  solitary 
and  lymphatic  glands,  and  that  these  serous  sacs  communicate  by 
openings  or  stomata  with  the  lymphatics.  Indeed,  these  sacs  are  now 
regarded  as  being  lymphatic  glands  unravelled,  having  essentially  the 
structure  and  function  of  the  glands  already  described. 

We  have  already  seen  that  the  lymph  differs  from  the  blood  quanti- 
tatively, rather  than  qualitatively,  and  that  the  chyle  is  lymph  with 
the  products  of  digestion  added  to  it,  more  especially  of  the  emulsified 
fats  and  oils.  The  lymph  and  chyle  corpuscles,  which  are  undistin- 
guishable  from  the  white  corpuscles  of  the  blood,  seem  to  consist  at  first 
of  fatty  nuclei,  which,  acquiring  an  envelope  through  diffusion  in  an 
albuminous  fluid,  gradually  become  white  corpuscles.  In  examining 
the  chyle  of  the  lacteals  in  the  villi,  in  the  mesenteric  glands,  and  in 
the  thoracic  duct,  it  was  noticed  that  the  so-called  molecular  base  of 
the  chyle  consisted  largely  of  fatty  matter,  and  that  the  chyle  corpus- 
cles were  probably  due  to  an  aggregation  of  the  minute  bodies  forming 
the  base  of  the  chyle.  It  seems  probable,  therefore,  that  the  chyle  cor- 
puscles, or  white  corpuscles  of  the  blood,  are  elaborated  in  the  lymphatic 
glands  out  of  the  fatty  food. 

In  addition  to  containing  white  corpuscles,  the  chyle  resembles  an 
early  stage  of  the  blood  in  other  respects,  thus  between  the  mesenteric 
glands  and  thoracic  duct  it  will  coagulate — that  is,  separate  into  clot 
and  serum,  while  the  chyle  of  the  thoracic  duct  exhibits  a  reddish  color, 
as  if  the  white  corpuscles  were  gradually  becoming  red  ones.  While 
the  fats  and  oils  are  usually  taken  up  by  the  lymphatics  of  the  small 
intestine,  we  have  seen  that  the  albuminose,  glucose,  salts,  etc.,  are 
absorbed  by  the  radicles  of  the  mesenteric  veins.  Were  these  substances 
in  a  proper  condition  for  assimilation,  it  might  be  expected  that  they 
would  at  once  pass  into  the  general  circulation.  They  are.  however, 
first  mixed  with  the  blood  coming  from  the  splenic  vein,  and  then  expe- 
rience still  further  changes  as  they  pass  through  the  liver  on  their  way 
to  the  heart.  Inasmuch  as  the  lymphatic  glands  seem  to  be  the  organs 
in  which  the  fatty  portions  of  the  food  are  further  elaborated  analogy 
Avould  lead  us  to  expect  that,  in  certain  parts  of  the  economy,  certain 
organs  exist  which  effect  for  the  albuminose  substances,  etc,  what  the 
lymphatic  glands  do  for  the  fats. 

In  examining  the  structure  of  the  spleen  one  cannot  but  be  impressed 
with  its  great  similarity  to  a  lymphatic  gland.  Like  the  lymphatie 
gland,  the  spleen  (Fig.  Ill)  consists  externally  of  a  fibrous  capsule, 
from  which  pass  inward  numerous  strands,  constituting  the  so-called 
trabecular,  in  the  meshes  of  which  is  contained  the  splenic  pulp.  This 
consists  of  white  blood-corpuscles,  of  red  corpuscles  in  various  stages  of 
development  or  disintegration,  of  granular  matter  of  a  reddish-brown 
hue,  blood  crystals,  etc.      The  only  difference  between  the  spleen  and  a 

1  Anatomy  of  the  Lymphatic  System.  1873.  -  Strieker's  Histology. 


STRUCTURE    OF    SPLEEN 


229 


lymphatic  gland  consists  in  the  fact  that  the  cells  found  in  the  spleen 
pass  directly  into  the  blood. 


Fig.  111. 


Vertical  section  of  a  small  superficial  portion  of  the  human  spleen.  Low  power.  A.  Peritoneal  and 
fibrous  covering,  b  Trabecule,  c,  c.  Malpighian  corpuscles,  in  one  of  which  an  artery  is  seen  cut 
transversely,  in  the  other  longitudinally,     d.  Injected  arterial  twigs,     e.  Spleen-pulp.     (Kolliker.) 

That  the  spleen  is  structurally  a  lymphatic  gland  seems  confirmed 
by  the  fact  that  usually  when  the  spleen  is  small  in  man  or  an  animal 
the  lymphatic  glands  are  large,  and  vice  versa.  Not  only  is  this  inverse 
ratio  observed  in  the  same  animal,  but  also  in  different  species.  Thus, 
among  other  instances,  in  the  manatee  (Manatus  Americanus)  the  spleen 
is  very  small,  while  the  glands  are  very  large ;  while  in  the  sea  lion 
(Zalophus  Gillespii)  the  spleen  is  large,  and  the  glands  are  small. 

One  of  the  most  striking  peculiarities  of  the  spleen  is  its  great  vas- 
cularity. Not  only  does  a  large  quantity  of  blood  flow  into  the  organ, 
but  in  certain  parts  of  it  capillaries  are  absent,  the  blood  of  the  splenic 
artery  passing  directly  into  the  interstices  of  the  splenic  pulp,  from 
which  it  is  taken  up  by  the  veins. 

It  is  an  interesting  fact  that  this  lacunar  type  of  circulation  exhibited 
by  the  spleen  is  what  usually  obtains  in  the  invertebrata.  It  may  be 
mentioned  in  this  connection  that  the  so-called  Malpighian  corpuscles 
attached  to  the  branches  of  the  splenic  artery  in  the  spleen  do  not 
appear  to  differ  essentially  in  their  minute  structure  from  that  of  the 
solitary  glands.  A  significant  fact,  in  connection  with  the  development 
of  the  white  corpuscles,  is  their  great  number  in  the  blood  of  the  splenic 
vein,  one  white  corpuscle  being  found  to  every  70  red  ones,  whereas, 
in  the  blood  of  the  splenic  artery  the  proportion  is  only  one  of  white 
to  2000  of  red.  The  conclusion  from  such  a  contrast  would  not,  how- 
ever, be  that  the  white  corpuscles  found  in  the  splenic  vein  are  devel- 
oped in   the  spleen   out  of  the  red  ones  brought   to  that  organ   by  the 


230  THE    BLOOD. 

splenic  artery,  bui    rather  that   the   red   blood-corpuscles  are  destroyed 

in  the  spleen,  the  disintegrated,  broken-down  corpuscles  furnishing  not 
only  material  for  the  development  of  new  red  blood-corpuscles,  but  of 
the  coloring  matter  of  the  bile,  the  elaboration  of  the  latter  being 
effected  in  the  liver.  Further,  in  leukemia,  where  the  spleen  and 
lymphatic  glands  are  enlarged,  we  have  seen  that  the  number  of  the 
white  corpuscles  is  so  great  that  the  general  color  of  the  blood  is  affected 
by  them.  Naturally  the  question  will  then  suggest  itself  as  to  what 
becomes  of  the  white  corpuscles  produced  in  the  spleen.  Of  what  use 
are  they  if  they  simply  disappear,  and  are  not  further  elaborated  ? 
That  they  do  not  pass  away  is  shown  by  their  great  number  in  the 
disease  just  referred  to,  in  which  possibly,  as  already  suggested,  the 
conditions  or  the  materials  for  their  metamorphosis  into  the  red  corpus- 
cles are  absent,  such  a  transformation  probably  taking  place  in  health. 

An  interesting  fact  in  connection  with  the  number  of  red  corpuscles 
brought  to  the  spleen  is  the  large  quantity  of  iron  found  in  the  splenic 
pulp,  amounting  to  over  seven  per  cent.,  and  which  may  be  regarded  as 
being  derived  from  the  disintegration  of  the  old  red  blood-corpuscles 
and  serving  as  material  for  the  development  of  the  new  ones. 

We  have  seen  that  the  portal  vein  is  formed  through  the  union  of 
several  veins,  among  others  by  the  mesenteric  and  splenic,  and  that  the 
portal  blood  passes  into  the  liver.  Now,  if  the  blood  of  the  hepatic  vein 
which  comes  from  the  liver  be  compared  with  that  of  the  portal  vein 
which  goes  to  the  liver,  it  will  be  found  that  there  are  more  corpuscles, 
both  red  and  white,  in  the  former  than  in  the  latter.  It  must  be  ad- 
mitted, however,  that  according  to  some  observers  there  are  relatively 
fewer  red  corpuscles  in  the  blood  of  the  hepatic  vein  than  in  that  of 
the  portal.  This  may  be  due,  however,  to  the  destruction  of  the  red 
corpuscles  in  the  liver  during  the  intervals  of  digestion. 

The  liver  must,  therefore,  have  in  the  adult,  as  in  the  embryo,  an 
influence  in  the  elaboration  of  the  blood  corpuscles.  If  it  be  admitted 
that  the  Avhite  corpuscles  are  produced  in  the  spleen  and  are  then  car- 
ried by  the  splenic  vein  to  the  portal,  where  they  can  absorb  fresh  nutri- 
tive matter,  albuminous  substances,  etc.,  and  that  they  then  undergo  a 
further  elaboration  in  the  liver,  becoming  red  ones,  we  have  an  expla- 
nation of  the  interesting  anatomical  relations  of  the  parts  just  referred 
to.  That  the  spleen  has  some  such  function  in  the  process  of  sanguinifi- 
cation,  as  just  indicated,  similar  to  the  influence  exerted  by  the  lymphatic 
glands  upon  the  fatty  food  passing  through  them,  is  confirmed  by  a 
consideration  of  the  absorbent  system  in  the  animal  kingdom  generally. 

In  the  invertebrata  and  the  amphioxus  there  is  no  distinction  between 
the  lymph  and  blood,  the  nutritive  fluid  being  comparable  rather  to  the 
lymph  of  the  vertebrates  than  to  their  blood.  There  is  also  only  one 
set  of  absorbents  in  the  invertebrata.  The  spleen  is  absent  in  the  am- 
phioxus, while  true  lymphatic  glands  cannot  be  said  to  exist  in  fishes 
and  reptiles,  and  are  only  sparingly  developed  in  birds. 

The  lymphatics  of  the  small  intestine  in  the  three  latter  classes  are 
so  rarely  filled  with  chyle  that,  according  to  some  anatomists,  lacteals 
cannot  be  said  to  exist.  It  is  only  in  the  mammals  that  we  find  the 
digested  food  is  absorbed  by  two  distinct  sets  of  vessels,  and  even  in 


PRODUCTION    OF    WHITE    CORPUSCLES. 


231 


these,  as  we  have  seen,  one  set  of  vessels  does  at  times  absorb  all  kinds 
of  food.  In  a  word,  both  sets  of  vessels  are  combined  in  the  lower  ani- 
mals, while  in  the  higher  the  work  of  elaboration  is  divided  between  the 
lymphatic  glands  on  the  one  hand  and  the  spleen  and  the  liver  on  the 
other. 

Admitting  that  the  spleen  is  a  lymphatic  gland,  and  that,  like  the 
latter,  it  elaborates  white  corpuscles  out  of  fat.  it  may  be  supposed  that 
the  materials  supplying  the  fatty  principles  are  brought  to  the  spleen  by 
the  splenic  artery  ;  or  it  may  be  possible  that  the  white  corpuscles  de- 
veloped in  the  mesenteric  lymphatic  glands  having  reached  the  spleen 
by  the  route  of  the  thoracis  duct,  heart,  and  splenic  artery,  undergo 
there  a  further  elaboration,  finally  becoming  in  the  liver  red  corpuscles. 

The  investigations  of  Neuman,1  Bizzozero,2  and  others,  appear  to 
show  that  lymph  corpuscles  are  developed  in  the  red  marrow  of  the 
cancellous  tissue  of  bones  as  well  as  in  the  lymphatic  glands  and  spleen. 
According  to  Neuman,  not  only  are  both  white  and  red  corpuscles  found 
in  the  red  marrow  but  also  all  kinds  of  transitional  forms  between  the 
two,  nucleated  granular  cells  of  a  yellowish  color  passing  insensibly  into 
non-nucleated  cells  of  a  reddish  hue,  and  these  gradually  leading  on  to 
the  red  corpuscles  proper. 

It  is  possible  that  the  tonsils,  the  glands  found  in  the  tongue,  palate, 
etc.,  may  also  have  an  influence  in  the  production  of  the  white  corpus- 


Fio.  112. 


Pig.  113. 


Front  view  of  the  right  kidney  and  supra 
renal  body  of  a  full-grown  foetus.  Thisfigure 
shows  the  lobulated  form  of  the  foetal  ki.l- 
ney.  r,  v.  The  renal  vein  and  artery,  u. 
The  ureter,  g.  The  suprarenal  capsule,  the 
letter  is  placed  near  the  sulcus  in  which 
the  large  veins  ((,•')  are  seen  emerging  from 
the  interior  of  the  organ.    (Allen  Thomson.) 


Portion  of  thymus  of  calf,  unfolded,  o. 
.Alain  canal,  b.  Glandular  lobules,  c.  Iso- 
lated gland-granules  seated  on  the  main 
canal.     (CakPENTEB.) 


cles.     From  this  general  survey  it  will  be  seen  that  probably  the  white 
corpuscles  are  produced  in  several  parts  of  the  economy,  and  that  a  kind 


1  Archiv  der  Ileilkunde,  1809. 


-  Centralblatl 


282 


THE    BLOOD. 


of  vicarious  action  may  take  place  among  the  organs  concerned  in  their 
production.  Thus,  if  the  spleen  be  extirpated,  the  lymphatic  glands 
become  enlarged  and  more  active.  With  hypertrophy  of  spleen  we 
have,  coincidently,  disease  of  the  bones,  which  becomes  intelligible 
when  it  is  remembered  what  has  just  been  said  with  reference  to  the 
marrow  and  the  blood  corpuscles,  and  that  the  function  of  the  spleen  is 
of  such  a  supplementary  character  to  that  of  the  lymphatics  as  already 
described  is  still  further  shown  from  the  fact  that  it  can  be  entirely 
removed  from  the  body  of  an  animal  without  the  functions  of  the  latter 
being  apparently  in  any  way  interfered  with,  the  lymphatic  glands 
then  enlarging  proportionally  to  the  greater  amount  of  work  thrown 
upon  them. 

The  suprarenal  capsules,  Fig.  11:2,  and  thymus  glands,  Fig.  113,  are 
at  the  present  day  considered  by  many  physiologists  as  having  the  same 


Fig.  114. 


Fig.  115. 


Vertical  section  of  suprarenal  capsule  of  man. 
1.  Cortex.  2.  Medulla,  a.  Capsule,  b.  Layer  of 
external  cell-masses,  c.  Columnar  layer  (zona 
fasciculata).  d.  Layer  of  the  internal  cell-masses, 
c.  Medullary  substance.  /.  Section  of  a  vein. 
(Carpenter.) 

of  oil  and  pigmentary  matter,  yet  it 
tions  are  still  very  obscure. 


Section  oi  human  thymus,  showing  a  cavity  in 
the  wide  portion,  and  numerous  orifices  leading 
to  its  lobular  cavities.      (Carpenter,  ) 

function  as  the  spleen  and  lymph- 
atic glands,  at  least  in  the  em- 
bryo if  not  in  the  adult.  The 
structure  of  the  suprarenal  cap- 
sules (Fig.  114)  recalls  that  of  a 
lymphatic  gland,  consisting,  as  it 
does  to  a  great  extent,  of  tra- 
becule, in  the  ovoid  meshes  of 
which  are  imbedded  nuclear  cap- 
sules, cells  with  granular  con- 
tents, with  and  without  nuclei, 
must  be  admitted  that  their  func- 


THYMUS    GLAND. 


233 


From  the  fact  that  the  suprarenal  capsules  being  relatively  most  de- 
veloped in  the  embryo,  their  function,  whatever  it  may  be,  is  possibly 
restricted  to  foetal  life. 

The  immense  number  of  nerves  distributed  to  these  bodies  is  one  of 
their  most  remarkable  peculiarities,  the  significance  of  which  is,  how- 
ever, unknown.  The  bronzing  of  the  skin  often  associated  with  disease 
of  the  suprarenal  capsules,  does  not  as  yet  throw  light  upon  the  func- 
tions of  these  bodies,  inasmuch  as  the  bronzing  may  be  present  without 
disease  of  the  suprarenal  capsules,  and  these  bodies  may  be  diseased 
and  yet  the  skin  unaffected. 

It  is  generally  stated  that  the  thymus  gland  is  also  restricted  in  its 
functions  to  foetal  life.  According  to  Carpenter,1  however,  it  is  soon 
after  birth  that  the  gland  is  most  active,  and  that  even  till  the  age  of 
puberty  it  continues  to  increase  in  size.  The  thymus  gland  appears 
in  the  embryo  first  as  a  solid  body,  but  soon  becomes  a  tube  closed 
at  both  ends  and  filled  with  granular  matter.  From  this  tube  (Fig. 
115)  there  bud  out  at  intervals,  on  either  side,  hollow  lobular  processes, 
the  cavities  of  which  communicate  with  that  of  the  central  axis.  The 
thymus  in  the  adult  consists  of  a  series  of  such  offshoots  or  lobules  united 
by  connective  tissue  and  opening  into  the  central  tube,  to  which,  how- 
ever, there  is  no  outlet.     Each  lobule  (Fig.  116)  consists  of  an  external 


Pig.  ll'i. 


lill ' '""" 

.(H^'S^'-'J     *     Acini. 

tegr 


7  ""      Fibi 


Section  <>l  lobule  of  thymus. 

fibrous  capsule  which  sends  prolongations  into  its  interior  consisting  of 
acini,  in  the  meshes  of  which  are  seen  the  thymus  substance.  This 
contains  lymph  corpuscles,  spheroidal  granular  bodies,  and  concentric 
corpuscles.  In  the  expressed  thymus  juice  are  found  corpuscles  which 
are  undistinguishable  from  those  of  the  fluids  of  the  lymphatic  glands. 
The  thymus"  gland,  in  its  whole  structure,  is  very  much   like  a  Fever's 

i  Physiology,  p.  216. 


234 


THE    BLOOD. 


patch.  The  fact  of  the  thymus  being  most  active  during  foetal  life,  and 
for  some  time  after  birth,  makes  it  probable  that  it,  and  possibly  the 
suprarenal  capsules,  influences  the  elaboration  of  blood  in  the  embryo  in 
the  same  manner  as  the  spleen  and  the  lymphatic  glands  do  in  the  adult. 

The  thyroid  gland,  like  the  thymus,  relatively  larger  in  the  foetus 
and  in  the  infant  than  the  adult,  is  also  regarded  at  present  by  many 
physiologists  as  having  an  influence  in  sanguinification.  Its  remarkably 
rich  vascular  supply  would  lead  one  to  consider  it  as  performing  some 
function  in  the  elaboration  of  the  blood,  either  as  eliminating  some  effete 
material  from  the  blood  or  furnishing  it  with  nutritive  material.  As 
there  is  no  excretory  duct  to  the  thyroid  gland,  the  latter  view  of  its 
function  is  the  more  probable.  The  development  of  a  goitre  or  enlarge- 
ment of  the  thyroid  gland,  may  be  possibly  due  to  the  retention  of 
matters  by  the  gland  which  are  ordinarily  given  up  to  the  blood  circu- 
lating through  it,  while  the  want  of  such  material  in  the  blood  circulating 
through  the  brain  may  be  connected  with  the  idiocy  so  often  associated 
with  goitre.  In  the  same  way  the  white  appearance  of  young  women 
affected  with  tumors  of  the  thyroid  gland  may  be  due  to  the  retention 
by  the  gland  of  material  which  it  usually  furnishes  to  the  blood  sup- 
plying it. 

The  structure  of  the  thyroid  gland  diners  from  the  spleen  or  lymphatic 
glands,  it  consisting  of  a  collection  of  vesicles  (Fig.  117)  imbedded  in 


Fig.  117. 


Fig.  118. 


Group  of  gland-vesicles  iron 
a  child,     o    Connective  tissue. 


the  thyroid  gland  of 

b.   Membrane  ol  the 


Diagram  illustrating  the  relation  of  the  respira- 
tory chamber,  G,  to  the  hypobranchial  groove, 
H,  in  ascidians.     (Gegenbaur.) 

connective  tissue,  which  also  sup- 
ports a  network  of  lymphatics. 
These  vesicles  are  lined  with  epi- 
thelial cells,  from  which  there 
exudes  an  albuminous  granular 
material.  According  to  Wilhelm 
Muller,1  however,  the  thyroid  gland  in  man  is  to  be  viewed  as  the 
rudiment  of  the  hypobranchial  groove  of  the  ascidians  and  the  am- 
phioxus,  which,  traversing  the  middle  of  the  gill  body  (Fig.  118)  of 
these  animals,  assists  in  conducting  the  food  into  the  stomach.  When 
all  the  facts  are  considered  together,  the  following  general  conclusion 
may  be  drawn  :   that  the  spleen,  the  lymphatic  and  solitary  glands,  the 


vesicles,     c.  Epithelial  cells.     (Carpenter.) 


•  Jenaishe  Zeitschrift,  1873,  Band  viii.  S.  327. 


ELEMENTARY    CORPUSCLES.  235 

Peyer's  patches,  have  essentially  the  same  structure  and  perform  the 
same  functions,  that  of  producing  the  lymph  or  white  corpuscles ;  that 
probably  the  thymus,  and  possibly  the  suprarenal  capsules,  lias  the 
same  function,  but  restricted  in  its  performance  to  the  early  periods  of 
life;  that  the  thyroid,  while  differing  from  the  glands  just  mentioned 
in  its  minute  structure,  yet  has  some  influence  in  the  process  of  san- 
guinification  :  that  the  red  corpuscles  are  developed  from  the  white,  the 
elaboration  taking  place  in  different  parts  of  the  economy — the  red 
marrow  and  the  liver,  for  example — and  that,  having  played  their  part, 
they  pass  away  like  all  other  organites. 

The  blood  contains,  in  addition  to  the  red  and  white  corpuscles, 
minute  granules  or  molecules.  These  are  of  a  circular  form,  attaining 
sometimes  the  size  of  the  -§- oVo*n  °^  an  mcn'  DlJt  are  usually  much 
smaller.  They  resemble  the  minute  fatty  particles  of  which  the 
molecular  base  of  the  chyle  consists.  Some  of  them  are,  however,  of 
an  albuminous  nature.  It  is  possible  that  these  elementary  corpuscles, 
as  they  have  been  called,  are  undeveloped  lymph  or  white  corpuscles. 


CHAPTER    XV. 

THE  BLOOD.— (  Continued.) 

One  of  the  most  interesting  facts  about  blood  is  its  power  of  coagula- 
tion, or  of  its  separation  into  clot  and  serum.  Before  coagulation  the 
blood  consists  of  the  liquor  sanguinis  or  plasma  and  the  corpuscles  ; 
after  coagulation  it  will  be  found  that  the  corpuscles  are  entangled  in 
the  meshes  of  the  coagulated  fibrin,  the  two  constituting  the  clot  or 
crassamentum,  while  the  albumen,  salts,  and  water  remain  together  as 
the  serum.  It  is  important  to  notice  that  the  liquor  sanguinis,  or  the 
plasma,  is  not  identical  with  the  serum.  As  may  be  seen  from  Table 
XLII.,  the  liquor  sanguinis  is  serum  with  the  addition  of  fibrin,  and 
that  serum  is  liquor  sanguinis  without  fibrin.  Serum  differs  also  from 
what  are  known  as  serous  effusions,  which  are  due  to  transudations, 
not  to  coagulation. 

Table  XLII. — Blood. 


Before  coagulation. 

|  Water 

Liquor       j  Salts 

sanguinis     |  Albumen 

I  Fibrin 
Corpuscles 


After  coagulation. 
I 

Serum. 
I 
\  Clot. 


When  the  blood  is  allowed  to  flow  into  a  tolerably  deep,  smooth 
vessel,  according  to  Nasse,1  in  from  about  one  minute  and  forty-five 
seconds  to  six  minutes  a  gelatinous  layer  Avill  be  seen  to  form  on  its 
surface,  in  from  two  to  seven  minutes  the  sides  of  the  vessel  are  covered 
with  a  similar  layer,  and  in  from  seven  to  sixteen  minutes  the  whole 


Fig.  119. 


Fio.  120. 


Bowl  of  recent!;  coagulated  blood,  showing  tin 

whole  mass  uniformly  solidified.     (Dalton.) 


Bowl  of  coagulated  blood,  after  twelve  hours ; 
showing  the  clot  contracted  and  floating  in  the 
fluid  serum.     (Dalton.) 


of  the  blood  becomes  jelly-like  (Fig.  119)  ;  gradually  there  exudes  from 
the  contracting  jelly-like  mass,  drop  by  drop,  a  fluid,  the  serum,  and  in 


Wagner:  Physiologic,  18-12.  Band  1,  S.  104. 


COAGULATION    OF    THE    BLOOD, 


287 


from  ten  to  twelve  hours  the  coagulation  is  complete — that  is,  the 
separation  of  the  blood  into  clot  and  serum  (Fig.  120.)  The  contracted 
jelly-like  red  mass,  the  clot,  being  heavier  (specific  gravity  of  corpuscles, 
1.088),  usually  falls  to  the  bottom  of  the  straw-colored  or  reddish  liquid, 
the  serum  (specific  gravity.  1.028),  surrounding  it.  which  has  exuded 
from  it. 

Usually,  according  to  Milne  Edwards,1  the  clot  retains  about  one- 
fifth  of  the  entire  volume  of  the  serum  ;  this  should  be  remembered 
when  the  proportion  of  clot  to  serum  is  estimated  ;  it  is  generally  stated 
that  they  are  equal.  AVhen  the  coagulation  has  been  slow,  the  clot  will 
be  found  to  be  firm  ;  on  the  other  hand,  when  the  coagulation  has  been 
rapid,  the  clot  is  soft.  When  blood  coagulates  slowly,  and  so  remains 
fluid  for  some  time,  the  red  corpuscles,  on  account  of  their  weight,  sink 
and  settle  at  the  bottom  of  the  clot ;  the  upper  part  of  the  clot  will  be, 
therefore,  much  lighter  in  color  than  the  lower,  and,  when  white,  is 
known  as  the  buffy  coat  (Fig.  121) ;  it  is  almost  always  seen  in  the 
blood  of  the  horse,  which  coagulates  slowly  (Table  XLIIL),  while  it  is 
absent  in  the  pigeon,  in  which  the  blood  coagulates  almost  instanta- 
neously. 

Table  XLIIL2— Length  of  Time  of  Coagulation. 

Animal. 

Man  .... 

Horse 

Ox     ...        . 

Dog  .         .        .         . 

Sheep 

Hog  .... 

When  contraction  of  the  clot  takes  place  most  rapidly  at  the  edges, 
these  curl  up  and  the  upper  surface  becomes  concave  or  cupped  (Fig. 
122).      For  many  years  it  was  supposed  that  the  buffy  coat  was  char- 


Minutes. 

Animal. 

Minutes. 

2    to  16 

Babbit 

.     1    to    H 

5    to  13 

Lamb 

.     .1    to    1 

2    to  12 

Duck 

.     .5    to    2 

I  to    3 

Fowl 

I    to    LI 

I  to    1.', 

Pigeon 

almost  instantaneously. 

.',  to  n 

Fig.  121. 


Fig.  122. 


Vertical  section  of  a  recent  coagulum,  showing 
the  greati-r  accumulation  of  Mood  globules  at  the 
bottom.     (Daltox.) 


Bowl  of  coagulated  blood,  showing  the  clot  buffed 
and  cupped. 


acteristic  of  inflammation,  whereas  it  is  now  known  that  the  buffy  coat 
is  also  present  in  diseases  of  a  totally  opposite  character — in  chlorosis, 
for  example,  it  depending  here  upon  a  diminution  of  the  blood- 
corpuscles.       It   is  obvious    that    bleeding   in   such   cases   would   only 


1  Physiologic,  tome  i.  p.  124. 


-  Thakrah  :  Inquiry  into  the  Nature  of  Blood,  1819,  p.  29. 


238  THE    BLOOD. 

increase  the  buffy  coat  by  diminishing  still  further  the  corpuscles,  and 
yet,  when  it  is  remembered  that  bleeding  was  once  the  sovereign  remedy 
for  inflammation,  one  can  readily  imagine  the  number  of  lives  that  must 
have  been  sacrificed  through  the  mistaken  idea  of  the  buffy  coat  being 
always  due  to  inflammation. 

We  shall  see  that  the  fibrin  is  increased  in  inflammation,  and  in 
inflammation  the  blood  also  coagulates  slowly;  the  appearance  of  the 
buffy  coat  under  such  circumstances,  therefore,  is  perfectly  intelligible. 
It  must  not  be  forgotten  that  the  formation  of  the  buffy  coat  is  simply 
a  question  of  time,  as  shown  by  the  researches  of  Polli,1  for  as  coagula- 
tion is  either  retarded  or  accelerated,  so  will  the  buffy  coat  be  formed 
or  not  formed. 

There  is  no  better  illustration  of  the  great  influence  that  the  progress 
of  physiology  exerts  upon  the  practice  of  medicine,  than  the  history  of 
the  blood.  Dr.  Carpenter,2  in  his  most  thoughtful  work,  in  speaking 
of  this  subject,  well  says:  "  If  Andral  had  made  no  other  contribution 
to  medical  science  than  the  demonstration  of  the  real  nature  of  this 
condition  of  the  blood,  and  of  further  depletion  in  promoting  it,  he 
would  have  rendered  a  most  essential  service  to  the  multitude  of  females 
who  are  unfortunate  enough  to  suffer  from  this  kind  of  deterioration  of 
their  vital  fluid."' 

It  is  well  known  that  there  are  various  circumstances  which  modify 
the  coagulation  of  the  blood.  Thus,  blood  flowing  from  a  small  orifice 
coagulates  more  quickly  than  when  flowing  from  a  large  one,  and  more 
quickly  when  it  is  received  in  a  shallow  rough  vessel  than  when  in  a 
deep  smooth  one.  Blood  coagulates  more  rapidly  in  a  vacuum  than  in 
the  air.  Rapid  freezing  prevents  the  coagulation  of  the  blood;  this 
will  take  place,  however,  after  careful  thawing.  This  fact  is  of  impor- 
tance from  a  medico-legal  point  of  view. 

Elevation  of  temperature  between  32°  and  140°  Fahr.  increases  the 
rapidity  of  coagulation.  Chemical  substances,  like  solutions  of  soda 
and  potash,  ammonium  and  sodium  sulphate  and  carbonate,  will  retard 
or  prevent  coagulation.  It  is  due  to  the  vaginal  secretions  that  the 
menstrual  blood  is  kept  fluid. 

The  blood  not  only  coagulates  outside  the  body,  but  also  after  death 
within  it;  less  rapidly,  however,  and,  as  a  rule,  in  from  twelve  to  twenty- 
four  hours  after  death.  It  is  not  unusual,  also,  during  life  to  find  clots 
in  the  heart  and  other  parts  of  the  vascular  system.  As  it  is  often 
important  to  be  able  to  distinguish  an  ante-mortem  from  a  post-mortem 
heart-clot,  it  may  be  stated  that  the  former  are  whiter,  denser,  and 
adhere  more  closely  to  the  walls  of  the  heart  than  the  latter.  Coagula 
are  also  found  when  an  artery  is  ligated,  in  the  enlarged  veins  of 
hemorrhoids,  in  the  varicose  veins  of  the  extremities.  Usually  the 
blood  coagulates  when  effused  into  the  areolar  tissue  or  the  cavities  of 
the  body.  It  is  an  interesting  fact,  however,  that  the  blood  may 
remain  fluid  in  the  serous  cavities  for  days  and  weeks  at  a  time.  When 
coagula  are  formed  in  the  heart,  and  being  swept  into  the  circulation 
are  carried  thence  into  the  small  vessels  of  the  brain,  etc.,  they  consti- 

i  Annali  universal*  tli  medicina,  1843.  -  Physiology,  p.  267. 


COAGULATION    OF    THE    BLOOD.  239 

tute  what  are  known  as  emboli.  When  the  blood  coagulates  in  the 
economy  it  acts  as  a  foreign  body,  but  is  usually  absorbed,  though  this 
may  take  a  long  time.  The  corpuscles  first  disappear,  then  the  fibrin 
softens,  breaks  down,  and  is  finally  carried  away. 

The  coagulability  of  the  blood  is  nature's  cure  for  hemorrhage,  and 
when  this  power  is  diminished  or  wanting  we  have  the  hemorrhagic 
diathesis,  where  the  slightest  wounds  are  followed  by  severe,  and  some- 
times fatal  hemorrhage.  As  the  above  facts  belong  rather  to  the  prov- 
ince  of  pathology  I  merely  mention  them  here  in  an  incidental  way. 

From  time  immemorial  various  explanations  have  been  offered  of  the 
coagulation  of  the  blood.  A  favorite  one  has  been  that  of  the  blood 
being  maintained  in  the  body  in  a  liquid  condition  through  the  influ- 
ence of  life.  Apart  from  this  being  no  explanation  at  all,  but  simply 
a  statement  of  the  phenomena  to  be  explained,  it  is  not  even  a  fact,  as 
we  have  seen  that  the  blood  coagulates  in  the  living  body.  In  the  last 
century  it  was  generally  held  that  what  we  call  fibrin  was  produced  in 
some  way  at  the  expense  of  the  corpuscles,  which  run  together  in  coagu- 
lation, etc.  Petit,  Davies,  and  Hewson,1  however,  held  that  coagulation 
was  due  to  some  substance  separate  from  either  the  corpuscles  or  the 
serum,  and  Hewson  performed  several  experiments  to  prove  that  coagu- 
lation was  due  to  the  fibrin.  For  example,  Hewson2  added  a  little 
sodium  sulphate  to  fresh  blood,  which  prevented  coagulation.  After  the 
mixture  had  remained  standing  some  time  the  corpuscles  sank  to  the 
bottom,  the  clear  fluid  which  remained  on  top  was  then  decanted,  twice 
its  quantity  of  water  was  then  added  to  this,  when  the  fibrin  coagulated. 
On  another  occasion,  this  most  able  observer3  tied  the  jugular  veins 
at  the  sternum  of  a  dog  just  dead,  and  hung  his  head  over  the  edge  of 
a  table,  so  the  ligatures  might  be  highest,  the  upper  part  of  the  vein 
became  transparent,  the  red  corpuscles  sinking ;  he  then  tied  the  vein, 
separating  the  clear  from  the  muscular  part,  and  let  the  clear  part  out, 
which  was  fluid,  but  coagulated  soon  after.  These  experiments  showed 
that  the  coagulation  was  due  to  the  fibrin,  but  they  did  not  demonstrate 
that  this  fibrin  did  not  come  from  the  corpuscles,  which  was  the  view 
that  prevailed  at  that  time.  To  do  this  it  was  necessary  to  show  that 
the  corpuscles  were  unaffected  to  coagulation. 

With  reference  to  determining  this  point,  Johannes  Muller,4  the  great 
Berlin  physiologist,  in  1832  experimented  in  the  following  ways :  He 
added  a  little  solution  of  sugar  to  frog's  blood,  which  retarded  the  coagu- 
lation, and  then  filtered  the  mixture;  the  corpuscles,  which  are  very 
large,  were  retained  in  the  filter,  and  the  clear  fluid  which  passed 
through  coagulated.  Muller  then  showed  that  in  blood  which  was 
defibrinated  by  whipping,  and  therefore  incoagulable,  that  the  cor- 
puscles were  not  altered  in  any  appreciable  manner ;  and  further,  that 
when  blood  to  which  had  been  added  serum  (which  separated  the  cor- 
puscles from  each  other)  was  observed  under  the  microscope  coagu- 
lating, the  corpuscles  were  seen  to  remain  intact. 

Inasmuch  as  the  white  stringy  substance  appearing  at  the  moment 

1  Milne  Edwards,  op.  cit.,  tome  i.  p.  119.  -  Works,  p.  12.  ■'<  [bid.,  p.  32. 

*  Physiology,  transl.  by  1'aly,  1840,  vol.  i.  p.  123. 


240  THE    BLOOD. 

of  coagulation,  which  we  call  fibrin,  evidently  does  not  exist  as  such  in 

* 

the  blood  before  coagulation,  it  remains  to  be  determined,  if  possible, 
under  what  form  it  then  docs  exist.  If  blood  be  drawn  into  a  concen- 
trated solution  of  sodium  sulphate  to  prevent  its  coagulation,  and  sodium 
chloride  be  added  to  the  mixture  in  the  proportion  of  ten  per  cent.,  a 
whitish,  pastv  substance  is  thrown  down,  amounting  to  about  25  parts 
per  1000  of  the  blood  used,  and  called  by  Denis,1  who  first  described  it, 
plasmin,  and  which,  together  with  serin,  constitutes  blood  albumen. 
Now,  wheu  plasmin  is  redissolved  in  water,  the  solution  splits  into 
fibrin  3  p;irts,  and  paraglobulin  22  parts,  the  former  coagulating,  the 
latter  remaining  liquid.  It  would  appear,  therefore,  that  fibrin  exists 
in  the  blood  combined  with  paraglobulin,  as  plasmin  or  some  form 
closely  allied  to  it;  and  further,  as  with  the  withdrawal  of  the  plasmin 
from  the  blood,  the  latter  loses  its  power  of  coagulating,  the  serin 
remaining  liquid,  that  coagulation  of  the  blood  consists,  first,  in  the 
splitting  of  albumen  into  serin  and  plasmin,  and  secondly,  in  the  latter 
splitting  into  fibrin  and  paraglobulin,  or  of  the  breaking  up  of  albumen 
directlv  into  serin,  fibrin,  and  paraglobulin. 

On  the  other  hand,  the  observation,  made  many  years  ago  by 
Buchanan,2  that  two  fluids,  like  that  of  hydrocele  and  ascites,  for 
example,  or  of  ascites  and  pleurisy,  when  added  together,  coagulate, 
though  when  separate  show  no  such  tendency,  has  led  many  to  infer 
that  the  production  of  fibrin  is  rather  due  to  the  union  of  substances 
in  the  blood  than  to  the  decomposition  of  the  same,  as  just  explained. 
Indeed,  according  to  Schmidt,3  two  such  principles  actually  do  exist  in 
the  blood,  a  fibrinoplastic  substance,  paraglobulin,  and  a  fibrinogenous 
one,  fibrinogen,  whose  union  brought  about  by  the  presence  of  a  ferment 
at  the  moment  of  coagulation  constitutes  fibrin. 

Paraglobulin  can  be  readily  obtained  from  the  serum  of  the  blood 
through  precipitation  by  the  addition  of  sodium  chloride  in  excess,  and 
fibrinogen  in  the  same  way  free  from  the  liquor  sanguinis,  in  which 
coagulation  has  been  prevented  by  the  addition  of  magnesium  sulphate, 
and  the  corpuscles  have  been  removed  by  filtration. 

Now.  while  it  is  an  interesting  fact  that  if  paraglobulin  in  a  saline 
solution  be  added  to  either  fibrinogen  or  hydrocele  fluid,  or  if  fibrinogen 
as  obtained  either  from  the  liquor  sanguinis  or  hydrocele  fluid  be  added 
in  saline  solution  to  serum,  fibrin  will  be  produced,  it  does  not  necessarily 
follow  that  such  a  union  as  that  of  paraglobulin  and  fibrinogen  actually 
takes  place  in  the  blood  at  the  moment  of  coagulation.  Indeed,  it 
is  yet  to  be  proved  that  paraglobulin  exists  as  such  in  the  clot,  seeing 
that  if  Ave  obtain  it  from  the  serum  it  must  be  assumed  that  it  exists 
in  excess  partly  in  the  serum  and  partly  in  the  clot.  Again,  as 
under  certain  circumstances,  paraglobulin  when  mixed  Avith  fibrinogen 
does  not  produce  fibrin,  it  is  still  further  assumed  that  the  presence 
of  a  ferment  is  necessary  to  effect  the  union  of  the  two  fibrin  factors. 
As  a  matter  of  fact,  an  aqueous  extract  can  be  obtained  from  the  serum 
by  coagulating   the  latter  with  alcohol,  allowing  the  mixture  to  stand, 

1  Annates  dea  Sciences  Natureltes   iv.  I.  p.  25.  -  Proc.  of  Glasgow  Philos.  Soc,  1845. 

:l  Du  Bois  Reymoud  :  Arehiv.  1861,  S.  545  ;  1862,  S.  42S.     Pfluger's    \<rhiv.  1872,  S.  413;  1875,  S.  291  : 
1876,  S.  515. 


COAGULATION    OF    THE    BLOOD.  241 

drying  and  pulverizing  the  clot,  and  then  adding  water  and  filtering, 
which,  when  added  to  fibrinogen  will  cause  the  coagulation  of  the  latter 
like  a  ferment.  According  to  Schmidt,  such  a  ferment  is  derived  from 
the  disintegration  of  the  white  corpuscles,  the  latter,  as  is  well  known, 
being  always  present  in  spontaneously  coagulable  fluids  and  very  abun- 
dant if  the  coagulation  is  marked. 

It  remains  to  be  shown,  however,  that  this  ferment  is  actually  present 
at  the  moment  of  coagulation  and  exercises  then  the  influence  attributed 
to  it  of  effecting  the  union  of  the  fibrin  factors,  supposing  such  to  exist 
in  the  blood.  It  is  far  therefore  from  being  proved,  as  is  often  assumed, 
that  the  formation  of  fibrin  is  due  to  the  union  of  paraglobulin  and 
fibrinogen  through  the  influence  of  a  ferment.  Indeed,  according  to 
some  experimenters,  Fredericq,1  Hammers  ten2,  the  clot  is  due  to  the 
coagulation  of  the  fibrinogen  alone  through  the  influence  of  a  ferment; 
the  paraglobulin,  however,  not  entering  into  the  formation  of  the  clot  at 
all,  the  amount  of  the  clot  depending  only  on  that  of  the  fibrinogen 
present. 

The  fibrin  factor  theory  offered  of  coagulation  is  based  rather  upon 
assumptions  and  inferences  than  upon  demonstrations.  There  appears 
to  be  a  tendency  at  present3  also  to  return  to  the  view  of  the  older 
physiologists,  already  referred  to,  that  the  red  corpuscles  contribute  to 
the  formation  of  the  clot  in  coagulation,  since  if  these  elements  are 
separated  by  decantation  from  a  given  quantity  of  blood  and  added  to 
an  equal  amount  of  serum  the  latter  will  coagulate,  while  the  quantity  of 
fibrin  produced  bears  a  very  considerable  proportion  to  the  whole  quan- 
tity which  the  blood  would  have  yielded. 

It  is  difficult  to  see  how  the  corpuscles  can  contribute  to  the  formation 
of  the  clot,  supposing  this  to  consist  of  paraglobulin  and  fibrinogen,  since 
the  former  is  obtained  from  either  the  serum  or  the  plasma  and  the 
latter  from  the  liquor  sanguinis.  Further,  the  lymph  coagulates  even 
in  the  absence  of  red  corpuscles.  In  truth  it  must  be  admitted  that, 
whether  we  suppose  with  Denis  that  coagulation  is  due  to  the  decompo- 
sition of  certain  principles  in  the  blood,  or  with  Schmidt  to  the  union 
of  others,  the  cause  of  the  phenomena  is  as  obscure  as  the  assumption 
that  fibrin  exists  in  a  liquid  condition  in  the  blood  and  coagulates 
through  some  unknown  influence,  as  albumen  does  by  heat. 

1   Hoppe-Seyler  :  Physiologic  Chemie,  1879,  S.  416.  -  Pfluger'B  Archiv,  Band  xix.  S.  563. 

3  Sanderson  :  Handbook,  1873,  p.  182. 


16 


CHAPTER    XVI. 

COMPOSITION  OF  THE  BLOOD. 

We  have  seen  that  the  blood  contains,  either  directly  or  indirectly,  all 
the  proximate  principles  of  which  the  body  is  composed,  including  also 
the  excrementitious  matters,  and  that  the  food  furnishes  the  materials 
out  of  which  the  vital  fluid  is  elaborated. 

As  the  composition  of  the  blood  must  therefore  vary  in  different  indi- 
viduals, and  even  in  the  same  person  from  day  to  day  and  from  hour  to 
hour,  anything  more  than  an  approximate  analysis  cannot  be  expected. 
The  discrepancies  as  offered  by  the  analyses  of  different  chemists  are  due 
not  only  to  this  cause,  but  to  the  various  methods  made  use  of  by  them. 

As  the  object  of  an  analysis  of  the  blood  from  a  physiological  point  of 
view  is  to  show  not  only  the  ultimate  chemical  elements  entering  into 
its  composition,  but  the  manner  in  which  these  exist  in  the  blood,  it  will 
be  readily  understood  that  the  investigation  is  an  extremely  difficult  one. 

While  it  is  not  necessary  to  describe  in  detail  the  analyses  of  the 
blood  that  have  been  made  by  different  chemists,  it  seems  proper  that, 
at  least,  attention  should  be  called  to  the  general  methods  of  investiga- 
tion made  use  of  at  the  present  day. 

During  the  last  and  preceding  century  a  number  of  observations  were 
made  by  which  it  was  shown  that  the  blood  consisted  of  different  prin- 
ciples. Thus  Harvey  discovered  the  albumen,  Malpighi  and  Ruysch 
the  fibrin,  Guglielmini  and  Menghini  some  of  the  salts,  Badia  the  iron, 
Rouelle  the  soda,  etc. 

Passing  over  these  early  and  isolated  observations,1  it  may  be  said 
that  Macquer,  a  little  more  than  a  century  ago,  made  the  first  analysis 
of  the  blood  as  a  whole.  With  improved  methods  of  chemical  investi- 
gation the  blood  was  more  successfully  analyzed  by  Berzelius  in  1808. 
Some  years  later,  1823,  Prevost  and  Dumas2  published  the  results  of 
their  elaborate  researches  upon  the  constitution  of  the  blood,  and  as 
their  investigations  have  served  as  the  starting-point  for  later  analyses 
let  us  briefly  review  the  method  employed  by  these  eminent  chemists. 

The  blood  to  be  analyzed  is  received  into  two  equal  vases,  that  of  one 
vase  is  whipped  so  as  to  obtain  the  fibrin,  which  when  entirely  separated 
is  weighed.  The  blood  in  the  other  vase  is  set  aside  to  coagulate — 
that  is,  to  separate  into  clot  (fibrin  and  corpuscles)  and  serum  (albu- 
men, salts,  water).  The  clot  and  serum  are  then  separated  and  des- 
iccated so  as  to  obtain  the  amount  of  water  in  them,  and  therefore  in  the 
blood  of  the  second  vase.  As  the  clot  consists  of  fibrin  and  corpuscles, 
if  we  subtract  from  the  clot  the  fibrin  obtained  from  the  blood  of  the 
first  vase,  the  remainder  will  give  the  quantity  of  the  corpuscles  in  the 

1  Milne  Edwards  :  Physiologie,  tome  i.  p.  141. 

2  Ann.  de  Chemie  et  de  Physique,  1823,  tome  xxiii.  \t.  50. 


COMPOSITION    OF    THE     BLOOD. 


243 


blood  of  the  second  vase,  or  one-half  the  quantity  in  the  whole  blood 
examined.  Having  determined  then  the  fibrin,  water,  and  corpuscles, 
there  remains  the  desiccated  serum  of  the  second  vase  to  be  analyzed 
for  the  albumen  and  the  salts ;  the  latter  are  determined  by  ordinary 
chemical  analysis.  Becquerel  and  Rodier  determined  the  amount  of 
albumen  by  treating  the  desiccated  serum  with  boiling  water,  which 
separates  the  undetermined  extractive  matters  and  soluble  salts,  and 
then  with  alcohol,  which  dissolves  the  fats,  the  remainder  being  the  albu- 
men.1 Figuier2  suggested  the  improvement  of  estimating  the  corpuscles 
by  adding  to  the  defibrinated  blood  twice  its  volume  of  a  solution  of 
sodium  sulphate  and  then  filtering,  the  corpuscles  can  be  counted,  the 
saline  retaining  them  on  the  filter  ;  any  sodium  sulphate  that  remains 
on  the  filter  can  be  removed  by  boiling  water.  Figuier's  method  of  esti- 
mating the  corpuscles  can  also  be  used  as  confirmatory  of  that  of  Dumas. 
The  quantity  of  the  corpuscles  is  estimated  in  their  dry  condition. 

Table  XLIV. — Composition  of  the  Blood. 


Water 

781.600 

Globules  . 

135.000 

70.000 

Fibrin 

2.500 

Serolin 

0.025 

Cholesterin 

[Oleate      '  ] 
s  Margarate   > 

0.125 

Sodium 

1.400 

1  Stearate 

Potassium 

r 

Sodium 

[  Chloride      ■ 

3.500 

Magnesium 

J 

Sodium 
Potassium 

f  Carbonate 
-  Sulphate 

I  Phosphate 

Free  Soda 

\ 2.850 

Magnesium 

f  Sulphate 
1  Phosphate 

Calcium  phosphate  . 

0.550 

Extractives 

undetermined 

2.450 

1.000.000 

The  general  results  of  an  analysis  of  the  blood  by  such  a  method  as 
that  just  given  may  be  seen  from  Table  XLIV.,  taken  from  Becquerel 
and  Rodier's  work,  and  which  undoubtedly  gives  a  very  fair  idea  of  the 
average  composition  of  the  blood  from  a  purely  chemical,  and,  indeed, 
to  a  certain  extent,  from  a  physiological  point  of  view  also.  It  will  be 
noticed  at  once,  however,  that  in  this  analysis  of  a  1000  parts  of  blood, 
there  are  present  only  1 35  parts  of  corpuscles  ;  whereas,  anyone  who  is 
familiar  with  the  appearance  of  living  blood  under  the  microscope  knows 
that  the  corpuscles  bear  a  much  larger  proportion,  forming,  perhaps, 
half  of  the  mass  of  blood  examined.  This  discrepancy  is  perfectly 
accounted  for  when  we  remember  that,  by  the  method  of  Becquerel  and 
Rodier,  the  clot  from  which  the  corpuscles  are  estimated  is  dried  and 


1  Traite  de  chimie  de  pathologiqne,  p.  20.     Paris,  1854. 

2  Ann.  de  Chemie,  et  de  I'hye.,  1844,  3me  serie,  tome  xi.  p.  506. 


244  COMPOSITION    OF    THE    BLOOD. 

their  water  therefore  driven  off;  the  135  parts  of  corpuscles  represent, 
therefore,  dry  ones  and  not  the  living  corpuscles,  which,  when  united 
with  their  370  parts  of  water,  will  amount  to  nearly  500  parts  in  the 
1000  of  blood  analyzed. 

Judging,  also,  from  the  boiled  serum,  we  should  expect  to  find  a 
greater  quantity  of  albumen  than  70  parts  per  1000  of  blood.  In  the 
analysis  just  given  the  serum  from  which  the  albumen  is  determined  is 
dried  like  the  clot,  hence  the  water  present  in  living  albumen  is  not 
given.  When  the  water,  however,  is  taken  into  consideration,  the 
albumen  wTill  then  amount  to  more  than  300  parts  in  1000  of  blood. 
As  the  object  of  the  physiologist  is  to  ascertain  if  possible  the  quantity 
of  albumen,  fibrin,  and  corpuscles,  as  they  exist  in  living  blood,  and  as  in 
this  condition  water  is  an  indispensable  element  of  their  composition,  it 
becomes  a  matter  of  importance  to  determine  the  quantity  of  these 
principles  in  a  moist  as  well  as  in  the  dry  condition.  For  these  reasons 
Prof.  Flint,  in  his  excellent  work,1  suggests  that,  while  the  fibrin  be 
obtained  in  the  usual  manner  of  whipping — with  broom-corn,  for  ex- 
ample— and  the  corpuscles  by  Figuier's  filtering  method,  both  these 
principles  should  be  estimated  in  their  moist  condition,  and  not  after 
desiccation;  and  that  in  determining  the  albumen  from  the  serum,  this 
should  be  treated  as  described  above,  but  in  the  condition  that  it  is  found 
after  coagulation — that  is,  with  its  water. 

The  difference  between  the  results  of  an  analysis  of  the  blood  by  the 
method  of  Prof.  Flint  and  that  of  MM.  Becquerel  and  Rodier,  may  be 
seen  from  Table  XLV.  The  excess  of  water  in  the  analysis  of  the 
latter  is  distributed  between  the  albumen,  fibrin,  and  corpuscles  in  that 
of  the  former. 

Table  XLV. — Composition  of  the  Blood 
(as  analyzed  by  the  methods  of  Flint,  and  Becquerel  and  Bodier).2 


Flint. 

Becquerel  ami 

Difference  is 

Bodier. 

in  water. 

Water     . 

.  154.870 

790.070 

635.200 

Albumen 

.  329.820 

71.530 

258.290  ) 

Fibrin     . 

.       8.820 

2.500 

6.320  [r  635.200 
370.590 ) 

Corpuscles 

.  495.590 

125.000 

Bemaining 

matters. 

salts,  etc.     10.900 

10.900 

00.000 

1000.000        1000.000 

We  say  the  method  of  Becquerel  and  Rodier,  not  their  actual  analysis, 
for  the  quantities  of  albumen,  fibrin,  and  corpuscles  given  under  the 
methods  of  Becquerel  and  Rodier  in  Table  XLV.,  were  experimentally 
obtained  by  Prof.  Flint  by  weighing  the  dry  residue  after  desiccating 
these  principles  obtained  by  his  method.  It  is  very  satisfactory,  how- 
ever, to  see  that  the  difference  between  the  quantities  of  dry  albumen 
and  corpuscles  given  by  Prof.  Flint  (Table  XLV.)  and  Becquerel  and 
Rodier  (Table  XLV.)  are  very  slight,  and  that  the  quantity  of  fibrin  is 
the  same  according  to  both.  The  remaining  matters  of  the  blood  are 
determined  in  the  same  manner  by  these  and  other  authorities  by  the 
ordinary  methods  of  chemical  analysis. 

l  Physiology,  vol.  ii.  p.  133.  2  Becquerel  and  Rodier,  op.  cit.,  86. 


COMPOSITION    OF    THE    BLOOD.  245 

Of  these,  the  larger  proportion  are  the  inorganic  principles,  and  from 
a  purely  chemical  point  of  view  have  been  very  satisfactorily  determined, 
both  quantitatively  and  qualitatively  ;  but  of  the  exact  manner  in  which 
they  exist  in  the  living  blood  little  is  known  beyond  a  few  general 
statements  to  be  noticed  shortly. 

The  analyses  of  Prevost  and  Dumas,  Andral  and  Gavarret,  Lehmann, 
Becquerel  and  Rodier,  Simon,  Denis,  Gorup  Besanez,  etc.,  while  differ- 
ing in  detail,  agree  substantially  in  showing  that  the  blood  consists  of 
water  in  molecular  combination  with  or  holding  in  solution  albuminous 
substances,  fats  and  sugars,  and  saline  matters.  It  is  interesting  to 
observe  in  this  connection  that  milk  and  eggs,  the  food  of  the  young 
animal  and  embryo,  consist  of  a  mixture  of  water,  albumen,  fats,  sugars, 
and  salines,  approximating  closely  in  their  composition  to  that  of  the 
blood ;  the  value  of  such  articles  of  food  at  all  stages  of  life  will  be 
therefore  readily  understood. 

We  have  seen  that,  under  natural  circumstances,  the  diet  of  man  is 
a  mixed  one,  and  that  beyond  a  limited  period  of  time  no  single  article 
of  food,  solid  or  liquid,  will  sustain  life.  As  the  blood  is  elaborated 
from  the  food  it  becomes  impossible,  therefore,  to  say  positively  that 
any  one  of  its  constituents  is  more  indispensable  to  life  than  another. 
It  is  immaterial,  therefore,  with  which  I  commence  in  describing  their 
quantitative  relations.  I  will  follow,  then,  the  order  in  which  they 
present  themselves  in  the  analysis  given  by  Becquerel  and  Rodier 
(Table  XLIV.). 

The  absolute  amount  of  water  found  in  the  blood,  according  to  this 
analysis,  amounts  to  781.600  parts  in  the  1000  ;  of  this  we  have  seen 
in  life  that  over  600  parts  enter  into  molecular  combination  with  the 
albumen,  fibrin,  and  corpuscles,  forming  an  integral  part  of  their  com- 
position. As  the  great  use  of  water  to  the  system  has  already  been 
pointed  out,  it  will  not  be  necessary  to  dwell  further  on  the  importance 
of  the  large  proportion  in  which  it  is  present  in  the  blood,  merely 
stating  that  while  the  quantity  varies  within  slight  limits,  any  excess 
that  may  be  taken  in  as  food  is  rapidly  eliminated  by  the  skin,  kidneys, 
etc.,  and  that  a  deficiency  in  any  amount  materially  alters  the  character 
of  the  blood. 

Although  water  forms  three-fourths  of  the  blood,  and  however  indis- 
pensable it  may  be  to  health,  yet  the  researches  of  Prevost  and  Dumas 
showed  long  since  that  there  exists  an  intimate  relation  between  the 
richness  of  the  blood  in  organic  matters  and  the  vital  activity  of  the 
organism. 

A  glance  at  Table  XL VI.  shows  that  the  quantity  of  water  is  large 
in  all  vertebrates,  but  that  there  is  more  water  in  the  blood  of  the  com- 
paratively inactive  fishes  and  batrachia  than  in  birds  and  mammals,  and 
that  in  those  mammals  which  hibernate  implying  a  low  order  of  vitality, 
the  blood  contains  more  water  than  in  the  ordinary  members  of  this 
class.  As  regards  the  quantity  of  solid  matters  contained  in  the  blood 
of  vertebrates,  the  birds,  whose  vital  activity  is  very  high,  come  first,  the 
mammals  next,  and  finally  the  cold-blooded  batrachia  and  fishes.  Al- 
though in  Table  XLVI.  the  fibrin  and  corpuscles  are  estimated  together, 
we  shall  see  in  a  moment,  from  numerous  facts,  that  this  vital  power 


246 


COMPOSITION     OF    THE     BLOOD. 


Water. 

Clot. 

Albumen  and  salts 

780 

157 

63 

797 

156 

47 

765 

150 

85 

797 

146 

56 

308 

132 

59 

776 

146 

78 

784 

129 

87 

785 

128 

87 

812 

124 

65 

795 

102 

84 

814 

103 

83 

826 

!)1 

83 

838 

94 

68 

818 

92 

89 

836 

86 

77 

846 

94 

60 

884 

69 

46 

864 

64 

72 

886 

48 

66 

depends  upon  the  corpuscles  especially,  which  vary  in  quantity  under 
different  conditions,  whereas  the  proportion  of  fibrin  and  albumen  is 
not  so  materially  changed. 

Table  XLVI.' — Proportion  or  Water,  etc.,  in  1000  parts  of  Blood  of 

Vertebrates. 

Animal. 

Chicken     . 

Pigeon 

Duck 

Raven 

Heron 

Monkey 
Man  . 
Guinea-pig 
Dog   . 
Cat     . 
Goat  . 
Calf  . 
Rabbit 
Horse 
Sheep 

Eel  . 
Frog  . 
Trout 
Lotte 

Milne  Edwards,  in  his  elaborate  work,2  cites  as  examples  the  following 
facts.  The  number  of  corpuscles  is  greater  in  man  than  in  woman,  in 
the  adult  than  in  youth  or  in  old  age,  in  the  sanguineous  than  in  the 
lymphatic  temperament,  in  pregnant  than  in  non-pregnant  women,  in 
plethoric  than  in  anaemic  persons,  or  in  those  who  have  lost  blood  or 
have  been  without  food.  According  to  Bakewell,3  the  number  of  cor- 
puscles differs  in  the  blood  of  the  Mohamedan,  Hindoo,  and  Negro  races 
so  much  so  that  their  blood  can  be  distinguished  by  this  characteristic. 

In  all  these  instances  where  the  corpuscles  are  in  excess  the  vital 
activity  is  high.  This  statement  holds  good  when  classes  of  animals 
are  compared,  as  may  be  seen  from  Table  XLVI.  by  estimating  separ- 
ately the  corpuscles  and  fibrin  which  constitute  the  clot,  and  when  par- 
ticular animals  in  a  class  are  considered.  Thus  in  the  hibernating 
mammals,  which  sleep  for  months  at  a  time,  the  number  of  corpuscles  is 
less  than  in  the  more  active  ones.  The  blood  of  the  pig,  whose  nutrition 
is  most  active,  contains  more  corpuscles  than  that  of  any  other  mammal. 
Numerous  other  examples  might  be  offered,  but  the  above  will  suffice 
to  illustrate  the  view  that  the  normal  amount  of  the  blood  corpuscles  is 
the  most  important  condition  in  maintaining  the  force  of  the  constitution, 
and  that  any  deficiency  entails  feebleness.  This,  indeed,  was  the 
opinion  held  more  than  a  century  ago  by  that  most  profound  of  phys- 
iologists, John  Hunter. 

Let  us  now  consider  the  composition  of  the  corpuscles.  We  shall  see 
in  a  moment  that  when  the  blood  is  first  cooled  and  then  heated  the 


1  Ann.  de  Phys.  et  de  Chemie,  182o,  Ire  serie,  t.  xxiii.  p.  64. 

2.Op.  cit.,  tome  i.  pp.  23l-2o4.  3  Med.  Times  and  Gazette,  p.  514.     London,   Nov    1872. 


COMPOSITION    OF    THE    CORPUSCLES. 


247 


material  of  which  the  corpuscles  are  composed  separates  into  two  sub- 
stances, the  colorless  stroma  or  globulin,  and  the  coloring  matter,  the 
haemoglobin  or  the  hsematocrystallin,  which  when  further  modified 
becomes  hrematin.  As  these  two  substances  are  albuminous  in  nature, 
it  may  be  said  that  they  represent  in  the  corpuscles  (Table  XL VII.) 
the  albumen  and  fibrin  of  the  liquor  sanguinis. 

Table  XLVII.1 — Blood,  in  1000  parts  each. 


i  lorpuscles,  513. 

Liquor  sanguinis,  487 

Density  . 

.       1.0885 

1.028 

Water     . 

.  681.63 

901.51 

Solid  matters 

.  318.37 

98.49 

1000.00 

1000.00 

Haematin 

.     15.02 

Fibrin 

8.06 

Globulin 

.  296.07 

Albumen  and  )  „,  ^ 
extractives  [ 

Inorganic  salts 

.       7.28 

8.51 

318.37 

98.49 

Sodium  chloride     . 

5.546 

Potassium  chloride 

.       3.679 

0.359 

Potassium  phosphate 

.       2.343 

Potassium  sulphate 

.      0.132 

0.281 

Sodium  phosphate 

.       0.633 

0.271 

Soda 

.      0.341 

1.532 

Calcium  phosphate 

.       0.094 

0.298 

Magnesium  phosphate 

.       0.060 

0.218 

Iron 

undetermined 

.281 


8.505 


The  water  of  the  corpuscles  has  already  been  referred  to.  The  cor- 
puscles contain  the  phosphorized  fats,  the  fatty  acids  being  rather  found 
in  the  liquor  of  the  blood;  the  potash  salts  are  also  confined  almost  en- 
tirely to  the  corpuscles,  there  being  about  four  times  as  much  soda  in  the 
liquor  as  in  the  corpuscles.  All  of  the  iron  of  the  blood  is  contained  in 
the  corpuscles,  whereas  the  greater  portion  of  the  earthy  phosphates 
is  found  in  the  liquor  sanguinis.  By  consulting  Table  XLVII.  the 
relative  densities,  quantity  of  water,  solid  matters,  and  proportion  of 
salts  in  the  corpuscles  and  liquor  sanguinis  may  be  seen  somewhat  in 
detail. 

An  important  practical  fact  in  reference  to  the  red  corpuscles  is  that 
their  number  is  increased  by  the  use  of  animal  food  and  iron,  but  di- 
minished by  a  vegetable  diet.  When  the  importance  of  the  corpuscles 
is  considered,  it  is  well  that  the  physician  should  bear  this  in  mind. 


i  Eanke  :  Physiologic,  S.  350.     Leipsig,  1875. 


CHAPTER    XVII. 

COMPOSITION  OF  THE  BLOOD.— (Continued.) 

Having  contrasted  in  a  general  way  the  composition  of  the  liquor 
sanguinis  with  that  of  the  red  corpuscles,  it  remains  for  us  now  to  con- 
sider a  little  more  in  detail  the  haemoglobin  of  the  latter,  as  this  sub- 
stance is  of  special  interest  from  several  points  of  view.  When  blood, 
drop  by  drop,  is  exposed  to  a  cold  of  about  8°  F.,  and  then  quickly 
warmed  to  68°  F.,  it  will  be  observed  that  the  corpuscles  gradually  lose 
their  color,  and  that  the  serum  becomes  stained.  This  coloring  matter 
from  the  corpuscles  is  capable  of  assuming  the  crystalline  form,  and  has 
been  indifferently  called  oxyhemoglobin,  luematocrystallin,  haemato- 
globulin,  hemoglobin,  and  hrematosin,  though,  according  to  some  chem- 
ists, the  ultimate  chemical  composition  of  these  principles  is  slightly 
different. 

The  corpuscles,  left  colorless  by  the  giving  up  of  their  haemoglobin, 
will  retain  for  some  time  their  form  and  elasticity,  and  consist  largely 
of  globulin.  In  this  colorless  condition  the  matter  of  which  the  cor- 
puscles consist  is  generally  termed  the  stroma.  The  coloring  matter  of 
the  blood  corpuscles,  or  the  haemoglobin,  can  be  obtained  in  several  ways. 
Among  others,  the  following  method,  that  of  Preyer,1  will  usually  give 
good  crystals  :  Add  enough  water  to  a  small  quantity  of  blood  free  from 


Fig.  123 


Prismatic  crystals  from  human  blood. 
(Kirkes.) 


Tetrahedral  crystals,  from  blood  of  guinea-pig. 
(Kirkes.) 


fibrin,  to  make  a  clear  solution  and  evaporate  a  drop  under  a  thin  cover- 
glass  in  a  cool  place.     Should  this  plan  fail  add  a  little  alcohol  to  the 


i  Die  Blutcfystalle,  S.  18.     Jena,  1871. 


HAEMOGLOBIN. 


249 


Fig.  125. 


solution  and  place  it  in  a  freezing  mixture.  Usually  crystals  will  at 
once  form.  These  crystals  are  more  readily  obtained  from  some  animals 
than  others — with  greater  facility, 
for  example,  from  the  blood  of  the 
dog,  horse,  and  guinea-pig,  than 
from  that  of  man,  and  only  with 
difficulty  from  that  of  the  bat,  mole, 
and  mouse.  The  form  of  these 
blood  crystals  varies  also  in  differ- 
ent animals.  Thus  they  are  pris- 
matic in  form  in  man  (Fig.  123), 
tetrahedral  in  the  guinea-pig  (Fig. 
124),  hexagonal  in  the  squirrel 
(Fig.  125). 

From  whatever  source  they  are 
obtained  they  are  transparent  and 
doubly  refracting,  and  when  oxy- 
genated exhibit  the  color  of  the 
blood  from  which  they  were  ob- 
tained. When  deoxidized,  however, 
they  alternate  from  red  to  purple  or  green.  They  are  soluble  in  Avater, 
alkalies,  and  most  acids ;  insoluble  in  alcohol,  and  will  remain  un- 
changed for  some  time  in  urine,  bile. 

Oxyhemoglobin  from  the  dog  consists  chemicallv,  according  to  Hoppe- 
Seyler,1  of  C  53.85,  H  7.32.  N  16.17,  0  21.84,  SO  39,  FeO  43. 

The  amount  of  haemoglobin  present  in  a  given  quantity  of  blood  can 
be  determined  from  the  amount  of  iron,  by  the  spectroscope,  and  by 
colorometric  methods.  The  ferric  method  is  based  upon  the  fact  that 
dry  (100  C.)  haemoglobin  contains  0.42  per  cent,  of  iron.  Knowing 
the  amount  of  the  latter  in  the  blood  the  amount  of  haemoglobin  can  be 
at  once  calculated  by  the  following  equation  : 

^  ,    100  Fe 

v   :    te,  x  equals 


Hexagonal  crystals  from  blood  of  squirrel. 


100    :    0.42 


0.42 


in  which  x  is  the  unknown  quantity  of  haemoglobin,  Fe  the  known 
quantity  of  iron  in  the  blood,  and  0.42  the  per  cent,  of  iron  in  100 
parts  of  haemoglobin.  To  obtain  the  amount  of  iron  in  the  blood  whose 
haemoglobin  is  to  be  determined,  a  known  quantity  of  blood  is  calcined, 
the  ash  is  then  treated  with  hydrochloric  acid  to  obtain  ferric  chloride, 
which  is  then  transformed  into  ferrous  chloride  by  boiling  with  zinc 
until  the  liquid  is  colorless.  The  liquid  being  diluted,  the  amount  of 
iron  in  it  is  determined,  volumetrically2  by  adding  from  a  burette  per- 
manganate of  potassium  in  standard  solution  until  the  rose  color  becomes 
permanent  after  agitation,  0.0056  gramme  of  iron  being  present  for 
each  centimetre  of  standard  solution  used.  The  haemoglobin,  as  deter- 
mined from  the  quantity  of  iron  (27  grammes),  amounts,  according  to 
Preyer,3  in  human  blood  to  about  12.34  per  cent. 

The  spectroscopic  method  depends  upon  it  having  been   shown  by 
Preyer4  that  through  an  0.8   per  cent,  solution  of  haemoglobin  the  red, 


i  Med.  Cheni.  Unters.,  S.  370. 
3  Op.  tit  .  S   117. 


'-'  Sutton  :  Volumetric  Analysis,  4th  ed.,  pp.  88,  94. 
*  Ibid..  S.  124. 


250 


COMPOSITION    OF    THE    BLOOD, 


yellow,  and  first  band  of  the  green  can  be  seen,  and  that  such  a  solution 
can  be  taken  as  a  standard  for  comparison.  A  known  amount  of  the 
blood  whose  haemoglobin  is  to  be  determined  is  therefore  diluted  until 
the  same  bands  are  seen  spectroscopically,  as  with  the  standard  solution; 
that  having  been  done  the  amount  of  haemoglobin  can  be  determined  by 
the  following  equation  : 


k 

:    h  +  c  :    h 

xb   = 

=   k  (b   +   c) 

x   = 

--    k  (b   +   c) 

b 

x  =  k  (1  +  e) 

in  which  x  =  unknown  quantity  of  haemoglobin. 

k  =  per  cent,  of  haemoglobin  in  solution  (0.8). 
b  =  volume  of  blood  =  1  centimetre. 
o  =  volume  of  distilled  water. 

The  colorometric  method  depends  upon  the  comparison  of  the  tint  of 
the  blood  to  be  investigated  with  that  of  a  standard  solution.  In  de- 
termining the  amount  of  haemoglobin  in  this  way  we  make  use  of  the 
hsemoglobinometer  of  Gowers.     This  consists  (Fig.  120)  of  two  glass 

Fig.  126. 


A.  Pipette  buttle  for  distilled  water.   B.  Capillary  pipette.    C.  Graduated  tube.    1).  Tube  with  standard 
dilution.     F.  Lancet  for  pricking  the  finger. 

tubes  (D  and  C)  of  exactly  the  same  size.  Into  D  are  placed  20  cubic 
mm.  of  blood  diluted  with  2000  mm.  of  water,  the  strength  of  the  solu- 
tion is  therefore  1  per  cent.  C  is  graduated,  the  scale  of  100  decrees 
extending  over  a  space  equal  to  that  in  D  containing  the  1  per  cent, 
diluted  blood.  The  manner  of  using  the  apparatus  is  as  follows :  Into 
C  are  placed  20  cubic  mm.  of  the  blood  to  be  examined,  which  is  then 
diluted  until  its  color  is  the  same  as  that  in  D.      Suppose,  for  example, 


H  M  M  A  T  I N . 


251 


Fig.  Vl'i 


that  we  have  to  add  to  the  blood  to  be  investigated  placed  in  C  only  30 
degrees  of  water  (600  mm.),  in  order  to  obtain  the  same  tint  of  color  as 
that  in  D,  instead  of  as  in  the  latter  case  100  degrees  of  water  (2000 
mm.),  it  follows  that  the  blood  in  B  contains  only  30  per  cent,  of  the 
.  normal  quantity  of  haemoglobin.  Further,  if  the  number  of  corpuscles 
in  the  investigated  blood  has  also  been  shown  to  be  only  60  per  cent,  of 
the  normal  amount,  we  have  a  fraction  |-g-  =  -|,  the  numerator  being 
the  per  cent,  of  the  haemoglobin  and  the  denominator  the  per  cent,  of 
corpuscles,  giving  the  average  value  of  each  corpuscle,  or  half  the  normal 
amount. 

When  haemoglobin  is  subjected  to  the  action  of  heat,  acids,  or  caustic 
alkalies,  its  red  color  changes  to  a  smutty  hue,  by  decomposing  into  an 
albuminous  substance  and  a  colored  one  closely  resembling  bilirubin, 
and  which  has  been  described  under  the  different  names  of  haemin, 
haeruatin,  haematoin,  haematoidin, 
and  haematosin,  and  is  found  in  ex- 
travasations like  apoplectic  clots, 
corpora  lutea,  etc.  (Fig.  127). 

We  can  obtain  from  100  parts  of 
haemoglobin,  by  adding  hydrochloric 
acid,  about  4  parts  of  haematin  hv- 
drochlorate,  C34  1I35  N4  Fe  05 II  CI, 
and  96  parts  of  an  albuminous  sub- 
stance. Haematin  is  insoluble  in 
alcohol  and  water  but  soluble  in 
acids  and  alkalies,  and  can  be  ob- 
tained from  a  very  minute  portion 
of  blood  by  the  following  method : 
Triturate  the  suspected  substance 
with  a  little  common  salt  and  add 
glacial  acetic  acid,  then  warm  the 
mixture  till  bubbles  appear  and  then 
cool  it.  If  the  substance  thus  treated 
contain  blood  crystals  of  haematin, 
hydrochlorate  of  haematin  will  ap- 
pear as  rhombic  tablets,  disposed 
sometimes  as  stars  or  crosses  of  a  red 
or  brown  color:  if  oxygen  be  added, 
the  crystals  become  violet,  and  under 
the  influence  of  carbonic  acid  lose  their  transparency.  In  medico-legal 
questions,  where  there  may  be  a  very  small  quantity  of  a  material  to 
be  examined,  the  development  of  haematin  crystals  will  settle  the  ques- 
tion as  to  whether  the  suspected  material  is  or  is  not  blood,  hence  the 
importance  of  the  method  just  given  from  this  point  of  view.  It  should 
be  mentioned,  however,  that  while  the  obtaining  of  haematin  as  well  as 
haemoglobin  crystals,  by  whatever  method  used,  proves  that  the  sub- 
stance from  which  they  are  extracted  was  blood,  it  does  not  follow 
that  it  was  human  blood.  A  still  more  delicate  means  of  determining 
the  presence  of  haemoglobin,  and  therefore  of  blood,  is  by  spectrum 
analvsis,  since  both  the  arterial  and  venous  blood  through  the  haemo- 


Rhonibic  crystals  of  hsemin  or  hydrochlorate  of 
haematin,  obtained  by  Lehman's  method.  They 
are  obtained  when  blood  is  subjected  to  the  action 
of  a  mixture  of  1  part  of  alcohol,  4  parts  of  ether, 
and  1-16  of  oxalic  acid,  and  appear  as  thin  brown- 
ish and  brownish-green,  striated,  transparent 
crystalline  laminae,  often  curiously  twisted  upon 
their  long  axes,  and  soon  spontaneously  changing 
into  flat  rhombic  octahedra.     (Carpenter.) 


252  COMPOSITION    OF    THE    BLOOD. 

globin  they  contain  prevent  the  passage  of  certain  rays  of  light,  and 
so  give  rise  to  the  dark  absorption  bands  of  the  blood  spectrum.  In 
order  to  understand  the  manner  in  which  spectrum  analysis  is  applied 
to  the  study  of  the  blood,  let  us  first  endeavor  to  explain  briefly  what 
is  meant  by  spectrum  analysis  in  general. 

As  is  well   known,  when  sunlight  is  transmitted  through  a  prism,  as 
in  Fig.  128,  it  is  decomposed  into  the  seven  colors,  violet,  indigo,  blue, 

Pig.  128. 


Scheme  of  a  spectroscope  for  observing  the  spectrum  of  blood.  A.  Tube.  S.  Slit  mm.  Layer  of 
blood  with  flame  in  front  of  it.  P.  Prism.  M.  Scale.  B.  Eye  of  observer  looking  through  a  telescope, 
r  v.  Spectrum. 

green,  yellow,  orange,  and  red.  This  is  called  the  solar  spectrum.  In 
the  early  part  of  this  century  Fraunhofer  described  certain  lines  situated 
in  these  colors,  and  which  since  then  have  been  known  as  Fraunhofer's 
lines  (Fig.  129,  7),  and  which  in  all  probability  are  due  to  the  presence  of 
certain  chemical  elements  existing  in  the  form  of  vapor  around  the  sun 
and  which  prevent  the  passage  of  certain  rays  emitted  by  the  solar 
nucleus,  it  having  been  demonstrated  that  a  vapor  absorbs  rays  of 
light  having  the  same  refrangibility  as  that  which  it  emits.  Thus  a 
bright  yellow  line  in  the  spectrum,  due  to  incandescent  sodium,  will  be 
replaced  by  a  dark  one  if  the  light  from  the  burning  metal  be  intercepted 
by  the  vapor  of  the  same.  Since  then  it  has  been  shown  by  Brewster, 
Herschell,  and  Miiller,  that  various  colored  solutions  prevent  the  passage 
of  certain  of  the  rays  of  light,  dark  bands  appearing  in  the  spectrum  in 
the  place  of  the  rays  or  colors  arrested.  In  the  same  manner  the  influ- 
ence of  blood  upon  the  passage  of  light  through  it  was  investigated  spec- 
troscopically  (Fig.  128),  more  particularly  by  Hoppe-Seyler,1  Stokes,2 
and  Sorby,3  and  it  was  shown  by  these  observers  that  when  arterial 
blood  is  used  two  dark  bands  appear  (Fig.  129,  1)  between  the  Fraun- 
hofer lines  D  and  E — that  is,  in  the  yellow  of  the  spectrum,  whereas  if 
venous  blood  is  used  only  one  dark  band  (Fig.  129,  3)  appears  in  the 
yellow  near  the  line  D.  Further,  it  was  demonstrated  that  this  differ- 
ence between  arterial  and  venous  blood  was  solely  due  to  whether  the 

1  Virchow's  Archiv,  1862,  Band  xxiii.  S.  446. 

2  Proc.  of  Royal  Society  London,  1863,  1864,  vol.  xiii.  p.  355. 
;;  Quarterly  Journal  of  Science,  1865,  vol.  ii.  p.  1U8. 


HAEMOGLOBIN 


253 


coloring  matter  or  the  haemoglobin  was  oxygenated  or  not,  and  that  the 
fact  of  the  arterial  blood  being  red  or  scarlet,  and  of  venous  blood  being 
blue  or  purple,  "was  owing  to  oxyhemoglobin  being  of  a  red  hue  and 
haemoglobin  of  a  bluish  one.     That  the  difference  between  arterial  and 


Fig.  129. 

Red.  Orange. Yellow.  Green.  Blue. 


Indigo. 


si  aJB  C      _Z> 


i  ixyhsemoglobin 
and  NOo-Ha;- 
moglobin. 


CO-Hsenioglobiu. 


Reduced   Haemo- 
globin. 


Hajmatin  in  acid 
solution. 


Hwmatin   in    al- 
kaline solution. 


Reduced  Hsema- 
tin. 


•olar     spectrum 
with     Fraun- 

hofer's    lines. 


jo       M       J2       js       1-t 


venous  blood  spectroscopically,  and  as  regards  color,  is  due  simply  to 
the  haemoglobin  being  oxygenated  in  the  former  case  and  unoxygenated 
in  the  latter,  can  be  readily  demonstrated.  Thus,  if  some  reducing 
agent  like  ammonium  sulphide  or  an  alkaline  solution  of  ferrous  sul- 
phate, kept  from  precipitation  by  tartaric  acid,  be  added  to  arterial 
blood  or  the  washings  from  a  blood  clot,  the  oxygen,  being  loosely  com- 
bined with  haemoglobin,  is  at  once  seized  with  avidity  by  the  reducing 
agent,  the  two  dark  absorption  bands  disappear,  being  replaced  by  the 
one  dark  band  characteristic  of  venous  blood,  and  the  color  changes 
from  red  to  blue.  On  the  other  hand,  with  the  exposure  of  venous 
blood  or  a  solution  of  haemoglobin  to  oxygen,  or  air  containing  such, 
the  one  dark  band  will  disappear,  being  replaced  by  the  two  dark  bands 
so  characteristic  of  arterial  blood,  and  the  color  will  change  from  blue 
to  red  again. 

According  to  the  amount  of  oxyhaemoglobin  present  in  the  blood, 
or  solution  of  haemoglobin  used,  the  dark  bands  will  vary  in  extent. 
Thus,  in  a  concentrated  solution  the  two  bands  run  into  one,  there 
being  a  general  absorption  at  the  blue  and  red  ends  of  the  spectrum, 
also  the  light  then  passing  through  only  the  green  and  red  parts.  With 
a  still  further  increase  in  the  strength  of  the  solution  light  will  be  trans- 
mitted through  only  the  red  portions  of  the   spectrum,  hence  its   red 


254  COMPOSITION    OF    THE    BLOOD. 

color,  as  seen  by  transmitted  light.  It  is  hardly  necessary  to  add  that 
the  red  rays  are  the  last  to  disappear. 

The  extreme  delicacy  of  spectrum  analysis,  as  applied  to  the  deter- 
mination of  the  presence  of  blood,  may  be  appreciated  from  the  fact  of 
the  two  bands  appearing  in  the  spectrum  of  light  transmitted  through 
a  layer  1  centimetre  thick  of  a  solution  containing  only  1  gramme  (15.4 
grains)  in  10,000  c.  cm.  (20  pints  of  water,  or,  in  round  numbers,  about 
1  grain  of  haemoglobin  in  a  pint  and  a  third  of  water.  This  is  an  im- 
portant fact,  since,  under  certain  circumstances,  in  medico-legal  cases, 
for  example,  the  quantity  of  the  suspected  substance  being  exceedingly 
small,  spectrum  analysis  would  be  the  only  means  by  which  it  could  be 
determined  whether  it  was  blood  or  not.  Indeed,  substances  already 
decomposed  and  putrid,  solutions  made  by  washing  with  water,  old 
stains  upon  iron,  wood,  linen  that  may  have  lain  aside  unnoticed  for 
years,  can  be  shown  by  the  spectroscope  to  contain  hgemoglobin.  and 
necessarily,  therefore,  to  have  been  derived  from  blood,  since  no  other 
known  substance  affects  light  as  haemoglobin. 

Even  if  the  spectrum  obtained  was  that  of  carbonic  oxide,  or  haema- 
toin  (acid  haematin),  characterized  by  two  and  one  absorption  bands 
respectively  (Fig.  129,  2,  4),  as  in  the  case  of  arterial  and  venous  blood, 
this  need  be  no  source  of  confusion,  since  the  absorption  bands  of  car- 
bonic oxide  and  hsematin  are  not  situated  in  exactly  the  same  part  of 
the  spectrum  as  those  of  arterial  and  venous  blood,  and  even  if  a  doubt 
existed  as  to  the  exact  locality  of  the  bands,  there  could  be  none  with 
reference  to  the  presence  of  blood,  as  it  is  the  haemoglobin  in  such  case, 
combined  with  either  oxygen  or  carbonic  acid,  or  otherwise  modified, 
which  is  the  cause  of  the  appearing  of  the  bands.  It  should  be  men- 
tioned in  this  connection  that  spectrum  analysis,  like  all  other  means 
at  present  at  our  command,  enables  us  only  to  determine  that  a  sub- 
stance is  blood,  but  not  necessarily  human  blood.  In  examining  the 
blood  spectroscopically,  while  the  ordinary  spectroscope  can  be  used, 
the  microspectroscope  will  be  found  more  convenient,  and  especially  the 
form  described  by  Vierordt.1 

In  the  fact  of  the  oxygen  of  the  blood  existing,  for  the  most  part,  in 
a  state  of  loose  chemical  combination  with  the  haemoglobin  lies  the 
explanation  of  the  manner  in  which  blood  absorbs  or  gives  off  oxygen. 
Did  the  oxygen  exist  simply  in  a  state  of  solution  in  the  blood  then  the 
amount  absorbed,  or  given  off,  would  depend  upon  the  amount  of  pres- 
sure present.  That  such  is  not  the  case,  however,  can  be  shown  by 
exposing  venous  blood,  containing  little  or  no  oxygen,  to  a  succession 
of  atmospheres  containing  increasing  quantities  of  oxygen.  At  first 
there  is  a  very  rapid  absorption  of  oxygen,  but  afterward  this  dimin- 
ishes or  ceases  altogether.  On  the  other  hand,  if  arterial  blood,  con- 
taining a  considerable  quantity  of  oxygen,  be  exposed  to  successively 
diminishing  pressures,  at  first  little  oxygen  is  given  off,  but  afterward 
the  escape  is  sudden  and  rapid.  The  amount  of  oxygen  taken  up  or 
given  off  by  blood  is  not,  therefore,  dependent  upon  pressure,  except  so 

1  Die  Quantitative  Spectral  Analyse  in  ihrer  Anwendung  auf  Physiologic.     Tubingen,  1876, 


GASES    OF    THE    BLOOD.  255 

far  as  the  latter  influences  the  passages  to  or  from  the  plasma,  but  upon 
chemical  affinity ;  the  amount  of  oxygen  absorbed,  or  given  up  by  the 
haemoglobin,  is,  therefore,  a  given  amount,  1.76  c.  cm.  of  oxygen  for  1 
gramme  of  haemoglobin.  In  this  connection  it  may  not  be  inappro- 
priate to  mention  that  the  oxygen  absorbed,  or  given  off*  by  the  haemo- 
globin, has  nothing  to  do  with  the  oxygen  entering  into  its  molecular 
composition,  and  as  already  given  in  its  chemical  formula. 

That  the  haemoglobin  is  that  part  of  the  blood  which  absorbs  and 
gives  up  the  greatest  part  of  the  oxygen  there  can  be  no  doubt,  since, 
if  serum  freed  of  the  corpuscles,  and  therefore  of  haemoglobin  (the  latter 
constituting  90  per  cent,  of  the  former),  be  experimented  with,  instead 
of  blood,  little  or  no  oxygen  is  absorbed,  or  given  off",  perhaps  ^  per 
cent,  of  the  entire  blood,  of  which  the  serum  was  a  part,  and  that  pro- 
portional to  the  pressure.  It  is,  therefore,  to  their  haemoglobin  that 
the  red  corpuscles  owe  their  function,  as  we  have  seen,  of  being  oxygen 
carriers,  and  since  the  haemoglobin  at  low  pressure  readily  gives  up  its 
oxygen,  the  significance  of  this  substance,  in  respiration,  becomes  very 
evident.  In  this  connection  it  may  be  mentioned  that  the  carbonic 
acid  present  in  the  blood  does  not  appear  to  be  simply  dissolved  there, 
since  the  absorption  and  giving  up  of  carbonic  acid  by  the  blood,  as  in 
the  case  of  oxygen,  is  not  dependent  upon  pressure. 

It  is  highly  probable  that  the  carbonic  acid  exists  in  the  blood  as 
sodium  bicarbonate  and  carbonate,  and  quite  possible  that  the  hiemo- 
globin  of  the  red  corpuscles  may  play  the  part  of  an  acid,  decomposing 
these  salts,  and  setting  the  carbonic  acid  free,  since  more  carbonic  acid 
is  given  off*  when  blood  is  subjected  to  a  mercurial  vacuum  than  when 
serum  alone  is  used.  It  is  well  known  that  after  all  the  carbonic  acid 
has  been  extracted  from  the  serum  that  is  possible  by  the  gas  pump,  two 
to  five  per  cent,  more  can  be  obtained  by  adding  acid  to  the  serum. 

The  small  amount  of  nitrogen  that  the  blood  contains  appears  to  exist 
there  in  a  simple  state  of  solution,  the  blood  absorbing  but  little  less 
nitrogen  than  that  absorbed  by  water:  the  amount  depending,  at  least. 
within  limits  upon  the  law  of  pressure. 

The  gases  of  the  blood,  as  has  just  been  incidentally  mentioned,  can 
be  obtained  by  subjecting  the  blood  to  the  mercurial  vacuum.  For  this 
purpose  we  make  use  of  Grehaut's  gas  pump,  as  constructed  by  Alver- 
gniat,  of  Paris.  This  consists  (Fig.  130)  of  a  glass  reservoir  (15 ).  which 
can  be  lowered  or  raised  by  a  rack  and  pinion,  and  which  communicates 
by  the  flexible  tubeb  with  the  vertical  glass  tube  c,  one  metre  in  length, 
and  which  is  firmly  secured  to  the  stand.  The  vertical  tube  expands 
into  the  oval-shaped  dilatation  A.  which  is  continued  upward  as  the 
narrow  tube  f,  and  whose  cavity,  by  means  of  the  stopcock  R,  can 
be  put  in  communication  either  with  that  of  the  lateral  tube  h,  or  of 
the  tube  i  terminating  above  in  the  cup  C,  or  cut  off*  from  either. 
The  lateral  tube  h  is  connected  through  tubing  (h/)  with  the  stem  e 
of  the  bulb  D,  into  which  is  inserted  a  flexible  tube  (1)  furnished  with 
a  stopcock  (r),  for  the  transference  of  the  blood  whose  gases  are  to  be 
determined.  The  stopcock  (R)  being  in  the  position  1,  Fig.  130 — 
that  is,  all  communication  between   the  cavity  of  the  vertical  tube  c 


256 


COMPOSITION     OF    THE     BLOOD. 


being  completely  cut  off'  from  that  of  the  lateral  and  terminal  tubes  h  and 
i,  mercury  is  poured  through  the  reservoir  B  until  it  not  only  rises  to  the 
level  of  the  stopcock,  but  completely  fills  the  reservoir  itself.    The  reser- 


Fig.  130. 


Alvergniat's  gas  pump.     (Bert.) 


voir  being  then  lowered  the  mercury  will  fall  in  the  vertical  tube  c,  a 
vacuum  being  produced  in  consequence  above  it.  If  the  stopcock  be 
now  turned  into  the  position  2  (Fig.  130),  the  air  will  pass  in  from  the 
lateral  tube  and  its  appendage  into  the  vertical  tube  c,  and  the  mer- 
cury will  fall  still  lower.  The  stopcock  being  now  returned  into  the 
position  1  (Fig.  130),  the  reservoir  is  then  elevated,  and  the  mercury 
with  the  included  air  will  ascend   into  the  oval  dilatation  A.      The 


GASES    OF    THE    BLOOD. 


257 


Fig.  131. 


(After  Sanderson.) 


stopcock  being  now  turned  into  the  position  3  (Fig.  130),  the  air  that 
was  just  drawn  into  the  vertical  tube  c  from  the  lateral  tube  h 
passes  out  of  the  tube  i  into  the  atmosphere.  The  stopcock  is  then 
returned  to  the  original  position  (Fig.  130,  1).  By  depressing  and  ele- 
vating the  reservoir  B,  and  manipulating  the  stopcock  R  in  the 
manner  just  explained,  in  a  very  short  time  a  good  vacuum  is  produced 
in  the  lateral  tube  h  h/  e,  and  its  appendage  D.  A  tube  having  been 
inserted  into  the  artery  or  vein,  the 
blood  to  be  analyzed  is  then  trans- 
ferred from  the  vessel  in  the  living 
animal  to  the  vacuum  in  the  follow- 
ing manner  :  A  tube  (M)  of  known 
capacity,  say  50  c.  c,  tapering  oft* 
at  one  end  (G),  and  guarded  by 
a  stopcock  (B)  at  the  other,  is 
filled  with  mercury  by  aspiration. 
The  tube  is  then  at  the  end  B 
put  in  communication  with  the 
bloodvessel,  by  means  of  a  rubber  tube  readily  slipping  over  the  canula 
previously  inserted  into  the  vessel,  which  is  closed  by  a  clip.  The  stop- 
cock being  now  opened,  and  the  clip  removed,  the  blood  is  allowed  to 
flow  away  for  a  moment,  and  then  (connection  being  made  by  the 
tubing)  into  the  tube  M,  driving  out  of  the  latter  the  mercury,  which 
can  be  received  into  a  convenient  receptacle.  As  soon  as  the  tube  is 
filled  with  blood,  the  stopcock  being  closed,  connection  is  broken  with 
the  vessel,  and  the  tube  reversed  in  position,  so  that  its  tapering  end  G 
(Fig.  131)  may  be  inserted  into  the  small  mercury  trough  U,  previously 
placed  in  the  large  trough  N  containing  ice-water,  to  retard  the  coagu- 
lation of  the  blood  in  the  tube.  The  glass  tube  is  then  joined  by  the 
end  B  to  the  rubber  tube  D  containing  boiled  distilled  water,  and 
previously  placed  over  the  tube  t  (Figs.  130,  131),  the  latter  being 
furnished  with  a  stopcock  (Fig.  130,  r)  and  leading  to  the  vacuum. 
Both  stopcocks  (B  and  r)  being  now  opened,  the  blood  passes  from  the 
glass  tube  (Fig.  131,  M)  into  the  vacuum  D  e  (Fig.  130),  its  place 
being  filled  with  mercury  from  the  trough  ;  the  stopcocks  are  then 
closed.  The  blood  having  passed  through  the  tube  into  the  bulb  D, 
gives  up  its  gases  readily  into  the  vacuum,  the  liberation  of  which  is 
greatly  facilitated  by  surrounding  the  bulb  with  water  (Fig.  130)  at 
a  temperature  of  about  40°  Cent.  (104°  Fahr.).  As  it  is  also  desirable 
to  keep  back  the  froth  and  foam  arising  from  the  blood  as  much  as 
possible,  the  lateral  tube  e  is  surrounded  by  a  tin  one,  through 
which  ice-cold  water  flows  from  a  reservoir  (z),  and  which  effectually 
accomplishes  the  object.  The  gases  having  been  separated  from  the 
blood,  are  next  transferred  into  the  vertical  tube  c,  and  thence  through 
the  terminal  one  i  into  a  eudiometer,  standing  over  mercury  in  the 
cup  C,  by  depressing  the  mercurial  reservoir  B,  and  turning  the 
stopcock  R  in  the  same  manner  as  just  explained.  The  quantity  of 
blood  from  which  the  gases  are  obtained  will,  of  course,  depend  upon 
the  size  of  the  tube  transmitting  the  blood  from  the  vessel  to  the 
vacuum,  the  vessel  being  clamped  as  soon  as  the  tube  is  full  of  blood. 

17 


258  COMPOSITION    OF    THE    BLOOD. 

In  order  to  determine  the  nature  ami  amount  of  the  gases  given  off 
from  the  blood  we   make   use  of  a  eudiometer,  slightly  bent    up  at   the 
end.     Supposing  that  the  gases  have  passed  out  of  the  pump  and  have 
displaced  part  of  the  mercury  in  the  eudiometer,  we  then  add  caustic 
potash  in  solution,  and  to  drive  out  all  bubbles  of  air  close  the  tube  by 
inserting  a  cork  through  which  a  capillary   tube  passes  of  the  shape 
represented  in  Fig.  132.      The  tube  is  then   tilted,  the  fin- 
Fig.  132.      ger  being  firmly  placed  on  the  top  of  the  capillary  opening, 
and  the  caustic  potash   makes  its  way  up  through   the  mer- 
cury and  combines  with  the  carbonic  acid  gas.     The  eudi- 
ometer being   then    placed    in   the  mercurial    trough    and 
shaken  up  a  few  times,  until  the  level  of  the  mercury  in 
the  eudiometer  and  the  trough  are  the  same,  the  amount  of 
carbonic  acid  is  read  off,  the  condition  of  the  barometer  and  temperature 
of  the  laboratory  being  at  the  same  time  noted. 

In  determining  the  presence  and  amount  of  the  oxygen  gas  Ave  pro- 
ceed in  precisely  the  same  way,  only  making  use  of  a  solution  of  pyro- 
gallic  acid  instead  of  caustic  potash.  After  having  determined  the  amount 
of  carbonic  acid  and  oxygen,  what  remains  in  the  eudiometer  may  practi- 
cally be  regarded  as  consisting  of  nitrogen.  The  volume  of  the  gas 
obtained  must  be  reduced,  of  course,  to  standard  pressure  760  mm. 
mercury,  and  standard  temperature  0°  C,  which  can   be  done  by  the 

V'  X  h 
following  formula :    F"=— — — — ,   in    which    V    is    the    required 

760(1  +  at)  l 

volume  at  standard  temperature  0°  C.  and  standard  pressure  760  mm. 
V  the  volume  at  the  observed  temperature  and  pressure,  h  the  observed 
pressure,  a  the  coefficient  of  expansion,  a  constant  (.003665),  and  t  the 
observed  temperature. 

The  formula  is  derived  as  follows.  Firstly,  with  reference  to  the 
correction  of  the  given  volume  for  temperature  : 

1  +  at    :    1    :  :     V    :     V  or    V 


1  +  at 


And  secondly,  for  pressure  : 


V    :    :  :   h  :   io<'  or   J 


1  +  at  700  (1  +  at) 

As  an  illustration  of  the  manner  of  using  the  formula  the  following 
example  will  suffice.  Suppose  the  given  volume  V  of  gas  to  be  cor- 
rected for  temperature  and  pressure  amounts  to  30  c.  c,  the  observed 
barometric  pressure  h  being  740  mm.  and  the  temperature  t  of  the  room 
15°  C. :  then  the  required  volume,  or 

v  _  30  X  740  22200  -  g 

760  (1  +  .003665)  "  '    80.178200  " 

that  is  to  say,  30  c.  c.  of  a  gas,  the  temperature  being  15°  C.  and  the 
pressure  740  mm.,  are  reduced  to  27.0  c.  c.  at  standard  temperature 
0°  C.  and  pressure  700  mm. 

In  purely  physical  researches  upon  gases,  still  further  corrections  are 


ARTERIAL    AND     VENOUS    BLOOD.  259 

made  for  the  tension  of  the  aqueous  vapor,  and  for  the  meniscus;  the 
errors  due  to  these  influences  are,  however,  so  small  that  in  physiological 
investigations  they  are  usually  neglected. 

It  will  be  found  on  an  average  that  for  100  vol.  of  blood  used  there 
will  be  extracted  by  means  of  the  mercurial  pump  about  60  vols,  of  gas, 
the  barometric  pressure  being  760  mm.  (30  cub.  in.)  and  the  tempera- 
ture 0°  C.  (32°  F.),  and  that  the  composition  of  this  gas 'will  be  accord- 
ing to  the  kind  of  blood  examined,  as  follows  : 


Oxygen. 

Carbonic  acid. 

Nitrogen. 

Arterial  blood 

20  vol. 

39  vol. 

1  to  2  vol 

Venous  blood 

.  8  to  12    " 

46     " 

1  to  2     " 

It  is  evident,  therefore,  that  arterial  does  not  differ  from  venous  blood 
in  containing  more  oxygen  than  carbonic  acid,  since  there  is  more  car- 
bonic acid  than  oxygen  in  arterial  as  well  as  in  venous  blood,  but  in  the 
fact  that  while  the  carbonic  acid  is  in  excess  in  both  instances  there  is 
more  oxygen  in  arterial  than  in  venous  blood,  and  more  carbonic  acid 
in  venous  than  in  arterial  blood. 

It  will  be  observed,  according  to  Table  XL VIII.,  that  there  are  fewer 
red  corpuscles  in  arterial  than  in  venous  blood.  According  to  some 
other  authorities,  however,  the  reverse  is  the  case,  the  arterial  containing 
more  corpuscles  than  the  venous  blood.  It  must  be  remembered,  how- 
ever, that  the  red  or  blue  color  of  the  blood  depends  not  so  much  upon 
the  relative  number  of  corpuscles  present  as  upon  the  fact  of  the  haemo- 
globin of  the  same  being  oxidized  or  deoxidized.  There  are  other 
minor  differences  between  arterial  and  venous  blood,  as  may  be  seen 
from  Table  XLVIII.,  but  the  essential  difference  depends  upon  the 
amount  of  oxyhemoglobin  present,  the  analyses  of  Poggiale,1  Nasse,2 
Lehmann,3  etc.,  showing  that  while  there  is  a  variability  in  the  relative 
quantity  of  the  other  substances  the  differences  are  only  fractional. 

Table  XLVIII.4— Blood. 

Arterial  (red).  Venous  (blue). 

/-1  f  Oxygen  20  per  cent.  vol.  10  per  cent.  vol. 

"  \  Carbonic  acid  29  per  cent.  vol.     46  per  cent.  vol. 
Water. 
Fibrin. 

Extractives  .     More.  Less. 

Salts. 
Sugar. 
Corpuscles. 

Albumen  .     .     Less.  More. 

Fats. 

The  composition  of  the  blood  in  the  arterial  system  is  pretty  much 
the  same  throughout  the  body  :  that  of  the  venous,  however,  differs  con- 
siderably according  to  the  parts  and  time  of  examination.  We  have 
already  studied  the  blood  of  the  splenic  vein,  and  have  seen  how  that  of 
the  portal  is  modified  by  admixture  with  that  of  the  former  and  by  the 
products  of  digestion,  and  have  considered  the  difference  in  the  blood  of 

1  Comptes  Rendus,  1848,  t.  xxvi.  p.  143.  -  Wajnier :  Physiologic,  Band  i.  S.  170. 

3  Physiologie  Chemie,  Band  ii.  S.  203.  4  Ranke  :   Physiologic,  1875,  S.  358. 


260  COMPOSITION    OF    THE    BLOOD. 

the  hepatic  vein  as  compared  with  that  of  the  portal.  The  peculiarities 
of  the  blood  of  the  pulmonary  and  renal  veins  will  be  deferred  till  the 
lungs  and  kidneys  have  been  considered. 

As  the  albuminous  principles  of  the  body  agree  essentially  in  their 
general  chemical  composition  with  each  other  and  with  the  albumen  of 
the  blood  and  food,  and  as  all  these  principles  are  readily  transformed 
into  each  other,  it  is  probable  that  the  albuminous  substances  of  the 
body  generally,  like  ostein,  cartilagin,  globulin,  etc.,  are  derived  directly 
or  indirectly  from  the  albumen  of  the  blood.  This  view,  if  correct, 
explains  why  the  blood  contains  such  a  large  quantity  of  albumen, 
amounting  to  71  parts  when  dry  or  329  in  a  moist  condition  in  1000 
parts  of  blood. 

Generally  speaking,  the  blood  of  strong,  vigorous  persons  contains 
most  albumen,  that  of  weak  ones  the  least. 

The  amount  of  albumen  may  in  health  vary  slightly  above  or  below 
the  normal  standard,  but  if  it  falls  much  below  it  is  an  evidence  of  dis- 
ease. Thus  there  is  a  diminution  in  Bright' s  disease  of  the  kidneys, 
where  a  large  amount  of  albumen  disappears  from  the  blood,  transudes 
through  the  vascular  system,  and  escapes  in  the  urine.  As  the  character 
of  albumen  has  been  already  described,  I  will  not  dwell  further  upon  it. 

There  has  always  been  and  is  still,  a  considerable  difference  of  opinion 
among  physiologists  as  to  the  role  of  fibrin  in  the  blood ;  as  to  whether 
it  is  effete  and  useless,  or  whether  it  is  susceptible  of  being  elaborated 
into  something  further  and  useful.  Among  the  many  views  that  have 
been  offered  as  to  the  nature  of  fibrin  that  of  Milne  Edwards  is,  perhaps, 
the  most  plausible.  According  to  this  distinguished  physiologist,  fibrin 
is  a  product  of  the  activity  of  the  tissues,  and  in  normal  circumstances 
is  as  rapidly  destroyed  as  formed  in  the  blood  by  the  corpuscles,  being 
burnt  up  by  the  oxygen  carried  by  these  bodies  and  converted  into 
excrementitious  material. 

The  correctness  of  this  view  can  be  tested  by  considering  whether  it 
will  explain  the  different  amount  of  fibrin  present  in  the  blood  in  the 
various  conditions  that  the  system  may  be  subject  to.  Thus,  if  the 
theory  be  correct,  the  proportion  of  two  to  three  parts  of  fibrin  in  1000 
of  blood  should  increase  or  decrease  as  the  activity  of  the  tissues  increases 
or  decreases,  the  amount  of  the  corpuscles  remaining  unchanged.  Should 
the  number  of  the  corpuscles,  however,  diminish,  the  activity  of  the  tis- 
sues remaining  the  same,  the  fibrin  ought  to  increase  in  amount.  If, 
however,  the  number  of  corpuscles  diminishes  at  the  same  time  that  the 
activity  of  the  tissues  is  lowered,  the  amount  of  fibrin  will  remain  unaf- 
fected. Let  us  see  whether  these  theoretical  conditions  are  ever  realized 
in  the  living  animal.  It  is  well  known  from  the  researches  of  patholo- 
gists, more  particularly  from  those  of  Andral,  that  there  is  invariably 
an  increase  of  fibrin  in  acute  inflammations  like  those  of  pneumonia, 
pleurisy,  diseases  in  which  there  is  an  excess  at  first  of  vital  action  in 
the  tissues  affected.  On  the  other  hand,  in  diseases  like  typhoid  fever, 
when  the  vital  forces  are  greatly  prostrated,  the  amount  of  fibrin  is 
diminished.  In  these  diseases,  at  least  in  the  early  stages,  the  number 
of  the  corpuscles  remains  the  same.  In  chlorosis,  however,  where  the 
number  of  corpuscles  is  diminished,  the  amount   of  fibrin    increases. 


SALTS    OF    THE    BLOOD.  261 

Anaemia  is  an  illustration  of  the  amount  of  fibrin  remaining  constant 
while  the  vital  powers  are  lowered  and  the  number  of  corpuscles  dimin- 
ished coincidently.  This  inverse  ratio  between  the  corpuscles  and  the 
fibrin  is  seen  also  in  gestation,  where  the  fibrin  is  increased  and  the  cor- 
puscles are  diminished.  The  blood  from  the  splenic  vein  is  also  rich  in 
fibrin,  but  deficient  in  red  corpuscles,  and  it  is  well  known  that  repeated 
bleedings  increase  the  fibrin  but  diminish  the  corpuscles.  Many  facts 
like  the  above,  and  others  often  apparently  contradictory,  illustrate 
this  antagonism,  so  to  speak,  between  the  corpuscles  and  the  fibrin.1  It 
must  be  admitted,  however,  that  in  all  the  analyses  made  of  the  blood 
there  are  white  corpuscles,  etc.,  in  the  fibrin  which  are  estimated  with 
it,  and  this  should  be  remembered  when  the  amount  of  fibrin  stated  to 
have  been  found  in  an  analysis  is  taken  as  the  basis  of  a  theory. 

It  is  well  known  that  in  some  cases  the  increase  in  the  amount  of  the 
fibrin  corresponds  exactly  to  a  diminution  in  that  of  the  albumen,  so  that 
one  source  of  the  fibrin  may  be  due  to  a  transformation  of  the  albumen. 
The  very  small  amount  of  fibrin  in  the  blood,  even  when  estimated  in 
the  moist  condition,  being  only  then  about  8  parts  in  the  100",  together 
with  facts  like  those  mentioned  above,  leads  one  to  consider  fibrin  rather 
as  effete  matter.  Still  further  investigation  may  assign  some  function 
to  it  as  yet  unknown. 

The  fatty  matters  that  are  found  in  the  blood  consist  of  serolin, 
cholesterin,  phosphorized  fats,  and  saponified  principles  like  the  oleates, 
margarates,  etc.  Sometimes  the  oleic  acid  exists  in  a  free  state.  The 
fatty  substances,  as  may  be  seen  from  Table  XLIV.,  exist  only  in  small 
quantities  in  the  blood,  and  often  depend  upon  the  kind  of  diet.  Thus 
fatty  food  increases  the  amount  of  fat  in  the  blood.  The  use  of  these 
fatty  substances  in  the  blood  is  not  exactly  understood.  According  to 
some  physiologists,  it  is  thought  that  the  fats  contribute  to  the  forma* 
tion  of  the  corpuscles,  it  being  well  known  that  the  number  of  these 
bodies  increases  under  the  administration  of  cod-liver  oil. 

The  saline  materials  of  the  blood  consist  of  sodium,  potassium,  and 
magnesium  chlorides,  some  free  soda,  of  sodium  and  potassium  carbo- 
nates, of  sodium,  potassium,  and  magnesium  sulphates,  of  sodium,  potas- 
sium, magnesium,  and  calcium  phosphates:  in  a  word,  three  chlorides, 
free  soda,  two  carbonates,  three  sulphates,  four  phosphates.  It  is  pos- 
sible that  these  salts  do  not  always  exist  in  the  blood  in  the  above  form, 
that  arrangement  being  due  perhaps  to  the  difficult  and  complicated 
processes  incidental  to  their  analysis.  It  is  well  known  that  a  con- 
siderable quantity  of  the  earthy  phosphates  is  molecularly  united  with 
the  fibrin  and  part  of  the  sodium  chloride  with  the  albumen.  The 
natural  relation  of  these  salts  as  well  as  that  of  the  others  must,  there- 
fore, to  a  certain  extent,  at  least,  be  disarranged  in  an  analysis. 

The  importance  of  these  salts  is  seen  not  only  in  the  nutrition  of  the 
tissues,  the  calcium  and  magnesium  phosphates,  for  example,  supplying 
material  for  the  production  of  bone,  but  they  are  also  indispensable  in 
maintaining  the  blood  in  its  proper  chemical  and  physical  condition. 
Thus  the  alkalinity  of  the  blood  is  due  to  its  sodium  carbonate,  while 

i  Milne  Edwards:  Op.  tit.,  tome  i.  pp.  258-274. 


262  COMPOSITION    OF    THE    BLOOD. 

the  sodium  phosphate  dissolves  the  albuminous  principles  and  inorganic 
"matters  which  are  insoluble  in  pure  water.     The  earthy  phosphates  are 
held  in  solution  in  the  serum  through  the  presence  of  this  salt,  and  to 
it  is  due  the  fact  that  so  much  carbonic  acid  is  dissolved  in  the  blood. 

The  existence  of  the  corpuscles  depends  on  the  presence  of  sodium 
chloride  and  other  salts  in  the  serum,  which,  absorbing  any  superfluous 
water,  prevent  their  dissolution.  According  to  Milne  Edwards,1  the 
coloring  matter  of  the  corpuscles  is  very  soluble  in  water,  but  not  so  in 
water  to  which  have  been  added  albumen  and  sodium  chloride,  both  of 
which  are  found  in  the  serum.  While  probable,  yet  it  cannot  be  stated 
positively,  that  age  or  sex  influences  the  quantity  of  these  salines.  There 
is  no  doubt,  however,  that  these  principles  vary  in  quantity  according  to 
the  kind  of  food.  An  exclusively  animal  or  vegetable  diet  will  affect  the 
amount  of  alkaline  phosphates  respectively.  Thus  the  former  are  most 
abundant  in  the  blood  of  the  carnivora,  the  latter  in  that  of  the  her- 
bivora.  The  proportion  of  the  saline  principles  of  the  blood  is  also  known 
to  vary  in  disease ;  but  the  limited  data,  however,  that  have  been  col- 
lected are  of  more  interest  at  present  to  the  pathologist  than  to  the 
physiologist.  One  of  the  most  important  substances  found  in  the  blood 
is  iron.  Indeed,  when  it  is  deficient  the  red  corpuscles  diminish  in 
number.  The  normal  standard  is  soon  regained,  however,  when  iron  is 
administered.  The  iron  exists  in  the  blood  combined  with  the  coloring 
matter  of  the  corpuscles  ;  the  color  of  the  latter,  though,  does  not  depend 
upon  the  iron,  as  was  once  supposed,  for  the  color  will  remain  after  the 
iron  is  removed,  while  the  blood  of  certain  invertebrates  like  the  Limulus 
(horseshoe  crab)  is  colorless,  though  iron  is  present.  As  to  the  exactv 
amount  of  iron  in  the  blood  there  is  still  some  difference  of  opinion. 
According  to  Schmidt  (Table  XL VII.),  it  is  still  undetermined.  Bec- 
querel  and  Rodier  give  0.5  part  in  the  1000  of  blood,  while  Kuss2 
estimated  it  at  7  per  cent,  of  the  hsematosin  or  hsemacrystallin  or 
coloring  matter,  which  would  give  about  7  grammes  of  iron  (over  100 
grains),  there  being,  according  to  that  physiologist,  about  100  grammes 
of  luematosin  in  the  blood. 

Various  other  substances  are  found  in  the  blood  in  addition  to  those 
already  mentioned,  which  I  will  consider  when  the  subject  of  excretion 
is  taken  up  ;  such  are  urea,  uric  acid,  creatin,  creatinin,  etc. 

Summing  up,  it  may  be  said  that  the  blood  consists  largely  of  water 
carrying  in  solution  corpuscles,  albumen,  salts,  and  excrementitious  mat- 
ters, and  that  the  corpuscles  are  a  source  of  powTer,  while  the  albumen 
and  salts  furnish  materials  to  the  tissues,  the  salts,  in  addition,  regu- 
lating the  character  of  the  blood. 

In  concluding  this  sketch  of  the  blood  a  few  words  may  be  said  in 
reference  to  transfusion,  though  this  subject  is  usually  considered  as 
belonging  to  therapeutics.  About  the  middle  of  the  seventeenth  cen- 
tury experiments  were  performed  which  showed  that  life  could  be  saved 
in  an  animal  dying  from  a  copious  hemorrhage,  for  example,  by  intro- 
ducing into  its  vessels  fresh  blood  from  an  animal  of  the  same  species. 
Application  was  soon  made  of  this   fact   in   the  treatment  of  human 

1  Op.  cit.,  tome  i.  p.  177.  -  Op.  cit.,  p.  118. 


TRANSFUSION.  263 

beings,  and  the  wildest  enthusiasm  was  excited,  great  hopes  being 
entertained  that  old  age  could  be  rejuvenated,  etc.  Several  fatal  cases 
of  transfusion,  however,  occurring,  the  practice  was  prohibited  in  many 
places,  by  law.  It  was  revived  in  the  early  part  of  this  century,  and 
with  success.  There  are  a  number  of  cases  on  record1  which  would 
have  undoubtedly  proved  fatal  had  not  transfusion  been  used.  It  seems 
to  be  particularly  efficacious  in  cases  of  uterine  hemorrhage.  When 
blood  is  transfused  it  should  be  introduced  very  slowly,  and  great  cau- 
tion should  be  exercised  lest  any  air  be  mixed  with  it,  and  the  quantity 
used  be  small,  not  exceeding  three  or  four  ounces. 

Having  studied  the  general  character  of  the  blood,  let  us  now  turn  to 
the  consideration  of  its  circulation. 

1  Beranl  :  Physiologic,  tomo  iii.  p.  219.     Paris,  18.51. 


CHAPTER   X  Y  1 1 1 


CIRCULATION  OF  THE  BLOOD. 


We  have  seen  that  the  use  of  the  food  is  to  repair  the  waste  of  the 
tissues,  to  supply  fuel  for  the  production  of  heat  and  force,  and  that  the 
food  is  digested,  absorbed,  and  gradually  elaborated  into  blood.  To 
supply  the  wants  of  the  system,  to  furnish  the  tissues  with  material  for 
their  maintenance  and  repair,  to  carry  away  that  which  has  become 
worn  out  and  effete,  the  blood  must  move  freely  through  all  parts  of  the 
economy.  It  must  circulate.  By  the  circulation  of  the  blood  is  meant 
that  the  blood  moves  in  a  circle — that  is,  if  we  follow  its  course,  for 
example  (Fig.  133),  after  it  passes  from  the  left  ventricle  of  the  heart 
to  the  aorta  we  shall  see  that  the  blood  flows  from  the  aorta  into  the 
arteries,  thence  into  the  capillaries,  from  there  into  the  veins,  from  the 
latter  by  the  vena  cava  into  the  right  side  of  the  heart,  from  the  right 
side  of  the  heart  through  the  lungs  back  to  the  left  side  of  the  heart  to 
the  left  ventricle,  where  it  started. 

Usually  the  passage  of  the  blood  from  the  right  auricle  of  the  heart 
through  the  lungs  and  left  ventricle  is  known  as  the  lesser,  or  pulmonary 
circulation,  while  the  route  from  the  left  ventricle  through  the  arteries, 
capillaries,  and  veins  to  the  right  auricle  is  distinguished  as  the  greater 
or  systemic  circulation.  Using  the  word  circulation  in  the  sense  in 
which  it  is  ordinarily  accepted,  the  terms  lesser  and  greater  circulations 
are  not  appropriate,  and  may  mislead,  inasmuch  as  we  have  seen  that 
the  blood  does  not  pass  directly  back  from  the  lungs  to  the  right  auricle 
of  the  heart,  whence  it  came,  but  indirectly,  first  coursing  through  the 
system,  and  that  the  blood  flowing  from  the  left  ventricle  only  returns 
there  after  having  passed  through  the  lungs.  There  is,  in  this  sense, 
then,  only  one  circulation,  however  conveniently  the  latter  may  be 
divided  into  the  so-called  lesser  and  greater  circulations.  In  another 
sense,  however,  there  are  innumerable  circulations,  greater  and  lesser, 
since  the  blood,  after  leaving  the  heart  (Fig.  133),  may  go  either  to  the 
head,  or  viscera,  or  extremities  before  returning  to  the  heart. 

As  the  motion  of  the  blood  is  in  a  circle,  it  is  immaterial  at  what  part 
of  the  vascular  system  we  begin  its  study.  We  shall  see,  however,  that 
in  exposing  any  of  the  great  functions  of  the  body,  if  we  follow,  as  far 
as  practicable,  the  order  in  which  the  facts  were  actually  discovered,  and 
the  phenomena  generalized  by  the  human  mind,  that  the  subject  will 
be  presented  in  the  most  natural  logical  sequence.  We  will  begin, 
therefore,  the  study  of  the  circulation  of  the  blood,  with  the  demonstra- 
tion of  the  structure  and  function  of  the  heart. 


THE    HEART. 


265 


The  Heart. 

The  heart  is  a  hollow  pear-shaped  muscular  organ.  It  is  situated  in 
the  thoracic  cavity,  and  lies  between  the  lungs,  with  which  it  is  con- 
nected by  the  great  bloodvessels  arising  from  its  base  (Fig.  134).      The 


Fig.  133. 


Fio.  134 

c.  a.        j.  v. 


Lungs. 


Diagram  of  the  circulation.  1.  Heart. 
2.  Lungs.  3.  Head  and  upper  extremi- 
ties. 4.  Spleen.  5.  Intestine.  6.  Kid- 
ney. 7.  Lower  extremities.  8.  Liver 
(Dat.ton.) 


i.  ii.         r.  v.    a,     r.  a.  1.  r. 

Heart  and  lungs  of  man.     (Milne  Ei. wards.) 

heart  is  loosely  enclosed  in  a  sac.  the  peri- 
cardium. This  sac.  having  the  form  of 
the  heart,  and  of  a  bluish-white  color, 
consists  of  two  layers.  The  external 
fibrous  layer,  continuous  with  the  exter- 
nal coat  of  the  great  bloodvessels,  con- 
sists of  fibrous  tissue,  and  is  a  strong, 
inextensible  membrane.  The  internal 
delicate  serous  layer  does  not  differ  essen- 
tially in  its  general  character  from  that 
of  serous  membrane.  It  surrounds  the 
heart,  closely  adhering  to  it,  and  is  then 
reflected  over  the  commencement  of  the 
great  bloodvessels  and  the  interior  sur- 
face of  the  external  fibrous  membrane. 
The  cavity  of  the  pericardium  contains 
about  a  drachm  or  two  of  a  serous  fluid, 
through  the  presence  of  which  the  opposed 
internal  surfaces  of  the  pericardium  glide 
smoothly  over  each  other,  the  movements 
of  the  heart  being  thereby  facilitated. 


266 


CIRCULATION    OF    THE    BLOOD. 


The  pericardium  is  attached  by  connective  tissue  to  the  pleura  on  each 
side,  and  tlit*  tendinous  centre  of  the  diaphragm  below.  It  is  not  neces- 
sary to  give  a  detailed,  minute  description  of  the  disposition  of  the  mus- 
cular fibres  of  the  heart,  which  is  quite  complex,  a  general  account  in 
connection  with  the  present  subject  being  sufficient.  The  auricles,  or 
upper  cavities  of  the  heart  (Fig.  135,  d,  e),  are  encircled  by  a  thin  layer 


Fro.  135. 


WM 
111 


Anterior  view  of  heart.     (Quain 


Fig.  136. 


of  muscular  fibres,  common  to  both  these  cavities,  and  surrounding  the 
auricular  appendages,  the  entrance  of  the  vena  cava,  the  coronary  and 
pulmonary  veins.  Beneath  this  superficial  layer 
are  the  fibres  of  the  deep  layer  attached  to  the 
fibrous  rings  of  the  auriculo-ventricular  orifices, 
and  disposed  in  an  annular  and  loop-like  man- 
ner. The  muscular  fibres  of  the  ventricles,  like 
those  of  the  auricles,  are  also  arranged  in  two 
sets,  superficial  and  deep.  The  superficial  fibres 
(Fig.  135,  a,  6),  which  are  common  to  both  ventri- 
cles, run  from  base  to  apex,  and  at  this  point  pass 
into  the  interior  of  the  ventricle  in  the  form  of  a 
whorl  or  spiral,  some  of  the  fibres  terminating  in 
the  columns  carnete  and  papillary  muscles,  others 
returning  after  a  twisting  course  to  the  point  from 
which  they  started.  The  fibres  of  the  deep  set 
(Fig.  136)  surround  each  ventricle  separately,  and 
are  disposed  in  a  circular  or  transverse  manner 
between  the  external  and  internal  layers  of  the  superficial  fibres,  and 
are  much  better  developed  in  the  left  ventricle  than  in  the  right. 


Left  ventricle  of  bullock's 
heart,  sh  owing  the  deep 
fibres.     (Dalton.) 


THE    HEART, 


267 


Microscopically  the  muscular  substance  of  the  heart  consists  of 
transverse  striated  muscular  fibres.  These  fibres,  however,  differ  from 
the  ordinary  fibres  of  voluntary  muscles  in  several  particulars.  They 
are  destitute  of  sarcolemma,  much  smaller  and  more  granular,  not  col- 
lected into  bundles,  and  are  separated  by  comparatively  little  connective 
tissue.  The  most  interesting  peculiarity,  however,  about  these  fibres, 
is  their  anastomosing  or  inosculation  with  each  other  (Fig.  137).  Their 
connecting  fibres,  no  doubt,  favor  the  contraction  of  the  heart  and 
thorough  expulsion  of  the  blood  from  its  cavities. 

If  a  longitudinal  section  be  carried  through  the  heart  from  base  to 
apex,  its  interior  will  be  seen  from  such  a  section  to  consist  of  four 


Fig.  137. 


Fig. 138. 


Heart  of  manatee.     RV.  Right  ventricle.    LV.   Left  ventricle. 


Muscular  fibres  of  tlie  heart.     (Qoain 

cavities :  two  auricles,  so 
called  from  their  auricular 
appendages,  and  two  ven- 
tricles; that  the  right  aur- 
lcle  communicates  with  the 
venas    cavae    and  with   the 

right  ventricle,  and  the  left  auricle  with  the  pulmonary  veins  and 
the  left  ventricle,  but  that  there  is  no  communication  between  the 
two  auricles  or  between  the  two  ventricles ;  the  right  or  venous  side  of 
the  heart  being  completely  separated  from  the  left  or  arterial  side  by 
the  septum  of  the  heart,  which  is  imperforate. 

In  certain  mammals  in  the  dugong  (halichore)  and  manatee  (man- 
atus)  for  instance,  this  distinction  of  the  right  from  the  left  side  of  the 
heart  is  to  a  certain  extent  visible,  even  externally  (Fig-  138),  the 
ventricles  at  the  apex  being  separated  by  quite  an  interval. 

We  have  just  seen  that  the  heart  is  covered  with  the  serous  layer 
of  the  pericardium.  It  will  be  observed  that  the  interior  of  the  heart 
is  also  lined  by  a  thin  translucent   membrane,  the  endocardium,  which 


268 


CIRCULATION    OF    THE    BLOOD. 


is  continuous  with  the  internal  coat  of  the  bloodvessels  and  consists  of 
a  fibrous  elastic  and  epithelial  layer.  Just  at  the  point  where  the 
auricle,  that  of  the  right  side,  for  example,  passes  into  the  ventricle, 
the  endocardium  projects  into  the  cavity  of  the  heart  from  the  wall  of 
the  heart  on  one  side,  and  from  the  septum  on  the  other.  This  portion 
of  the  endocardium   is  strengthened  by  the  addition  of  fibrous  tissue. 

Fig   139. 


The  right  auricle  and  ventricle  opened,  and  a  part  of  their  right  and  anterior  walls  removed  so  as  to 
show  their  interior.     %.     (Quai.v.) 

It  is  these  projections  that  serve  to  divide  the  auricle  from  the  ven- 
tricle. The  interval  left  between  these  projections  constitutes  the 
auriculo-ventricular  orifice.  The  fibro-elastic  tissue  in  this  situation 
forms  a  slight  ring,  to  Avhich  is  attached  the  tricuspid  valve  (Fig. 
139,  141,  5,  L',  b"),  three  membranous  folds,  which  consist  of  doublings 
of  the  endocardium  thickened  by  the  included  fibrous  tissue.  By 
means  of  these  curtains  or  valves,  the  auriculo-ventricular  orifice  can 
be  closed,  the  edges  of  the  valves  being  then  pressed  together  (Fig. 
141),  as  we  shall  see  by  the  blood,  and  are  kept  stretched  by  the  ten- 
dinous cords  as  the  sail  of  a  boat  is  kept  stretched  against  the  wind 
by  the  sheet  line. 

The  chordee  tendinese  are  tendinous  cords  inserted  into  the  valve,  and 
arise  either  directly  from  the  walls  of  the  ventricle  or  are  connected  with 


THE     HEART, 


269 


it  by  the  papillary  muscles.  Of  these  latter  many  pass  directly  again 
into  the  substance  of  the  heart  and  are  then  known  as  the  fleshy 
columns  or  columnse  carnese.  During  the  repose  of  the  ventricle 
the  auriculo-ventricular  orifice  is  open,  the  valves  then  lying  loosely 
against  the  walls  of  the  ventricle.     The  same  disposition,  such  as  we 


Fig.  140. 


h  rv*jiC\if: 


WMmW 


The  left  auricle  and  ventricle  opened  and  a  part  of  their  anterior  and  left  walls  removed  so  as  to  show 

their  interior.     %.     The  pulmonary  artery  has  1 n  divided  at  its  commencement  so  as  to  show  the 

aorta ;  the  opening  into  the  left  ventricle  has  been  carried  a  short  distance  into  the  aorta  between  two  of 
the  segments  of  the  semilunar  valves  ;  the  left  part  of  the  auricle  with  its  appendix  has  been  removed. 
The  right  auricle  has  been  thrown  out  of  view.     (Quain.) 

have  just  described,  obtains  essentially  in  the  left  side  of  the  heart. 
The  mitral  valve,  however  (Figs.  140  and  141,  6,  6'),  by  which  the  left 
auriculo-ventricular  orifice  is  closed,  consists  of  two  membranous  folds 
instead  of  three,  as  is  the  case  in  the  tricuspid  valve,  and  is  stronger 
than  the  latter. 

It  will  be  observed  that  the  tricuspid  and  mitral  valves  open  from 
the  auricle  toward  the  ventricle,  but  do  not  project  from  the  ventricle 
into  the  auricle.  At  the  anterior  angle  of  the  base  of  the  right  ven- 
tricle (Fig.  141,  7),  may  be  seen  an  orifice  guarded  by  three  cresentic 


270 


CIRCULATION    OF     THE    BLOOD, 


membanous  folds,  the  semilunar  valves.  Through  this  orifice  the 
right  ventricle  communicates  with  the  pulmonary  artery.  The  semi- 
lunar valves  consist  of  doublings  of  the  endocardium,  strengthened  by 
fibrous  tissue.  The  convex  border  of  each  valve  is  attached  to  the 
edge  of  the  ring-like  orifice  of  the  pulmonary  artery,  the  free  edge 
projecting  into  the  latter.  Behind  each  semilunar  valve  the  artery  is 
dilated  into  a  pouch,  the  sinus  of  Valsalva.  This  sinus  prevents  the 
valve  when  open  from  adhering  to  the  walls  of  the  artery,  and  enables 
the  blood  to  get  behind  each  valve  and  press  it  down  so  that  the  three 
valves  meet  (Fig.  141,  7),  and  so  close  the  orifice,  but  readily  separate 


Fig.  141. 


View  nf  the  base  of  the  ventricular  part  of  the  heart,  showing  the  relative  position  of  the  arterial  and 
auriculo-veutricular  orifices.  %.  The  muscular  fibres  of  the  ventricles  are  exposed  by  the  removal  of 
the  pericardium,  fat,  bloodvessels,  etc.;  the  pulmonary  artery  and  aorta  have  been  removed  by  a  section 
made  immediately  beyond  the  attachment  of  the  semilunar  valves,  and  the  auricles  have  been  removed 
immediately  above  the  auriculo-ventricular  orifices. 

when  the  flow  is  from  the  ventricles  toward  the  great  vessels,  preventing 
a  reflux  from  the  great  vessels  back  into  the  ventricle. 

At  the  middle  of  the  free  border  of  the  semilunar  valves  may  be 
seen  a  little  nodule  of  fibrous  tissue.  These  nodules,  or  corpora  Arantii 
serve  as  a  common  central  point  of  contact  when  the  valves  are  closed. 
The  semilunar  valves  of  the  aorta  (Fig.  141,  8)  do  not  differ  in  their 
structure  or  function  from  those  of  the  pulmonary  artery,  and,  like 
the  latter,  act  when  in  contact  in  closing  the  orifice  of  communica- 
tion between  the  left  ventricle  and  the  aorta.  The  manner  in  which 
the  tricuspid  and  mitral  valves  act  can  be  readily  demonstrated  by 
filling  the  ventricles  with  Avater  by  means  of  a  funnel  introduced  into 
the  orifices  of  the  pulmonary  artery  and  aorta ;  the  water  rising  up 
between  the  walls  of  the  ventricles  and  the  valves  will  float  the  valves 
up  until  their  edges  are  approximated,  so  closing  the  auriculo-ventric- 
ular orifices.  By  pouring  water  into  the  pulmonary  artery  and  aorta 
it  will  be  seen  that  the  water  gets  in  between  the  wall  of  the  vessel 
and  the  valve,  into  the  sinus  of  Valsalva,  and  so  forces  the  free  edges 
of  the  semilunar  valves  toward  each  other,  thus  effectually  closing  the 
orifices  at  the  mouths  of  the  great  vessels. 


THE     HEART.  271 

Such  being  the  general  structure  of  the  heart,  let  us  consider  now 
the  course  that  the  blood  takes  in  passing  through  it.  In  watching  the 
heart  beating  in  a  living  animal,  a  mammal,  for  example,  it  will  be  ob- 
served that  at  the  same  moment  the  right  auricle  is  dilated  by  the  venous 
blood  flowing  from  the  system  through  the  vense  cava;,  the  left  auricle  is 
dilated  by  the  arterial  blood  flowing  into  it  through  the  pulmonary  veins 
from  the  lungs.  This  synchronous  dilatation  of  the  auricles  is  known  as 
the  auricular  diast<  >le.  Suddenly,  and  succeeding  this  auricular  diastole, 
or  filling  up  of  the  auricles,  both  auricles  simultaneously  contract,  the 
venous  blood  passing  from  the  right  auricle  into  the  right  ventricle,  the 
arterial  blood  from  the  left  auricle  into  the  left  ventricle,  regurgitation 
to  any  extent  into  the  venae  cavee  or  pulmonary  veins  being  prevented 
by  the  muscular  fibres  encircling  these  vessels  and  the  pressure  of  the 
blood.  This  synchronous  contraction  of  the  auricles  is  called  the 
auricular  systole.  As  in  the  experiment  just  performed  with  the 
water,  so  the  blood  within  the  ventricles  of  the  heart  of  the  living 
animal  gets  in  between  the  walls  of  the  ventricles  and  the  flaps  of  the 
tricuspid  and  mitral  valves  and  floats  the  edges  of  the  valves  up  until 
the  auriculo-ventricular  orifices  are  closed.  At  this  moment,  the  ven- 
tricles being  fully  dilated  simultaneously  contract,  with  the  effect  of 
still  more  thoroughly  approximating  the  tricuspid  and  mitral  valves 
than  is  the  case  at  the  end  of  the  auricular  systole,  and  so  of  more 
completely  closing  the  auriculo-ventricular  orifices.  The  papillary 
muscles  contracting  at  the  same  time  as  the  walls  of  the  ventricles  and 
acting  through  the  chorda;  tendineae  upon  the  valves  stiffen  them  and 
prevent  their  inversion  into  the  auricles.  The  synchronous  filling  up 
and  contraction  of  the  ventricles  is  known  as  the  diastole  and  systole 
of  the  heart,  but  more  properly  as  the  ventricular  diastole  and  ven- 
tricular systole.  During  the  ventricular  systole  the  auricles  are  receiv- 
ing blood  from  the  venae  cava?  and  the  pulmonary  veins. 

Inasmuch  as  regurgitation  backward  from  the  ventricles  into  the 
auricles  is  prevented  through  the  auriculo-ventricular  orifices  being 
closed  by  the  approximation  of  the  tricuspid  and  mitral  valves  during 
the  ventricular  systole,  the  venous  blood  passes  from  the  right  ventricle 
through  the  pulmonary  artery  to  the  lungs,  and  the  arterial  blood  from 
the  left  ventricle  through  the  aorta  to  the  system.  Immediately  after  the 
ventricular  systole  or  contraction  of  the  ventricles  follows  their  relaxa- 
tion. During  this  period  the  heart  is  in  repose.  The  auriculo-ventricular 
orifices  are  again  open,  the  venous  and  arterial  blood  that  has  accumu- 
lated in  the  right  and  left  auricles  respectively  during  the  contraction 
of  the' ventricles  and  while  the  auriculo-ventricular  orifices  were  closed, 
now  flows  into  the  ventricles,  while  this  blood  is  replaced  by  the  venous 
blood  flowing  into  the  right  auricle  from  the  vense  cavae,  and  the  arterial 
blood  flowing  from  the  pulmonary  veins  into  the  left  auricle.  Toward 
the  end  of  the  ventricular  systole  the  venous  and  arterial  blood,  forced 
respectively  into  the  pulmonary  artery  and  the  aorta,  gets  in  between 
the  walls  of  the  vessels  and  the  semilunar  valves  in  the  sinuses  of  Val- 
salva, and  forces  their  free  edges  toward  each  other  as  in  the  experiment 
just  performed  with  the  water.  At  the  end  of  the  ventricular  systole, 
the  semilunar  valves  being  closely  approximated  and  the  orifices  of  the 


272  CIRCULATION    OF    THE    BLOOD. 

great  vessels  closed,  through  the  elastic  recoil  of  the  arteries  on  their 
contents,  the  blood,  being  unable  to  regurgitate  backward  from  the 
pulmonary  artery  and  aorta,  is  forced  on  to  the  lungs  and  the  system. 
It  will  be  seen  from  the  phenomena  just  described  that,  while  the  right 
side  of  the  heart  containing  venous  blood  is  entirely  distinct  from  the 
left  containing  arterial,  nevertheless,  the  two  sides  of  the  heart  act  as 
one — the  venous  blood  flowing  into  the  right  auricle  as  the  arterial  blood 
flows  into  the  left,  the  synchronous  filling  up  and  emptying  of  the  auri- 
cles being  followed  by  the  synchronous  dilatation  and  contraction  of  the 
ventricles,  both  ventricles  relaxing  together,  while  the  blood  forced  out 
of  them  passes  to  the  lungs  and  the  system  through  the  pulmonary 
artery  and  aorta  respectively. 

The  beating  of  the  heart,  as  Ave  have  endeavored  to  describe  it,  in  an 
animal,  a  dog  or  a  rabbit,  for  example,  has  been  shown  to  be  essentially 
the  same  in  man,  at  least  so  far  as  comparison  has  been  possible.  As 
might  be  expected,  cases  of  ectopia  cordis  are  very  rare,  but  there  has 
been  a  sufficient  number  of  such  cases  to  demonstrate  that  the  manner 
in  which  blood  flows  through  the  heart  in  man  does  not  differ  from  that 
of  the  mammal. 

While  the  action  of  the  tricuspid  valve  and  semilunar  valves  of  the 
pulmonary  artery  is  essentially  the  same  as  that  of  the  mitral  valve 
and  semilunar  valves. of  the  aorta,  nevertheless  the  valves  on  the  right 
side  of  the  heart  do  not  close  their  respective  orifices  as  perfectly  as 
those  on  the  left  side  of  the  heart,  there  being  some  little  regurgitation 
possible  back  from  the  pulmonary  artery  to  the  right  ventricle,  and  from 
the  right  ventricle  to  the  right  auricle.  The  effect  of  this  insufficiency 
of  the  valves  on  the  right  side  of  the  heart  is  obviously  of  advantage ; 
were  it  otherwise,  an  excess  of  blood  driven  from  the  right  ventricle 
through  the  pulmonary  artery  to  the  lungs  might  rupture  those  delicate 
organs.  This  danger  is  avoided  through  the  imperfect  closure  of  the 
pulmonary  and  the  right  auriculo-ventricular  orifices,  since,  when  resist- 
ance is  offered  by  the  pulmonary  capillaries,  the  blood  will  regurgitate 
backward  through  the  pulmonary  artery  to  the  ventricle  and  thence  to  the 
auricle.  There  is  no  insufficiency,  however,  on  the  left  side  of  the  heart, 
the  auriculo-ventricular  and  aortic  orifices  being  completely  closed  by  the 
mitral  and  semilunar  valves  respectively.  It  will  be  observed  also  that 
the  walls  of  the  left  ventricle  are  three  or  four  times  as  thick  as  those  of 
the  right  (see  Table  L.).  This  is  due,  as  might  have  been  anticipated, 
to  the  fact  of  the  contraction  of  the  left  ventricle  forcing  the  blood  to 
all  parts  of  the  system,  whereas  the  right  ventricle  forces  the  blood  only 
to  the  lungs.  For  the  same  reason  the  walls  of  the  auricles  are  thinner 
than  those  of  the  ventricles,  little  force  being  required  to  drive  the 
blood  from  the  former  cavities  into  the  latter. 

The  muscular  substance  of  the  heart,  like  that  of  muscles  generally, 
is  therefore  developed  according  to  the  amount  of  muscular  force  to  be 
expended. 

As  the  period  which  elapses  in  mammals  during  a  cardiac  revolu- 
tion— that  is,  the  time  during  which  all  the  cavities  of  the  heart  fill  and 
empty  themselves — is  only  about  one  second,  actually  less  in  man,  it  is 
evident  that  close  and  careful  observation  is  necessary  in  order  to  dis- 


RHYTHM    OF     MOTION     OF     HEART.  273 

tinguish  the  successive  phenomena  that  we  have  endeavored  to  describe 
in  the  beating  heart.  It  is  well,  therefore,  to  begin  the  study  of  the 
action  of  the  heart  by  observing  the  phenomena,  first,  as  they  present 
themselves  in  the  lower  vertebrates,  for  example,  in  frogs,  snakes,  turtles, 
and  alligators.  Such  animals  are  not  only  readily  procurable,  but 
are  particularly  suitable  for  the  purpose,  since  in  them  the  cardiac 
revolutions  succeed  each  other  much  more  slowly  than  is  the  case  in 
mammals,  and  in  the  frog  especially  there  is  an  appreciable  interval 
between  the  systole  of  the  auricle  and  that  of  the  ventricle,  whereas,  in 
most  mammals  the  systole  of  the  auricle  runs  so  into  that  of  the  ven- 
tricle that  it  is  impossible  to  say  exactly  where  the  first  ends  and  the 
second  begins,  the  muscular  contraction  running  as  a  continuous  wave 
over  auricle  and  ventricle  from  base  to  apex.  Further,  the  heart  of  the 
frog  has  only  one  ventricle,  and  while  there  are  two  such  cavities  in  the 
heart  of  the  turtle,  nevertheless,  they  communicate,  the  septum  being 
but  little  developed.  In  these  animals,  then,  the  single  ventricle  acts 
like  the  two  ventricles  of  the  mammalian  heart,  and  familiarizes  one  with 
the  synchronous  action  of  the  ventricles  when  two  such  cavities  are 
present.  Again,  these  animals  offer  through  their  mode  of  breathing 
another  advantage,  in  that  the  heart  will  continue  beating  even  after 
the  thorax  has  been  opened,  there  being  no  necessity  of  keeping  up 
artificial  respiration.  We  shall  see,  however,  when  we  wish  to  study 
the  action  of  the  heart  in  mammals,  that  artificial  respiration  must  be 
maintained,  for  with  the  opening  of  the  chest  the  lungs  collapse,  respira- 
tion ceases,  and  the  circulation  stops.  Notwithstanding  that,  in  mam- 
mals, a  cardiac  revolution  occupies  such  a  small  period  of  time — about 
one  second — nevertheless,  the  relative  parts  of  the  second  elapsing  during 
which  the  auricular  and  ventricular  systole  take  place  and  the  heart  is 
in  repose,  have  been  experimentally  determined,  as  in  the  horse,  for 
example,  by  Marey  and  Chauveau.1  The  general  results  of  their  ob- 
servations are  embodied  in 

Table  XLIX.— Rhythm  of  Motion  of  Heart. 

Auricular  systole.  Ventricular  systole.  Repose. 

'1  4  4 

TQ-th  sec.  TtT^n  sec.  ~W^  sec- 

from  which  it  will  be  observed  that  the  auricular  systole  lasts  two-tenths 
of  a  second,  the  ventricular  systole  four-tenths  of  a  second,  and  the  re- 
pose of  the  heart  four-tenths  of  a  second,  one  second  being  supposed  to 
elapse  during  an  entire  cardiac  revolution.  From  the  observations  of 
Franck,2  made  upon  a  woman  with  ectopia  cordis,  there  is  little  reason  to 
doubt  that  the  above  table  represents  tolerably  well,  also,  the  relative 
durations  of  the  successive  motions  and  repose  of  the  human  heart.  The 
apparatus  necessary  for  the  above  determination  of  the  rhythm  of  the 
heart's  movements  as  they  occur  in  the  horse,  and  made  by  Verdin,  of 
Paris,  as  used  by  Marey,  consists  essentially  of  a  sound  (Fig.  142)  to 
be  introduced  through  the  jugular  vein  into  the  heart  of  the  animal. 
The  sound  is  divided  into  two  tubes,  one  of  which  is  a  distinct  tube,  the 

1  Comptes  RenduB  Sue   Biol.,  Paris,  1861.     Comptes  Rendus.  Acad.  Sciences,  1862. 
-  Tiavaux  du  Lab.  de  Marey,  1877,  iii.  p.  311. 

18 


274 


CIRCULATION    OF    THE     BLOOD. 


other  being,  however,  only  the  space  around  the  tube.  The  tube  ter- 
minates at  one  end  in  a  little  elastic  bag  (i>),  to  be  inserted  into  the  ven- 
tricle, and  at  the  other  cud  in  a  drum  provided  with  a  registering  level' 
(h).     The  space  surrounding  the  tube  communicates  on  the  one  hand 


Fig.  L42. 


Cardiograph.  The  instrument  is  composed  of  two  principal  elements  :  A  E,  Ihe  registering  apparatus, 
and  A  S,  the  sphygmographic  apparatus — that  is  to  say,  which  receives,  transmits,  and  amplifies  the 
movements  which  are  to  be  studied.  The  compression  exerted  upon  the  bag  c,  which  is  placed  over  the 
apex  of  the  heart  between  the  intercostal  muscles,  is  conducted  by  the  tube  l.c,  which  is  filled  with  air,  to 
the  first  lever.  The  compression  exerted  upon  the  bags  o  and  v,  in  the  double  sound,  is  conducted  by  the 
tubes  to  and  tv  to  the  two  remaining  levers.  The  movements  of  the  levers  are  registered  simultaneously 
by  the  cylinders  A  E.     (Chauveau  and  Marey.) 

with  a  similar  elastic  bag  (o)  to  be  inserted  into  the  auricle,  and  at  the 
other  end  with  a  tube  passing  into  a  drum  provided  with  a  second  simi- 
lar recording  lever  (16).  The  object  of  the  elastic  bags  o  and  v  is  that 
the  successive  contractions  of  the  auricle  and  ventricle  in  which  they  are 
placed  will  be  transmitted  through  them  to  the  registering  levers  lo  and 
lv,  and  as  the  auricle  contracts  before  the  ventricle  it  is  evident  that  the 
lever  lo  connected  with  the  elastic  bag  (o)  in  the  auricle  will  move  before 
the  lever  (J,v)  connected  with  the  bag  (v)  in  the  ventricle.  If  the  regis- 
tering levers  are  placed  in  contact  with  a  recording  surface  (AE) 
moving  at  a  uniform  rate,  and  if  this  surface  be  marked  by  vertical 
parallel  lines,  each  intervening  space  representing  the  one-tenth  of  a 
second,  the  lengths  of  time  during  which  the  auricular  and  ventricular 
systole  and  the  repose  of  the  heart  last  will  be  graphically  recorded 
(Fig.  148').  The  cardiac  revolution  in  this  instance  lasted  twelve- 
tenths  seconds. 

In  order  to  divide  the  surface  of  the  recording  cylinder  into  a  number  of 
spaces  each  equal  to  the  one-tenth  of  a  second,  a  vibrating  reed  (A)  and 
an  electro-magnet  (B,  Fig.  144)  are  used.  The  reed  clamped  under  the 
electro-magnet  by  one  end  to  a  stand  (C),  the  other  end  dipping  into 
mercury  (D),  is  connected  on  the  one  hand  with  a  battery  (E).  and  on  the 


1   La  Circulation  du  Sang,  p.  85.     Paris,  1881. 


VIBRATOR. 


275 


other  with  another  small  electro-magnet  (F).      Such  being  the  disposi- 
tion at   the  moment  that   the   current   is  made,  the  electro-magnet  (B) 


Fig.  143. 


Tracing  of  the  variations  of  pressure  in  the  right  auricle  and  ventricle,  aud  of  the  cardiac  impulse, 
in  the  horse.     (To  I e  read  from  left  tu  right.)     (Ma rev  ) 

Fig.   ]44. 


being  magnetized,  will  attract  the  reed,  drawing  it  out  of  the  mercury; 
but  the   current   being  thereby  broken,  the  electro-magnet  being  thru 


276 


CIRCULATION'    OF    THE    BLOOD. 


demagnetized,  will  cease  to  attract,  and  the  reed  will  fall  hack  into  the 
mercury,  remaking  the  current ;  the  reed  will  then  he  again  raised,  the 
current  broken,  and  the  reed  fall  again  into  the  mercury,  the  number 
of  these  alternate  elevations  and  depressions  per  second  depending  upon 
the  number  of  vibrations  of  the  reed  in  that  time.  Inasmuch,  how- 
ever, as  the  small  electro-magnet  (F)  is  magnetized  and  demagnetized 
in  the  same  manner  as  the  large  one,  the  bar  attached  to  it  and  carrying 
the  pen  (P)  will  approach  and  recede  from  it  synchronously  with  the 
vibrations  of  the  reed.  By  placing  the  pen  in  contact  with  the  record- 
ing cylinder,  a  trace  is  obtained  in  which  the  equal  spaces  between 
the  vertical  lines  made  by  the  marker  are  equal  t<>  the  one-tenth  of  a 

Fig.  145. 


Double  myograph.    (Vekdin.) 

second,  the  reed  used  vibrating  at  that  rate.  By  substituting  reeds  or 
tuning  forks  vibrating  at  the  rate  of  15,  20,  50,  or  100  times  a  second,  we 
get  traces  in  which  the  equal  spaces  represent  the  corresponding  fractional 
parts  of  a  second.  Usually,  there  is  also  a  third  registering  lever  (Fig. 
142,  /c),  below  the  ventricular  one,  connected  by  tubing  with  a  cardio- 
graph (c),  the  object  of  which  is  to  transmit  the  cardiac  impulse  caused 
by  the  beating  up  of  the  heart  against  the  chest.  This  impulse  is  shown 
to  be  absolutely  synchronous  with  the  ventricular  beat  as  recorded  by 
the  second  lever  (iv). 

By  means  of  the  double  myograph  the  time  elapsing  during  the 
successive  contractions  of  the  auricle  and  ventricle,  and  the  repose  of 
the  heart,  can  be  conveniently  observed  in  the  living  frog  or  turtle. 

The  instrument  as  described  by  Franck,1  and  constructed  for  the 
author  by  Verdin,  consists  (Fig.  145)  of  two  levers,  to  which  are 
attached  delicate  rods,  ending  in  aluminium  plates,  which  rest  upon  the 
auricle  and  ventricle  of  the  heart  of  the  animal  examined.  The  levers 
can  be  shortened  or  lengthened,  their  pressure  diminished  or  increased 
by  appropriate  mechanical  arrangements,  and  the  movements  of  the 
auricle  and  ventricle  transmitted  by  them  are  recorded  upon  a  cylinder 
moving  at  a  uniform  and  known  rate,  by  which  the  time  elapsing  can 
be  determined. 

The  further  consideration  of  the  cardiograph  and  the  cardiac  impulse 
we  will  defer  till  the  next  chapter,  and,  in  concluding,  call  attention  to 


1  Travaux  du  Lab.  de  Marey,  t.  iv.  p.  407.     Paris,  1877. 


CAPACITY    OF    HEART.  277 

Table  L.,  in  which   are  synoptically  arranged  the  most  important  ana- 
tomical facts  concerning  the  heart  having  for  us  a  functional  significance. 


Weight 


Table  L. — Heart. 

(  in  male,  1<>  to  12  ounces 

j  in  female,  8  to  10      " 


f  length,  5  inches. 

Size  '  breadth,  :V,     " 

(thickness,  21     " 

|  right  auricle,  1    line. 

Thickness     |  left  auricle,  1'     "       Base-  Middle.       Apex, 

of  walls     I  right  ventricle,  l|a  i|  1-^  lines. 


left  ventricle,  4J  5£  3^ 

f  left  ventricle,       4^  to  7  ounces,  usually  2  ounces. 

Canacitv      J  right  auricle>         r5  u'  •'  greater  than  left, 
F       i        I  right  ventricle,       "        "         "         "         " 

I  each  ventricle,        ]    to  £  greater  than  auricle. 

From  this  table  it  will  be  seen  that  the  heart  weighs,  in  the  male  sex, 
from  ten  to  twelve  ounces,  and  is  heavier  than  in  the  female  ;  that,  on  an 
average,  it  attains  a  length  of  five  inches,  and  a  breadth  of  three  and  one- 
half.  It  will  also  be  noticed  from  the  table,  and,  as  already  observed,  that 
the  walls  of  the  ventricles  are  thicker  than  those  of  the  auricles,  while 
the  wall  of  the  left  ventricle,  on  an  average,  may  be  about  four  times  as 
thick  as  that  of  the  right.  As  regards  the  capacity  of  the  cavities  of 
the  heart,  it  might  be  inferred  from  what  was  said  of  the  regurgitation 
of  the  blood  backward  from  the  lungs,  that  the  right  side  of  the  heart 
is  more  capacious  than  the  left ;  it  will  be  seen,  also,  from  the  table, 
that  the  ventricles  are  more  capacious  than  the  auricles.  There  is  still 
much  difference  of  opinion  as  to  the  absolute  capacity  of  the  left  ventrjcle. 
The  question  to  determine,  however,  is  not  so  much  the  amount  of 
blood  that  the  left  ventricle  can  hold,  as  to  what  it  usually  does  hold. 
This  has  been  variously  estimated  at  from  two  to  seven  ounces.  Probably, 
four  ounces,  or  a  mean  between  these  two  extremes,  will  represent  about 
the  amount  of  blood  that  the  left  ventricle  usually  forces  into  the  aorta 
at  each  systole. 


CHAPTER   XIX. 


THE  HEART. 


In  examining  the  heart  in  a  living  animal,  as  described  in  the  last 
chapter,  it  will  be  observed  that  with  each  ventricular  systole  the  heart, 
as  a  whole,  moves  forward  and  upward,  the  apex  more  particularly 
beating  up  against  the  chest,  and  so  giving  rise  to  what  is  known  as  the 
cardiac  impulse.  If  a  finger  be  placed  within  the  thoracic  cavity  of  a 
living  animal,  between  the  heart  and  the  side  of  the  chest,  with  every 
contraction  of  the  ventricle  the  finger  will  be  pressed  against  the  chest 
by  the  apex.  Pathological  cases,  like  that  of  the  Ariscount  Mont- 
gomery, so  graphically  described  by  Harvey,1  have  given  physiologists 
the  opportunity  of  showing  that  the  cardiac  impulse  is  produced  in  men 
as  in  animals  by  the  striking  of  the  heart  against  the  chest. 

In  man  the  cardiac  impulse  is  most  distinctly  felt  in  the  fifth  left 
intercostal  space,  about  two  inches  below  the  left  nipple,  and  one  inch 
to  its  sternal  side.  The  force  and  extent  to  which  the  cardiac  im- 
pulse may  be  perceived  varies  very  much  in  different  individuals,  and 
in  the  same  individual,  according  to  circumstances.  Thus,  it  is  more 
perceptible  in  emaciated  than  in  fat  persons,  during  expiration  than  in 
inspiration,  in  one  lying  upon  the  left  side  than  in  one  lying  upon  the 
right,  etc.  The  movement  of  the  heart  forward  and  upward  producing 
the  cardiac  impulse  seems  to  be  due  to  several  causes.  Thus,  the  sudden 
distention  of  the  great  elastic  vessels  at  its  base  would  throw  the  entire 
organ  forward,  the  recoil  of  the  ventricles,  as  they  discharge  their  con- 
tents, further  aiding  the  movement.  The  disposition  of  the  muscular 
fibres  is  also  such  that  the  heart  during  its  ventricular  svstole  chancres 
its  form,  bulging  somewhat  forward,  the  spiral  muscular  fibres,  at  the 
same  time,  tilting  up  the  apex. 

For  ordinary  purposes  the  force  and  extent  of  the  cardiac  impulse  can 
be  sufficiently  well  appreciated  by  the  hand.  The  cardiograph,  how- 
ever, furnishes  us  with  the  means  of  a  far  more  accurate  study  of  the 
beat  of  the  human  heart  than  that  afforded  by  the  sense  of  touch  alone. 
The  cardiograph  (Fig.  146)  consists  of  a  disk-shaped  box,  one  side  of 
which  is  formed  by  an  elastic  membrane.  In  the  centre  of  the  latter  is 
inserted  an  ivory  knob  (^4),  which  is  applied  to  the  chest  over  the  place 
where  the  cardiac  impulse  is  greatest.  The  box,  or  tympanum,  com- 
municates by  an  elastic  tube  (/)  with  a  second  tympanum  (b),  with 
which  is  connected  a  registering  lever  (d).  It  is  evident  that  when 
the  cardiograph  is  firmly  fastened  to  the  chest  that  the  shock  of  the 

1  Exercit.  de  generat.  Animalium,  p.  156.     Lond.  1651. 


CA  RDIOGRAPrT. 


279 


cardiac  impulse  will  be  transmitted  to  the  ivory  knob,  thence  to  the  first 
tympanum  and  through  the  column  of  air  in  the  communicating  tube  to 
the  interior  of  the  second  tympanum,  and  so,  by  means  of  the  elastic 
and  movable  lid  of  the  latter,  to  the  registering  lever.     If  the  point  of 


The  cardiograph. 


the  lever  be  placed  in  contact  with  a  cylinder  revolving  at  a  uniform 
rate,  we  obtain  a  graphic  representation  or  trace  of  the  heart's  impulse 
(Fig.  147).     By  such  an  apparatus  variations  in  the  heart's  bent,  which 


Fig.  147. 


a^Va^^-a 


^vyv^-A 


Tracing  of  heart's  impulse  in  man,  tak«-n  with  cardiograph.     To  be  read  from  left  to  right. 

are  so  slight  as  to  be  quite  inappreciable  by  the  sense  of  touch  alone, 
become  very  perceptible. 

When  it  is  desired  to  take  a  cardiography  tracing  in  a  small  animal, 
like  a  rabbit,  guinea-pig.  or  cat,  a  very  convenient  form  of  cardiograph  is 
that  described  by  Marey1  (Fig.  148),  and  made  for  the  author  by  Verdin. 
The  instrument  consists  of  two  tambours  (a,  b),  each  of  which  contains 
a  spring,  through  which  the  membrane  is  kept  projected.  The  two  tam- 
bours are  joined  to  one  another  pincer-like,  by  a  hinge,  and  grasp  the  car- 
diac region  on  each  side  of  the  sternum.  A  girdle  (c)  attached  by  hooks 
to  the  tambours  passes  around  the  body  of  the  animal,  and  secures  the 
apparatus  firmly.  The  compression  of  the  air  in  the  tambours  due  to 
the  cardiac  impulse  is  transmitted  by  the  tubes  (d,  e)  to  a  second  tambour, 
to  which  is  attached  a  recording  lever,  like  that  represented  in  Fig. 
146.      Fig.  149  gives  the  traces  taken  by  this  instrument. 


Op     H  .  p.  155. 


280 


THE     HEART. 


Fig.  i  is. 


It  will  be  remembered  that  it  was  by  means  of  the  cardiograph  and 
the  sound  introduced  into  the  heart  of  the  horse  that  Marey  and  Chau- 

veau  demonstrated  experimentally  that  the 
cardiac  impulse  is  absolutely  synchronous 
with  the  ventricular  systole.  Whatever 
difference  of  opinion  may  exist  as  to  the 
relative  importance  of  the  different  causes 
assigned  for  the  production  of  the  cardiac 
impulse,  there  can  he  no  doubt,  then,  that 
its  immediate  cause  is  the  ventricular  sys- 
tole. 

The  spiral  arrangement  of  the  muscular 
fibres  at  the  apex  of  the  heart,  already 
alluded  to,  explains  another  phenomenon 
accompanying  the  ventricular  systole,  the 
twisting  of  the  heart.  If  the  apex  of  the 
heart  be  closely  watched,  it  will  be  noticed 
that  the  point  twists  upon  itself  from  left  to 
right  with  the  systole,  returning  to  its  former 
position  with  the  diastole.  The  heart,  like  a  voluntary  muscle,  which  it 
closely  resembles  in  its  substance,  also  hardens  during  contraction.    This 


(';ii'lii>,i_'rapli.     (Marey.) 


Fig.  149. 


Tracings  taken  with  cardiograph.     Co.  Guinea-pig.     X.  Rabbit.     Ch.  Cat.     (Marey.) 


becomes  very  evident  if  the  organ  be  grasped  by  the  hand  while  beat- 
ing. Like  voluntary  muscles,  the  heart  also  shortens  during  contrac- 
tion. This  can  be  demonstrated  by  quickly  cutting  the  heart  out  of 
a  living  animal,  pinning  it  down  on  a  board  by  passing  a  needle  ver- 
tically through  its  base,  and  then  inserting  a  second  needle  into  the 
board  parallel  with  the  first,  so  that  the  apex  of  the  heart  just  touches 
the  second  needle.  With  each  systole  it  will  be  seen  that  the  ventricles 
invariably  shorten,  the  apex  distinctly  receding  from  the  second  needle. 
If  the  beating  heart  be  examined  in  situ  there  is,  on  the  contrary,  an 
apparent  elongation  of  the  heart  during  its  systole.  This  is  due,  how. 
ever,  not  to  any  elongation  of  the  ventricles,  but  to  the  fact  that  at  the 
moment  of  the  cardiac  impulse,  which  is  synchronous  with  the  ventricular 


WORK     DONE    BY    THE    HEART.  281 

systole,  the  whole  heart,  as  we  have  seen,  is  moved  forward  and  pro- 
truded ;  at  this  moment  the  apex  is  apparently  elongated,  while,  in 
reality,  it  is  shortened. 

We  shall  see  that,  on  an  average  in  man,  the  ventricles  contract 
ahout  70  times  in  a  minute,  and  assuming,  as  we  have  done,  that  with 
each  systole  about  four  ounces,  or  a  quarter  of  a  pound,  of  blood  are  forced 
into  the  pulmonary  artery  and  aorta  respectively,  it  is  evident  that  in 
Twenty-four  hours  the  heart  must  perform  a  great  deal  of  work.  It  can 
be  demonstrated,  as  was  first  shown  by  Hales,1  that  the  blood  will  rise 
about  nine  feet  in  a  glass  tube  inserted  into  the  aorta  of  a  horse,  and 
the  experiments  of  Haughton,2  of  which  we  will  speak  again,  prove  that 
this  estimate  can  be  accepted  as  representing  the  pressure  exerted  by 
the  left  ventricle  of  man,  as  shown  by  the  distance  to  which  blood  will 
jet  from  a  divided  artery.  In  demonstrating  the  height  to  which  blood 
will  rise  in  a  glass  tube  inserted  into  the  aorta  we  usually  make  use  of  a 
large  turtle,  which  suffices  very  well,  as  illustrating  the  work  done  by 
the  left  ventricle  of  the  heart  of  an  animal. 

In  mechanics  the  work  done  by  a  machine  is  usually  estimated  in 
foot-pounds — that  is,  the  number  of  pounds  the  machine  can  raise 
through  one  foot,  or  the  number  of  feet  that  the  machine  can  raise  one 
pound — i.  e.,  the  work  equals  the  weight  multiplied  by  the  height.  The 
work  accomplished  by  the  heart  in  twenty-four  hours  can  be  estimated 
approximately  in  the  same  way,  and  amounts  to  138  foot-tons  (Table 
LI.) — that  is,  the  heart  performs  in  twenty-four  hours  an  amount 
of  mechanical  work  equivalent  to  that  of  a  machine  that  will  raise 
during  the  same  time  138  tons  through  one  foot,  or  1  ton  through  138 
feet.  If.  however,  we  assume,  as  is  sometimes  done,  that  each  ventricle 
discharges  only  two  ounces  of  blood,  of  course  the  work  done  by  the 
heart  will  be  that  much  less ;  on  the  other  hand,  the  work  done  will  be 
greater  if  the  ventricles  are  supposed  to  discharge  more  blood  into  the 
great  vessels  at  each  systole.  In  other  words,  the  work  done  by  the 
heart  will  be  a  maximum  or  minimum,  according  to  the  accepted 
capacity  of  the  ventricles. 

Table  LI. 

Work  done  by  the  heart  in  24  hours  =  138  foot-tons. 
!  lb.  of  blood  expelled  bv  left  ventricle  at  each  systole. 

right       "_ 
Blood  flowing  from  aorta  into  a  vertical  glass  tube  will  rise  9  feet. 
"      pulmonary  artery  into  a  vertical  glass  tube  will 
rise  3  feet. 

1  9 

—  V  9  =  —  =  2;  lbs.  raised  through  1  root. 
4  4 

JL  x  3  =  —  =    I  lb.       - 
4  4 

3  lbs. 
3  X  72  X  60  X  24  =  31104O  lbs.  in  24  hours. 

311040  =  138.8  foot-tons. 

2240 

1  Statical  Essays,  vol.  ii.  p.  11.     London,  17:io.  '-'  Animal  Mechanics,  p.  1li7.      London,  1873. 


282  THE    HEART. 

It  will  be  observed,  also,  that  it  is  assumed  in  man,  such  being 
essentially  the  case  in  animals,  as  shown  experimentally  by  Milne 
Edwards,1  that  the  right  ventricle  does  only  a  fourth  of  the  work  per- 
formed by  the  Left  one. 

If  in  a  living  animal  the  ear  be  applied  to  the  precordial  region, 
and  in  man  more  particularly  to  the  third  intercostal  space  a  little  to 
the  left  of  the  median  line  of  the  chest,  accompanying  the  beat  of  the 
heart  two  successive  sounds  will  be  heard,  followed  by  a  silence.  After 
a,  little  practice  it  will  be  recognized  that  these  two  sounds  differ  from 
each  other  in  their  quality,  pitch,  and  duration.  The  first  sound  is  a 
dull,  confused  one,  of  a  booming  character,  low  in  pitch,  and  lasts  longer 
than  either  the  second  sound  that  follows  it,  or  the  silence  intervening 
between  the  second  sound  and  the  first  one.  The  second  sound,  as  com- 
pared with  the  first  one,  is  a  clear  sound,  well  defined,  sharp,  high  in 
pitch.  While,  for  all  practical  purposes,  it  may  be  said  that  the  second 
sound  immediately  follows  the  first,  there  is  quite  an  appreciable  inter- 
val of  silence  between  the  second  and  the  first  sound,  this  interval  of 
silence  lasting  about  the  same  length  of  time  as  the  second  sound.  By 
looking  at  Table  LII.  it  will  be  seen  that,  supposing  one  second  elapses 
during  the  period  in  which  the  first  and  second  sounds  and  silence  are 
heard,  that  the  first  sound  lasts  four-tenths  of  the  second,  the  second 
sound  three-tenths  of  a  second,  and  the  silence  three-tenths  of  a  second. 
It  will  be  also  observed,  from  Table  LII.,  that  the  period  of  four-tenths 
of  a  second  during  which  the  first  sound  is  heard,  is  absolutely  syn- 
chronous with  the  four-tenths  of  a  second  of  the  ventricular  systole, 
that  the  three-tenths  of  a  second  during  which  the  second  sound  is  heard 
the  heart  is  in  repose,  and  that  the  silence  is  synchronous  partly  with 
the  last  one-tenth  of  a  second,  during  which  the  heart  is  in  repose,  and 
during  the  two-tenths  of  a  second  of  the  auricular  systole.  This  com- 
parison of  the  rhythm  of  the  sounds  of  the  heart  with  the  rhythm  of  its 
movements,  is  based  upon  the  manner  in  which  the  sounds  are  produced. 

Table  LII. — Rhythm  of  Movements  and  Sounds  of  Heart  during 

one  Second. 

Ventricular  systole .  Repose.  Auricular  systole. 

/\  /\ 

4  8  1 

K)  10  10  lo 

First  sound.  Second  sound.  Silence. 

From  the  fact  of  the  first  sound  being  confused  and  muffled  in  char- 
acter, one  would  suppose  that  numerous  causes  contribute  in  producing 
it.  From  Table  LII.  we  see  that  the  first  sound  is  heard,  and  lasts 
during  the  ventricular  systole  ;  now  at  the  moment  the  auriculo-ven- 
tricular  valves  flap  together  their  movement  must  be  then  one  cause  of 
the  first  sound  of  the  heart,  and  accounts  for  its  valvular  element.  That 
the  closure  of  the  auriculo-ventricular  valve  contributes  in  the  produc- 

1  Physiologic,  tome  iii.  p.  I  IN. 


CAUSE     OF     SOUNDS    OF    HEART. 


288 


tion  of  the  first  sound  can  be  further  demonstrated  by  experiments  like 
those  of  Chauveau  and  Faivre,1  who  either  modified  the  first  sound  or 
abolished  it  altogether  by  preventing  the  closui'e  of  these  valves  by 
cutting  the  chordse  tendinese,  or  introducing  a  wire  ring  into  the 
auriculo-ventricular  orifices.  Further,  pathology  shows  that,  in  man, 
the  character  of  the  first  sound  is  changed  if  the  auriculo-ventricular 
valves  are  diseased,  and  it  is  well  known,  also,  that  in  auscultation  the 
first  sound  is  heard  with  its  maximum  intensity  over  these  valves,  and 
that  it  is  propagated  downward  along  the  ventricles  to  which  they  are 
attached  toward  the  apex.  It  is  well  known,  and  readily  shown  by  the 
application  of  the  myophonic  telephone  (Fig.  150).  that  when  a  muscle 
contracts,  being  thrown  into  vibration,  a  sound  is  produced;  now.  as 
the  ventricular  systole  is  caused  by  the  contraction  of  the  muscular 
fibres  of  the  ventricle,  at  this  moment  a  sound  will  be  produced  which. 


Fro.  150. 


Helmoltz's  myophone.      b.  Button  to  be  placed  on  muscle,     p.  Handle. 

to  telephone. 


Wires  for  attachment 


in  the  case  of  the  frog,  can  be  made  audible  by  the  cardiophonic  telephone 
(Fig.  151),  and  which  contributes  undoubtedly,  in  man,  to  the  produc- 
tion of  the  first  sound.  Finally,  the  beating  up  of  the  heart  against 
the  chest  in  itself  is  partly  a  cause  of  the  first  sound.  There  appear, 
then,  to  be  three  distinct  causes,  each  contributing  in  the  production  of 
the  first  sound.  First,  the  closure  of  the  auriculo-ventricular  valves; 
second,  the  muscular  contraction ;  third,  the  cardiac  impulse — hence 
the  confused,  muffled  character  of  the  first  sound  of  the  heart.  As  has 
already  been  observed,  the  second  sound  differs  from  the  first  in  being 
a  clear,  well-defined  sound,  and  is  essentially  of  a  valvular  character.    It 


1  Xouvelle  recherches  experimentales  sur  lea  Mouvements  in  Coeur,  etc.,  p.  30.     Paris,  1856. 


1^-1 


THE     HEART, 


is  heard  (sec  Table  LIII.)  during  the  first  three-quarters  of  the  period 
in  which  the  heart  is  in  repose.  Now,  at  this  moment  the  semilunar 
valves  of  the  pulmonary  artery  and  aorta  are  Mapping  together  through 
the  blood  <fettintr  in  between  the  valves  and  the  walls  of  the  vessels. 
The  closure  of  these  valves  will  account  for  the  second  sound  of  the 
heart  and  its  simple  valvular  character.  The  second  sound  of  the  heart 
can  be  imitated  by  suddenly  closing  the  aortic  valves  by  a  column  of 
water,  as  was  first  shown  by  Rouanet,1  and  can  be  abolished  by  hooking 
back  the  semilunar  valves  in  a  living  animal,  as  was  first  demonstrated 
by  Williams.2  and  confirmed  by  the  Dublin  Committee  in  their  report 
presented  to  the  meeting  of  the  British  Association  in  1836.      Finally, 

Fig.  151. 


Cardiophone, 


b.  Button  to  be  placed  upon  heart.      W,  W.  Wires  for  attachment  to  telephone. 
T.  Telephone. 


the  period  of  silence  coincides  with  the  last  one-tenth  of  a  second  of  the 
period  of  repose,  and  the  two-tenths  of  a  second  during  which  the 
auricles  silently  contract. 

We  learn  also  through  the  changes  produced  in  the  character  of 
the  second  sound  of  the  heart  from  disease  of  the  semilunar  valves, 
and  from  auscultation  that  the  second  sound  is  heard  most  distinctly  op- 
posite the  semilunar  valves,  and  is  propagated  upward  along  the  great 
vessels  to  which  they  are  attached.  There  can  be  no  doubt,  then,  that 
the  second  sound  of  the  heart  is  caused  simply  by  the  closure  of  the 
semilunar  valves  of  the  pulmonary  artery  and  aorta. 


1  Cyclopaedia  of  Anat.  and  Phys.,  vol.  ii.  p.  617. 


2  Ibid.,  p.  618. 


CONDITIONS    INFLUENCING    HEART'S    ACTION.  285 

Table  LIII. — Position  of  Valves  of  Heart. 

Aortic.  Opposite   third    intercostal   space   on    left   side,    close   to 

sternum. 
"2d.    Pulmonary.       Opposite  junction  of  third  rib  with  the  sternum. 
3d.    Mitral.  Opposite  third  intercostal  space  one  inch  to  left  of  sternum. 

1st.  Tricuspid.  Behind  middle  of  sternum  at  level  of  fourth  rib. 

The  o;reat  practical  importance  to  the  physician  of  a  thorough  knowl- 
edge of  the  manner  in  which  the  sounds  of  the  heart  are  produced,  and 
of  the  position  of  the  valves  in  reference  to  the  walls  of  the  chest,  as 
aiding  him  in  diagnosing  diseases  of  the  heart,  is  so  obvious  that  it  will 
not  be  considered  superfluous  in  attention  being  called  to  the  topographi- 
cal anatomy  of  the  valves  as  given  in  Table  LIII. 

When  it  is  considered  that  age,  sex,  food,  exercise,  etc.,  influence  the 
rapidity  of  the  action  of  the  heart,  it  becomes  evident  that  an  intimate 
sympathy  must  exist  between  the  circulation  and  the  other  great  func- 
tions of  the  economy.  From  time  immemorial,  therefore,  the  frequency 
of  the  heart's  action  has  always  been  regarded  as  one  of  the  most  im- 
portant indications  of  the  general  health  of  the  system.  The  practical 
importance,  therefore,  of  determining,  as  far  as  possible,  the  average 
beat  of  the  heart  in  a  given  time,  within  the  limits  of  health,  must  be 
obvious  to  every  physician.  We  shall  see  in  the  next  chapter  that  with 
each  ventricular  systole  or  cardiac  impulse  there  is  an  expansion  of  the 
arteries  due  to  the  blood  being  forced  out  of  the  left  ventricle  into  the 
aorta.  This  expansion  of  the  arteries  or  pulse,  which  we  will  consider 
again  in  detail,  is,  for  convenience'  sake,  usually  felt  and  counted  instead 
of  the  beat  of  the  heart  itself,  and,  other  things  being  equal,  the  result  of 
such  examination  can  be  accepted  as  a  criterion  of  the  condition  of  the 
heart  and  vascular  system  generally.  It  will  be  observed  from  Table  LIV., 
compiled  from  the  observations  of  Guy1  and  Milne  Edwards,2  that  the 
average  number  of  cardiac  beats  per  minute  varies  according  to  the  age 
and  sex,  and  this  should  always  be  remembered  when  the  pulse  is  counted 
in  man.  Thus  in  the  foetus,  while  the  number  of  pulsations  per  minute 
is  140  (determined  by  listening  to  the  foetal  heart),  at  birth  the  number 
falls  to  136,  and  that  up  to  the  third  year  of  life,  while  the  pulse  is  still 
the  same  in  both  sexes,  it  now  averages  only  about  107  beats  to  the 
minute.  As  we  pass,  however,  from  infancy  to  youth,  it  will  be  seen 
that  the  number  of  pulsations  per  minute  gradually  diminishes,  and  that 
at  the  same  period  the  pulse  of  the  female  is  a  little  quicker  than  that 
of  the  male.  In  adult  life  the  average  number  of  pulsations  in  the  male 
may  be  said  to  be  from  70  to  72  per  minute,  and  from  6  to  8  beats  more 
in  the  female.  At  the  approach  of  old  age  the  pulse  becomes  a  little 
more  frequent,  at  eighty  years  of  age  the  number  of  beats  usually  being 
about  80  a  minute. 

1  Cyclopedia  of  Anat.  and  Phys.,  vol.  iv.  p.  181.  -  Ph3'siologie,  tome  iv.  p.  62. 


286  THE    EEAET. 

Table  LI V. — Frequency  of  Heart's  Action. 

Pulsations  per  minute. 
Age. 


[<Vta]  . 

At 

birth 

1 

year 

2 

years 

2 

to    7 

8 

"    14 

1  1 

"    21 

21 

"    28 

28 

"   35 

35 

"    42 

42 

"    49 

49 

"    56 

56 

'■    63 

63 

"   70 

7n 

"    1 1 

77 

"   84 

Male. 

Female. 

.     140 

1  to 

.     L86 

136 

.     128 

L28 

.     107 

107 

.       97 

98 

.       84 

94 

.       76 

82 

.       7:: 

80 

7d 

78 

.       68 

78 

.       70 

77 

.       67 

76 

.       68 

77 

.       70 

78 

.       67 

81 

.       71 

82 

As  is  well  known,  in  animals  of  different  species,  but  which  are  closely 
allied  in  their  general  organization,  the  pulse  varies  with  the  size  of  the 
animal,  being  slowest  in  the  largest  and  fastest  in  the  smallest  animals. 
Thus  in  the  horse  the  number  of  beats  is  only  40  to  the  minute,  in  the 
ass  about  50,  in  the  sheep  from  60  to  80,  in  the  dog  100  to  120,  in  the 
rabbit  150,  and  in  some  of  the  smallest  rodents  even  175.  The  cir- 
culation is  also  more  rapid  in  small  insects  than  in  large  ones,  and  it 
has  long  been  a  matter  of  observation  that  in  man  the  pulse  is  slower 
in  persons  of  large  stature  than  in  those  of  small.  This  connection  be- 
tween the  rapidity  of  the  pulse  and  the  size  of  the  animal  seems  to  be  a 
very  general  one  in  the  animal  kingdom,  so  far  as  has  been  observed, 
and  its  significance  will  become  apparent  when  we  study  the  production 
of  animal  heat  in  the  economy,  for  we  shall  see  then  that  the  rapidity 
of  the  circulation  is  directly  correlated  with  the  production  of  heat  and 
force,  and  that,  as  a  general  rule,  the  greatest  amount  of  nervo-muscular 
activity  is  exhibited  by  the  smallest  animals  of  any  one  order  rather 
than  by  the  largest  ones. 

This  dependence  of  the  pulse  on  the  size  may  to  a  certain  extent  ex- 
plain the  difference  between  the  pulse  of  the  young  and  of  the  old,  and  of 
the  sexes  as  just  given  in  Table  LIV.,  but  it  should  be  remembered  that 
the  observations  of  Volkmann1  show  that  youth  and  sex  in  themselves, 
without  regard  to  size,  influence  the  rate  of  the  pulse,  for  in  individuals 
of  equal  size  the  youngest  had  the  quickest  pulse,  and  the  pulse  of  the 
woman  was  always  quicker  than  that  of  the  male. 

It  must  not  be  forgotten,  however,  in  counting  the  pulse  that  often 
individuals  are  met  with  in  perfect  health  in  whom  the  pulse  is  extremely 
rapid,  or  just  the  reverse.  Thus,  according  to  the  late  Prof.  Dunglison,2 
the  pulse  of  Sir  William  Congreve  never  fell  below  128  beats  per  minute, 
while,  as  is  well  known,  on  the  other  hand,  that  of  Napoleon  I.  often  did 
not  exceed  40  beats  to  the  minute.3  Haller4  refers  to  cases  where  the 
pulse  was  still  slower,  being  only  23  beats  to  the  minute. 

1  Die  Hsemodynamik,  S.  30,  36.     Leipzig,  1850.         -  Human  Physiology,  1856,  8th  eel.,  vol.  i.  p.  440. 
'  Berard  :  Physiologic,  tome  iv.  p.  113.  4  Elements  Physiologic,  tome  ii.  p.  256. 


CONDITIONS    INFLUENCING    PULSE.  287 

Among  the  six  hundred  gentlemen  who  have  annually  honored  the 
author  in  attending  his  lectures,  there  have  been  several  instances  in 
which  almost  as  marked  a  difference  in  the  heat  of  the  pulse  was  ob- 
served as  in  that  of  the  two  celebrated  cases  first  referred  to.  Idiosyn- 
crasy may,  therefore,  have  a  greater  influence  in  modifying  the  beat  of 
the  pulse  than  is  usually  assigned  to  it. 

As  is  Avell  known,  the  action  of  the  heart  is  also  influenced  by  diges- 
tion; according  to  Milne  Edwards,1  there  is  an  increase  of  from  five  to 
ten  beats  after  each  meal.  On  the  other  hand,  prolonged  fasting  dimin- 
ishes the  frequency  of  the  pulse  from  twelve  to  sixteen  beats.  Accord- 
ing to  the  same  high  authority,  while  vegetable  food  diminishes  the 
action  of  the  heart  animal  food  increases  it,  fermented  drinks  at  first 
diminish  then  accelerate  the  movements  of  the  heart.  Coffee  is,  how- 
ever, in  the  highest  degree  a  cardiac  stimulant.  Every  one  is  familiar 
with  the  fact  that  any  violent  exercise,  like  running  or  jumping,  in- 
creases the  action  of  the  heart.  As  long  ago  as  the  early  part  of  the 
last  century  it  was  shown,  by  the  experiments  of  Bryan  Robinson,2  that 
the  pulse  of  a  man  in  the  recumbent  position  being  64  to  the  minute, 
was  increased  to  78  during  a  slow  walk,  and  still  further  increased  to 
100  by  walking  a  league  and  a  half  in  an  hour,  and  rose  as  high  as  140 
to  150  after  running  as  rapidly  as  possible.  It  is  also  well  known,  from 
the  experiments  of  Guy,3  that  if  the  number  of  pulsations  on  the  average 
be  66  to  the  minute  in  a  man  lying  down,  the  number  will  be  increased 
to  71  if  he  sits  up,  and  will  be  still  further  increased  to  81  if  he  stands 
up.  After  what  has  just  been  said  in  reference  to  muscular  activity 
increasing  the  action  of  the  heart,  the  results  of  Guy's  experiments  are 
just  what  might  have  been  expected,  since  muscular  force  is  developed 
in  changing  the  position  of  the  body  and  maintaining  it  in  equilibrium. 

Indeed,  it  was  in  this  way  that  many  of  the  older  physiologists 
theoretically  explained  the  acceleration  of  the  heart's  beat  observed  in 
the  change  of  posture  just  referred  to.  It  was  Guy,  however,  who  first 
demonstrated,  by  means  of  a  revolving  board  which  supported  the  per- 
son who  was  the  subject  of  the  experiment  and  so  relieved  him  of  the 
necessity  of  supporting  himself  by  muscular  exertion,  that  the  varia- 
tions in  the  frequency  of  the  heart,  according  to  the  position  of  the  body, 
was  dependent  upon  the  quantity  of  muscular  force  put  forth  in  maintain- 
ing equilibrium  in  each  of  the  positions.  The  practical  importance  of  these 
facts  for  the  physician  cannot  be  exaggerated,  since  it  is  obvious  that,  in 
a  person  suffering  with  heart  disease,  it  is  of  the  utmost  importance 
that  any  increase  in  the  action  of  the  heart  should  be  avoided.  The 
greatest  caution,  under  such  circumstances,  should  be  advised  in  the 
taking  of  exercise  ;  any  sudden  or  violent  effort,  like  quickly  lifting  up 
a  trunk,  or  running  rapidly  up  stairs,  should  be  strictly  prohibited, 
the  slight  acceleration  in  the  heart's  beat  from  such  an  effort  being 
frequently  a  cause  of  death  in  persons  affected  with  heart  disease. 

It  is  well  known  that  during  the  day  there  is  a  variation  in  the  action 
of  the  heart,  and  for  a  long  time   it  was  supposed  that  the  pulse  was 

1  Physiol ogie,  tome  iv.  p.  79. 

-  A  Treatise  on  the  Animal  Economy,  p.  ITT.     Dublin,  1732. 
Cyclopaedia  oi    \nat.  and  Phys.,  vol.  iv.  p.  188. 


288  THE    HEART. 

quicker  in  the  evening  than  in  the  morning.  According  to  the  older 
physiologists,  "  Pulsus  nocturnus  m  ill  to  celerior  est."1  When,  however, 
the  action  of  the  heart  at  evening  is  considered  uninfluenced  by  food, 
exercise,  etc.,  it  has  heen  found  that  the  pulse  at  that  period  of  the  day 
is  really  slower  than  in  the  morning,  and  that  the  heart  is  less  suscepti- 
ble to  the  action  of  stimulants.  This  condition  is  due,  no  doubt,  to 
muscular  fatigue. 

In  sick  persons,  however,  it  is  otherwise,  since  at  evening  there 
is  usually  some  fever  present,  and  this  is  accompanied  by  a  quicker 
pulse.  According  to  Milne  Edwards,2  while  sleep  tends  to  diminish  the 
action  of  the  heart,  the  number  of  pulsations,  at  least  in  man,  is  not 
diminished  to  any  extent  by  that  circumstance.  In  women,  and  es- 
pecially children,  in  that  condition,  however,  there  seems  to  be  con- 
siderable difference  as  compared  with  the  wakeful  state.  The  tempera- 
ture of  the  surrounding  atmosphere  influences  also  the  rapidity  of  the 
action  of  the  heart — heat  increasing  and  cold  diminishing  the  number 
of  heart  beats. 

De  la  Roche'  found  that  his  pulse  was  increased  to  160  beats  per 
minute  in  an  atmosphere  of  150°  Fahr.,  and  it  is  well  known  that  the 
pulse  is  quicker  in  hot  countries  than  in  cold  ones.  Among  the  other 
influences  that  accelerate  or  diminish  the  action  of  the  heart  must  be 
mentioned  the  condition  of  the  respiration.  When  the  manner  in  which 
the  blood  flows  through  the  pulmonic  capillaries,  and  the  changes  pro- 
duced in  it,  have  been  described,  the  mutual  sympathy  existing  between 
the  heart  and  lungs  will  then  be  fully  appreciated.  It  would  be 
anticipating  too  much  to  give  a  detailed  account  of  this  mutual  influence 
at  present ;  a  few  words  now,  therefore,  will  suffice.  If  the  heart  ceases 
to  beat,  the  muscles  involved  in  respiration  not  receiving  their  accus- 
tomed amount  of  fresh  blood,  lose  their  contractility,  will  not  respond 
to  their  natural  stimuli,  and  respiration  ceases.  On  the  other  hand,  if 
respiration  ceases  first,  the  heart  soon  stops  beating.  This  is  due  to  the 
fact  that  unaerated  blood  will  not  flow  through  the  systemic  capillaries, 
and  that,  in  consequence,  the  whole  arterial  system  becomes  gorged  with 
black  blood  that  has  flown  from  the  right  side  of  the  heart  through  the 
lungs  back  to  the  left  side  of  the  heart,  and  so  into  the  aorta  unaerated. 
While  at  first  under  such  circumstances  the  heart  will  continue  to  con- 
tract, forcing  the  blood  into  the  great  vessels,  soon  the  resistance  offered 
by  the  engorged  state  of  the  pulmonary  capillaries  and  the  arterial 
system  becomes  so  great  that  the  heart  can  no  longer  empty  its 
cavities ;  it  then  becomes  enormously  distended  with  unaerated  blood, 
such  distention  finally  producing  a  paralysis  of  the  muscular  fibres 
of  the  heart,  and  so  arresting  its  action.  Such  a  condition  of  things 
is  well  seen  in  cases  of  death  from  asphyxia.  The  influence  of 
the  cessation  of  respiration  as  a  cause  of  the  arrest  of  the  heart's 
action,  also,  by  the  mere  pressure  of  the  air  enclosed  within  the 
chest  upon  the  heart,  has  been  more  than  once  demonstrated  in  man, 
and  sometimes  probably  fatally.      Thus,  by  closing  the  mouth  and  con- 

1  Keill  :  Teutamina  medico-physica,  p.  178.     Lond.  1730. 

2  Physiologie,  tome  iv.  p.  74.  *  These,  Paris,  1806,  p.  :s:5. 


CAUSE    OF    HEART'S    CONTRACTION.  289 

tracting  the  walls  of  the  chest  simultaneously,  respiration  can  be  volun- 
tarily suspended,  with  the  effect  of  diminishing  the  action  of  the  heart, 
and  even  of  stopping  it  entirely.  By  suspending  his  respiration  and 
contracting  forcibly  at  the  same  time  the  Avails  of  the  chest,  Prof.  E.  F. 
Weber,  of  Leipsic,  was  able  to  diminish  the  cardiac  beats  to  three  to  five  a 
minute,  which  were  unaccompanied  with  the  cardiac  impulse  or  sounds, 
and  with  the  result,  finally,  of  stopping  the  action  of  the  heart 
altogether.  On  one  occasion,  having  suspended  his  respiration  longer 
than  usual.  Professor  Weber l  fell  into  a  syncope.  This  case,  concern- 
ing the  truth  of  which  there  can  be  no  question,  confirms  the  state- 
ments made  by  Galen,2  and  others,  that  death  in  certain  individuals  had 
been  caused  by  the  voluntary  suspension  of  their  breathing.  One  of 
the  most  interesting  and  best  authenticated  cases  of  the  possibility  of 
temporarily  arresting  the  action  of  the  heart  was  that  of  Colonel 
Towhnsend,  reported  in  the  early  part  of  the  last  century  by  Cheyne.3 
This  physician  relates  how  Colonel  ToAvhnsend  could  so  arrest  the 
breathing  and  the  beating  of  his  heart  that  death  was  simulated.  In 
this  condition  the  pulse  could  not  be  felt  at  the  wrist ;  there  was  no 
cardiac  impulse ;  a  mirror  placed  in  front  of  the  mouth  was  not  tar- 
nished, and,  apparently,  he  was  dead.  On  the  occasion  reported  by 
Cheyne,  Colonel  Towhnsend  remained  in  this  condition  for  half  an  hour  ; 
gradually,  however,  the  respiration  and  circulation  became  reestablished. 
It  should  be  mentioned,  however,  that  Colonel  Towhnsend  died  later  in 
the  afternoon  of  the  same  day  that  the  facts  just  described  occurred. 

Having  described  the  motion  of  the  heart  and  the  various  influences 
that  modify  it,  it  remains  for  us  now  to  consider  what  is  known  of  the 
cause  of  this  motion.  When  we  come  to  the  special  study  of  muscular 
contractility  we  shall  learn  that  an  ordinary  voluntary  muscle  usually 
contracts  in  response  to  a  stimulus,  the  will  emanating  in  the  brain 
and  transmitted  through  a  nerve  to  the  muscle. 

While  the  heart  is  a  muscular  organ,  its  action  (lifters  from  that  of  the 
ordinary  muscle  in  being  involuntary  in  character.  The  voluntary 
muscle,  however,  not  only  contracts  through  the  influence  of  the  will  or 
nerve  force,  but  also  in  response  to  mechanical,  electrical,  or  chemical 
stimuli,  and,  in  this  respect,  the  heart  does  the  same.  Thus,  if  the 
chest  of  a  living  animal  be  opened,  and  the  heart  mechanically  irritated 
by  an  instrument,  a  scalpel,  for  example,  it  will  be  seen  to  contract  like 
any  other  muscle  stimulated  in  a  similar  manner.  The  same  effect  fol- 
lows the  application  of  electricity  by  means  of  the  electrodes.  The 
addition  of  warm  water,  and  exposure  to  the  air  will  also  cause  the  heart 
to  contract.  A  significant  fact  to  be  noticed  in  all  of  these  experiments 
is  that  the  effect  of  the  stimulus  is  much  greater  when  it  is  applied  to 
the  inner  rather  than  to  the  outer  surface  of  the  heart,  and  that,  even 
after  the  outer  surface  of  the  heart  has  ceased  to  respond  to  stimuli  the 
inner  surface  will. 

The  muscular  substance  of  the  heart,  then,  like  that  of  any  other 
muscular  organ   is  endowed  with  the  property  of  contractility,  through 

1  Milne  Edwards:  Physiologie,  tome  iv.  p.  8S-.  '-'  (Euvres  trad,  de  Daremberg,  tome  i.  p.  366. 

s  The  English  Malady,  p.  307.     London,  1734. 

19 


290  THE     HEAHT. 

which  the  organ  contracts  in  response  to  various  stimuli.  The  nature 
of  this  property  of  muscular  substance,  contractility,  and  its  relation  to 
stimuli,  will  be  considered  hereafter.  Of  the  different  kinds  of  stimuli 
that  are  known  to  produce  contraction  of  the  heart,  none  are  so  impor- 
tant as  the  contact  of  blood  with  the  inner  wall  of  its  cavities.  Indeed, 
since  the  time  of  Haller,  the  presence  of  blood  within  the  cavities  of  the 
heart  lias  been  regarded  as  an  indispensable  condition  in  the  production 
of  its  contractions,  if  not  the  cause  itself.  While  there  were  physiolo- 
gists, prior  to  the  time  of  Haller,  who  held  this  view,  it  is  to  that  phys- 
iologist that  science  is  indebted  for  most  of  the  facts  that  can  be 
brought  forward  even  now  in  support  of  it.  Among  the  many  experi- 
ments performed  by  Haller1  may  be  mentioned  the  following  striking 
ones.  The  vena  cava  and  the  branchial  artery  being  ligated  in  an  eel 
by  the  contraction  of  the  auricle  the  blood  was  forced  into  the  ventricle, 
and  the  auricle  not  receiving  any  more  blood  through  the  ligation  of  the 
vena  cava  soon  ceased  to  beat.  On  the  other  hand,  the  ventricle  being 
unable  to  empty  itself  entirely,  the  branchial  artery  being  tied,  continued 
to  dilate  and  contract.  When,  however,  the  ligature  was  removed  from 
the  vena  cava  the  auricle  began  to  beat  again. 

In  another  experiment,  performed  on  a  cat,2  the  superior  vena  cava 
was  divided,  and  the  inferior  vena  cava  ligated,  with  the  effect  of  cutting 
off  the  supply  of  blood  to  the  right  auricle;  then  the  pulmonary  artery 
was  opened  and  the  right  ventricle  consequently  emptied.  On  the  other 
hand,  by  the  ligating  of  the  aorta  the  blood  was  retained  in  the  left  ven- 
tricle. It  was  observed  that  the  right  auricle  soon  ceased  to  beat,  then 
the  left  ventricle,  whereas  the  left  ventricle  continued  to  beat  for  four 
hours. 

To  appreciate  fully  the  importance  of  these  experiments,  particularly 
the  latter,  it  must  be  remembered  that  usually  the  right  auricle  is  the 
last  part  of  the  heart  to  cease  beating,  and  that  the  left  ventricle  stops 
beating  before  the  right,  whereas,  in  the  experiment  just  described, 
exactly  the  reverse  was  the  case. 

These  experiments  prove,  therefore,  the  importance  of  the  presence 
of  blood  in  the  cavities  of  the  heart  as  an  indispensable  condition  in 
producing  its  contraction.  It  is  also  well  known  that  when  an  animal 
is  dying  of  hemorrhage,  and  the  heart  has  stopped  beating,  the  intro- 
duction of  a  little  fresh  blood  by  transfusion  will  reestablish  its  move- 
ments. Further,  when  the  heart  is  taken  entirely  out  of  an  animal,  a 
frog,  for  example,  and  completely  emptied  of  blood,  with  the  effect  of 
stopping  the  beat,  the  contractions  will  recommence  with  the  introduc- 
tion of  a  few  drops  of  blood  into  the  ventricle.  Even  fragments  of  the 
heart  can  be  made  to  contract  and  dilate  by  the  addition  of  a  few  drops 
of  blood.  It  appears,  then,  from  experiments  of  this  kind  that  the 
most  important  cause  of  the  movement  of  the  heart  is  the  presence  of 
blood  in  its  cavities. 

The  stimulating  effect  of  the  blood,  however,  is  not  limited  to  the 
interior  of  the  heart,  for  with  each  ventricular  systole  blood  is  forced 

1  jMemoires  sur  la  Nature  Sensible  et  Irritable  des  Parties  du  corps  animal  a  Lauss.inne,  1756,  tome  i. 
p.  370. 

2  Op.  cit. ,  tome  i.  p.  363. 


STIMULUS    TO    HEART'S    ACTION.  291 

through  the  aorta  into  the  coronary  arteries,  and  thence  into  the  sub- 
stance of  the  heart,  and  this  blood  will  act  as  a  stimulus  to  the  external 
parts  of  the  heart,  just  as  we  have  seen  the  blood  acts  as  a  stimulant  to 
the  internal  ones.  During  the  systole  of  the  heart,  however,  the  minute 
vessels  being  compressed  by  the  contracted  muscular  fibres  the  flow  of 
the  blood  will  be  limited  principally  to  the  superficial  parts  of  the  heart, 
so  that  it  is  during  the  diastole  rather  that  the  coronary  capillaries 
receive  blood.  This  view  does  not  imply,  as  held  by  Brucke,1  that  the 
orifices  of  the  coronary  orifices  are  closed  by  the  semilunar  valves  of  the 
aorta  during  the  ventricular  systole,  and  that  these  vessels  are  filled 
during  the  diastole,  for,  as  Hyrtl2  demonstrated,  the  coronary  arteries 
arc  filled  during  the  ventricular  systole,  but  only  supposes  that  the 
coronary  capillaries  receive  their  maximum  amount  of  blood  during  the 
diastole.  The  filling  up  of  these  interstitial  vessels  is,  therefore,  coin- 
cident with  the  filling  up  of  the  cavities  of  the  heart  itself. 

The  stimulus  is,  therefore,  exerted  by  the  blood  simultaneously  upon 
the  inner  and  outer  parts  of  the  heart.  The  importance  of  the  blood 
flowing  through  the  coronary  system  of  vessels,  not  only  as  contributing 
a  part  of  the  stimulus  necessary  for  the  heart's  action,  but  of  furnishing 
its  muscular  substance  with  fresh  material  for  the  elaboration  of  muscular 
or  contractile  force,  is  well  seen  when  the  coronary  arteries  are  ligated, 
the  effect  of  which,  as  Erichsen3  showed,  is  to  stop  almost  immediately 
the  beating  of  the  heart.  According  to  Brown-Sequard,4  while  the 
arterial  blood  in  the  coronary  vessels  furnishes  the  nutritive  materials 
out  of  which  the  muscular  or  contractile  force  of  the  heart  is  developed, 
the  venous  blood,  on  account  of  the  carbonic  acid  it  contains,  supplies 
the  necessary  stimulus  to  excite  this  force,  carbonic  acid  being  a 
stimulus  to  muscular  contractility.  If  this  view  be  accepted,  it  offers, 
perhaps,  an  explanation  of  the  fact,  already  referred  to,  that  the  right 
auricle  is  the  last  part  of  the  heart  to  cease  beating,  and  that  the  left 
ventricle  stops  beating  before  the  right,  as  the  stimulating  effect  of  the 
venous  blood  on  the  right  side  of  the  heart  will  last  longer  than  that  of 
the  arterial  blood  on  the  left  side  on  account  of  its  containing  more  car- 
bonic acid.  There  must  be  taken  into  consideration  also  in  studying 
the  action  of  the  heart,  as  we  shall  soon  see,  that  as  blood  is  flowing 
into  the  aorta  during  the  ventricular  systole  blood  is  flowing  out  of  the 
other  end  of  the  arterial  system  through  the  capillaries  into  the  venous 
system,  and  therefore  that  blood  is  flowing  into  the  auricle.  The  con- 
traction of  the  ventricles  is  therefore  the  cause  of  the  dilating  of  the 
auricles,  while  the  filling  up  of  the  auricles  is  the  cause  of  the  emptying 
of  these  cavities,  and  ultimately  of  the  ventricles  also.  The  action  of 
the  heart  must,  therefore,  be  of  this  intermittent  character. 

During  the  diastole,  the  repose  of  the  heart,  blood  is  flowing  into  its 
cavities;  when  an  amount  has  accumulated  sufficient  to  furnish  the 
necessary  stimulus  to  the  contractility  of  the  muscular  substance,  the 
contraction  or  systole  takes  place  and  blood  is  forced  out ;  but  as  the 
circulatory  system  maybe  regarded  as  a  closed  tube,  while  venous  blood 

1  Sitzber.     d.  Wiener  Acad.,  1855,  Band  xiv.  S.  345  -  Ibid.,  S.  373. 

3  London   Medical  Gazette,  1842,  2d  ser.  toI.  ii.  p.  561.  4  Experimental  Researches,  1853,  p.  114. 


292  THE    HEART. 

is  flowing  into  one  end  of  the  system  the  arterial  blood  will  be  flowing 
into  the  other  or  venous  end.  The  intermittent  flow  of*  the  blood,  or 
the  stimulus  to  the  movements  of  the  heart,  further  makes  possible  a  far 
greater  accumulation  of  the  contractile  force  than  if  the  stimulus  were  a 
continuous  one.  Were  the  heart  to  beat  continuously,  it  would,  like 
any  other  muscle,  under  similar  circumstances,  soon  become  exhausted, 
and  indeed  such  is  the  case  if  the  blood  be  retained  indefinitely  in  any 
of  the  cavities  of  the  heart.  It  is  true  that  the  part  will,  for  some  time, 
exhibit  rhythmical  movements,  but,  sooner  or  later,  the  movements  will 
become  infrequent,  irregular,  and  finally  cease  altogether. 

It  is  a  matter  of  daily  observation  that  the  circulation,  like  the  other 
functions,  is  influenced  by  the  nervous  system,  but  as  the  relation  of  the 
nervous  system  and  the  circulatory  organs  is  quite  a  complex  one,  the 
consideration  of  this  part  of  the  subject  will  be  for  the  present  deferred. 

In  concluding  our  account  of  the  heart  it  may  be  now  appropriately 
mentioned,  however,  that  while  the  action  of  the  heart  is  greatly  influ- 
enced by  the  nervous  system,  the  heart  itself  is  insensible.  The  insen- 
sibility of  the  heart  is  often  observed  in  cases  where  it  has  been 
wounded,  the  patient  being  unconscious  of  pain,  or,  indeed,  of  any 
feeling  at  all.  In  the  celebrated  case  of  the  Viscount  Montgomery,  so 
often  mentioned  by  authors,  and  so  well  described  by  Harvey,  the 
opportunity  was  offered  of  directly  inspecting  and  feeling  the  heart. 
Harvey  tells  us,  in  the  work1  already  referred  to,  that  this  individual 
was  entirely  unconscious  of  the  application  of  his  finger  to  the  heart. 

1  Op.  cit.,  p.  375. 


CHAPTER   XX. 


THE  ARTERIES. 


We  have  seen  that  at  each  ventricular  systole  the  blood  Is  forced 
from  the  heart  into  the  pulmonary  artery  and  aorta.  The  manner  in 
which  the  venous  blood  passes  through  the  pulmonary  capillaries,  and 
returns  aerated  arterial  blood  to  the  heart,  will  be  described  when  the 
subject  of  respiration  is  considered,  for  the  present  let  us  follow  the 
blood  as  it  flows  through  the  aorta  and  its  branches,  the  arteries. 

The  arterial  system,  by  means  of  which  the  blood  is  circulated  to  all 
parts  of  the  body,  consists  of  musculo-elastic  tubes,  which,  in  their 
general  disposition,  may  be  compared  te  a  cone  of  which  the  heart  is 
the  apex,  and  the  base  the  periphery  of  the  body,  or  to  a  tree  of  which 
the  aorta  represents  the  trunk,  and  the  arteries  the  branches.  As  we 
recede  from  the  heart  to  the  periphery  the  branches  divide  and  subdivide, 
and  anastomose,  until,  becoming  microscopic,  they  pass  into  the  capil- 
laries. With  few  exceptions,  the  combined  calibre  of  the  branches  of 
an  artery  is  greater  than  that  of  the  artery  itself.  There  is  a  gradual 
increase,  therefore,  in  the  capacity  of  the  arterial  system  as  we  pass 
from  the  heart  to  the  capillaries.  This  increase  of  capacity,  however, 
is  not  always  as  great  as  might  be  supposed,  since  the  capacity  of  tubes 
are  to  each  other  as  the  squares  of  their  diameters.  For  example,  if 
an  artery  with  a  diameter  of  4  cent.  (1.6  in.)  divides  into  two  branches, 
each  with  a  diameter  of  3  cent.,  the  difference  between  the  capacity  of 
the  main  trunk  and  its  branches  will  be  2  cent.  Thus,  42  equals  16, 
32  4-  32  equals  9  -f  9  equals  18  ;  18  — 16  equals  2.  As  a  general  rule, 
the  arteries  run  in  nearly  a  straight  course  to  the  parts  which  they 
supply  with  blood.  The  branches  gradually  diminish  in  size,  and  com- 
paratively few  are  given  oft*  between  the  main  trunk  and  the  capillaries. 
The  aorta  and  the  arteries,  like  the  heart,  are  not  nourished  by  the 
blood  circulating  in  their  cavities,  but  by  blood  from  adjacent  vessels, 
the  arterial  vasa  vasorum,  which  have  no  direct  connection  with  the 
arteries  which  they  supply.  The  vasa  vasorum,  which  include  little 
veins,  as  well  as  arteries,  are  mostly  restricted  to  the  outer  coat  of  the 
artery,  but  few  penetrating  the  middle  coat.  The  vasa  vasorum  of  the 
arteries  bear  the  same  relation  to  the  arteries  that  the  coronary  arteries 
and  veins  bear  to  the  heart  itself.  The  arteries  are  also  supplied  by 
nerves  derived  from  both  the  cerebro-spinal  and  sympathetic  systems, 
Inn  principally  from  the  latter.  The  manner  in  which  these  nerves 
modify  the  calibre  of  the  arteries  will  be  understood  when  their  minute 
structure  has  been  studied,  to  the  consideration  of  which  let  us  now  turn. 

The  arteries,  including  the  aorta,  consist  essentiallv  of  three  coats 
(Fig.  152),  an  external  fibrous,  a  middle  elastic  muscular,  an  internal 
epithelial.     Each  of  these  coats,  however,  can  be  shown  to  consist  of 


294 


THE     A  R  T  K  1 !  I  K  S  , 


several  subcoats,  or  layers,  more  or  less  developed,  according  to  the  size 
and  situation  of  the  artery. 

The  external  or  fibrous  coat  of  the  artery  is  mainly  composed  of  fine 
bundles  of  white  connective  tissue,  the  filaments  of  which  are  usually 
disposed  in  a  spiral  manner  around  the  vessel,  and  on  the  surface  are 
often  loosely  adherent  to  surrounding  parts:  the  inner  surface  of  the 
fibrous  coat,  however,  is  intimately  blended  with  the  middle  coat.  Be- 
tween the  bundles  of  the  connective  tissue  fibres,  of  which  the  external 
coat  consists,  are  disposed  in  various  amounts  fine  nets  of  elastic  tissue ; 
these  nets  are  most  abundant  in  the  inner  part  of  the  external  coat.  To 
their  internal  coat  the  arteries  owe  chiefly  their  strength.  The  middle 
coat  of  the  artery  consists  of  layers  of  elastic  and  muscular  tissue,  which 
are  disposed  around  the  vessel  in  a  circular  manner.  The  relative  amount 
of  these  tissues,  however,  varies  according  to  the  size  and  position  of 
the  vessel.     In  the  largest  arteries,  those  nearest  the  heart,  the  middle 


Transverse  section  of  the  walls  of  the  aorta,  treated  with  acetic  acid,  and  magnified.  1.  Internal  coat. 
a.  Epithelium  and  basement  membrane.  6,  c.  Layers  of  elastic  tissue.  2.  Middle  coat.  d.  Layers  of 
elastic  tissue,  e.  Muscular  and  connective  tissue.  3.  External  coat,  composed  of  fibrous  tissue  and  fine 
nets  of  elastic  tissue.     (Leidy.) 

coat  is  composed  mainly  of  elastic  tissue,  there  being  very  little  muscular 
tissue  present,  whereas,  in  the  medium  size  arteries,  the  middle  coat  chiefly 
consists  of  muscular  tissue,  and  in  the  smallest  arteries  of  muscular 
tissue  only.  The  muscular  tissue  is  of  the  unstriated  character,  and 
consists  of  fusiform  cells,  or  bands,  with  oval  nuclei ;  they  do  not  entirely 
surround  the  artery ;  the  elastic  tissue  forms  a  more  or  less  close  net- 
work of  fibres,  which,  from  its  membranous  perforated  character,  is  often 
known  as  the  fenestrated  membrane.  A  great  deal  of  the  elasticity, 
and  all  the  contractility  with  which  the  arteries  are  endowed,  are  due 
to  their  middle  coat. 

The  internal  coat  of  the  artery  is  essentially  a  continuation  of  the  endo- 
cardium, or  lining  membrane  of  the  heart,  and  consists  of  three  layers, 
an  outer  elastic  of  the  membranous  fenestrated  kind,  a  middle  basement 
membrane,  and  an  inner  epithelial  layer,  composed  of  elongated  lozenge- 
shaped  cells.  The  outer  elastic  layer  of  the  internal  coat  of  the  artery  is 
intimately  connected  with  the  inner  portion  of  the  middle  coat,  while  the 
basement  membrane  is  that  part  of  the  artery  which  ultimately  becomes 
the  capillary.  We  have  seen  that  the  action  of  the  heart  is  intermittent 
in  character,  each  ventricular  svstole  bein^:  followed  bv  the  diastole,  a 


FLOW    OF    LIQUIDS    THROUGH    TUBES.  295 

period  of  repose  during  which  no  blood  flows  into  the  arterial  system 
from  the  heart.  If,  however,  a  large  artery  near  the  heart  be  opened, 
it  will  be  observed  that  the  blood  flows  out  of  the  artery  continuously, 
both  during  the  systole  and  diastole.  With  each  ventricular  systole, 
however,  the  jet  becomes  stronger;  the  flow  in  the  artery,  therefore,  is 
not,  like  that  in  the  heart,  intermittent,  but  remittent.  If  the  artery 
examined  be  situated,  however,  at  a  distance  from  the  heart,  near  the 
periphery,  the  flow  of  the  blood  will  be  found  to  be  but  slightly  remit- 
tent, indeed  almost  uniform,  while  finally,  as  we  shall  see  in  the  capil- 
laries, it  is  entirely  so.  The  flow  of  the  blood,  then,  as  it  passes  from 
the  heart  through  the  arteries  to  the  capillaries  from  being  intermittent 
becomes  remittent,  and  finally  uniform.  It  is  to  the  property  of  elas- 
ticity, with  which  we  have  seen  arteries  are  endowed,  that  this  trans- 
formation of  an  intermittent  motion  into  a  remittent  one  is  due.  For, 
during  each  ventricular  systole,  of  the  blood  that  is  forced  into  the  arte- 
ries a  part  only  presses  onward,  the  blood  already  in  the  arteries,  the 
remaining  part,  presses  outward  the  walls  of  the  artery.  From  the 
moment,  however,  that  the  effect  of  the  systole  ceases — that  is,  during 
the  diastole — through  its  elasticity  the  walls  of  the  artery  recoil  on 
the  blood  which  has  distended  them,  and  press  it  onward  (the  aortic 
valves  preventing  any  regurgitation)  immediately  after  the  part  of  the 
blood  that  has  just  preceded — that  is,  the  part  forced  forward  during 
the  systole.  There  are  two  successive  waves  of  blood  then  in  the  artery, 
that  of  the  systole  and  that  of  the  diastole;  they  follow  each  other,  how- 
ever, so  rapidly,  that  ultimately  they  merge  into  one,  the  movement  of 
the  blood  in  the  capillaries  becoming  finally  uniform.  The  elasticity  of 
the  artery  favors,  therefore,  the  onward  movement  of  the  blood. 

Did  the  arteries  consist  of  rigid  tubes  the  blood  would  flow  through 
them  in  the  same  intermittent  manner  as  it  does  through  the  heart. 
With  each  ventricular  systole  blood  would  flow  from  the  arteries  into 
the  capillaries  in  an  amount  equal  to  that  which  flowed  from  the  heart 
into  the  aorta,  with  the  diastole  of  the  heart,  however,  the  flowT  from  the 
arteries  would  entirely  cease.  We  are  in  the  habit  of  demonstrating  the 
difference  between  the  flow  of  liquids  in  elastic  and  rigid  tubes  by  means 
of  the  apparatus  described  by  Marey,1  and  which,  slightly  modified,  is 
represented  in  Fig.  153.  The  apparatus  consists  of  an  elevated  reser- 
voir (A)  holding  about  20  litres  (5  gallons)  of  water  colored  by  aniline, 
and  furnished  with  a  stopcock  (B)  by  means  of  which  the  supply  of 
fluid  can  be  regulated.  To  the  stopcock,  the  orifice  of  which  has  a 
diameter  of  1  cm.  (|-th  of  an  inch),  is  connected  a  flexible,  and,  if 
possible,  a  non-elastic  tube  (C)  about  70  cm.  (28  inches)  in  length. 
The  latter  passes  around  a  tin  tube  (D),  which  bifurcates  so  that 
the  fluid  from  the  reservoir  can  pass  through  the  tube  G  into  the  tubes 
E  and  F  simultaneously.  One  of  these  tubes  consists  of  glass  (E),  the 
other  of  caoutchouc  (F),  the  former  (E)  is  connected  with  the  tube  D 
by  caoutchouc.  The  two  tubes  (E  F)  have  a  length  of  1.6  m.  (5.12 
feet)  and  a  diameter  of  1  cm.  (fth  of  an  inch).  At  their  distal  ends 
the  tubes  are  bent  downward  so  that  the  fluid  flowing  from  them  can 

1  Op.  Cit.,  1881,  p.  163. 


296 


THE    ARTERIES. 


be  conveniently  collected  in  the  jars  P  I.  The  glass  tube,  as  it  termi- 
nates, is  drawn  out  so  as  to  simulate  the  capillary  end  of  an  artery,  its 
orifice  having  a  diameter  of  2.5  mm.  (y-yth  of  an  inch).  The  same 
effect  is  accomplished,  as  regards  the  caoutchouc  tube,  by  inserting  into 
its  distal  end  a  tube  of  glass  of  the  same  length  and  diameter  as  that 
of  the  distal  end  of  the  glass  tube.  The  tubes  E  F  are  supported  by, 
and  firmly  bound  to,  the  table  K,  which  is  painted  white  so  that  the 
colored  fluid  can  be  readily  seen  in  the  glass  tube. 

The  reservoir  being  filled  and  the  stopcock  turned  on,  the  colored 
fluid  passes  into  the  bifurcated  tube  and  thence  through  the  elevation 
and  depression  of  the  lever  (G),  worked  by  hand,  in  an  intermittent 
manner,  into  the  rigid  glass  tube  and  elastic  caoutchouc  one.  The  lever 
should  be  uniformly  depressed  and  elevated  at  the  rate  of  about  sixty 
times  to  the  minute  and  the  fluid  watched  as  it  escapes  from  the  tubes. 

Fig.  153. 


Apparatus  to  demonstrate  tlie  fiovv  of  a  fluid  through  rigid  and  elastic  tidies.     I  Mabey.  I 


It  will  be  observed,  from  the  reasons  already  given,  that  the  flow  from 
the  rigid  glass  tube  is  absolutely  intermittent,  with  each  depression  of 
the  lever  the  flow  entirely  ceasing.  On  the  other  hand,  the  flow  from 
the  caoutchouc  tube  is  distinctly  remittent,  the  jet  not  ceasing  but  only 
diminishing  with  the  depression  of  the  lever  and  increasing  again  with 
its  elevation.  It  is  needless  to  add  that  the  elevation  and  depression  of 
the  lever  represent  the  opening  and  closing  of  the  aortic  valves,  the 
escape  of  the  fluid  from  the  tubes  the  flow  of  blood  through  the  con- 
stricted arteries  toward  the  capillaries. 

This  experiment  not  only  proves  that  the  elasticity  of  a  tube  influ- 
ences the  character  of  the  movement  of  the  fluid  flowing;  through  it,  but 
also  of  the  quantity  that  escapes  from  it,  for  if  the  jars  P  I  be  exam- 
ined it  will  be  seen  that  the  one  collecting  the  liquid  from  the  elastic 
tube  is  almost  three  times  as  full  as  that  collecting  from  the  rigid  one. 
During  an  experiment  lasting  three  minutes,  while  2800  c.  cm.  (2.8 


ELASTICITY     AND    CONTRACTILITY    OF    ARTERIES.       297 

pints)  of  fluid  flowed  into  the  one  jar,  only  1000  c.  cm.  (1  pint)  flowed 
into  the  other.  This  is  as  might  have  been  expected  when  it  is  remem- 
bered that  an  elastic  tube  is  capable  of  receiving  more  fluid  than  a  rigid 
one,  for  two  reasons  :  first,  there  is  not  only  the  quantity  of  fluid  which, 
after  entering  the  tube  presses  directly  onward  and  which  corresponds 
to  the  fluid  in  the  rigid  tube,  but  also  an  additional  quantity  which 
presses  the  walls  of  the  elastic  tube  outwardly.  It  is  this  lateral  fluid. 
so  to  speak,  that  follows  and  adds  itself  to  the  part  which  presses  di- 
rectly onward  that  converts  the  intermittent  motion  into  the  remittent 
one,  and  by  just  so  much  as  the  walls  of  the  tube  will  give  to  this  lateral 
pressure  the  amount  of  fluid  entering  the  elastic  tube  will  be  in  excess 
of  that  entering  the  rigid  one.  Second,  it  being  remembered  that  the 
principal  obstacle  to  the  flow  of  a  liquid  through  a  tube  is  the  friction 
of  its  walls,  and  that  the  friction  is  proportional  to  the  square  of  the 
velocity  of  the  current,  it  follows  that  as  the  effect  of  the  dilatation  of  the 
artery  is  to  diminish  the  velocity  of  the  current  through  it,  and  there- 
fore to  diminish  tbe  amount  of  friction  according  to  the  square  of  the 
velocity  of  the  current,  the  quantity  of  fluid  delivered  from  the  elastic 
tube  will,  therefore,  be  greater  than  that  from  the  rigid  one. 

We  have  seen  that  the  arteries  are  not  only  endowed  with  elasticity, 
but  also  with  contractility  or  tonicity,  as  it  was  called  by  Bichat,  and  it 
has  been  shown,  experimentally,  by  Poisseuille,1  that  the  recoil  of  the 
walls  of  the  artery  upon  the  blood  that  had  previously  distended  it  is 
greater  than  can  be  accounted  for  by  the  elasticity  of  the  artery  alone. 
Indeed,  the  tendency  of  an  artery  is  always  to  contract,  to  empty  itself 
of  its  blood.  For  this  reason  difficulty  is  always  experienced  in  inject- 
ing the  vessels  of  an  animal  immediately  after  death. 

If,  during  life,  the  calibre  of  the  arteries  is  about  equal  to  that  ob- 
served after  death,  it  is  because  the  arteries  are  during  life  distended 
with  blood. 

That  the  arteries  will  contract  independently  of  the  elasticity  or  the 
recoil  following  upon  the  distention  of  its  walls  through  the  blood  forced 
into  the  vessel  by  the  heart,  can  be  demonstrated  by  ligating  an  artery 
in  two  places  and  in  a  part  of  its  course  where  no  branches  are  given  off, 
so  as  to  exclude  the  influence  of  the  general  circulation,  and  then  open- 
ing the  artery  at  a  point  situated  between  the  ligatures.  Under  such 
conditions,  although  the  artery  is  uninfluenced  by  the  action  of  the 
heart,  etc.,  the  blood  will  jet  out  with  force  and  the  artery  will  be  almost 
completely  emptied.  When  it  is  remembered,  as  we  have  seen,  that  in  the 
smallest  arteries  the  middle  coat  consists  entirely  of  muscular  fibres,  there 
being  no  elastic  tissue  present,  it  becomes  evident  that  the  contractility, 
in  such  cases  at  least,  must  be  due  entirely  to  the  action  of  the  muscular 
fibres.  Hence  the  distinction  clearly  made  by  John  Hunter,  that  in  the 
large  arteries  the  recoil  of  the  walls  was  due  almost  entirely  to  the  elas- 
ticity;  in  the  smallest  arteries,  on  the  contrary,  to  the  contractility. 
The  physiological  significance  of  this  distinction  was  also  seen,  Hunter 
attributing  to  the  elasticity  the  conversion  of  the  intermittent  action  of 
the  heart  into  the  remittent  one  of  the  artery,  to  the  contractility  the 

1  Journal  de  Magendie,  t.  i.\.  p.  44. 


298  T.HE    ARTERIES. 

regulating  of  the  calibre  of  the  arteries,  and,  therefore,  the  supply  of  the 
blood  to  the  system.  Inasmuch  as  arteries  therefore  contract  in  virtue 
of  their  contractility  as  well  as  of  their  elasticity,  and  as  after  death  the 
contractility  disappears,  as  might  be  expected,  the  amount  of  contraction  is 
greater  in  the  living  artery  than  the  dead  one.  The  contractility  of  the 
arteries  can  be  easily  demonstrated  by  the  application  of  various  stimuli, 
mechanical,  chemical,  electrical,  exposure  to  air,  application  of  cold,  etc. 
Thus  the  mere  scraping  of  the  walls  of  an  artery  or  the  pricking  of  a 
needle  will  cause  them  to  contract.  Various  chemical  substances,  such  as 
sulphuric  acid,  ammonia,  alum,  and  ergot,  are  among  the  most  powerful 
stimuli  to  muscular  contractility.  Indeed,  the  usefulness  of  haemostatics 
in  arresting  hemorrhage  depends  upon  this  property. 

The  smallest  arteries  readily  contract  under  the  influence  of  both  the 
direct  and  indirect  electrical  currents.  Simple  exposure  of  the  arteries 
to  air  suffices  to  produce  a  slow  but  permanent  constriction  of  the  vessel. 
The  local  application  of  cold — ice,  for  example — in  stopping  bleeding 
after  wounds,  is  well  known  to  the  uneducated,  the  effect  being  clue  to 
contractility.     The  stimulus  of  great  heat  produces  the  same  result. 

We  have  already  seen  that,  through  nervous  influence,  the  arteries 
contract.  In  speaking  of  the  structure  of  the  arteries,  it  was  men- 
tioned that  the  muscular  fibres  are  supplied  by  nerves  derived  from  the 
sympathetic  and  cerebro-spinal  systems.  The  stimulation  by  electricity 
of  these  vasomotor  nerves,  as  they  are  called,  is  followed  by  contraction 
of  the  arteries  they  supply,  while  division  or  paralysis  of  these  nerves 
is  followed  by  a  dilatation  of  the  vessels.  The  phenomena  of  blushing, 
of  sudden  pallor  in  the  face,  are  familiar  examples  of  the  influence  of  the 
vasomotor  nerves  in  modifying  the  amount  of  blood  in  a  part ;  in  the 
one  case  the  vessels  dilating,  in  the  other  contracting.  When  it  is  re- 
membered  that  more  blood  is  demanded  by  an  organ  at  one  time  than 
another,  a  gland  when  secreting,  for  example,  requiring  more  arterial 
blood  than  when  quiescent,  it  becomes  evident  that  there  must  be  some 
means  in  the  economy  by  which  the  amount  of  blood  supplying  any 
organ  can  be  varied.  It  is  through  the  vasomotor  filaments  that  the 
nervous  system  modifies  the  calibre  of  the  arteries,  and,  in  that  way, 
regulates  the  amount  of  blood  distributed  to  different  parts  of  the  body. 
The  origin  and  distribution  of  the  vasomotor  nerves  will  be  considered 
in  detail  hereafter. 

While  it  must  be  admitted  that  the  contractility  of  the  arteries  favors 
somewhat  the  onward  flow  of  the  blood  within  them,  without  doubt 
the  principal  effect  of  their  contractility  is  the  regulation  of  the  supply 
of  blood  through  the  modification  of  their  calibre.  It  should  be  men- 
tioned, as  regards  this  contractility,  that,  by  whatever  means  it  is  in- 
duced, whether  the  stimuli  be  mechanical,  chemical,  or  electrical,  that, 
unlike  ordinary  striated  muscle,  it  does  not  immediately  follow  the 
application  of  the  stimulus,  more  or  less  time  intervening,  according  to 
the  stimulus  used.  It  is  also  to  be  noticed  that  a  temporary  relaxation 
usually  follows  a  contraction,  and,  if  the  stimulus  be  very  intense,  the 
contraction  is  followed  by  a  dilatation,  as  if,  for  the  moment,  the  con- 
tractility had  been  exhausted  in  producing  its  effect. 


DILATATION     OF    ARTERIES-  299 

We  have  seen  that  during  each  ventricular  systole  the  aorta  and 
arteries  generally  become  distended  with  the  blood  forced  into  them  by 
the  heart,  and  as  the  pressure  of  the  blood  is  exerted  both  laterally  and 
longitudinally,  the  artery  must  therefore  enlarge  in  both  these  direc- 
tions. The  longitudinal  enlargement  of  the  artery  is,  however,  so  much 
more  apparent  than  the  transverse  one,  as  will  be  explained  presently, 
that  the  latter  is  usually  masked  or  obscured.  So  much  so,  indeed,  is 
this  the  case,  that  for  a  long  time  it  was  denied  by  physiologists  that 
there  was  any  transverse  dilatation  of  the  artery.  While  Harvey,1  it  is 
true,  states  that  when  an  artery  is  divided,  and  held  at  the  cut-end  by 
the  fingers,  the  dilatation  is  apparent,  it  must  be  admitted,  however, 
that,  to  the  ordinary  eye,  this  is  far  from  evident.  The  proof  of  the 
transverse  dilatation  of  the  artery,  however,  does  not  rest  on  the  mere 
assertion  of  a  physiologist,  however  celebrated,  but  can  be  readily 
demonstrated,  either  as  shown  by  Flourens,2  by  placing  around  a  living 
artery  a  watch-spring,  the  ends  of  which  just  meet  during  the  relaxa- 
tion of  the  vessel,  and  which  separate  during  the  lateral  distention,  or, 
by  Poisseuille's3  method,  which  consists  in  enclosing  an  artery  in  a 
living  animal  within  a  tube  filled  with  water  (the  ends,  of  course,  being 
closed),  and  the  interior  of  which  communicates  with  a  capillary  tube, 
serving  as  an  indicator,  in  which  the  water  rises  or  falls,  according  as 
the  water  is  forced  out  of  the  tube  by  the  lateral  distention  or  transverse 
dilatation  of  the  artery,  or  is  sucked  back  again  by  the  recoil  of  the 
wall  of  the  vessel,  due  to  its  elasticity.  The  longitudinal  expansion  of 
the  artery,  or  the  elongation,  is  more  easily  demonstrated  than  the 
expansion  in  the  transverse  direction.  As  also  shown  by  Flourens 
it  is  very  evident,  if  the  artery  examined  be  slightly  colored,  and  a 
needle  as  a  guide  be  immovably  placed  on  one  side  of  the  vessels 
with  each  ventricular  systole  and  diastole  the  colored  point  on  the 
artery  will  be  observed  to  advance  and  recede  in  a  longitudinal  direc- 
tion. The  elongation  of  the  artery  is  also  very  apparent  in  the  vessels 
of  the  stump  of  an  amputated  extremity,  and  becomes  quite  evident  in 
a  vessel  in  which  the  blood  flowing  meets  with  an  obstacle,  as  where  the 
artery  bifurcates,  or  runs  in  a  tortuous  course  rather  than  a  straight 
one.  During  the  elongation  of  an  artery  the  vessel  frequently  rises  up 
out  of  its  bed,  experiencing  considerable  displacement ;  this  is  known 
as  the  locomotion  of  the  artery,  and  is  often  seen  in  the  temporal  and 
radial  arteries  of  old  and  emaciated  persons. 

On  account  of  the  extent  of  the  vessel  exposed  during  the  elonga- 
tion, the  longitudinal  expansion  is  far  more  evident  than  the  transverse 
one,  and,  as  we  have  already  observed,  quite  obscures  it.  The  increase 
of  capacity  due  to  the  longitudinal  expansion  of  the  artery  is,  however, 
less  than  that  due  to  the  transverse  one,  for,  as  is  well  known,  the 
capacity  of  the  tube  increases,  as  regards  the  length,  in  a  simple  ratio 
only,  whereas,  the  capacity  of  tubes  in  the  transverse  direction  in- 
creases not  in  a  simple  ratio,  as  the  diameters,  but  as  the  squares  of 
the  diameters.     For  example,  while  a  tube  51  cm.  (20  inches)  in  length 

1  Exercitatio  altera  ad  J   Biolanum  Opera  Omnia,  17;>(i,  p.  112. 

2  Anuales  des  Sciences  Nat.,  1837,  t.  vii.  p.  106.  :i  Op.  eit,  t.  ix.  ]>.  46 


300  THE     ARTEEIES. 

and  2.5  cm.  (1  inch)  in  breadth,  will  contain  about  2t»0  c.  cm.  (0.2  pint), 
a  tube  51.5  cm.  (20.5  inches)  in  breadth,  will  contain  2Hl'  c.cm.,  or 
only  2  cm.  more,  thus  : 

51:  51.5  ::  290:  a?  equals  202: 

whereas,  a  tube  51  cm.  long,  but  2.8  cm.  (1  inch)  in  breadth,  will  con- 
tain 360,  thus  : 

6.2",.  or  (2.5)2  :  7.84,  or  (2.8)2  :  :  200  :  x  equals  360,  or  nearly  70 
c.cm.  more  than  the  tube  51.5  cm.  long,  but  onlv  2.5  cm.  in  breadth — 
350-292  equals  68. 

The  elongation  and  transverse  dilatation  of  the  arteries  due  to  the 
distention  of  their  walls  by  the  blood  forced  into  them  by  the  heart  at 
each  ventricular  systole  constitute  the  pulse.  It  will  be  observed  that 
the  pulse,  or  the  expansion  of  the  artery,  is  synchronous  with  the  con- 
traction of  the  ventricle  of  the  heart,  not  with  the  heart's  expansion, 
as  was  thought  by  Galen,  and  the  ancients  generally.  Although  this 
truth  seems  to  have  been  known  to  a  writer  who  lived  during  the 
early  part  of  our  era,  it  remained  for  Harvey  to  demonstrate  it  in 
modern  times.  Ordinarily,  neither  the  elongation  nor  transverse  dilata- 
tion of  an  artery  or  its  pulse  is  visible  to  the  naked  eye,  or  appreciable 
even  by  touch  alone.  It  is  for  this  reason  that  the  observer  presses 
with  his  finger  more  or  less  the  artery  examined,  thereby  constricting 
the  vessel  and  so  increasing  the  velocity  of  the  blood,  it  flowing  faster 
as  the  artery  becomes  smaller,  the  same  amount  of  blood  passing 
through  in  a  given  time  ;  this,  as  we  have  seen,  increases  friction,  and 
so  causes  an  obstacle  to  the  flow,  which,  Avithin  limits,  increases  the 
force  of  the  heart,  and,  therefore,  the  distention  of  the  artery,  and  so 
makes  the  beating  of  the  vessel  or  the  pulse  more  apparent. 


CHAPTER     XXI. 

THE  ARTEBIES.— (Qmtinued.) 

Sphygmograph,  Arterial  Schema. 

No  artery  in  man  can  be  directly  measured,  either  as  regards  its 
expansion  or  its  pressure.  In  feeling  the  pulse,  however,  the  endeavor 
is  made  to  measure  both  by  the  sense  of  touch  alone. 

While  the  experience  of  every  physician  shows  to  what  an  extent 
slight  variations  in  the  pulse  can  be  appreciated  by  the  tactus  eruditus 
alone,  nevertheless  it  is  only  by  means  of  the  graphic  method  that  the 
conditions  on  which  the  production  of  the  pulse  and  its  variations  de- 
pend can  be  successfully  investigated.  By  the  graphic  method,  as  we 
have  seen,  a  pictorial  representation,  a  trace  of  some  kind  of  the  phe- 
nomena occurring  can  be  obtained  and  preserved,  by  means  of  which 
slight  variations,  due  to  change  of  conditions,  become  at  once  evident 
that  would  be  entirely  unappreciable  by  the  eye  or  touch  unaided,  and 
that  by  a  comparison  of  the  traces  obtained  from  the  examination  of 
the  living  artery  with  those  obtained  from  a  tube  corresponding  to  an 
artery  in  an  artificial  apparatus  representing  the  general  vascular  sys- 
tem, the  manner  in  which  the  pulse  is  produced,  and  the  conditions  on 
which  its  variations  depend,  can  be  "demonstrated. 

The  advantage  of  such  an  experimental  investigation  of  the  pulse, 
the  practical  application  that  can  be  made  of  it  in  investigating  the 
cause  of  disease,  will  be  at  once  appreciated  after  the  sphygmograph 
and  the  arterial  schema,  the  apparatus  we  use  in  studying  the  pulse, 
have  been  described,  and  the  results  obtained  by  them  shown. 

The  object  of  the  sphygmograph  (sphygmos,  a  trace,  and  grapho,  to 
write)  is  to  measure  the  succession  of  the  alternate  dilatations  and 
contractions  of  an  artery  due  to  the  blood  forced  into  it  bv  the  beating 
heart,  to  magnify  these  movements,  and  to  register  them  on  a  surface 
moving  at  a  uniform  rate  by  clock-work.  The  arterial  schema,  or  arti- 
ficial artery  is  an  apparatus  representing  the  general  vascular  system 
by  means  of  which  we  can  produce  an  experimental  pulse,  and  from  it, 
by  means  of  the  sphygmograph,  obtain  a  trace,  which  can  be  compared 
with  that  obtained  bj  the  sphygmograph  from  the  natural  pulse.  By 
such  a  comparison  it  will  be  observed  that  the  trace  made  by  the  pulsa- 
tion of  the  artificial  artery,  differs  from  that  made  bv  the  living  one 
only  in  degree,  not  in  kind  ;  the  natural  inference  is,  therefore,  that  the 
cause  of  both  traces  must  be  essentially  the  same.  Further,  by  slightly 
changing  the  action  of  the  arterial  schema,  traces  can  be  produced 
which  so  closely  simulate  those  obtained  from  the  living  pulse  in  various 
diseases  that  there  can  be  but  little  doubt  that  the  cause  of  both  is  the 
same. 


302 


THE    ARTERIES. 


The  sphygmograph  was   originally  invented   by  Vierordt,  and  after- 
ward greatly  improved  by  Marey.     It  is  the  latter  form,  as  modified  by 


Fig   154. 


Mechanical  arrangement  of  the  sphygmograph.     (Sandekson.) 
Fig.   155. 


Marey's  sphygmograph  applied  to  arm.     (Marey.) 


Fig-  156-  Sanderson,  and  constructed  by  Hawks- 

ley,  that  we  shall  use.  The  instru- 
ment (Fig.  154)  consists  of  a  brass 
frame  (0  R),  the  under  surface  of 
which  is  covered  with  ebonite,  and 
which  can  be  applied  to  the  outer 
edge  of  the  volar  aspect  of  the  fore- 
arm so  that  it  rests  immovably  in  this 
position  with  reference  to  the  radius  and 
wrist-bones,  particularly  the  scaphoid. 
The  pulsations  of  the  radial  artery  are 
received  by  an  ivory  button  (K),  placed 
at  the  free  end  and  under  the  surface 
of  the  steel  spring  I ;  the  other  fixed 
end  of  the  spring  is  attached  to  the 
brass  work  at  P.  By  means  of  the 
ivory  button  and  spring  the  pulsations 
of  the  artery  are  transmitted  to  the  ver- 
tical screw  T,  which  passes  through  the 
brass  bar  N,  whose  centre  of  motion 
is  at  E,  above  the  attachment  of  the 
steel  spring  I ;  the  free  end  (B)  of  the  brass  bar  is  bent  upward  at 
right  angles,  and  carries  a  knife-edge  (D),  well  seen  in  Fig.  154.  The 
elevation  of  the  screw  T,  through  the  pulsation  of  the  artery,  raises 


Scale  for  determining  pressure  excited  by 
artery.    (Sanderson.) 


SPHYGMOGRAPH.  303 

the  brass  bar  N,  carrying  the  knife-edge  D,  the  latter,  in  turn,  ele- 
vating the  registering  lever  A,  of  which  one  end  (C)  is  supported  by 
a  horizontal  rod  passing  through  it  and  connecting  the  sides  of  the  brass 
frame,  while  the  other  movable  end  (A)  terminates  in  a  metal  joint, 
which  registers  the  motion  of  the  pulsation  on  a  piece  of  paper 
(Fig.  155)  blackened  by  passing  it  to  and  fro  through  the  flame  of  a 
kerosene  lamp.  The  paper  is  fastened  to  a  copper  plate,  which  is 
moved  at  a  uniform  rate  by  the  clock-work  (Fig.  155).  As  the  distance 
between  the  supporting  rod  C  and  the  knife-edge  D  is  much  less  than 
the  length  of  the  lever,  the  vibrations  of  the  extremity  of  the  lever 
(A)  are  far  more  extensive  than  the  vertical  movement  of  the  spring 
I  and  screw  T.  By  means  of  the  screw  T  the  distance  between 
the  steel  spring  I  and  the  registering  lever  A  can  be  varied 
at  will  without  interfering  with  the  mechanism  by  which  the  move- 
ment is  transmitted.  The  distance  between  the  brass  frame  and  the 
ebonite  surface  can  also  be  increased  or  diminished,  according  to 
the  direction  in  which  the  screw  Y  is  turned,  and,  in  this  way,  the 
pressure  on  the  artery  may  be  varied ;  the  variation  in  the  pressure  is 
measured  by  the  scale  (Fig.  156),  which  has  been  experimentally  gradu- 
ated by  turning  the  instrument  upside  down,  and  successively  placing 
a  series  of  weights  on  what  would  be  ordinarily  the  lower  surface  of 
the  spring,  but  which  is  now  the  upper  surface,  and  observing  the 
extent  of  its  deflection  and  marking  the  scale  correspondingly.  Finally, 
by  means  of  a  movable  clamp,  there  can  be  adapted  to  the  sphygmo- 
graph,  when  desirable,  a  delicate  tympanum,  with  registerig  lever,  in 
connection  with  a  cardiograph,  so  that  the  traces  of  the  cardiac  and 
arterial  pulsation  can  be  registered  simultaneously  on  the  blackened 
surface. 

To  take  a  trace  with  the  sphygmograph  of  the  radial  artery,  which  is 
the  vessel  usually  examined,  the  forearm  should  be  supported  on  some- 
thing, a  table,  for  example,  the  back  of  the  wrist  resting  on  a  cushion 
or  padding,  so  that  the  dorsal  surface  of  the  hand  will  be  inclined,  with 
reference  to  the  forearm,  at  an  angle  of  20  to  30  degrees.  The  instru- 
ment must  be  so  placed  on  the  wrist  that  the  block  rests  upon  the  tra- 
pezium and  scaphoid,  while  the  extremity  of  the  spring  is  opposite  the 
styloid  process  of  the  radius,  the  general  direction  of  the  sphygmograph 
will  then  be  parallel  with  that  of  the  radius.  In  making  an  observation 
it  is  best  to  begin  by  adjusting  the  instrument  so  that  the  ivory  button 
on  the  under  surface  of  the  spring  is  at  such  a  distance  from  the  bone 
that  the  artery  is  pressed  upon  during  its  entire  expansion,  and  yet  not 
so  compressed  as  to  obliterate  at  any  moment  its  cavity. 

To  those  unfamiliar  with  the  use  of  the  sphygmograph,  perhaps  it 
will  be  well  to  begin  by  arranging  the  spring  so  that  it  will  exert  a 
pressure  sufficient  to  flatten  the  artery  against  the  radius  and  then  to 
diminish  the  pressure  until  the  effects  of  such  compression  disappear, 
and  thus  to  take  traces  of  the  maximum  and  minimum  pressures,  and 
one  then  of  an  intermediate  character. 

Having  described  the  sphygmograph  and  the  manner  of  using  it,  the 
following  figures  will  illustrate  the  character  of  the  traces  taken  by  it. 
Thus,   for  example,  Figs.   157,  158,  and  159  are  obtained  from   the 


304 


THE    A  K  T  E  II I  E  S  . 


radial  ami  femoral  arteries  in  a  healthy  man  of  about  thirty  years  of 
age.  Figs.  1<><)  and  161  are  from  the  radial  of  a  woman  tet.  sixty-five 
and  of  a  man  ;et.  seventy  respectively,  in  both  of  which  cases  the  arteries 
were  in  an  atheromatous  condition. 

Let  us  now  consider  the  arterial  schema  and  the  manner  in  which  the 
artificial  pulse  is  produced,  and  then  compare  the  tracing  of  such  a  pulse 

Fig.  157. 


Sphygmographic  tracing  from  radial  artery  of  a  man  set.  twenty-five. 
Fig.  158. 


Sphygmographic  tracing  from  radial  artery  of  a  man  set.  thirty. 
Fig.  159 


Sphygmographic  tracing  from  femoral  artery  of  a  man  a?t   thirty.     (A.  P.  B.) 

Fig.  100. 


Sphygmographic  tracing  from  radial  artery  of  a  woman  at.  Bixty-five.     Atheromatous  arteries. 


Fig.  161. 


[XjVJ 


Sphygmographic  tracing  tram  radial  artery  of  a  man  set.  seventy.     Atheromatous  arteries. 

with  those  just  exhibited.  There  are  several  different  kinds  of  arterial 
schema,  from  the  simple  one  of  Weber  to  the  elaborate  apparatus  of 
Marey,  that  are  used  in  studying  the  phenomena  of  the  circulation. 
For  our  present  purpose  the  instrument  (Fig.  162)  described  by  San- 
derson1 and  constructed  for  the  author  by  Ltawksley,  will  suffice.  It 
is  true  that  the  apparatus  does  not  resemble  in  form  at  all  the  heart, 
aorta,  etc.,  but  as  the  object  of  the  arterial  schema  is  not  meant  to  illus- 
trate the  structure  of  the  parts  but  their  action,  this  is  a  matter  of  no 
moment. 

1  Handbook  Phys.  Lab.,  p.  230.     Phila.,  1873. 


ARTERIAL    SCHEMA 


305 


It  consists  essentially  of  a  reservoir  supplying  the  colored  water  rep- 
resenting blood,  which  should  stand  at  a  height  of  from  2  to  3  metres 
(6  to  9  feet),  of  an  elastic  tube  (B  D  0,  etc.)  several  metres  long,  repre- 
senting the  left  side  of  the  heart,  aorta,  arterial  system,  etc.,  of  a  lever 
(C)  53  cm.  (21  in.)  in  length  and  which  is  so  arranged  that,  as  it  is 
depressed  at  the  end  nearest  D,  it  closes  the  elastic  tube  at  D  and  opens 
it  at  E,  and  when  elevated  opens  the  tube  at  D  and  closes  it  at  E.  This 
alternate  closing  and  opening  of  the  tube  at  Eand  I)  imitate  the  action  of 

Fig.  162. 


Schema  for  demonstrating  the  nature  of  the  arterial  movements.  A-  Glass  tube  which  represents  the 
heart.  B.  The  tube  by  which  A  communicates  with  a  cistern  at  a  height  of  ten  or  twelve  feet  above  it 
(A  much  smaller  head  of  water  is  sufficient.)  C.  The  lever  by  which  the  two  valves  E  and  D  are  worked, 
the  same  act  which  shuts  the  one  opening  the  other.  F.  Commencement  of  the  experiment  tube,  which 
is  of  black  vulcanite.  At  Fthe  tube  communicates  with  a  long  vertical  tube  of  glass,  only  part  of  which 
is  seen  ;  it  is  closed  at  the  top,  anil  usually  shut  off  from  F  by  a  pinchcock  At  G  the  tube  passes  under 
the  spring  of  the  sphygmograph,  the  frame  of  which  rests  on  a  block  (below  G).  By  error,  the  tube  has 
been  drawn  on  the  wrong  side  of  the  block  H.  The  blackened  plate  of  the  sphygmograph.  To  the  left 
of  it  is  seen  the  cylinder,  with  its  needle  for  recording  the  time  which  intervenes  between  the  opening 
and  closing  of  the  aortic  valve,  L.  A  rod  which  is  firmly  fixed  in  the  lever,  and  is  connected  by  two 
cords,  one  of  which  is  elastic  with  the  cylinder.     (Sanderson.) 


the  mitral  and  aortic  valves  by  means  of  the  spring  at  C\  when  the  ap- 
paratus is  not  working  the  aortic  orifice  is  kept  closed.  The  portion  of 
the  tube  lying  between  D  and  E,  which  represents,  therefore,  the 
left  ventricle,  is  30  cm.  (12  in.)  in  length,  communicates  with  the  ver- 
tical glass  tube  (A)  54  cm.  (21  in.)  high  and  with  a  diameter  of  9  cm. 
(3.5  in.);  this  tube  can  be  opened  or  closed  at  its  upper  end  by  a  stop- 
cock. When  the  lever  is  elevated  and  the  tube  opened  at  E,  or  the 
mitral  orifice,  the  colored  fluid  from  the  reservoir  flows  up  into  the  tube 
A  compressing  the  air  within  it,  according  to  Mariotte's  law,  the 
volume  of  air  diminishing  as  the  pressure  increases  ;  when  the  lever  is 
depressed  and  the  tube  open  at  D,  or  the  aortic  orifice,  the  compressed 

20 


306  THE     ARTERIES. 

air  in  the  tube  A  suddenly  expands  and  forces  the  water  into  the  tube 
beyond  (/>),  which,  of  course,  corresponds  to  the  aorta.  The  expansion 
of  the  air  theD  represents  the  force  of  the  contracting  heart.  At  a  dis- 
tance of  L5  cm.  (6  in.)  from  the  aortic  orifice  the  elastic  tube  communi- 
cates through  a  T-shaped  connecting  tube  on  the  one  hand,  with  a  long 
vertical  glass  tube  (i),  and  on  the  other  with  the  tube  F,  which,  gradu- 
ally becoming  smaller  and  then  larger  again,  represents  the  arteries, 
capillaries,  and  veins.  The  communication  between  the  tube  F  and  the 
tube  /  can  be  opened  or  closed  by  means  of  a  pinchcoek.  The  use  of 
the  tube  /  will  be  explained  presently.  For  the  moment  we  will  con- 
sider that  the  communication  between  it  and  the  arterial  tube  is  closed. 
At  a  convenient  distance  from  the  aortic  orifice  there  is  placed  upon  the 
tube,  which  we  will  consider  represents  the  radial  artery,  a  sphygmo- 
graph  (h),  of  which  the  lever,  properly  supported,  will  be  elevated  or 
depressed  as  the  tube  expands  or  contracts  by  the  fluid  forced 
through  it  with  the  opening  and  closing  of  the  aortic  orifice.  Just 
at  the  position  of  the  fulcrum  of  the  lever  there  is  fixed  a  vertical  rod 
(X),  which  is  connected  by  means  of  two  cords,  the  upper  one  being 
elastic,  with  the  pulley  m.  The  pulley,  through  a  marker  attached  to  it, 
will  make  a  straight  line  on  the  blackened  recording  surface  of  the 
sphygmograph  as  long  as  the  lever  is  depressed  at  E — that  is,  as  long  as 
the  aortic  orifice  is  open.  With  the  closure  of  the  aortic  orifice  through 
the  elevation  of  the  lever,  the  marker  will  be  drawn  upward,  away 
from  the  blackened  surface,  through  the  elastic  cord,  and  the  absence 
of  the  mark  on  the  blackened  surface  will  indicate  the  closure  of  the 
aortic  orifice.  As  the  mark  on  the  recording  surface  is  coincident  with 
the  elevation  of  the  lever  of  the  sphygmograph  and  the  absence  of  the 
mark  with  its  depression,  it  is  therefore  shown,  from  what  has  just  been 
said,  that  the  elevation  of  the  sphygmograph  lever  is  coincident  with  the 
opening  of  the  aortic  orifice,  and,  therefore,  with  the  ventricular  systole, 
while  the  depression  of  the  lever  is  coincident  with  the  diastole. 

The  construction  of  the  apparatus  being  now  understood,  let  the 
sphygmographic  trace  Fig.  161,  taken  by  it,  be  compared  with  that  of 
Fig.  157,  representing  the  sphygmographic  trace  of  the  natural  pulse. 
By  such  a  comparison  it  will  be  observed  that  the  difference  between 
the  traces  of  the  natural  pulse  and  that  of  the  schema  is  one  of  degree 
rather  than  of  kind.  In  both  traces  we  have  seen  the  same  movements 
succeeding  each  other  in  the  same  order.  With  the  expansion  of  the 
artery  we  have  the  elevation  of  the  lever  with  the  contraction,  the  de- 
scent, then  the  secondary  rise  or  dicrotism,  and  finally  the  descent  again. 
As  in  the  case  of  the  natural  heart  so  in  that  of  the  schema,  it  is  seen 
that  as  the  aortic  valve  (D)  is  opened  the  artery  expands,  the  lever  rising 
and  the  vessel  remains  full  as  long  as  the  artificial  heart  is  acting,  that 
with  the  cessation  of  the  flow  of  liquid  from  behind  the  artery  contracts 
the  lever  descending.  That  the  ascent  and  descent  of  the  lever  are  due 
to  the  cause  just  assigned  can  be  shown  by  the  motion  of  the  marker 
attached  to  the  pulley  m  in  the  manner  explained  above.  As  long  as 
the  aortic  orifice  I)  is  open  the  marker  remains  in  contact  with  the  re- 
cording surface  of  the  sphygmograph,  but  with  the  closure  of  the  aortic 
orifice  the  marker  is  pulled  away.      The  trace  (Fig.  161),  as  recorded, 


PERCUSSION     AND    PRESSURE    WAVES. 


307 


exhibits  then  a  line  broken  at  regular  intervals.  When  this  is  com- 
pared with  the  sphygmographic  trace  of  the  artery  it  will  be  observed 
that  there  is  an  exact  correspondence  between  the  time  during  which 
the  heart  is  acting  and  the  time  elapsing  between  the  beginning  of  the 
expansion  and  the  commencement  of  the  contraction,  the  expansion  evi- 
dently, therefore,  depends  upon  the  contraction  of  the  heart.  By  a 
careful  examination  of  the  traces  produced  by  the  arterial  schema  it  can 
be  seen  also  that  the  forcing  of  liquid  into  the  arterial  tube  by  the 


Fig.  163. 


Tracing  obtained  with  arterial  schema. 


artificial  heart  produces  two  effects,  which  can  be  demonstrated  to  be 
independent  of  each  other.  One  of  these  is  a  molecular  vibratory 
oscillating  motion — that  is,  a  to  and  fro  pendulum-like  movement,  which 
has  been  appropriately  called,  from  its  mode  of  producing  the  percussion 
wave,  the  other  the  transmission  of  the  pressure  of  the  artificial  heart 
at  the  moment  the  aortic  orifice  is  open  to  the  liquid  in  the  arterial 
tube,  and  which  is  known  as  the  pressure  wave.  To  produce  the  per- 
cussion wave  by  means  of  the  schema,  one  has  only  to  close  the  aortic 
orifice  D  and  arrange  the  lever  C,  so  that  by  suddenly  rapping  it  with 
a  hammer  a  percussion  shock  can  be  imparted  to  the  tube  beneath. 
The  trace  of  the  percussion  wave  produced  in  this  way  (Fig.  164)  shows 
that  the  sphygmographic  lever  is  jerked  up  the  initial  ascent,  the 
descent  being  extremely  abrupt.      In  order  to  obtain  a  trace  of  the 

Fio.  104. 


Tracing  of  percussion  wave  obtained  with  arterial  schema. 

pressure  wave,  which  is  also  a  vibratory  motion  (Fig.  165),  it  is  best  to 
use  an  elastic  bag  (Fig.  166,  B).  which  communicates,  on  the  one  hand, 
with  a  reservoir  of  water  and  on  the  other  with  a  long  elastic  T-tube, 
to  which  are  adapted  at  intervals  three  tambours  with  levers  (I  I'  1")  re- 
cording upon  the  same  cylinder,  or  the  tube  can  be  placed  under  three 
levers  provided  with  tambours  (one  of  which  is  represented  in  Fig.  167), 
the  latter  being  connected  bv  tubing  with  the  tambours  of  the  secondary 
levers.  The  bag  should  be  of  a  size  that  it  can  be  squeezed  by  the 
hand.  The  object  of  having  three  such  sphygmographic  arrangements  is 
to  obtain  traces  at  different  distances  from  the  heart,  the  source  of  the 
pressure,  as  well  as  to  demonstrate  the  postponement  of  the  pulse,  which 


308 


THE    ARTERIES. 


Avill  be  shown  immediately.  Inasmuch  as  the  action  of  the  squeezing 
hand  is  very  unlike  that  of  the  contracting  heart,  the  hand  contracting 
gradually  and  weakly  relatively  to  the  resistance,  the  heart,  on  the  other 
hand,  contracting  suddenly  and  most  powerfully  at  the  beginning  of  its 
action  as  might  be  expected,  the  traces  of  the  pressure  wave,  like  that  of 


if;.-). 


HBBBSflBHHIGHBBSBBBIIBBBHBBBBBI 


B™5H!S§iaMBMHB»»««"" 
BMflBHBBBflBHBBBBBflBBnnHI 
^SSSSS^SSSSS^SS    BBBBBBMBBI 

BUBBBflKJiaiBSBtflBafiH'jaHgSB'JBBfi 
_  JSBMBHHlBGBBBBBBBBMa  BHHHH 

BBBBBBaiiaMBBBBBBBBBBBBBBBBBB 


m 


Tracings  showing  the  contractions  and  expansion  of  an  India-rubber  tube,  along  which  water  is  propelled 
in  an  intermitting  6tream  by  squeezing  with  the  baud,  at  regular  intervals  of  time,  an  elastic  bag  pro- 
vided with  valves,  with  which  the  tube  is  in  communication  ;  the  bag  thus  represents  the  heart.  The 
three  tracings  are  drawn  simultaneously,  and  exhibit  the  expansive  movements  of  the  tube  at  three  dif- 
ferent distances  from  the  bag,  the  upper  tracing  being  taken  at  the  greatest  distance.     (Sanderson.) 

the  percussion  wave,  will  be  entirely  different  from  the  trace  of  the 
natural  pulse  or  that  produced  by  the  arterial  schema. 
•  It  will  be  seen  by  examining  the  traces  of  the  pressure  wave  (Fig. 
165)  that  the  lever  does  not  descend  as  abruptly  as  in  the  case  of  the 
percussion  wave,  as  the  recoil  of  the  arterial  wall  due  to  its  elasticity 
is  not  instantaneous,  hence  the  lever  will  momentarily  remain  at  the 
height  to  which  it  has  been  elevated,  and  this  period  will  be  prolonged 
in  proportion  as  the  elasticity  of  the  artery  is  diminished ;  hence,  in  old 

Fig.  166. 


persons ;  in  whom  the  arteries  are  not  very  elastic,  the  curve  at  the 
summit  is  rounded  off  and  the  descent  is  a  gradual  one.  It  will  be 
also  noticed  that  the  expansion  in  the  distal  part  of  the  tube  (the 
upper  of  the  three  traces)  culminates  later  than  in  the  proximal  part. 


LENGTH    OF    PRESSURE     WAVE.  309 

In  the  traces  obtained  from  the  natural  pulse,  or  from  that  of  the 
arterial  schema,  we  see  the  effects  of  both  the  percussion  and  pressure 
waves :  the  abrupt  line  of  ascent  is  due  to  the  percussion  wave  the 
temporary  elevation  of  the  lever  being  due  to  the  recoil  not  at  once 
following  the  distention  due  to  the  pressure  wave.  As  a  general  rule, 
in  the  natural  pulse  both  these  effects  follow  each  other  very  quickly, 
and  are  merged  into  one  another.  As  we  shall  see,  however,  in  a 
moment,  under  certain  circumstances  one  may  be  far  more  evident  than 
the  other.  Did  the  natural  pulse  consist  of  the  percussion  wave  only, 
it  would  be  felt  at  the  same  time  in  all  parts  of  the  system,  as  the  per- 
cussion wave  is  practically  transmitted  instantaneously  through  tubes 
of  the  length  of  the  arteries.  Any  one  can  readily  convince  himself, 
however,  in  his  own  person,  that  there  is  a  gradual  retardation  of  the 
pulse  from  the  heart  to  the  periphery,  by  feeling  the  left  carotid  artery 
with  the  thumb  and  index  finger  of  the  left  hand,  and  the  left  radial 
with  those  of  the  right.  The  beat  of  the  radial  artery  will  be  felt 
later  than  that  of  the  carotid,  the  difference  in  the  time  of  the  beat 
being  quite  appreciable. 

This  postponement  of  the  pulse  is  due  to  the  fact  that  the  pressure 
wave  is  transmitted  at  a  slower  rate  of  vibration  than  the  percussion 
wave,  and  the  reason  is  obvious.  At  the  moment  that  the  blood  bursts 
out  of  the  contracting  heart  into  the  aorta,  the  wall  of  the  vessel 
yields  to  the  pressure  and  expands  during  the  relaxation  of  the 
heart,  the  walls  of  the  artery  through  its  elasticity  recoil  upon  the 
blood  and  add  pressure  to  the  heart  pressure  which  has  just  preceded 
it.  This  expansion,  however,  as  we  have  seen,  begins  at  the  proximal 
end  of  the  artery  and  is  transmitted  in  a  wave-like  manner  to  the 
distal  end  necessarily,  therefore  the  expansion,  or  the  pulse,  will  be 
felt  later  in  the  distal  than  in  the  proximal  end  of  the  artery.  Were 
the  artery  rigid  instead  of  elastic,  there  would  be  no  postponement, 
and  if  tense  at  the  moment  of  the  ventricular  systole,  little  or  none. 

It  was  shown  by  Weber  that  the  pulse  wave  (pressure  wave)  is 
transmitted  at  a  rate  of  about  9  metres  (28  feet)  a  second.  Weber1 
determined  this  velocity  by  observing  with  chronometers  the  difference 
in  time  of  the  beat  of  the  facial  and  dorsalis  pedis  arteries,  measuring 
the  distance  of  the  facial  artery  from  the  heart  as  accurately  as  possi- 
ble, and  the  distance  of  the  dorsalis  pedis  from  the  facial,  and  sub- 
tracting the  first  distance  from  the  second,  the  difference  of  distance 
the  pulse  wave  passed  over  in  the  second  case  as  compared  with  the 
first  will  account  for  the  difference  in  the  time  of  the  beats,  and  give 
approximately  the  distance  passed  over  by  the  pulse  wave  in  one 
second.  Supposing  that  the  ventricular  systole  lasted  four-tenths  of  a 
second,  the  pulse  wave  would  be  3.6  metres  (11  feet)  long  (9  X-tt7=3.6), 
and  there  would  be  two  and  a  half  waves  in  a  second  (-g9g-=2.5), 
consequently  the  anterior  end  of  a  pulse  wave  would  have  reached  the 
extremities  before  the  posterior  end  had  left  the  left  ventricle.  It 
would  appear,  however,  that  this  estimate  of  the  length  of  the  pulse 
wave  is  somewhat  exaggerated,  Czermak2  having  shown  by  the  photo- 

l  Midler's  Archiv,  1851,  S.  537.  2  Carpenter's  Physiology,  p.  316. 


310  THE    ARTERIES. 

sphygmograph  that  the  pulse  wave  is  about  1.5  metres  (5  feet)  long, 
requiring  about  one-sixth  of  a  second  to  pass  from  the  heart  to  the  foot, 
lu  speaking  of  the  velocity  of  the  pulse  wave,  of  course  it  is  to  be  under- 
stood that  this  has  no  reference  to  the  velocity  with  which  the  mass  of 
blood  flows  from  the  heart  to  the  periphery.  The  latter  motion  is  one 
of  translation,  and,  as  we  shall  see,  is  slower  than  the  former  or  the 
pulse  wave,  which  is  molecular  and  vibratory  in  character.  Weber1  well 
says  "  Unda  non  est  materia  progrediena  sed  forma  materise  pro- 
grediens."  "The  gradual  retardation  of  the  pulse  is  well  shown  in  the 
traces  (Fig.  165)  taken  by  means  of  the  apparatus  already  described  (Fig. 
1GG).  By  adapting  to  the  recording  cylinder  the  marker  of  a  chrono- 
graphic  apparatus,  the  exact  difference  in  the  time  of  the  beats  of  the 
proximal  and  distal  parts  of  the  tube  can  be  determined.  The  fact  of 
the  pulse  consisting  of  two  kinds  of  vibratory  movements,  the  percus- 
sion and  pressure  waves  differing  as  regards  their  velocity,  explains 
why  the  pulse  appears  in  some  persons  to  be  quickened,  while  in 
others  to  be   postponed.     In  certain  individuals  the  pressure  wave  is 

Fig.  167. 


Lever,  etc.,  fur  receiving  pressure  wave.     L.  Lever.     T.  Tambour      B.  Tube  conducting  to  recording 

tambour. 

instantaneously  transmitted,  is  most  felt,  and  the  pulse  seems  quick- 
ened ;  in  other  cases  the  pressure  wave  is  more  slowly  transmitted,  is 
most  sensible  to  the  touch,  and  the  pulse  seems  delayed.  By  examining 
the  sphygmographic  traces  of  the  natural  and  artificial  pulse  it  will  be 
observed,  as  has  been  already  mentioned,  that  the  lever  descends  for  a 
short  distance,  then  slightly  rises  again,  descends  to  the  level  from 
Avhich  it  was  first  elevated ;  in  some  cases  even  the  lever  rises  a  third 
or  a  fourth  time  before  finally  descending.  This  secondary  elevation  of 
the  lever  is  known  as  the  dicrotic  pulse,  and  is  caused  essentially  by 
the  return  of  the  pulse  wave  from  the  capillaries  back  toward  the  heart. 
We  have  just  seen  that  the  pulse  wave  is  retarded,  the  arteries  near 
the  heart  therefore  expand  before  those  near  the  periphery ;  while  the 
expansion  is  subsiding  in  the  smallest  ones  it  is  beginning  in  the  large 
arteries,  so  that  there  is  a  moment  when  the  pressure  is  greater  in  the 
latter  than  in  the  former,  the  aortic  valves  being  closed  behind,  and  the 
capillaries  offering  resistance  in  front,  the  only  way  in  which  equilibrium 
can  be  restored  is  by  increase  of  pressure  toward  the  heart  with  dimi- 
nution at  the  periphery.  As  regards  the  cause  of  the  dicrotic  pulse,  the 
only  question  about  which  there  still  appears  to  be  any  doubt  among 

i  Marey,  op.  cit.,  p.  '227. 


DICROTIC     PULSE.  311 

physiologists  is,  whether  the  aortic  valves  are  opened  or  dosed  during 
its   production,  and  whether  the  secondary  pulse  wave,  to  which  it  is 
due,  is  a  centripetal  or  centrifugal  one — that  is,  whether  the  pulse  wave 
as  it  returns  from  the  capillaries  toward  the  heart  elevates  the  lever 
the  second  time,  or  whether   it  passes  first  back  to  the  aortic  valves, 
and  after  it  is  reflected  back  toward  the  capillaries  then  elevates  the 
lever.     The  result  of  experiments  with  the  schema  would  lead  us  to 
conclude  that  in  some  cases  the  dicrotic  pulse  is  due  to  the    return 
of  the  pulse  wave  from  the  capillaries,   while  in  others    it  is    caused 
by  a  secondary  recoil  from  the  aortic  valves,  and  that  when  there  is 
a  tertiary  as  well  as  a  secondary  elevation  of  the  lever   the  former 
is  due   to  the  aortic,  the  latter  to  the  capillary   rebound.     It  will  be 
remembered    that,   in    describing    the  arterial   schema,   it    was   stated 
that  the  main  tube  bifurcated  at  F,  one  end  continuing  as  the  main 
arterial  tube,  while  the  other  could  be  closed  or  adapted  to  a  vertical 
glass   tube  (I).     This  tube,  which  is  about  01.1  metre  (4  feet)  high 
and  1  cm.   (fth  of  an  inch)  wide,  is  closed  at  the  top,  and   serves, 
through  the  rise  and  fall  of  the  level  of  the  fluid  it  contains,  as  an  indi- 
cator of  the  state  of  the  equilibrium  of  the  fluid  in  the  main  tube.  With 
the  opening  and  closing  of  the  aortic  valves  the  level  of  the  fluid  in  the 
tube  will  rise  and  fall,  and  if  there  be  any  dicrotism  present  it  will  be 
indicated  by  a  secondary  rise  of  the  level  of  the  fluid  in  the  tube,  and 
the  phenomena  of  the  dicrotic  pulse  in  this  way  made  quite  evident. 
Now,  if  there  be  placed  upon  the  main  tube  or  artery  a  sphygmograph, 
as  before,  and  also  a  second  sphygmograph  about  01.1  metre  (4  feet) 
from  the  first  one,  and  the  main  tube,  about  the  same  distance  from  the 
second  sphygmograph,  be  somewhat  constricted  to  represent  the  capil- 
lary resistance,  it  will  be  observed  that,  as  the  aortic  orifice  is  open,  the 
level  of  the  fluid  in  the  vertical  glass  tube  rises ;  that  the  levers  of  the 
sphygmographs  are  successively  elevated,  the  second  one  a  fraction  of  a 
second  later  than  the  first ;  that  the  elevation  of  the  fluid  and  the  levers 
is  succeeded  by  a  depression,  and  is  followed  by  a  secondary  elevation 
of  the  fluid  and  of  the  levers,  the  level  of  the  fluid  and  the  levers  finally 
descending  again  to  the  level  from  which  they  were  first  elevated.     If, 
during  this  experiment,  the  levers  of  the  sphygmographs  bo  carefully 
watched,  it  will  be  observed,  as  was  just  mentioned,  that  as  the  aortic 
valve  is  opened — that  is,  as  the  pulse  wave  passes  from  the  heart  toward 
the  capillaries,  the  elevation  of  the  lever  of  the  proximal  sphygmograph 
takes  place  sooner  than  that  of  the  distal  one,  the  pulse  wave  being 
retarded ;  whereas,  during  the  production  of  the  dicrotic  pulse  it  is  the 
lever  of  the  distal  sphygmograph  that  is  elevated  first,  showing  that  the 
dicrotic  elevation  is  due  to  the  return  of  the  wave  from  the  capillaries 
toward  the  heart,  and  that  the  dicrotism  occurs  at  a  distance  of  more 
than  a  metre  (4  feet)  from   the  aortic  orifice  as  the  wave  is  passing 
toward  the  heart.     On  the  other  hand,  if  the  levers  are  elevated  for  the 
third  time,  then  it  is  the  lever  of  the  proximal  sphygmograph  that  is 
elevated  first,  showing  that  the  tertiary  elevation  of  the  liver,  like  the 
primary,  is  due  to  a  pulse  wave  flowing  from  the  heart  to  the  periphery. 
The  dicrotic  pulse  can  be  produced  with  the  schema,  whether  the  main 
tube  be  constricted  at  some  distance  from  the  sphygmograph  or  at  its 
point  of  application,  and  whether  the  aortic  orifice  be  open  or  shut ;  in 


312  THE    ARTERIES. 

the  latter  case  the  aortic  valve  offers  a  resistance,  in  the  former  the 
column  of  liquid. 

According  to  Marey,1  if  the  aortic  valves  be  destroyed  there  is  no 

dicrotic  pulse.  This  is  as  might  be  expected,  as  under  such  circum- 
stances there  would  be  little  resistance  offered  to  the  return  pulse  wave, 
and  therefore  little  dicrotic  distention.  The  dicrotic  pulse  appears, 
therefore,  to  he  due  to  secondary  pulse  waves,  in  some  cases  trans- 
mitted in  a  centripetal,  in  others  in  a  centrifugal  direction.  The 
amount  and  exact  cause  of  the  dicrotic  pulse  must  therefore  vary  with 
the  general  condition  of  the  vascular  system.  In  health,  for  example, 
when  the  vessels  are  tense  it  is  seen  only  as  a  slight  interruption  in  the 
descent  of  the  lever.  In  fever,  on  the  other  hand,  when  the  vessels  are 
distensible,  it  is  so  marked  that  the  pulse  feels  as  if  it  were  double. 

When  it  is  remembered  that,  as  the  blood  is  propelled  forward  into 
the  arterial  system,  it  is  being  continually  diverted  laterally  through  the 
distensibility  of  the  walls  of  the  arteries,  and  that  as  the  quantity  of 
blood  forced  forward  at  each  ventricular  systole  is  limited  in  quantity, 
it  must  follow,  as  we  recede  from  the  heart  to  the  periphery,  that  there 
will  be  less  and  less  blood  forced  forward.  The  blood  having  been  pro- 
gressively absorbed,  so  to  speak,  by  these  lateral  distentions  in  the 
proximal  portion  of  the  arteries,  there  will  be  less,  therefore,  to  distend 
the  distal  parts.  The  pulse  being  due  to  this  distention,  must,  therefore, 
be  weaker  in  the  arteries  at  a  distance  from  the  heart  than  in  those  near 
it,  and  must  ultimately  disappear  in  the  smallest  arterioles  altogether. 
As  a  fact,  the  pulse  is  rarely  felt  in  arteries  having  a  diameter  less  than 
^  of  a  mm.  (yg-th  of  an  inch).  It  is  for  this  reason  that  in  the  case  of  an 
aneurism,  the  lateral  distention  being  here  greatly  exaggerated,  that  the 
pulse  is  often  absent  in  that  portion  of  the  artery  situated  beyond  the 
seat  of  the  disease.  In  the  case  of  aneurism  of  the  aorta,  the  pulse  may 
be  absent  in  all  of  the  arteries  of  the  body. 

While  the  description  of  the  pulse  in  disease  belongs  rather  to  works 
on  medicine  and  therapeutics,  it  may  not  appear  superfluous  to  mention 
that  pathology  confirms  the  views  that  have  just  been  offered  as  to 
the  production  of  the  natural  pulse.  Thus,  in  an  ossified  artery,  there 
is  no  pulse,  because  dilatation  is  impossible.  When  the  arteries  near 
the  heart  are  rigid,  the  pulse  is  jerky,  and  the  flow  of  blood  is  intermit- 
tent, not  remittent.  We  see  the  same  kind  of  pulse  when  the  walls  of 
the  arteries  are  relaxed,  unable  to  recoil  thoroughly  on  their  contents. 
If  the  artery  be  irritable,  and  at  the  same  time  distensible,  the  pulse 
will  be  exaggerated,  and  can  be  seen  by  the  naked  eye  when,  otherwise, 
it  is  usually  imperceptible.  The  character  of  the  pulse  is  profoundly 
affected  by  the  conditions  of  the  system,  modified  by  general  disease. 
Thus  the  large  compressible  pulse  of  fever,  the  hard  pulse  of  Bright's 
disease,  the  small  pulse  of  peritonitis,  the  soft  pulse  of  collapse,  etc.,  are 
well  known  to  the  physician. 

Finally,  it  has  been  shown  by  Vierordt  and  Aberle2  that  there  is  a 
daily  variation  in  the  calibre  of  the  arteries  that  must  influence  some- 
what the  character  of  the  pulse,  the  radial  artery,  for  example,  being 
larger  in  the  evening  than  in  the  morning. 

1  Op.  cit.,  p.  255.  2  Archiv  f.  physiol.  Heilkui.de,  1856,  B.  xv.  S.  574.. 


CHAPTER    XXII 


PRESSURE  AND  VELOCITY  OF  THE  BLOOD  IN  THE  ARTERIES. 


Fig.  168. 


By  blood  pressure,  whether  it  be  cardiac  or  arterial,  etc..  is  meant 
the  pressure  or  force  that  is  exerted  by  the  blood  upon  the  surface  of 
the  vessel  containing  it,  or,  what  is  the  same  thing,  the  force  that  is 
required  to  be  put  forth  by  the  walls  of  the  vessels  in  order  to  sustain 
the  column  of  blood  within  them.  Before  showing  the  manner  in  which 
the  blood  pressure  is  determined  in  a  living  animal,  let  us  first  endeavor, 
however,  to  illustrate,  by  a  few  simple  experiments,  the  manner  in 
which  the  pressure  of  liquids  in  general  is  determined. 

It  is  well  known,  as  first  shown  by  the  distinguished  geometrician 
Pascal,  that  the  pressure  exerted  anywhere  upon  a  mass  of  liquid, 
assuming  the  latter  to  be  perfectly  fluid  and  unin- 
fluenced by  gravity,  is  transmitted  undiminished  in 
all  directions,  acting  with  the  same  force  on  all  equal 
surfaces,  and  in  a  direction  at  right  angles  to  those 
surfaces.  That  the  force  exerted  upon  the  mass  of 
a  liquid  is  transmitted  in  all  directions,  and  at  right 
angles  can  be  readily  shown  by  means  of  the  apparatus 
represented  in  Fig.  168.  This  consists  of  a  cylinder 
provided  with  a  piston  fitting  into  a  hollow  sphere 
pierced  with  numerous  holes,  into  which  are  fitted 
small  cylindrical  jets  placed  perpendicularly  to  the 
sides.  The  sphere  and  cylinder  being  filled  with  water. 
and  the  piston  depressed,  the  water  will  be  observed 
to  spout  out  from  all  of  the  jets,  and  not  simply  from 
the  one  opposite  the  piston.  In  order  to  show  that 
the  pressure  is  transmitted,  not  only  in  all  direc- 
tions, but  equally,  we  make  use  of  an  apparatus  very 
similar  to  the  one  just  described,  and  represented  in  Fig.  169,  it  dif- 
fering only  in  that  the  perpendicular  jets  projecting  from  the  sphere 
contain  closely  fitting,  but  easily  movable  pistons,  each  piston  having 
the  same  area.  The  sphere  being  filled  with  water,  the  latter,  by  virtue 
of  its  weight,  will  press  equally  upon  the  surface  of  all  the  pistons. 
Neo;lectino;  the  influence  exerted  by  the  weight  of  the  water,  and  the 

•  •  /T)\    T-. 

friction  of  the  pistons,  it  will  be  observed  that  if  a  given  pressure  (r)  be 
exerted  upon  the  piston  A  the  water  will  transmit  the  same  pressure  to 
the  other  pistons  (B  C  D),  which  will  move  outwardly,  unless  they  are 
each  subjected  to  an  equal  and  opposite  pressure  (P).  It  is  evident, 
therefore,  that  the  pressure  (P)  exerted  upon  A  is  not  only  transmitted 
in  a  straight  line  upon  B,  but  equally  upon  C  and  D — that  is,  equally 
in  all  directions.  If  now  the  axes  of  the  jets  B  C  D  be  disposed 
parallel  to  each  other,  and  made  to  approach  until  they  form  one,  and 


Apparatus  to  demon- 
strate the  equality  of 
pressure  in  all  directions. 


314      PRESSURE    AND    VELOCITY    OF    BLOOD    IN    ARTERIES. 

for  the  three  pistons  a  single  one  be  substituted,  as  in  Fig.  170,  the 
conditions  of  the  pressure  are  in  nowise  changed,  but  it  becomes  at  once 
evident  that  the  pressure  exerted  upon  the  piston  A,  and  transmitted 
by  the  fluid,  is  proportional  to  both  the  number  and  area  of  the  pistons, 
whether  existing  separately  as  B,  C,  and  D,  or  combined  as  BCD. 
That  is  to  say,  if  n  weight  of  one  pound  be  placed  upon  the  piston  A, 
the  three  pistons  B,  C,  I),  or  the  one  piston  BCD,  will  be  pressed  out- 
ward by  the  pressure  transmitted  through  the  liquid,  unless  a  weight  of 
one  pound  be  placed  upon  each  of  the  pistons  B,  C,  D,  or  of  three 
pounds  upon  the  piston  BCD.  Suppose,  however,  that  the  apparatus 
be  constructed  of  the  form  represented  in  Fig.  171,  in  which,  as  before, 


Fig.  169. 


the  large  piston  A  has  three  times  the  area  of  the  small  one  B,  and 
carries  three  times  as  heavy  a  weight,  it  will  be  observed  that  while  the 
small  piston  B  with  a  weight  of  one  pound  and  an  area  of  one  inch, 
descends  through  three  inches,  the  large  piston  A,  with  an  area  of 
three  inches,  and  with  a  weight  of  three  pounds,  ascends  through  only 
one  inch,  equilibrium  being  then  established,  just  as  a  lever  whose  arms 
have  a  length  respectively  of  three  and  one  inches  will  be  balanced  by 
suspending  a  one  pound  weight  at  the  end  of  the  long  arm,  and  a  three 
pound  weight  at  the  end  of  the  short  one.  It  is  perfectly  evident  that 
in  neither  case  is  there  any  absolute  gain  of  power,  for  what  is  gained  in 
weight  is  lost  in  height  or  distance. 

In  practical  mechanics  the  B  rani  ah  press  is  a  beautiful  application 
of  the  principle  just  enunciated,  in  which  a  pressure  of  300  pounds 
exerted  upon  a  piston  corresponding  to  A  will  exert  a  pressure  of 
30,000  pounds  upon  a  piston  BCD,  supposing  the  sectional  area  of  the 
latter  to  be  100  times  that  of  the  former.     It  must  not  be  forgotten, 


PRESSURE    OF    LIQUIDS. 


315 


however,  that  in  the  Bramah  press,  as  in  the  simple  apparatus  just 
described,  and  in  the  case  of  the  lever  with  unequal  arms,  that  the 
greater  weight  is  elevated  only  a  fractional  part  of  the  distance  through 
which  the  lesser  weight  has  descended,  and  that  what  is,  therefore, 
gained  in  weight  is  lost  in  distance.  The  significance  of  this  important 
truth  in  the  study  of  blood  pressure  will  very  soon  become  evident. 

Now,  on  reflection,  it  will  become  evident  from  what  has  just  been 
said  with  reference  to  the  transmission  of  pressure  through  fluids,  that 
the  pressure  exerted  by  the  particles  of  water  against  each  other  must 
be  estimated  in  exactly  the  same  manner  as  we  have  estimated  the  pres- 
sure P  transmitted  to  the  base  of  the  pistons  (Fig.  171),  or,  what  is  the 
same  thing,  to  the  walls  of  the  vessel  containing  the  water.  It  follows, 
therefore,  that  if  the  weights  and  pistons  be  removed  from  the  apparatus 
(Fig.  171),  that  the  water  will  rise  to  the  same  level  in  both  of  its  limbs 
(Fig.  172),  proving  that  the  pressure  exerted  by  the  water  in  A  and  B 


Fig.  i; 


Fig.  172. 


Principle  ■>['  tin-  hydraulic  press. 

must  be  equal  and  opposite,  notwithstanding  that  the  limb  B  contains 
three  times  as  much  water  as  the  limb  A,  for  if  the  pressure  exerted  by 
the  water  in  B  were  greater  than  that  in  A  the  level  of  the  water  would 
rise  higher  in  the  latter  than  in  the  former.  It  follows,  therefore,  from 
the  principle  of  Pascal,  or  the  equality  of  pressures,  that  the  pressure 
exerted  by  a  fluid  is  independent  of  the  quantity  of  the  fluid,  and  of 
the  form  of  the  vessel  containing  it,  but  is  dependent  for  the  same  fluid 
on  the  area  of  the  base  upon  which  the  pressure  is  exerted,  and  the 
height  of  the  column  of  liquid  above  it.  For  let  us  suppose  that  the 
vessel,  whose  liquid  contents  press  upon  the  bottom,  be  of  a  tapering 
form,  such  as  is  represented  in  Fig.  173,  and  that  the  bottom  D  E  be 
divided  into  eight  areas  of  the  size,  as  that  of  the  mouth  F.  From  what 
has  been  said  of  the  pressure  being  transmitted  equally  in  all  directions, 
it  follows  that  the  weight  of  a  small  liquid  layer,  say  half  an  inch  thick 
at  the  top,  will  be  transmitted  undiminished  to  the  eight  areas  of  the 
bottom,  producing  the  same  pressure  as  if  eight  of  such  layers  of  liquid 
were  separately  placed  upon  them.  In  the  same  manner,  a  layer  half 
an  inch  thick,  but  situated  as  much  lower  down  in  the  liquid,  so  as  to 
have  twice   the   area  of  F,  will  produce  the  same  pressure  upon  the 


316       PRESSURE    AND    VELOCITY    OF    BLOOD    IN    ARTERIES. 

bottom  as  if  four  such  liquid  layers  were  laid  there — that  is,  the  same 
as  the  pressure  due  to  the  eight  small  layers.  It  follows,  therefore,  that 
each  horizontal  layer  of  the  same  thickness,  no  matter  where  it  lies  in  the 
liquid,  produces  the  same  pressure,  the  amount  depending  upon  its  thick- 
ness and  the  area  of  its  base.  The  total  pressure  of  the  liquid  upon  the 
bottom  must  depend,  therefore,  on  the  area  of  the  base,  and  its  vertical 
height  or  thickness — that  is,  equal  to  a  column  of  liquid  having  the  same 
base  and  the  same  vertical  height.     The  truth  of  the  theorem  so  deduced 


Pig.  173. 


Fig.  174. 


To  illustrate  the  pressure  exerted  by 
liquids. 


Apparatus  t<>  demonstrate  that  the  pressure  is  inde- 
pendent of  shape  and  size  of  vessel. 


is  experimentally  verified  by  the  experiment  just  performed,  since  the 
pressure  exerted  by  the  columns  of  liquid  in  A  and  B  (Fig.  172)  are 
the  same,  because  they  have  the  same  base  and  the  same  height  of  liquid 
above  it.  That  the' shape  of  the  vessel  has  no  more  influence  with 
regard  to  the  pressure  exerted  by  the  water  it  contains  than  that  exerted 
by  the  amount  will  become,  perhaps,  more  evident  if  the  apparatus  (Fig. 
174)  be  filled  with  water.  The  level  to  which  the  water  rises  being 
the  same  in  all  the  tubes,  though  of  very  different  shape,  proves  that 
the  pressure  exerted  by  the  water  must  be  the  same  in  all  of  them.  On 
account,  however,  of  the  practical  importance  of  the  law  of  the  pressure 
of  liquids,  and  of  the  necessity  of  keeping  clear  in  the  mind  the  distinc- 
tion between  the  pressure  exerted  by  the  liquid  and  its  weight,  let  us 
illustrate  the  principle  involved  a  little  more  in  detail  by  means  of  the 
apparatus  represented  in  Fig.  175. 

This  consists  of  a  balance,  in  one  of  whose  scale  pans  (A)  a  known 
weight  is  placed,  while  to  the  other  (B)  a  wire  is  attached,  terminating  in 
a  flat  disk  (C),  which  is  so  exactly  applied  to  the  lower  opening  of  the  sup- 
porting cylinder  (D)  that  it  practically  constitutes  its  bottom,  being  tightly 
drawn  up  by  the  counterpoising  weight  in  A.  A  known  weight  being  now 
added  to  that  already  in  A,  and  water  being  gradually  poured  into  the  cyl- 
inder, by  degrees  the  pressure  of  the  liquid  on  the  disk  or  bottom  increases, 
and  when  the  pressure  so  exerted  equals  the  counterpoising  weight  in 
A  the  least  excess  of  water  detaches  the  disk — that  is,  the  bottom  of 
the  cvlinder   falls  out,  and  the  water  flows  out;  but,  as  the  pressure  is 


HYDROSTATIC     PARADOX, 


317 


at  once  diminished  by  the  outflow,  the  disk  is  drawn  up  again,  and  ad- 
heres closely  to  the  cylinder.  The  pointer  touching  the  surface  of  tin- 
water  marks  its  level  at  the  moment  of  equilibrium. 


Fig.  1' 


Pressure  of  a  liquid  on  the  bottom  of  the  vessel  which  contains  it. 

In  this  experiment  it  is  obvious,  as  might  have  been  expected,  that 
the  pressure  exerted  by  the  water  upon  the  bottom  is  precisely  equal  to 
its  weight,  which  was  two  pounds.  Suppose,  now,  we  substitute  for  the 
cylinder  a  conical-shaped  vessel  (F),  with  the  same  sized  orifice  at  the 
bottom,  but  with  a  much  wider  one  at  the  top,  and,  therefore,  capable  of 
containing  more  water ;   nevertheless,  if  we  experiment  with  the  conical 


Fig.  176. 


e^ 


Fig.  177. 


Fig.  178 


Hydrostatic 
paradox . 


To  demonstrate  the  upward  pressure 
exerted  by  water. 


vessel  as  we  did  before  with  the  cylinder,  notwithstanding  that  the 
former  contains  three  times  as  much  water  as  the  latter,  the  pressure 
exerted  by  the  water  upon  the  bottom,  as  we  see,  is  the  same,  being  only 


818      PRESSURE    AND     VELOCITY    OF    BLOOD    IN    ARTERIES. 

two  pounds,  whereas,  the  water  weighs  six  pounds.  In  the  experiment 
with  the  conical  vessel  the  pressure  exerted  by  the  water  upon  the  bot- 
tom is,  therefore,  less  than  its  weight,  and  the  reason  is  very  obvious, 
since  it  is  only  that  part  of  the  water  within  the  dotted  lines  that  exerts 
pressure  upon  the  bottom,  the  pressure  of  the  remaining  extra  water, 
so  to  speak,  being  exerted  upon  the  walls  of  the  vessel,  and  not  upon 
its  bottom. 

Finally,  if  we  make  use  of  a  conical  vessel  (Fig.  175,  G),  or  of  one 
(Fig.  176)  consisting  of  two  cylindrical  parts  of  unequal  diameters,  of 
which  the  lower  one  has  the  same  sized  orifice  at  the  bottom  as  obtains 
in  the  two  vessels  just  used,  and  holding  less  water  than  either  of  the 
latter,  we  shall  still  find,  experimentally,  in  the  same  way,  that  the 
pressure  exerted  upon  the  bottom  is  undiminished  by  that  circumstance, 
being  two  pounds,  though  the  water  weighs  only  one  pound.  This 
must  be  so,  since  the  pressure  exerted  upon  the  bottom  is  due  to  a 
column  of  water  having  the  same  vertical  height  and  base  as  the  column 
of  Avater  included  between  the  two  dotted  lines  D  and  G  (Fig.  176) — 
that  is,  the  pressure  of  the  column  of  water  on  the  principle  of  the 
pressure  being  exerted  equally,  and  in  all  directions,  is  not  only  exerted 
upon  E  F  (Fig.  176),  or  the  part  of  the  bottom  directly  underneath 
it,  but  also  upon  the  remaining  part  of  the  bottom  on  both  sides  of 
E  and  F.  The  total  pressure  exerted  upon  the  bottom  is  therefore 
the  same  as  if  there  were  two  extra  columns  of  water  (D,  G)  pressing 
downward  in  addition  to  that  upon  E  F  actually  present.  It  will 
be  observed  in  this  experiment  that  the  pressure  exerted  by  the  water 
upon  the  bottom  is  therefore  greater  than  its  weight.  At  first  sight, 
this  result  may  appear  paradoxical,  it  being  perhaps  difficult  to  com- 
prehend why,  if  the  water  in  the  vessel  exerts  a  pressure  upon  the 
bottom,  that  when  the  vessel  is  placed  in  the  scale-pan  of  the  balance 
that  its  weight  should  be  only  equal  to  the  weight  of  the  water  and 
vessel.  The  reason,  however,  becomes  at  once  clear  when  it  is  re- 
membered that  the  pressure  of  the  water  is  exerted  in  all  directions, 
upward  as  well  as  downward,  and  that  when  the  vessel  is  placed  in 
the  scale-pan  (Fig.  176),  that  part  of  the  pressure  exerted  upward 
against  the  surface  of  the- vessel  in  the  direction  of  the  arrows,  being 
opposed  in  direction  to  the  force  of  gravity,  does  not  appear  as  weight ; 
consequently,  the  weight  is  simply  equal  to  the  weight  of  the  vessel 
and  of  the  water  it  contains.  If,  however,  this  upward  pressure  be 
balanced  by  an  equal  downward  pressure,  obtained  by  an  extra  quantity 
of  water,  equal  in  amount  to  the  volume  included  between  the  dotted 
lines,  then  the  pressure  and  weight  of  the  water  would  be  identical — 
that  is,  the  conditions  would  be  the  same  as  in  the  first  experiment. 

That  the  pressure  of  the  water  is  transmitted  upward  as  well  as 
downward  can  be  readily  demonstrated  by  the  following  simple  experi- 
ment. A  large  open  glass  tube  (A,  Fig.  177),  one  end  of  which  is 
ground,  is  fitted  with  a  thin  card  (B),  to  the  centre  of  which  is  attached 
a  string  (C)  by  which  it  can  be  held  against  the  bottom  of  the  tube. 
The  whole  is  then  immersed  in  a  jar  of  water,  and,  although  the  string 
be  allowed  to  hang  over  the  side  of  the  jar,  the  card  will  still  adhere  to 
the  mouth  of  the  jar,  it  being  kept  in  this  position  by  the  upward  pres- 
sure of  the  water. 


HYDROSTATIC    BELLOWS.  319 

If  now  water  be  slowly  poured  into  the  tube  the  disk  will  still  adhere 
to  the  latter,  not  sinking  until  the  height  of  the  water  inside  the  tube 
is  equal  to  the  height  outside.  Hence,  it  follows  that  the  upward 
pressure  is  equal  to  a  column  of  water  whose  area  is  that  of  the 
tube  (A),  and  whose  height  is  the  distance  from  the  disk  to  the  outer 
surface  of  the  liquid.  The  upward  pressure  is,  therefore,  governed  bv 
the  same  law  as  the  downward  pressure. 

The  hydrostatic  bellows  (Fig.  178)  is  an  interesting  instrument  in 
this  connection,  as  illustrating  the  principle  of  Pascal,  and  the  manner 
in  which  we  propose  to  study  blood  pressure.  It  consist  of  a  narrow 
tube  (A)  eight  feet  in  length,  with  a  sectional  area  of  one-fourth  of 
an  inch,  inserted  into  a  square  bellows  (C)  having  a  superficial  area  of 
one  hundred  and  forty-four  inches.  The  apparatus  having  been  filled 
with  water,  it  follows  that,  as  the  water  in  the  tube  weighs  fourteen 
ounces,  and  as  the  superficial  area  of  the  top  of  the  bellows  (144 
inches)  is  576  times  that  of  the  sectional  area  of  the  tube  (one-fourth 
of  an  inch),  the  bellows  (D,  D)  should  balance  a  weight  of  fourteen 
ounces  multiplied  by  576,  equals  8064  ounces,  equals  504  pounds, 
which,  as  a  matter  of  fact,  it  does.  At  first  sight  this  result  may  appear 
as  paradoxical  as  in  the  experiment  with  the  cylindrical  vessel ;  it  will 
be  observed,  however,  that  the  distance  through  which  the  504  pounds 
upon  the  bellows  are  elevated  is  but  the  one-sixth  of  an  inch,  a  fractional 
part  only  of  the  ninety-six  inches  through  which  the  pressure  was 
exerted.  It  is  only  another  illustration  of  what  we  gained  in  weight 
we  lost  in  height,  or  of  a  small  force  acting  throuo-h  a  great  height  beino- 
equal  to  a  large  force  acting  through  a  short  one,  fourteen  ounces  fall- 
ing through  ninety-six  inches,  being  equal  to  8064  ounces,  or  504 
pounds,  ascending  through  the  one-sixth  of  an  inch.  It  follows,  there- 
fore, that  the  pressure  even  of  a  small  quantity  of  water,  if  exerted 
from  a  sufficient  height,  will  be  very  great ;  indeed,  Pascal  succeeded 
in  bursting  a  strongly  made  cask  by  means  of  a  narrow  thread  of 
water  forty  feet  high,  and,  in  this  manner,  demonstrated  his  principle 
of  the  equality  of  pressure. 

In  considering  the  pressure  exerted  by  two  columns  of  liquid  such  as 
obtains  in  the  apparatus  (Fig.  172),  it  will  be  remembered  that  only  one 
liquid — water — was  used.  It  is  needless  to  say,  however,  that  if  two 
liquids  of  different  densities,  such  as  water  and  mercury,  were  experi- 
mented with,  the  level  of  the  water  would  stand  13.5  times  higher  than 
that  of  the  mercury,  the  latter  being  that  much  heavier,  the  altitudes 
of  the  liquids  being  inversely  as  their  densities.  In  other  respects,  what 
has  been  said  of  the  pressure  exerted  by  water  will  apply  equally  to 
mercury  or  other  liquids,  and  inasmuch  as  we  will  make  use  of  a  mer- 
curial column  as  a  measure  of  the  pressure  exerted  by  the  blood,  it  will 
not  be  superfluous  to  illustrate  first  the  manner  in  which  we  measure  by 
mercury  the  pressure  exerted  by  any  liquid;  this  we  do  bv  means  of 
Haldat's  apparatus  (Fig.  179).  This  consists  of  a  tube  (A  B  C)  bent 
at  both  ends  at  right  angles,  one  of  which  is  provided  with  a  stopcock 
(A)  on  which  can  be  screwed  vessels  (2),  F,  F,  etc.),  of  the  same  height 
but  differing  in  shape  and  capacity,  D  being  cylindrical  and  F  conical. 
The  tube  A  B  C'is  filled  with  mercury  until  it  reaches  the  level  P.     The 


320       PRESSURE    AND    VELOCITY    OF    BLOOD    IN     ARTERIES. 

vessel  E  is  first  screwed  on,  for  example,  to  the  end  at  A  and  water  is 
poured  into  it  until  it  reaches  the  level  G,  this  level  is  registered  by  the 
movable  rod  //.      The  pressure  of  the  water  in   the  vessel  E  upon  the 


Haldat's  apparatus. 

surface  of  the  mercury  in  the  limb  A  will  cause  the  mercury  to  rise  in 
the  tube  0  up  to  the  level  I,  and  is  there  registered  by  a  movable 
collar.  The  stopcock  A  is  then  opened,  which  allows  the  water  to  run 
out  of  the  vessel  E,  which  is  then  removed  and  is  replaced  by  the 
vessels  D  and  F;  these,  in  turn,  are  filled  with  water  up  to  the  level 
Gr,  when  it  will  be  observed  that  the  mercury  which  had  in  the  mean- 
time, in  each  case,  fallen  to  its  original  level  in  limb  A,  rises  again  to 
the  level  I  the  same  as  before,  thus  proving  that  the  pressure  exerted 
by  the  water  upon  the  mercury  is,  as  we  have  already  seen,  independent 
of  the  quantity  of  the  water  and  of  the  shape  of  the  vessel,  but  is  equal 
to  the  weight  of  a  column  of  water  whose  base  is  the  surface  of  the 
mercury  M  beneath  the  stopcock  in  limb  A,  and  whose  altitude  is  the 
height  (A  Gr)  of  the  level  of  the  water  above  the  surface  of  the  mercury ; 
that  is,  the  pressure  of  the  water  (P)  equals  altitude  (A  Gr)  multiplied  by 
area  [M ).  The  height  of  the  water  being  the  same  in  D  F  and  E,  and 
the  surface  of  the  mercury  (M)  representing  the  area  in  each  case,  the 
product  of  A  Gr  X  M  must  give  the  pressure  exerted  by  the  Avater  in 
all  three  vessels,  which  we  have  just  seen  is  the  case,  the  column  of 
mercury  being  the  same  in  both  experiments. 

The  column  of  mercury  is  then  the  measure  of  the  pressure  exerted 
by  the  water  in  D,  E,  or  Gr  sustaining  it.  It  is  obvious  that  we  must 
double  P I  as  the  mercury  is  proportionally  depressed  in  the  other 
limit  of  the  tube.  It  is  by  means  of  the  hydrostatic  principles  that  we 
have  illustrated  somewhat  in  detail  that  Stephen   Hales,  in  the  early 


BLOOD    PRESSURE.  321 

part  of  the  last  century,  first  determined  the  cardiac  blood  pressure  in  a 
living  animal  with  anything  like  accuracy,  and  estimated  what  it  would 
probably  be  in  man.  It  is  true  that  before  the  time  of  Hales  the  sub- 
ject of  blood  pressure  had  been  studied  by  physiologists  and  physicists, 
among  others,  notably  by  Borelli.1  As  this  distinguished  mathematician's 
calculation  was  based,  however,  upon  purely  theoretical  data,  and  as  his 
estimate  of  the  force  of  the  heart  being  equal  to  180,000  pounds  was 
such  a  gross  exaggeration  of  the  truth,  it  appears  strange  now  that  any 
importance  should  ever  have  been  attached  to  it.  Indeed,  any  reference 
to  Borelli's  views  as  regards  blood  pressure  has  at  the  present  day  only 
an  historical  interest.  Hales's  method  was,  however,  logical  in  principle, 
and,  indeed,  with  certain  modifications  in  the  construction  of  the  appa- 
ratus, is  the  one  made  use  of  at  the  present  day.  Hales's  method'1  of 
experimenting  was  as  follows  :  A  living  animal,  a  horse,  for  example, 
having  been  firmly  secured,  a  large  artery,  like  the  femoral  or  carotid,  was 
exposed,  and,  after  having  been  ligated,  was  opened.  A  brass  tube  was 
then  inserted  into  the  vessel,  to  which  was  adapted  a  glass  tube  ten  feet 
long.  The  connection  between  the  brass  and  the  glass  tube  was  made 
by  a  brass  pipe,  and  in  some  cases  by  a  portion  of  the  trachea  of  a  goose, 
the  latter  being  used  on  account  of  its  pliancy  so  that  no  disarrangement 
would  ensue  through  the  struggles  of  the  animal.  The  tube  having  been 
inserted  into  the  femoral  artery,  for  example,  the  blood  was  observed  to 
rise  in  the  glass  eight  feet  three  inches  above  the  level  of  the  left  ven- 
tricle of  the  heart.  In  the  case  of  the  carotid  artery  the  blood  rose 
even  higher,  attaining  a  height  of  nine  feet  six  inches,  or  144  inches. 
In  order  to  estimate  the  pressure  or  force  sustaining  such  a  column  of 
blood,  just  as  in  the  case  of  the  experiment  with  the  water  and  the 
mercury,  or  with  the  bellows,  the  altitude  144  cubic  inches  must  be 
multiplied  by  the  internal  surface  of  the  left  ventricle  of  the  horse's 
heart,  or  the  area.  Hales  determined  the  area  of  the  left  ventricle  of 
the  horse's  heart  by  injecting  it  with  hot  wax,  then  the  wax,  when 
cold,  Avas  removed  and  small  pieces  of  paper  properly  cut  were  placed 
upon  it  until  the  wax  was  perfectly  covered ;  the  small  pieces  of  paper 
were  then  removed  to  a  sheet  of  paper  which  was  ruled  off  into  squares, 
and  in  this  way  it  was  estimated  that  the  inner  surface  of  the  ventricle, 
or  the  area  needed  for  the  calculation,  was  equal  to  26  inches,  deducting 
1  inch  for  the  orifice  of  the  aorta.  The  pressure  or  the  force  of  the 
liquid,  in  this  case  the  blood  in  the  carotid  artery,  being  independent 
of  the  quantity  and  the  shape  of  the  vessel  containing  it,  but  equal  to 
the  altitude  of  the  column  of  the  blood  multiplied  by  the  area  or  its 
base,  the  product  of  144  inches  by  26 — that  is,  2964  inches  of  blood 
will  be  the  pressure  or  force  which  the  ventricle  sustains  at  the  moment 
of  its  systole.  Now,  as  a  cubic  inch  of  blood  weighs  267.7  grains,  the 
pressure  of  the  blood  amounts  to  267.7  X  2064,  or  7,933,628  grains, 
which  is  a  little  over  113  pounds,  there  being  7000  grains  to  the  pound.  • 
On  the  supposition  that  the  blood  would  rise  7^  feet  high  in  a  tube 

1  De  Motn  Animalium,  Pars  Secunda,  p.  104,  Prop,  lxxiii.     Lugd.  Bat.,  lfiS5. 

2  Statistical  Essays,  vol.  ii.  pp.  1,  2,  14,  15,  19,  20,  21,  39,  40.     London,  1740. 

21 


322  BLOOD    PRESSURE. 

inserted  into  the  carotid  artery  of  a  man.  and  that  the  internal  area  of 
the  left  human  ventricle  is  equal  to  15  square  inches,  Hales  estimated 
by  the  method  just  mentioned,  that  the  pressure  on  the  left  ventricle 
at  the  moment  of  contraction  would  amount  to  55  pounds  (25  kilo.). 
This  estimate  is  too  low,  both  in  the  case  of  man  and  the  horse,  as 
shown  by  the  later  investigations  of  Poisseuille,  Volkmann,  etc.,  to 
be  described  presently,  that  the  blood  would  probably  rise  in  a  tube 
placed  in  a  carotid  artery  of  a  man,  as  in  that  of  the  horse,  to  the  height 
of  9  feet,  there  being  but  little  difference  probably  in  this  respect  as 
regards  these  mammals.  Indeed,  Volkmann1  has  shown  that  even  in 
the  chicken  the  blood  rises  as  high  in  some  instances  as  in  the  dog  and 
the  horse.  The  area  of  the  left  ventricle  also,  as  determined  by  Collin,2 
is  greater  than  that  given  by  Hales.  Further,  Haughton,3  by  a  different 
method  from  that  of  Hales,  calculated  that  the  cardiac  blood  pressure 
in  man  ought  to  be  about  the  same  as  that  observed  in  the  horse,  his 
method  being  based  upon  a  knowledge  of  the  distance  to  which  a  divided 
artery  will  spurt,  which  in  the  case  of  man  was  learned  by  Haughton 
through  a  surgical  operation,  the  force  with  which  the  heart  contracts 
to  produce  such  an  effect  being  deduced  from  this  data. 

Modern  investigation,  as  we  shall  see,  has  shown  that  the  blood 
pressure  is  influenced  by  conditions  unknown  to  Hales,  nevertheless  his 
original  experiment  is  to  this  day  the  most  striking  way  of  demon- 
strating it,  and  his  application  of  hydrostatical  principles  in  measuring 
it  is  the  method  since  so  successfully  made  use  of  by  Poisseuille.  Volk- 
mann, Ludwig,  and  others. 

It  is  not  so  much,  however,  the  pressure  that  the  heart  sustains  which 
the  physiologist  wishes  to  determine  as  the  actual  force  with  which  the 
heart  drives  the  blood  into  the  aorta  at  each  ventricular  systole.  The 
difference  between  the  action  of  the  heart  and  that  of  the  hydrostatic 
apparatus  we  have  shown,  in  which  the  large  glass  tube  and  bellows  repre- 
sent the  aorta  and  heart,  is  that  the  heart,  like  any  other  muscle,  exerts 
itself  according  to  the  resistance  to  be  overcome.  Thus,  if  we  raise  a 
pound  with  our  hand,  the  muscles  of  the  extremity  make  a  greater 
effort  than  when  we  raise  a  feather,  so  according  to  the  resistance,  for 
example,  offered  by  the  capillaries  to  the  efflux  of  the  blood  into  them 
from  the  arteries,  will  the  heart  contract  more  forcibly,  and  the  blood- 
pressure  will  rise.  It  is  evident,  then,  that  the  possible  force  of  the 
heart  and  the  actual  force  usually  exerted  may  differ  very  much  in 
amount.  Before  demonstrating  this  experimentally  let  us  explain  the 
haunadynamometer,  the  apparatus  by  means  of  which  blood  pressure  is 
usually  studied  at  the  present  day,  and  then  compare  the  arterial  with 
the  cardiac  pressure.  The  hremadynamometer,  so  called  from  the 
Greek  words  hsemo,  blood,  dynamis,  force,  and  metros,  measure,  is 
essentially  a  mercurial  manometer  adapted  to  measure  the  blood  press- 
ure, hence  the  name  given  to  the  instrument  by  Poisseuille,4  who 
first,  in  1828,  made  use  of  it  for  this  purpose.  The  apparatus  that  we 
shall  use  (Fig.  180)  is  the  same  as  Poisseuille's,  with  some  modifications- 

i  Die  Hwmodynamik,  S.  177.  -  Comptes  Rendus,  xlvii.  tome  155. 

;  Animal  Mechanics,  p.  40.     London,  1873. 
4  Journal  de  physiologic  de  Magendie,  tome  viii.  p.  212,  1828. 


H.E  M  ADYXAMOMETER, 


323 


It  consists  of  a  U-shaped  glass  tube  (BCD  E),  of  which  the  distal  or 
ascending  limb  (DE)  is  longer — 32  cm.  (125  inches) — than  the  proximal 
or  descending  one  (B  C) — 20  cm.  (8  inches).     The  tube  has  a  diameter 


Fig.  180. 


The  mercurial  kymograph  a.  Vulcanite  rod  of  floating  piston,  b.  Tube  which  communicates  with 
the  pressure  bottle,  c.  Tube  which  communicates  with  the  artery,  d.  Feeding  cylinder.  1.  First  axis, 
which  revolves  once  in  a  minute.  2.  Second  axis,  which  revolves  once  in  ten  seconds.  3.  Third  axis, 
in  a  second  and  a  half  The  instrument  is  furnished  with  other  cylinders  suitable  for  the  reception  of 
single  bands  of  glazed  paper,  the  surface  of  which  can  be  blackened  after  they  are  fixed  on  to  the  cylin- 
ders, by  causing  the  latter  to  revolve  over  the  flame  of  a  petroleum  lamp.  These  cylinders  can  be  fitted 
on  to  either  of  the  axes  I,  2,  or  3,  and  are  always  used  when  it  is  necessary  to  employ  a  rapidly  moving 
surface,  as-e.  g.,  for  tracing  the  curves  of  muscular  contraction.     (Sanuebson.) 

of  1.25  cm.  (h  inch.).  From  the  distal  branch  B  is  given  off  a  short 
horizontal  one  A,  2.5  cm.  (1  inch),  by  means  of  which  the  manometer 
is  put  in  communication  with  the  artery  whose  blood  pressure  we  wish 
to  determine,  and  which,  in  this  case,  will  be  the  carotid  artery  of  the 
rabbit.  The  U-shaped  tube  being  clamped  in  a  vertical  position,  per- 
fectly clean  and  dry  mercury  is  poured  into  it  until  the  mercury  reaches 
a  given  level    in  the  two   limbs.      To  prevent  the  blood  coagulating 


324  BLOOD    PRESSURE. 

that  which  will  come  from  the  artery  a  saturated  solution  of  sodium 
carbonate  or  subcarbonate  is  allowed  to  flow  from  the  pressure-bottle  P 
through  the  tube  b  b  into  the  proximal  end  B  of  the  manometer,  and 
through  its  horizontal  branch  (A),  to  which  is  connected  by  a  short  piece 
of  tubing  a  glass  tube,  or  leaden  pipe  (e),  the  latter  being  stopped  tempo- 
rarily by  the  finger,  or  by  a  cork.  To  avoid  the  inconvenience  of 
inserting  the  horizontal  branch  of  the  manometer  A,  or  its  continuation 
the  pipe  c,  into  the  artery,  and  which  would  be  impossible  in  the  case 
of  the  rabbit,  the  vessel  being  so  small,  a  pointed  and  bevelled  glass 
canulais  first  inserted  into  the  artery,  the  vessel  having  been  previously 
ligated  at  its  distal  end,  and  clamped  at  its  proximal  end.  The  inser- 
tion of  the  canula  will  be  greatly  facilitated  if  a  small  piece  of  card  be 
placed  under  the  vessel  to  support  it,  and  by  making  the  opening  for 
the  canula  V-shaped.  The  canula  is  secured  in  the  artery  by  a  liga- 
ture, and  is  connected  with  the  pipe  c  by  a  small  piece  of  tubing.  The 
arterial  canula  is  filled  with  the  solution  of  sodium  bicarbonate  by  means 
of  a  syringe,  and  the  same  solution  allowed  for  a  moment  to  flow  from 
the  pressure-bottle  into  the  proximal  limb  of  the  manometer,  and  through 
its  horizontal  branch  and  the  pipe  c,  so  that  all  the  air  shall  be  driven 
out.  The  arterial  canula  and  the  pipe  e  are  then  connected  as  quickly 
as  possible,  and  the  tube  (b  b)  leading  from  the  pressure-bottle  to  the 
proximal  limb  of  the  manometer  clamped.  On  removing  the  clamp 
from  the  artery  the  blood  will  jet  out,  pressing  forward  against  the  soda 
solution,  which,  in  turn,  will  press  against  the  mercury  in  the  proximal 
end  of  the  manometer,  forcing  it  downward,  the  mercury  in  the  distal 
limb  being  proportionally  elevated.  It  is  evident  from  the  hydrostatical 
principles  just  illustrated  that  the  pressure  of  the  blood  in  the  artery 
will  be  measured  by  the  weight  of  the  column  of  mercury,  whose  base 
or  area  is  a  circle,  having  the  same  diameter  as  that  of  the  artery,  and 
whose  altitude  is  the  height  of  the  column  of  mercury — that  is,  the  dif- 
ference between  the  two  levels  F  and  G,  and  which,  in  this  particular 
experiment,  it  will  be  observed,  amounts  to  90  millimeters  (3.6  inches). 
The  arterial  pressure  can  be  briefly  and  conveniently  expressed  then  by 
the  formula  P  equals  ^R2  h  W,  in  which  P  equals  the  pressure,  R2  the 
area  of  the  artery,  h,  the  height  of  the  mercury,  and  w  its  weight,  it  being 
understood  that  the  symbol  t  is  the  ratio  of  the  circumference  to  the  diam- 
eter, and  R2  the  square  of  the  radius  of  the  circumference  of  the  artery, 
and  that  the  product  of  t  by  R2  gives  the  area.  Thus,  the  diameter  of 
the  aorta  at  the  level  of  the  semilunar  valves,  in  a  man  aged  twenty-nine 
years,  being  34  millimetres  (1.3  inches),  as  was  found  to  be  the  case 
by  Poisseuille,1  the  radius  R  would  be  17  millimetres,  and  the  square  of 
R2  289,  the  latter  multiplied  by  »r,  or  3.1416,  will  give  about  907  milli- 
metres (1.4  inches)  as  the  area  of  the  aorta  at  the  level  of  the  semi- 
lunar valves.  The  area,  or  907  millimetres,  multiplied  by  160,  or  the 
probable  height  to  which  the  mercury  would  be  elevated  could  the  mano- 
metric  tube  be  inserted  into  the  human  aorta,  gives  145120  millimetres 
as  the  volume  of  mercury  sustained  by  aortic  pressure.     On  the  suppo- 

1  Op.  cit.,  p.  304. 


ARTERIAL    PRESSURE.  325 

sition  that  1  millimetre  of  mercury  weighs  about  -^  of  a  gramme  (0.21 
grain),  145120  millimetres  will  weigh  ~^^  =  1988,  or  nearly  2000 

grammes,  or  nearly  2  kilogrammes — that  is,  about  4.4  pounds.     Sub- 
stituting the  value  in  the  formula  given  for  the  pressure,  we  have 

Pressure  equals  area  X  height  X  weight. 
Pressure  equals  ir  X  E2  X  h  X   W. 

4  lbs.  ==  3.1416  X  289  X  160  X    }  . 

It  may  be  said,  then,  that  the  actual  force  or  pressure  under  which 
the  blood  is  driven  into  the  aorta  at  each  ventricular  systole  amounts 
to  about  4.4  pounds  on  the  square  inch.  As  a  general  rule,  however, 
the  blood  pressure  is  estimated  by  simply  measuring  the  height  to  which 
the  mercury  is  elevated  in  the  distal  limb  of  the  manometer,  and  doub- 
ling the  result,  without  the  area  of  the  artery  or  the  weight  of  the  mer- 
cury being  taken  into  consideration.  By  that  method  the  aortic 
pressure  would  be  estimated  as  amounting  to  160  millimetres,  or  only 
about  2  grammes. 

The  disadvantage  of  such  a  manner  of  estimating  blood  pressure  is 
due  to  the  fact  already  mentioned  that  the  difference  between  animals 
as  regards  the  height  to  which  the  mercury  will  rise  in  the  manometer 
is  not  as  great  as  perhaps  might  have  been  at  first  imagined.  Since 
the  blood  "pressure  depends  not  only  on  the  height  of  the  mercury  in 
the  manometer,  but  also  on  the  area  of  the  artery,  we  should  expect  to 
find,  as  indeed  is  the  case,  that  while  the  height  of  the  mercury  is  about 
the  same  in  three  diiferent  species  of  animals,  that  the  blood  pressure 
may  be  very  different.  Thus  in  the  horse,  sheep,  and  dog,  the  mercury 
will  rise  in  the  manometer  to  about  the  same  level,  on  an  average  150 
millimetres  (6  inches).  As  the  aortic  force  or  blood  pressure,  however 
is  equal  to  this  height  multiplied  by  the  area  of  the  aortic  orifice,  it  is 
evident  that  the  pressure  will  be  proportional  to  the  size  of  this  orifice, 
and  will  therefore  be  greatest,  other  things  equal,  in  that  animal  which 
has  the  largest  aorta.  Thus  the  blood  pressure  of  man  as  estimated 
simply  in  millimetres  of  mercury  differs  but  little  from  that  of  the 
horse;  on  the  other  hand,  while  the  aortic  pressure  in  the  horse  amounts 
to  5  kilo.  (10  pounds),  that  of  man,  as  we  have  seen,  amounts  to  only 
2  kilo.  (4  pounds).  In  estimating  blood  pressure,  a  fact  must  be  taken 
into  consideration  which  is  usually  neglected,  and  that  is,  that  the  solu- 
tion of  sodium  carbonate  having  weight  must  exert  a  certain  amount 
of  pressure  upon  the  mercury  in  the  manometer.  The  height  to 
which  the  mercury  is  elevated  is  then  due  to  the  pressure  of  the  blood 
and  of  the  solution.  To  obtain  the  former  we  must  therefore  deduct 
the  latter  from  the  observed  altitude  of  the  mercury.  As  10  millime- 
tres (i  in.)  of  the  soda  solution  are  equal  to  1  mm.  of  mercury 
for  every  10  mm.  of  the  soda  solution  in  the  proximal  limb  of 
the  manometer  we  must  deduct  then  1  mm.  of  mercury  from  the 
altitude  of  the  mercury  in  the  distal  limb  of  the  manometer.  As  a 
general  rule,  the  amount  of  the  soda  solution  in  the  proximal  limb  of 


326 


BLOOD    PRESSURE, 


the   manometer    is 
mercury    need  not 
pressure   in 
the  solution 
only  J  mm 
altitude    of 


so  small  that  the  effect  of  its  weight  upon  the 
be  considered.  Thus,  in  determining  the  blood 
the  carotid  artery  of  the  rabbit  it  will  be  noticed  that 
of  soda  amounts  to  only  5  mm.  Q-  in.),  and  therefore 
must  be  subtracted  from  the  90  mm.,  or  the  observed 
the  column  of  mercury,  to  obtain  the  arterial  pressure. 
In  using  certain  kinds  of  manometer,  however,  as  we  shall  see, 
the  amount  of  the  soda  solution  being  greater  the  influence  of  its 
pressure  becomes  more  appreciable.  It  will  be  observed,  also,  that  the 
pressure  bottle  containing  the  solution  of  sodium  carbonate  is  sus- 
pended at  a  height  of  about  2  metres  (6.5  feet)  above  the  manometer, 
and  that  it  can  be  elevated  or  depressed  as  desirable.  The  object  of 
this  is  that  having  learned  by  experience  to  about  what  height  the 
mercury  will  be  elevated  by  the  arterial  pres-ure,  we  make  use  of  the 
soda  solution  not  only  to  prevent  the  coagulation  of  the  blood,  but 
also  to  exert  pressure  upon  the  mercury  to  the  same  extent  as  the 
arterial  blood  will  do.  As  soon  as  the  clamp  is  removed  from  the 
carotid  artery  the  blood  at  once  then  exerts  its  pressure  upon  the  soda 
solution,  but  advances  only  a  little  way  in  the  tube  c,  loss  of  blood  as 
well  as  coagulation  being  thereby  prevented.  The  pressure  of  the 
blood  is  then  transmitted  to  the  soda  and  thence  to  the  mercury;  if 
the  pressure  bottle  has  not  been  sufficiently  elevated,  then  the  level  of 
the  mercury  will  rise  in  the  distal  limb  of  the  manometer,  and  if  too 
much  elevated  the  reverse  will  be  the  case.  The  effect  of  the  arterial 
pressure  will  therefore  be  the  same  as  if  exerted  directly  upon  the 
mercury. 

In  speaking  of  the  connecting  tube  c,  it  was  mentioned  that  it 
should  be  of  glass  and  preferably  of  lead.  The  reason  of  this  is  now 
very  evident.  Did  the  tube  consist  of  an  extensible  material  the 
pressure  of  the  blood  would  be  exerted  to  a  great  extent  upon  the  walls 
of  the  tube  rather  than  upon  the  soda  solution,  and  indirectly  therefore 
not  upon  the  mercury. 

Various  methods  are  made  use  of  by  physiologists  to  secure  firmly 
the  animals  to  be  experimented  upon.     In  this  instance  we  make  use  of 


Fig.  181. 


Czermak's  rabbit  support.     (Sanderson.) 


Czermak's  rabbit  support,  and  as  the  apparatus  when  sufficiently  large, 
is  equally  convenient  for  other  animals,  and   as   we  shall  frequently 


AORTIC    PRESSURE.  327 

have  occasion  to  use  it,  a  short  description  seems  advisable.  It  con- 
sists (Fig.  181)  of  a  firm  wooden  stand  A,  1  metre  (3.2  feet)  long  and 
22  cm.  (9  in.)  wide.  The  end  B  with  the  large  opening  c  is 
made  stronger  than  the  rest  of  the  stand  by  an  iron  plate  into  which 
an  iron  rod  (d)  bent  twice  nearly  at  right  angles  is  screwed.  This  rod 
carries  a  movable  brass  ring  through  which  passes  horizontally  an  iron 
rod  /  movable  in  all  directions,  and  which  bifurcates  at  the  end,  the 
two  ends  of  the  horizontal  rod  being  adjustable  to  the  frame-like  clamp 
through  which  passes  the  rod  h  in  a  direction  at  right  angles  to  that 
of  the  horizontal  rod  /,  the  rod  supporting  a  second  clamp  of  the  same 
general  form  as  the  first  one,  and  which  by  means  of  the  screw  k  can 
be  brought  near  to  the  latter.  The  animal  being  placed  upon  its  back, 
and  resting  upon  a  mattress,  the  neck  supported  by  a  cylindrical 
cushion  and  the  extremities  fastened  by  strings  to  the  pegs  m  m,  the 
rod  h  is  placed  between  the  teeth  and  the  screw  k  so  adjusted  that 
while  the  clamp  g  presses  upon  the  lower  jaw  the  clamp  g  will 
press  upon  the  head.  In  this  way  the  animal  is  firmly  held,  and  yet 
does  not  receive  the  slightest  injury. 

We  have  just  seen  that  the  aortic  pressure  in  man  amounts  to  nearly 
2  kilo.  (4.4  pounds)  to  the  square  inch.  Now  since  the  pressure 
exerted  upon  the  mass  of  a  liquid  is  transmitted  undiminished  equally 
in  all  directions,  and  acts  with  the  same  force  on  all  equal  surfaces 
according  to  the  principle  of  Pascal,  to  obtain  the  cardiac  pressure 
we  have  only  to  multiply  the  2  kilo,  or  the  aortic  pressure  by  the 
internal  area  of  the  left  ventricle,  or  38.1  centimetres  (15  in.),  which 
gives  30  kilo.  (66  pounds).  This  result,  it  will  be  observed,  agrees  very 
closely  with  that  of  Hales.  This  should  be  so,  since  the  hydrostatic 
principle  made  use  of  by  both  Hales  and  Poisseuille  in  determining  the 
cardiac  and  aortic  pressure  was  the  same.  It  was  for  this  reason  on 
account  of  the  application  of  hydrostatic  principles  in  the  study  of  blood 
pressure  that  Ave  illustrated  these  principles  so  much  in  detail. 

If  now  the  hydrostatic  bellows  be  compared  to  the  heart  and  the 
aorta,  it  is  obvious  that  the  aortic  pressure  corresponds  in  the  bellows  to 
the  small  force  acting  through  a  great  height  in  the  narrow  tube,  while 
the  cardiac  force  is  the  great  force  acting  through  the  small  height 
corresponding  to  the  force  in  the  bellows.  It  must  not  be  forgotten, 
however,  that  the  pressure  in  the  heart  may  vary  according  to  circum- 
stances due  to  its  inherent  contractility  whereas  the  pressure  in  the 
bellows  is  constant  for  the  same  quantity  of  water  otherwise  the  princi- 
ples involved  are  the  same. 

That  the  cardiac  pressure  is  greater  than  the  aortic  is  shown  by  the 
fact  that  with  each  ventricular  systole  the  mercury  rises  in  the  manom- 
eter, falling  again  with  the  diastole,  the  mean  arterial  pressure  being, 
as  we  shall  see,  the  level  between  these  extremes.  Further,  as  we  have 
just  mentioned,  and  which  we  will  now  demonstrate,  the  cardiac  pres- 
sure will  be  greatly  increased  beyond  that  which  we  may  consider  as 
normal,  according  to  the  resistance  to  be  overcome.  This  is  usually 
shown  by  means  of  Coats's  apparatus,1  or  by  that  described  by  Marey,2 

1  Described  in  Handbook  Phvs.  Lab.,  p.  26S,  plate  xci. 
-  Circulation  du  Sang,  1881,  p.  70,  fig.  28. 


828 


BLOOD    PRESSURE. 


but,  as  both  these  methods  involve  taking  the  heart  out  of  the  animal, 
and  as  we  wish  to  show  the  phenomena,  the  heart  being  in  situ,  we  will 
make  use  of  the  convenient  little  apparatus  (Fig.  182)  as  arranged  by 
Dr.   A.   P.   Brubaker,  for  studying  blood  pressure  in   the  frog.      This 


Fio.  182. 


Brubaker's  frog  manometer. 


consists  of  a  mercurial  manometer  M  like  that  we  have  used  in  de- 
termining the  blood  pressure  in  the  rabbit,  only  that  it  is  smaller.  The 
arterial  canula  differs,  however,  from  the  one  used  in  that  experiment. 
In  this  instance  the  end  a  of  a  JL-shaped  glass  tube  is  inserted  into  the 
bulbus  arteriosus  of  the  frog,  the  end  b  being  adjusted  to  the  proximal 
end  of  the  manometer,  while  the  stem  c  is  connected  by  the  tube  d 
with  a  funnel  e  containing  a  solution  of  sodium  carbonate.  The  fun- 
nel corresponds  to  the  pressure  bottle  in  the  experiment  with  the  rabbit. 
The  frog  is  secured  to  a  piece  of  cork,  which  rests  within  the  stand 
supporting  the  manometer  ;  the  stand  can  be  raised  or  lowered  upon 
the  vertical  rod  ;  the  latter  also  supports,  by  the  horizontal  rod,  the 
funnel.  Having  first  determined  the  normal  blood  pressure,  it  will  then 
be  observed  that  as  the  tube  d  is  compressed,  an  obstacle  being  thereby 
interposed  to  the  flow  of  blood  from  the  aorta,  the  pressure  will  be  in- 
creased, the  mercury  rising  in  the  distal  limb  of  the  manometer,  thus 
showing  that  the  force  which  the  heart  exerts  is  proportional  to  the  re- 
sistance to  be  overcome. 


ARTERIAL    PRESSURE.  329 

While  the  flow  of  the  blood  through  the  arterial  system  generally 
is  influenced  by  the  length  of  the  vessel,  friction,  etc.,  the  capillary  sys- 
tem, as  we  shall  see,  is  a  constant  source  of  resistance.  In  proportion 
to  the  fulness  of  the  capillaries  a  greater  or  less  obstacle  is  offered  to 
the  flow  of  the  arterial  blood.  The  force  that  the  heart  exerts  must 
then  vary  according  to  the  resistance  to  be  overcome.  It  is  hardly 
necessary  to  state  that  the  constriction  of  the  tube  in  the  last  experi- 
ment would  represent  a  capillary  obstruction  in  the  living  animal. 
Theory  and  experiment,  therefore,  agree  in  showing  that  the  amount  of 
force  which  the  heart  usually  exerts  is  far  less  than  the  possible  force 
that  can  be  put  forth  if  occasion  demands  it.  Very  great  differences 
are  found,  also,  among  animals,  as  regards  the  proportion  of  the  cardiac 
to  the  arterial  pressures.  In  the  rabbit,  for  example,  the  force  of  the 
left  ventricle  exceeds  but  little  that  of  the  aorta,  whereas,  in  the  horse, 
the  excess  of  the  cardiac  pressure  as  compared  with  the  arterial  is  very 
marked.  Thus,  by  means  of  his  cardiometer,  Bernard1  has  shown  that 
the  arterial  pressure  in  the  rabbit  being  91  mm.  (3.8  inches),  with  each 
ventricular  systole  the  mercury  rose  to  100  mm.  (1  inches),  the  cardiac 
pressure  being  only  5  mm.  greater  than  the  arterial.  On  the  other 
hand,  in  the  horse,  the  arterial  pressure  being  100  mm.  (4  inches),  the 
cardiac  pressure  was  65  mm.  greater,  the  mercury  rising  to  175  mm. 
(7  inches)  with  the  systole. 

Just  as  we  have  seen  the  pulse  gradually  disappearing  as  we  recede 
from  the  heart,  so,  for  the  same  reason,  we  should  expect  to  find  this 
excess  of  cardiac  over  arterial  pressure  becoming  less  and  less  as  we 
pass  toward  the  periphery.  Experiment  confirms  in  this  respect  what 
theory  would  lead  us  to  expect.  Thus,  Volkmann2  has  shown  that,  while 
in  the  carotid  artery  of  the  dog  the  excess  of  the  cardiac  pressure,  as 
compared  with  the  arterial,  amounts  to  37  mm.  (1.4  inches) ;  in  the 
metatarsal  artery  the  excess  amounts  to  only  1  mm.  (33th  of  an  inch). 

In  making  the  distinction  between  cardiac  and  arterial  pressures,  it 
must  not  be  forgotten,  however,  that  the  latter  is  only  the  delayed 
effect  of  the  former,  since  the  cardiac  pressure  exerted  during  the  pre- 
vious systole  in  distending  the  arterial  wall  is  restored  during  the 
diastole  to  the  circulation  through  the  elasticity  of  the  artery  as  arterial 
pressure. 

The  cardiometer  we  make  use  of  in  demonstrating  the  difference  be- 
tween cardiac  and  arterial  pressure  is  that  shown  in  Fig.  183,  as  made 
by  Verdin,  of  Paris.  It  is  but  a  slightly  modified  form  of  the  cardi- 
ometer used  by  Magendie  and  Bernard,  and  consists  of  a  metallic  vessel 
containing  water,  within  which  is  suspended  an  elastic  capsule,  (M),  com- 
municating at  one  end  (T)  with  the  artery  whose  pressure  is  to  be  deter- 
mined, and  at  the  other  end  with  a  delicate  mercurial  manometer  (B)  for 
registering  the  pressure.  The  upper  part  of  the  vessel  is  closed  with  a 
cork,  through  which  passes  a  glass  tube,  into  which  the  water  rises,  and 
which  transmits  to  the  registering  tambour  R  the  distention  of  the 
capsule  M  due  to  the  varying  cardiac  pressure.  The  arterial  pressure, 
however,  when   once   attained,  remains  constant,  the  constriction  at  the 

1  Systeme  Xerveux,  tome  i.  pp.  S83,  '286.  -  Die  Hremodynamik,  S.  167. 


330 


BLOOD    PRESSURE. 


bottom  of  the  mercurial  manometer  B  offering  such  a  resistance  to  the 
rise  of  the  mercury  that  the  intermittent  action  of  the  heart  is  not  felt. 

Fig.  183. 


Cardiometer.     (Marey. 


Having  described  the  manner  in  which  the  mercurial  manometer  is 
used  in  determining  the  force  of  the  left  ventricle,  a  few  words  will 
suffice  as  to  the  force  exerted  by  the  right  ventricle.  According  to 
Marey1  and  Chauveau,  on  the  average  the  force  of  the  right  ventricle 
is  about  one-third  of  that  of  the  left ;  the  force  of  the  right  auricle 
being  about  one-tenth  that  of  the  right  ventricle,  it  is  about  1.30  to  1.7 
of  the  left  ventricle.  Inasmuch  as  the  left  auricle  is  inaccessible  in 
a  living  animal  to  experimental  investigation,  nothing  positively  is 
known  as  to  the  pressure  exerted  by  it.  It  is  reasonable  to  suppose  that 
it  is  equal  to  that  of  the  right  auricle. 

A  great  advance  was  made  by  Ludwig,2  in  1848,  in  the  manner  of 
investigating  blood  pressure,  by  his  invention  of  the  kymograph  (Fig. 
180).  This  consists  of  a  mercurial  manometer  like  that  of  Poisseuille, 
in  the  distal  limb  of  which  is  placed  a  vertical  rod  (a)  the  lever-end  of 
which  terminates  in  a  concave  cup-shaped  float,  and  rests  upon  the  con- 
vex surface  of  the  mercury,  while  the  upper  end  of  the  vertical  rod 
projects  out  of  the  upper  open  end  of  the  distal  limb  of  the  manometer, 
and  carries  a  delicate  sable  brush,  wetted  with  ink,  or  a  pen  of  glass, 
the  point  of  which  rests  against  the  cylinder  e.  The  vertical  rod  is 
kept  in  the  perpendicular  by  the  support  8,  through  which  it  passes, 
and  the  brush  or  pen  in  contact  with  the  cylinder  by  the  weighted 
string  o.     The  cylinder  e,  16  cm.  (6.5  inches)  high,  and  50  cm.  (20 


i  Op.  cit,  p.  115. 


-  Muller's  Archiv. 


KYMOGRAPH.  331 

incites)  in  circumference,  is  covered  with  either  white  or  smoked  paper. 
With  every  oscillation  of  the  mercury  in  the  distal  limb  of  the  mano- 
meter, the  rod  a  is  elevated  or  depressed,  and  a  vertical  line  is  made 
upon  the  cylinder  by  the  brush  or  pen.  If  now  the  cylinder  is  made 
to  revolve  at  a  uniform  rate,  the  vertical  mark  will  become  a  curve, 
like  that  represented  in  Fig.  184,  and  we  obtain  a  graphic  representa- 
tion  of   the    blood    pressure  in    this    of  the   rabbit,   hence   the    name 

Fig.  ]84. 


Trace  ut  blood-pressure  in  rabbit. 

kymograph — from  kumos,  a  wave,  and  grapho,  to  write — the  name 
given  to  the  instrument  by  Yolkmann,1  who  was  among  the  first  to 
use  it  successfully.  Ludwig2  tells  us  that  the  idea  of  the  recording 
pen,  etc.,  was  suggested  to  him  by  a  similar  contrivance  made  use  of  by 
Watt  for  registering  pressure  in  the  steam  engine.  The  immense  im- 
portance of  Ludwig's  invention  cannot  be  exaggerated,  for,  by  means 
of  the  kymograph,  the  study  of  blood  pressure  became  far  more  exact 
than  had  been  possible  previously. 

Slight  variations  in  the  oscillation  of  the  mercury,  for  example,  which 
were  entirely  inappreciable  in  the  hsemadynometer,  became  perfectly 
apparent  when  graphically  recorded  upon  the  revolving  cylinder.  The 
great  merit  of  Ludwig's  invention  did  not  consist  simply  in  the  applica- 
tion of  the  kymograph  to  the  study  of  the  blood  pressure,  but  the  appli- 
cation of  the  graphic  method  in  the  investigation  of  the  circulation  of 
the  blood  generally,  and,  indeed,  of  all  physiological  phenomena.  In 
truth,  it  is  not  saying  too  much  that  the  study  of  physiology  experi- 
mentally has  been  revolutionized  by  it,  results  having  been  obtained  by 
the  graphic  method,  as  Ave  have  already  seen,  which  had  been  considered 
impossible  by  the  physiologists  of  the  preceding  generation. 

As  the  mercurial  manometer  of  the  kymograph,  with  its  accessories, 
the  pressure  bottle,  connecting  tubes,  etc.,  is  the  same  as  that  already 
described,  it  is  only  necessary  to  say  that  the  mercurial  manometer, 
when  used  as  part  of  the  kymograph,  is  firmly  clamped  to  the  table (T) 
supporting  the  cylinders,  and  that  the  vertical  rod  in  its  distal  limb  is  so 
adjusted  that  the  brush  or  pen  which  it  carries  remains  in  contact  with 
the  cylinder.  The  latter  in  the  instrument  we  use,  made  by  Hawksley,  of 
London,  is  moved  by  clock-work  contained  in  the  box  II,  and  its  motion 
made  uniform  by  the  Foucault  regulator  (i?).  This  consists  of  two 
fans,  which,  when  the  velocity  is  increased  through  the  friction  engen- 
dered, expand  and  so  retard  the  motion,  and  when  the  velocity  dimin- 
ishes contract  again,  and  so  offering  less  resistance  it  increases  again, 
the  fans  being  approximated  and  separated  by  an  elastic  spring.  There 
are  three  axes  (1,  2,  3)  connected  with  the  clock-work,  and  according  to 
the  one  on  which  the  cylinder  is  placed  the  rate  of  its  revolution  can  be 
varied.     Thus,  when  the  cylinder  is  placed  upon  the  first -axis  it  makes 

»  Die  Ha>moilynaii)ik.  2  Physiologie,  1861,  S.  163,  Band.  i. 


332  BLOOD    PRESSURE. 

one  revolution  in  one  minute  fifty-two  seconds,  or  seventy-five  seconds 
upon  the  second  axis,  one  revolution  in  twelve  seconds;  upon  the  third 
axis  one  revolution  in  two  seconds.  It  will  be  observed,  therefore,  that 
when  the  cylinder  is  on  the  third  axis  it  revolves  nearly  forty  times  as 
rapidly  as  upon  the  first.  When  the  cylinder  used  is  that  covered  with 
smoked  paper,  it  is  held  on  the  axis  connected  with  the  clock-work  by 
a  vertical  rod  passing  from  its  centre  upward  into  the  frame,  and  which 
is  screwed  on  to  the  box.  By  means  of  this  vertical  rod  the  cylinder 
can  also  be  elevated  or  depressed  through  a  height  of  several  centime- 
tres. When,  however,  we  wish  to  take  a  trace  upon  white  paper,  and 
it  is  desirable  that  the  observation  shall  extend  over  a  long  period  of 
time  as  possible,  then  a  somewhat  different  arrangement  is  made  from 
that  just  described.  We  then  use  two  cylinders  (Fig.  180,  g,  d),  one 
of  which  (e)  is  to  record  the  trace,  and  which,  resting  upon  the  axis 
connected  with  the  clock-work,  is  supported  from  above  by  a  frame,  not 
represented  in  the  figure,  which,  like  the  other  frame,  can  also  be 
screwed  on  to  the  box.  The  other  cylinder  (e)  is  covered  with  white 
paper  rolled  around  it  by  machinery,  and  in  quantity  sufficient  to  last 
for  several  hundred  observations.  This  cylinder  acts  as  a  feeder  to  the 
recording  one,  for,  as  the  latter  revolves,  it  unwinds  the  white  paper 
around  the  former,  the  paper  being  kept  smooth  by  two  little  ivory 
wheels  on  the  frame  (not  represented  in  Fig.  180).  Having  explained 
the  construction  of  the  kymograph,  let  us  consider  now  the  traces  of 
blood  pressure  of  the  cat,  turtle,  frog,  for  example,  as  recorded  by  it, 
and  point  out  some  of  the  results  obtained  by  their  study,  and  which 
would  have  been  impossible  had  we  limited  our  study  of  blood  pressure 
to  the  use  of  the  mercurial  manometer  only.  By  an  examination  of 
Fig.  185,  illustrating  the  kymographic  trace  of  the  blood  pressure  in 
the  cat.  recorded  upon  the  smoked  paper,  it  will  be  observed  that  the 

Fig.   185. 


Trace  of  blood  jiressnre  in  cat 

trace  consists  of  a  number  of  large  curves,  each  of  which  is  made  up  of 
smaller  ones.  The  large  curves  extending  from  crest  to  crest  of  the 
wave,  being  to  a  certain  extent  respiratory  in  origin,  their  relations  to 
inspiration  and  expiration  will  be  considered  hereafter.  For  the  present, 
however,  it  may  be  said,  by  the  graphic  method  it  can  be  shown  that, 
during  a  part  of  the  period  of  inspiration,  the  blood  pressure  is  increased 
and  during  a  part  diminished,  and  that  in  the  same  way  the  blood 
pressure  is  both  diminished  and  increased  during  expiration.  The  small 
curves  are  cardiac  in  origin,  each  small  curve  corresponding  to  a  heart 
beat,  the  elevation  being  caused  by  the  systole,  the  depression  by  the 
diastole.  If  the  pen  be  watched  during  these  oscillations,  it  will  be  noticed 
that  there  is  an  average  height  above  and  below  which  the  pen  is  elevated 
and  depressed  with  each  cardiac  beat.  This  average  height  represents  the 
mean  arterial  pressure.     To  express  this  in  millimetres  of  mercury  we 


BLOOD  PRESSURE  IN    TURTLE  AND  FROG. 


333 


must  measure  the  distance  or  ordinate  between  the  line  representing  the 
average  height  and  the  straight  line,  or  abscissa,  representing  the  height 
at  which  the  pen  was  elevated  by  the  mercury  under  the  influence  of 
the  atmospheric  pressure  only,  before  the  blood  pressure  had  exerted 
any  force  and  then  double  this  distance ;  while  to  estimate  the  cardiac 
pressure  in  millimetres  of  mercury  we  must  add  to  the  mean  arterial 
pressure  twice  the  distance  of  the  excursion  of  the  pen  during  the  small 
oscillation.  If  we  wish  to  get  the  mean  of  either  the  cardiac  or  the 
arterial  pressure  of  a  number  of  pulsations,  we  must  add  up  the  ordi- 
nates  and  divide  by  the  number  of  ordinates.  As  pulmonary  respi- 
ration is  far  less  active  in  the  turtle  and  frog  than  in  the  rabbit  naturally, 
wre  should  not  expect  to  find  respiration  influencing  the  form  of  the 
curve  of  blood-pressure  in  these  animals  to  the  same  extent  as  in  the 
mammal.  The  large  curves  are  then  absent  in  the  traces  represented  in 
Tigs.  186  and  187  ;'   the  small  curves  are.  however,  <juite  as  distinct  and 

Pig.  186. 


Trace  of  blood  pressure  in  turtle. 
Fig.    187. 


Trace  of  blood  pressure  in  frog. 


Fig.  188. 


/vvM/v\A 


l/^Wk 


Influence  of  cardiac  inhibition  on  blood  pressure.  Current  sent  into  pneumogastric  nerve  at  <i,  shut  ofl 
at  6.  First,  there  is  a  rapid  fall,  and  when  the  heart  beats  return,  the  mercury  rises  by  successive  leaps 
to  the  normal. 

have  the  same  significance  as  those  in  Fig.  185.  Assuming  that  the 
blood  flows  through  the  arteries  according  to  hydraulic  laws  we  should 
expect  to  find  the 'pressure  diminishing  as  we  recede  from  the  heart  to 
the  periphery.  Thus,  if  we  watch  the  colored  fluid  as  it  flows  from  the 
reservoir  (a,  Fig.  189)  through  the  horizontal  tube  b,  it  will  be  observed 

1  In  the  case  of  the  frog  the  manometer  used  was  smaller  than  in  the  case  of  the  rabbit. 


834 


BLOOD    PEESSU RE 


that  the  height  to  which  the  fluid  rises  in  the  vertical  tubes  cl  and  c, 
inserted  into  the  horizontal  one  gradually  diminishes  as  we  recede  from 
the  first  (V)  to  the  sixth  tube  (c).     In  the  present  experiment,  where 


Kio.  18<f. 


Decrease  of  piessurc  in  tubes  of  equal  calibre. 

the  reservoir  holds  9  litres  (18  pints),  and  the  horizontal  tube  being  l-() 
cm.  (3  ft.  4  in.)  long,  the  last  25  cm.  (10  in.)  consisting  of  tubing,  and 
01.5  cm.  (|  in.)  wide,  the  vertical  tubes  38  cm.  (15  in.)  high  and  5  mm. 
(tL  in.)  wide,  the  colored  fluid  rose  in  the  first  tube  to  a  height  of  27  cm. 
(10.8  in.)  in  the  sixth  to  a  height  of  only  9  cm.  (-2-  in.),  the  level  of  the 
fluid  in  the  remaining  tubes  (2,  3,  4,  5)  being  intermediate  between 
these  extremes.  This  difference  in  the  level  of  the  fluid  in  the  vertical 
tubes  is  caused  by  the  resistance  due  to  friction  which  the  fluid  encoun- 
ters as  it  flows  from  the  reservoir  through  the  horizontal  tube,  and  as 
the  resistance  encountered  at  the  first  tube  gradually  diminishes  as  we 
approach  the  sixth  the  height  of  the  fluid  or  the  pressure  is  proportion- 
ally diminished  in  the  tubes  as  we  pass  from  the  reservoir  to  the  outlet. 
Poisseuille1  failed  with  his  mercurial  manometer  to  detect  any  difference 
in  the  blood  pressure  of  arteries  situated  at  different  distances  from  the 
heart,  such  as  theory  indicated  should  have  been  found.  Indeed,  the  dif- 
ference in  the  blood  pressure  of  two  arteries,  seen  even  when  one  is  situated 
at  a  considerable  distance  from  the  heart,  is  too  slight  to  be  appreciable 
by  the  mercurial  manometer  alone.  Volkmann,2  however,  showed  by 
means  of  the  kymograph,  that  there  was  a  difference  of  7  mm.  of  mer- 
cury between  the  blood  pressure  in  the  carotid  and  metatarsal  arteries 
of  the  dog,  the  pressure  amounting  in  the  first  case  to  172  mm.  (6.8  in.), 
and  in  the  latter  to  165  mm.  (6.6  in.)  In  the  rabbit  the  difference 
between  the  blood  pressure  in  the  carotid  and  femoral  arteries  is  only 
about  5  mm.  (\  of  an  inch) ;  in  the  calf,  however,  the  difference  amounts 
to  26  mm.  (1.04  in.). 

It  is  not  only  desirable  that  we  should  know  whether  there  exists  any 
difference  in  the  blood  pressure  of  two  arteries  like  the  carotid  and  meta- 
tarsal, but  also  if  the  pressure  in  two  arteries  like  the  two  carotids  or  the 
two  crurals  is  equal  or  different.  To  investigate  this,  or  if  we  Avant  to 
determine  the  difference  between  the  pressure  in  an  artery  and  a  vein,  the 
carotid  and  the  jugular  vein,  for  example,  we  make  use  of  the  differential 
manometer  of  Bernard3  (Fig.  190).      This  consists  of  a  U-shaped  glass 


1  Op.  cit.,  p.  37. 


Op.  cit,  S.  167. 


Systeme  Nerveux,  tome  i   p.  281. 


DIFFERENTIAL     MANOMETER, 


335 


tube  firmly  supported  upon  a  stand  which  carries  a  graduated  scale, 
and  by  means  of  which  the  tube  is  filled  with  mercury  to  a  certain 
level.  The  two  ends  of  the  U-tube  are  adapted  to  lead  pipes  which 
are  connected    with    the    pressure    bottle   containing    the    solution    of 


Differential  manometer  of  Bernard.     (Carpenter.) 

soda,  and  at  e  e  with  arterial  canuhie  to  be  inserted  into  the  vessels  to 
be  examined.  By  means  of  the  stopcocks  either  one  or  both  the  vessels 
can  be  placed  in  communication  with  the  manometer.  Suppose,  for  ex- 
ample, we  have  inserted  by  means  of  the  arterial  canula  the  two  ends 
of  the  manometer  into  the  carotids  of  a  rabbit.  Having  opened  both 
stopcocks  and  removed  the  clamps  from  the  arteries  and  allowed  the 
blood  to  press  against  the  solution  of  soda,  it  will  be  observed  that  the 
level  of  the  mercury  remains  unchanged,  showing,  therefore,  that  the 
blood  pressure  in  the  two  arteries  is  the  same.     If  now  one  of  the  stop- 


336 


BLOOD     I'  liESSf  i:  i; 


cocks  be  closed.  ;it  once  the  mercury  will  rise  in  the  limb  of  the  tube 
of  the  corresponding  side,  and  by  doubling  the  height  to  which  the  mer- 
cury  is  elevated,  and  deducting  1  nun.  for  every  1<>  mm.  of  solution  of 
sodium  carbonate  used,  we  obtain  the  blood  pressure  of  the  artery  on 
the  side  where  the  stopcock  remained  opened. 


Fig.  191. 


Fick's  spring  kymograph,  a.  C-spring.  s.  Support,  d.  Rod  which  communicates  the  movements 
of  the  spring  to  the  lever  I,  and  thus  to  the  writing-needle  G.  c.  Leaden  tube  by  which  the  cavity  of 
the  spring  is  in  communication  with  the  artery. 

Admirable  an  instrument  as  the  kymograph  undoubtedly  is,  and  how- 
ever accurately  it  fulfils  its  purpose,  it  must  not  be  forgotten  that  the 
trace  recorded  on  the  cylinder  is  due  to  the  oscillations  of  the  mercury, 
and,  therefore,  only  indirectly  to  the  pressure  of  the  blood.  On 
account,  however,  of  the  inertia  of  the  mercury  and  the  suddenness  of 
the  expansion  of  the  artery,  the  oscillations  of  the  mercury,  though 
caused  by  the  pressure  of  the  blood,  are  not  an  exact  measure  of  it, 
since  by  the  time  the  mercury  has  risen  to  its  highest  elevation  the 
artery  has  collapsed.  If  the  heart  is  beating  very  quickly  the  extent 
of  the  oscillations  of  the  mercury  is  relatively  too  small,  and  if  the  inter- 
val between  the  pulsations  is  prolonged  the  excursion  of  the  manometer 
is  too  great.  The  use  of  the  mercurial  kymograph  is.  therefore,  limited 
to  the  study  of  the  mean  pressure  and  of  variations  in  pressure  such  as 
occur  at  sufficiently  long  intervals  to  prevent  the  oscillations  being  mixed 
up  with  those  proper  to  the  instrument.  In  order  to  study  the  variations 
of  blood  pressure  in  the  exact  order  in  which  they  occur,  and  as  regards 
their  duration  and  degree,  etc.,  we  make  use  of  Fick's  spring  kymograph, 


SPRING    KYMOGRAPH.  337 

which  is  so  constructed  that  it  transmits  the  movements  communicated 
to  it  without  obscuring  them  by  any  movement  of  its  own. 

The  instrument  (Fig.  191)  consists  essentially  of  a  hollow  C-shaped 
thin  metal  spring  (a)  filled  with  alcohol  and  communicating  through  its 
proximal  end  (b)  by  means  of  a  connecting  tube  (e)  with  the  pressure 
bottle  containing  the  solution  of  the  sodium  bicarbonate  and  the  arterial 
canula.  The  proximal  end  of  the  spring  being  fixed,  as  the  blood  press- 
ure increases  the  spring  tends  to  straighten  itself  and  the  distal  or  free 
end  makes  the  movements  which  follow  exactly  the  variations  in 
the  arterial  tension.  These  movements  are  most  exact,  the  slightest 
variations  in  the  blood  pressure  being  expressed  by  them.  As  they  are, 
however,  very  small  before  being  recorded,  they  are  enlarged  by  the 
lever  which  is  carried  by  the  distal  end  of  the  spring.  It  will  be  seen 
from  Fig  192,  illustrating  a  trace  of  the  blood  pressure  in  the  carotid 

Fig.  192. 


Traces  in  rabbit  taken  with  Kick's  spring  kymograph. 

artery  of  the  rabbit,  taken  by  the  spring  kymograph,  that  the  ascent  of 
the  lever,  due  to  the  expansion  of  the  artery  caused  by  the  ventricular 
systole,  is  very  abrupt,  almost  vertical,  that  at  the  vertex  the  direction 
of  the  trace  is  horizontal,  that  the  lever  in  its  descent  pursues  an  oblique 
course  at  its  termination,  being  also  horizontal  in  direction,  and  that  the 
dicrotism  of  the  pulse  is  very  evident.  The  nature  of  these  peculiarities 
we  have  already  considered  in  describing  the  pulse.  If  we  wish  to  ex- 
press in  millimetres  of  mercury  the  absolute  blood  pressure  determined 
by  the  spring  kymograph,  the  instrument  must  first  be  graduated  by 
comparison  with  a  mercurial  manometer.  This  is  done  in  the  following 
way  :  The  spring  kymograph  being  so  placed  that  it  will  write  on  the  re- 
cording cylinder,  its  connecting  tube  in  communication  with  the  pressure 
bottle  is  adapted  to  the  proximal  end  of  the  mercurial  manometer.  The 
pressure  bottle  is  first  lowered  until  the  solution  it  contains  stands  at  the 
same  level  as  that  of  the  mercury  in  the  manometer.  The  clockwork 
being  put  in  motion  the  cylinder  revolves  and  a  trace  is  taken  which 
will  represent  the  abscissa.  The  pressure  bottle  is  then  raised  till  the 
mercury  is  elevated  in  the  distal  limb  of  the  manometer  10  mm.  (J-th  of 
an  inch)  higher  than  in  the  proximal  one,  and  a  second  tracing  taken, 
and  so  on  until  we  have  obtained  a  number  of  tracings  parallel  with  the 
first  one  or  abscissa,  and  therefore  with  each  other.  The  vertical  dis- 
tance between  the  abscissa,  and  these  lines  or  the  ordinates  measured  in 
millimetres  expresses  then  the  value  of  the  tracing  in  millimetres  of 
mercurial  pressure. 

We  have  already  alluded  incidentally  to  the  influence  of  respiration  in 
modifying  the  curve  of  the  blood  pressure,  and,  as  we  have  now  seen,  how 

22 


338  BLOOD    PRESSURE. 

the  latter  may  vary  according  to  the  part  of  the  vascular  system  gener- 
ally. It  is  probable,  also,  that  the  blood  pressure  depends,  to  a  certain 
extent,  upon  the  size  of  the  animal,  the  period  of  life,  and  general  health, 
cceteris  paribus,  the  blood  pressure  being  greater  in  larger  than  in 
smaller  animals,  in  those  of  middle  age  than  in  very  young  or  very  old 
animals,  in  strong,  healthy  than  in  weak,  sickly  ones.  Inasmuch  as 
the  pressure  of  the  blood  depends  upon  the  muscular  force  of  the  heart, 
and  as  the  muscular  substance  of  the  heart,  like  all  other  muscle,  is 
nourished  by  the  blood,  it  follows  that  loss  of  blood  in  weakening  the 
fibre  of  the  heart  and  the  amount  of  blood  expelled,  should  diminish 
blood  pressure.  The  experiments  of  Hales1  and  Colin2  have  shown  that 
such  is  the  case,  the  blood  pressure  being  diminished  in  proportion  to 
the  amount  of  blood  lost.  Finally,  we  shall  see  that  the  vasomotor 
nerves,  in  modifying  the  calibre  of  the  vessels,  greatly  influence  the 
bloodvessels.  In  concluding  our  account  of  the  arteries,  there  still 
remains  for  us  the  consideration  of  the  velocity  with  which  the  blood 
flows  through  them. 

Physiologists  have  endeavored  to  determine  the  velocity  of  the  blood 
by  means  of  the  theorem  of  Torricelli,  assuming  that  the  velocity  with 
which  a  fluid  escapes  from  a  reservoir  may  be  learned  from  observing 
the  height  to  which  it  will  flow  into  a  vertical  tube  connected  with  the 
same,  the  velocity  being  equal  to  that  which  a  body  would  acquire 
falling  in  vacuo  through  a  distance  equal  to  the  height  which  the  fluid 
attains  in  the  tube,  which  is  nearly  the  same  as  the  level  of  the  fluid  in 
the  reservoir.  The  velocity,  however,  that  a  body  acquires  while  falling 
through  a  given  height  is  expressed  by  the  formula,  V=  \/~lgh,  in 
which  V  is  the  velocity,  h  the  height,  and  g  the  accelerating  force  of 
gravity.  To  obtain  the  velocity  with  which  the  blood  flows  from  the 
heart  into  the  aorta  we  must  substitute,  therefore,  in  the  above  formula 
for  h  the  height  to  which  the  blood  rises  into  a  vertical  tube  inserted  in 
the  carotid  artery,  which,  in  the  case  of  the  horse,  for  example,  has 
been  found  to  be  3  metres  (117  inches),  and  for  g,  or  the  accelerating 
force  of  gravity.  9.8  metres  (32  feet),  then  V=\/%2  X  9.8  X  2>=V/W7% 
=  7.6  metres — that  is,  the  velocity  would  be  about  7.6  metres,  or  about 
24  feet  in  a  second.  Practical  engineers,  however,  know  that  in  hydro- 
dynamic  machines  the  velocity  of  the  flow,  on  account  of  friction,  etc.,  is 
rarely  what  theory  teaches  it  ought  to  be.  The  physiologist  has  still  less 
reason  even  to  find  much  agreement  between  the  results  of  theory  and 
experiment  as  regards  the  velocity  of  the  blood,  as  the  perturbing 
causes,  among  which  may  be  mentioned  the  resistance  offered  by  the 
column  of  blood  in  the  aorta,  are  so  numerous.  Indeed,  little  or  no  im- 
portance can  be  attached  to  this  manner  of  investigating  the  velocity  of 
the  blood  in  the  arteries.  In  fact,  we  will  see  that  the  velocity  just 
given  is  a  gross  exaggeration. 

Among  the  first  to  determine  Avith  anything  like  accuracy  the  velocity 
of  the  blood  may  be  mentioned  Hales,  who,  as  we  have  already  seen, 
studied  the  subject  of  blood-pressure  with  so  much  success.  Assuming, 
according  to   well-known  hydraulic   principles,  that  the  velocity  with 

1  Statical  Essays,  vol.  ii.  p.  10.     London,  1746. 

2  Milne  Edwards:  Physiologie,  tome  iv.  \>.  115. 


H-EMODROMOMETER. 


339 


which  a  fluid,  in  a  given  time,  flows  through  a  tube  is  equal  to  the  ratio 
of  the  efflux  to  the  sectional  area  of  the  tube,  Hales  estimated  that  the 
blood  in  the  horse  flows  from  the  left  ventricle  into  the  aorta  at  the  rate 
of  nearly  17  inches  in  a  second,  which  we  will  see  agrees  closely 
with  the  velocity  recently  determined  by  experiment.  Hales1  method 
of  calculation  is  as  follows.  Assuming  the  capacity  of  the  left 
ventricle  to  be  10  cubic  inches,  and  the  area  of  the  transverse 
section  of  the  aorta  1.036  inches,  the  ratio  of  these  two  quantities,  or 

,  equals  9.65  inches,  will  be  the  column  of  blood  that  passes  from 

1.036      !  '  l 

the  left  ventricle  into  the  aorta  during  each  systole.     Supposing  that 

the  heart  beats  36  times  in  a  minute,  then  9.65  X  36  equals  347.40 

inches  of  blood,  would  pass  from  the  heart  into  the  aorta  in  a  minute ; 


Fig.  193. 


Fig.  194. 


; 

— 

2 

-E 

3 

:: 

Volkraann's  haemodroinuuieter  for  measuring  the  rapidity  of  the  arterial  circulation. 

but  as  the  ventricular  systole  lasts,  according  to  Hales,  only  one-third 
(really  four-tenths)  of  the  period  intervening  between  two  cardiac 
beats,  the  velocity  must  be  three  times  as  great,  or  1042.20  in  a 
minute — that  is,  347.40  X  3  equals  1042.20  inches,  or  86.85  feet; 
dividing  this  by  60,  we  obtain  1.4  foot,  or  16.8  inches,  for  the 
velocity  with  which  the  blood  flows  from  the  heart  into  the  aorta  in 
a  second.  The  first  physiologist,  as  far  as  I  know,  who  endeavored 
to  determine,  not  what  the  velocity  of  the  blood  ought  to  be  from 
theory,  but  what  the  velocity  actually  is  in  a  living  animal  by  experi- 
ment,  was  Volkmann.2      The    haemodromometer,    or    the    instrument 


1  Hemostatics,  vol.  ii.  p.  46. 


-  Hsemodynamik,  s.  185 


340 


VELOCITY    OF    BLOOD. 


Fig.  195. 


which  he  invented  for  this  purpose,  consists  of  a  metallic  tube  (c), 
which  is  united  to  the  two  ends  of  a  divided  artery,  and  through  which 
the  blood  can  flow  in  the  same  direction  as  through  the  vessel  itself 
(Fig.  193).  To  the  metallic  tube  is  attached  laterally  a  U-shaped 
glass  tube  (d),  containing  water.  By  turning  stopcocks  the  metal 
tube  is  put  in  communication  with  the  U-shaped  tube  in  such  a  way 
(Fig.  194)  that  the  blood  cannot  pass  at  once  as  it  did  before  from 
the  artery  through  the  metal  tube  to  the  artery  again,  but  must  first 
pass  through  the  U-shaped  tube.  The  length  of  this  tube  being  known, 
and  the  time  it  takes  for  the  blood  to  flow  through  it  being  observed, 
the  velocity  with  which  the  blood  flows  through  the  artery  can  be  deter- 
mined approximately.  There  are  objections,  however,  to  the  use  of 
this  instrument,  as  the  blood  does  not  flow  through  the  glass  tube  as 
easily  as  it  does  through  the  artery,  both  on  account  of  the  curvature  of 
the  tube  and  of  the  difference  in  its  substance  as  compared  with  that  of 
the  artery,  and  as  the  blood  flows  from  the  proximal  end  of  the  artery 
into  the  glass  tube  it  drives  ahead  the  water  it 
contains  into  the  distal  end,  the  effect  of  which  is 
to  contract  the  vessels,  and  so  further  retard  the 
flow.  It  is  for  these  reasons,  probably,  that 
Yolkmann's  estimate  of  the  velocity  of  the  blood, 
for  example,  in  the  carotid  artery  of  the  horse  of 
254  millimetres  (10  inches)  in  a  second  is  too  low. 
By  the  invention  of  the  stromuhr,  in  1857, 
Ludwig  greatly  improved  Volkmann's  method  of 
measuring  the  velocity  of  the  blood.  This  in- 
strument, also  called  the  rheometer  (rheo,  to  flow, 
metron,  a  measure),  consists  (Fig.  195)  of  two 
glass  bulbs  (B,  C)  of  an  ovoid  shape,  and  of  a 
known  capacity,  communicating  superiorly  by  the 
curved  tube  and  terminating  so  inferiorly  as 
to  be  screwed  into  the  canulse  F  and  6r,  which 
are  only  large  enough  to  be  inserted  into  the  cut 
ends  of  the  artery  to  be  examined.  The  canulse 
having  been  ligated,  and  the  vessel  previously 
clamped,  by  means  of  the  small  tube  opening 
into  the  communicating  tube,  the  bulb  C  is 
filled  with  olive  oil  up  to  the  mark  M,  the  bulb 
B  with  serum.  The  small  tube  is  then  closed. 
The  clamps  having  been  removed,  the  blood  flows 
from  the  proximal  end  of  the  artery  by  means  of 
the  canula  jPinto  the  bulb  0,  driving  the  oil  ahead  of  it  through  the 
communicating  tube  into  the  bulb  B,  the  serum  in  the  latter  being  driven 
out  of  it  through  the  canula  Gf  into  the  distal  end  of  the  artery.  So  far, 
the  method  of  experimenting  with  the  stromuhr  is  essentially  the  same 
as  that  of  the  haemodromometer,  with  these  two  differences,  however,  that 
serum  being  used  instead  of  water  there  is  less  resistance  offered  to  the 
flow  of  the  blood,  and,  on  account  of  the  shape  of  the  bulbs,  a  greater 
quantity  of  blood  can  be  used,  which  is  also  of  advantage.  The  great 
improvement,  however,  in  Ludwig's  instrument,  as  compared  with  Yolk- 


1 

Ludwig's  stromuhr. 


STROMUHR.  341 

mann's,  consists  in  this,  that  by  turning  the  vertical  rod  H  through  180 
degrees,  by  means  of  the  mechanical  arrangement  to  be  explained  in  a 
moment,  the  bulb  B  now  filled  with  oil,  communicates  through  the  canula 
J7  with  the  proximal  end  of  the  artery,  and  the  bulb  C  filled  with  blood 
communicates  through  the  canula  Gr  with  the  distal  end.  The  blood 
still  flowing  from  the  proximal  end  of  the  artery  will  now  drive  the  oil 
out  of  B  into  0,  and  the  blood  displaced  by  the  oil  will  pass  into  the 
distal  end.  By  turning  the  rod  back  again  the  bulb  (7  will  communicate 
with  the  canula  F,  and  the  bulb  B  with  the  canula  Gr.  This  operation 
can  be  repeated  several  times  before  the  blood  coagulates.  The  mechan- 
ical arrangement,  by  which  the  bulbs  C  and  B  are  alternately  put  in 
communication  with  the  canulse  F  and  Gf,  consists  simply  in  fixing  the 
inferior  ends  of  the  bulbs  into  the  movable  disk  B,  into  which  the  ver- 
tical rod  H  is  inserted,  the  canulse  F  and  Gr  being  fixed  into  the  im- 
movable disk  I.  When  the  movable  disk  B  is  in  the  position  shown 
in  Fig.  191,  then  C  communicates  with  F,  and  B  with  Gr ;  when  the 
disk  has  been  rotated  through  180  degrees  then  B  communicates  with 
F,  and  C  with  Gr. 

To  illustrate  the  manner  in  which  the  velocity  of  the  blood  is  deter- 
mined in  a  living  animal  by  the  stromuhr  we  will  suppose  that  the 
instrument  has  been  adapted  to  the  carotid  artery  of  a  rabbit.  The 
animal  having  been  firmly  secured  to  the  Czermak  holder,  and  the 
artery  exposed  and  clamped  in  two  places,  the  clamps  separated  by  a 
distance  of  about  two  inches  and  about  an  inch  of  the  intervening 
vessel  cut  out.  The  stromuhr  being  attached  to  the  vertical  stem  of 
the  holder  by  the  horizontal  rod  and  the  bulbs  having  been  previously 
warmed  and  their  ends  screwed  into  the  canulse  which  have  been 
inserted  into  the  cut  ends  of  the  artery,  the  bulb  C  is  then  filled  with 
oil  up  to  the  mark  M,  it  containing  then  5  c.  cm.  (2  in.),  and  the  bulb 
B  with  serum.  The  clamps  are  now  withdrawn  from  the  artery  and 
the  blood  from  its  proximal  end  will  be  observed  to  drive  the  oil  from 
C  into  B,  the  oil  displacing  the  serum  in  B  which  passes  into  the  distal 
end  of  the  artery.  The  moment  that  the  blood  reaches  the  level  of  the 
mark  M  the  movable  disk  D  is  rotated  as  rapidly  as  possible  through 
180  degrees  with  the  effect  of  putting  the  bulb  B  filled  with  oil  in 
communication  with  the  proximal  end  of  the  artery  and  the  bulb  C 
filled  with  blood  in  communication  with  the  distal  end  of  the  vessel. 
The  blood  continuing  to  flow,  the  oil  is  now  driven  from  B  into  C,  the 
disk  being  rotated  back  again  the  moment  that  the  blood  reaches  the 
level  of  the  mark,  the  bulb  C,  now  filled  with  oil,  communicates  as  at 
first  with  the  proximal  end  of  the  artery.  The  experiment  may  be 
continued  in  this  way  for  a  minute  or  more  until  the  blood  begins  to 
coagulate.  Inasmuch  as  we  learn  how  often  in  a  given  time  a  definite 
quantity  of  oil  is  displaced  by  the  blood  we  learn  how  much  blood  is 
delivered  by  the  carotid  artery  in  that  time.  Suppose,  for  example, 
that  in  an  experiment  5  c.  cm.  (2  in.)  of  blood  have  been  delivered 
by  the  carotid  artery  10  times  in  100  seconds — that  is,  50  c.  cm,  then 
1  c.  cm.  of  blood  has  flown  from  the  artery  in  2  seconds,  or  0.5  c.  cm. 
equal  to  500  mm.  in  1  second.  Dividing  this  amount  by  the  sectional 
area  of  the  artery  through  which  it  has  flown — that  is,  b*y  3.14  mm.,  the 
diameter   of  the  artery  and   the   canulae   being  nearly  the  same,  or  2 


342 


VELOCITY    OF    BLOOD. 


mm.,  we  get  the  velocity,  or  nearly  159  mm.  (6  in.)  in  1  second: 
■.:{\{\  equals  159  mm.,  according  to  the  hydraulic  principle  that  the 
velocity  equals  the  ratio  of  quantity  to  sectional  area. 

The  stromuhr  is  a  most  excellent  and  reliable  instrument,  as  it  inter- 
feres so  little  with  the  circulation,  the  flow  of  the  blood  being  only 
stopped  during  the  instant  that  the  disk  is  rotated  and  the  blood  pressure 
being  little  altered  by  its  passage  through  the  instrument.  This  can 
be  shown  by  connecting  a  manometer  with  the  two  tubes  which  are  in 
communication  with  the  bulbs,  but  which  are  not  seen  in  the  illustration, 
the  tubes  being  placed  in  the  side  of  the  apparatus  not  shown  in  the 
figure. 

While  the  stromuhr  is  admirably  adapted  to  determine  the  exact 
amount  of  blood  passing  through  an  artery  and  the  mean  velocity 
of  the  flow,  it  does  not,  however,  enable  us  to  determine  the  in- 
cessant variations  experienced  by  the  blood  as  regards  its  velocity. 
For  this  object  we  make  use  of  the  hfemodromometer  of  Chauveau. 

Fig.  19G. 


Hsemodromograph  of  Chauveau  and  Lortet.1     (McKendrick.) 

The  construction  of  this  instrument,  like  the  luematachometer  of 
Vierorclt1,  is  based  upon  the  principle  of  measuring  the  velocity  of 
the  blood  by  observing  the  amount  of  deviation  undergone  by  a 
pendulum,  the  free  end  of  which  is  suspended  in  the  blood  current,  the 
amount  of  deviation  being  proportional  to  the  velocity.  It  is  essen- 
tially the  same  kind  of  instrument  as  the  hydrostatic  pendulum  used 
by  engineers  to  measure  the  velocity  of  a  current  of  water.  Chauveau's 
hsemodromometer,  invented  in  1858, 2  consists  of  a  brass  tube  about  4 
cm.  (1J  in.)  long  (Fig.  196,  A),  which  is  inserted  into  the  cut  ends  of  a 
divided  artery,  or  into  the  slit  made  in  the  vessel  of  the  horse  and 
ligated.  Part  of  the  wall  of  the  tube  is  of  India-rubber  membrane 
fastened  over  a  longitudinal  opening  in  the  tube,  and  through  which 
passes  a  light  lever  4  cm.  long.  The  short  expanded  arm  of  the 
lever  hangs  freely  in  the  blood,  and  is  moved  through  a  greater  or  less 
arc,  according  to  the  force  with  which  the'  blood  rushes  against  it,  in 
from  the  artery,  the  India-rubber  membrane  acting  as  a  fulcrum.  The 
movements  of  the  long  arm  of  the  lever  H  in  the  opposite  direction  to 


1  Die  Er.^ch^inungen  und  Gesetze  der  Stromgeschwindigkeit  des  Bhites,  1858. 
'-'  Journal  de  la  Physiologie,  tome  iii.  p.  695.     Paris,  1860. 


H^EMODROMOGR  APH.  343 

those  of  the  short  one  are  measured  by  means  of  a  graduated  scale.  The 
long  arm  of  the  lever,  it  will  be  observed,  projects  considerably  from  the 
tube  A.  In  order  to  determine  the  actual  velocity  of  the  flow  in  addi- 
tion to  the  varying  changes  the  instrument  must  be  first  experimentally 
graduated.  This  can  be  done  in  the  following  way:  A  current  of 
warm  water,  or,  better,  defibrinated  blood,  is  made  to  pass  through  the 
tube  of  the  haemodromometer  with  such  a  velocity  that  the  deviation 
undergone  by  the  pendulum  is  the  same  as  when  the  instrument  was 
inserted  in  the  artery.  The  velocity  of  the  current  can  be  easily  deter- 
mined by  receiving  the  fluid  from  the  tube  in  a  graduated  vessel,  and 
observing  the  time  occupied  in  discharging  a  given  quantity. 

When  a  marker  is  attached  to  the  end  of  the  long  lever  H,  the  move- 
ments can  then  be  recorded  on  the  cylinder,  and  we  obtain  a  graphic 
representation  of  the  velocity  and  its  variations.  The  hsemodro- 
mometer,  when  used  in  this  way,  becomes  the  hremodromograph.  Lortel 
has  modified  Chauveau's  instrument  so  that  a  trace  of  the  blood  pressure 
can  be  taken  simultaneously  with  that  of  the  velocity.  This  is  accom- 
plished (Fig.  196)  by  putting  in  communication  with  the  tube  A  the 
lever  of  which  through  its  movement  gives  a  trace  of  the  velocity  of  the 
blood,  a  sphygmoscope  (B),  the  blood  from  the  artery  after  passing 
through  the  tube  A,  enters  the  caoutchouc  bladder  B,  of  the  sphygmo- 
scope, and  expanding,  it  compresses  the  air  in  the  glass,  which,  acting 
through  the  tube  D,  upon  the  recording  lever  F,  gives  the  trace  of 
the  blood  pressure. 

Chauveau  has  determined,  by  means  of  his  hfemodromometer,  that  the 
velocity  of  the  blood  in  the  carotid  of  the  horse  at  each  ventricular  systole 
is  about  50  cm.  (20  in.)  in  a  second;  this  velocity,  however,  gradually 
diminishes  until  finally  the  blood,  for  a  moment,  stops  moving 
altogether.  Immediately  following  the  systole  and  synchronous  with 
the  closure  of  the  semilunar  valves,  a  second  impulse  is  given  to  the 
blood  by  the  recoil  of  the  arterial  walls,  and  the  blood  moves  now  at  a 
rate  of  about  20  cm.  (<S  in.)  a  second;  this  velocity  gradually  dimin- 
ishes, the  average  rate  being,  until  the  next  ventricular  systole,  about 
12  cm.  (5  in.)  in  a  second.  It  will  be  observed,  from  these  experi- 
ments, that  the  velocity  of  the  blood  is  at  times  much  more  rapid 
than  at  others.  This  is,  however,  only  true  of  the  arteries  near  the 
heart,  like  the  carotid,  the  acceleration  of  the  velocity,  like  the  pulse, 
gradually  disappearing  in  the  small  arteries,  and  for  the  same  cause, 
the  gradual  diminution  of  the  cardiac  pressure,  as  we  recede  from  the 
heart  to  the  periphery.  While  the  velocity  of  the  blood  in  the  arteries 
in  man  can  be  experimentally  determined  from  the  experiments  made 
upon  the  horse,  approximately,  it  may  be  considered  as  not  differing 
very  much  from  that  observed  in  that  animal.  The  velocity  of  the 
blood  in  the  arterial  system  is  not  only  modified,  as  we  have  seen  by 
the  cardiac  pressure,  but  is  influenced  by  other  causes. 

It  has  already  been  mentioned  that  the  capacity  of  the  arterial  sys- 
tem increases  as  we  pass  from  the  aorta  to  the  capillaries,  and,  as  fluids 
move  more  slowly  in  the  wide  tubes  than  in  narrow  ones,  the  velocity  of 
the  blood  ought  to  be  slower  in  the  peripheral  arteries  than  in  those  near 
the  heart.   Experimentally,  this  has  been  shown  to  be  the  case  ;  accord- 


344 


VELOCITY    OF    BLOOD. 


ing  to  Volkmann,  the  velocity  of  the  blood  in  the  metatarsal  artery  in 
the  dog  is  only  5  cm.  (2  inches),  that  of*  the  carotid  artery  being  25 
cm.  (10  inches)  in  the  second.  The  velocity  of  the  blood  will  vary, 
also,  according  to  the  resistance  offered  to  its  flow;  the  compression  of 
an  artery,  for  example,  offering  an  obstacle  to  the  circulation,  will 
diminish  the  velocity,  and  even  stop  the  movement  altogether.  The 
amount  of  resistance  offered  by  the  capillaries  greatly  influences  the 
velocity  of  the  blood.  The  capillary  resistance  remaining  constant,  an 
increase  in  the  force  of  the  heart  will  increase  the  velocity  ;  a  diminu- 
tion in  the  cardiac  force  will  diminish  it.  On  the  other  hand,  the  force 
of  the  heart  remaining  constant,  the  velocity  of  the  blood  will  be  either 
increased  or  diminished,  according  as  the  capillary  resistance  is  in- 
creased or  diminished.  It  will  be  observed  from  what  has  been  said  in 
reference  to  the  pressure  of  the  blood  and  its  velocity,  that,  with  the 
increase  or  diminution  of  the  one  we  have  often  a  corresponding  in- 


1    2  S  -1  1 

Tracings  of  variations  of  rapidity  and  of  pressure  of  blood  in  the  carotid  of  a  horse,  obtained  by 
Chauveau  and  Lortet.  The  line  v  represents  the  curve  of  the  rapidity  of  the  blood  ;  and  p  the 
curve  of  arterial  pressure.  The  figures  and  vertical  lines  represent  corresponding  periods  in  the 
tracings.    (McKendrick.) 

crease  or  dimunition  of  the  other.  Thus,  when  the  action  of  the  heart 
is  diminished  by  stimulation  of  the  pneumogastric  nerve,  the  velocity 
and  blood  pressure  are  diminished  at  the  same  time.  The  relation  of  the 
two,  however,  may  be  an  inverse  one — that  is,  the  velocity  may 
be  diminished,  and  yet  the  blood  pressure  may  be  increased  ;  for 
example,  if  an  artery  be  compressed  the  velocity  is  diminished,  and  yet 
the  blood  pressure  rises,  as  we  have  seen.  As  Marey  expresses  it,  any 
influence  which  increases  or  diminishes  the  force  of  the  heart,  which 
propels  the  blood  toward  the  periphery,  will  increase  or  diminish  at  the 
same  time  the  velocity  and  blood  pressure,  as  in  the  example  just  given 
of  the  effect  of  stimulation  of  the  pneumogastric  nerve  ;  on  the  con- 
trary, any  influence  which  will  increase  or  diminish  the  resistance  to 
the  arterial  flow  will  make  the  velocity  and  blood  pressure  vary  in  the 
inverse  relation  toward  each  other.  Thus,  if  the  capillary  resistance  be 
very  great  the  velocity  is  diminished  but  the  blood  pressure  rises. 

On  account  of  this  relation  between  the  pressure  of  the  blood  and  its 


TRA.CES    OF    PKESSURE    AND    VELOCITY    OF    BLOOD.       345 

velocity,  wherever  it  is  practicable  the  two  should  be  studied  together 
(Fig.  197),  since  it  is  impossible  to  learn  from  the  elevation  of  the 
mercury  in  the  manometer  alone  whether  the  rise  in  the  blood  pressure 
is  due  to  increased  cardiac  action,  or  increased  peripheral  resistance. 
If,  however,  the  trace  of  the  velocity  be  taken  simultaneously  with  that 
of  the  blood  pressure,  and  it  is  seen  that  the  velocity  is  diminished,  then 
the  rise  in  the  blood  pressure  will  be  due  to  peripheral  resistance  ;  on  the 
other  hand,  if  the  velocity  be  increased,  then  it  is  due  to  increased 
heart  action.  The  want  of  such  comparative  observation  leaves  us  often 
in  doubt  as  to  what  the  rise  in  the  blood  pressure,  as  indicated  by  the 
elevation  of  the  mercury,  was  really  due  to  in  many  of  the  recorded 
experiments  upon  blood  pressure.  The  result  of  Chauveau's  observa- 
tion upon  the  coronary  arteries  with  his  hremodromograph  illustrates 
the  importance  of  this  comparative  method  of  experimentation.  It 
being  demonstrated  that,  during  the  systole  of  the  ventricle,  the  velocity 
of  the  blood  is  diminished  in  the  coronary  arteries,  the  rise  in  the  blood 
pressure  observed  must  be  due  to  peripheral  resistance,  the  contracted 
state  of  the  muscular  substance  of  the  heart  during  the  systole  offering 
an  obstacle  to  the  flow  of  the  blood  through  the  coronary  arteries ;  the 
velocitv  being  increased,  however,  during  the  diastole,  and  the  blood 
pressure  falling,  shows  that  the  obstacle  has  been  removed,  the  muscu- 
lar fibres  of  the  heart  now  being  relaxed.  The  above  view  is  a  con- 
firmation of  what  has  been  already  said  in  reference  to  the  circulation 
of  the  blood  through  the  substance  of  the  heart  itself. 


CHAPTE R    X  XIII 


THE  CAPILLARIES. 


The  capillaries,  discovered  by  Malpighi,  in  1061,  are  the  minute  ves- 
sels through  which  the  blood  (with  few  exceptions)  flows  from  the 
arteries  to  the  veins.  As  an  artery  becomes  smaller  and  smaller  it 
gradually  loses  its  external  and  middle  coat,  and,  to  a  great  extent,  its 
internal  one  also,  the  epithelial  layer  alone  remaining.  This  constitutes 
a  capillary.  As  the  capillary  approaches  the  vein  it  not  only  becomes 
larger,  but  changes  the  character  of  its  structure,  developing  gradually 
three  coats,  until  finally  the  capillary  becomes  a  vein.  Practically,  it 
is  impossible  to  say  exactly  where  the  artery  ends  and  where  the  capil- 
lary begins,  or  where  the  capillary  ends  and  the  vein  begins,  the  transi- 
tion from  one  to  the  other  is  so  gradual.  It  is  for  this  reason  that  a 
difference  of  opinion  prevails  among  anatomists  as  to  what  consti- 
tutes a  capillary,  and   therefore  the  description  of  these  vessels   differs, 

Fig.  198. 


Capillary  plexus  in  the  portion  of  a  web  of  a  frog's  fojt,  magnified  110  diameters.     1.  Trunk  of  vein. 
2,  2,  2.    Its  branches.     3,  3.  Pigment  cells.     (Carpenter.) 

according  to  the  view  taken  of  their  structure.  According  to  some 
histologists  there  are  various  kinds  of  capillaries,  differing  from  each 
other  in  the  amount  of  muscular  and  fibro-elastic  tissue  present.  Such 
vessels  we  would  regard  as  either  small  arteries  or  veins,  considering  a 
capillary  to  be  a  transparent,  apparently  homogeneous,  elastic  vessel, 


STRUCTURE    OF    CAPILLARIES. 


347 


Fig.  109. 


whose  calibre  is  so  small  that  the  blood  corpuscles  can  pass  into  it  only 
one  at  a  time  (Fig.  198),  and  whose  wall  consists  (Fig.  199)  of  a  simple 
epithelial  layer  of  flattened  lanceolate  cells, 
with  oval  nuclei  joined  to  edge,  and  con- 
tinuous with  the  epithelial  layer  of  the 
arteries  on  the  one  hand,  and  with  that  of 
the  vein  on  the  other.  The  Avail  of  the  capil- 
lary is  apparently  almost  homogeneous,  it 
is  only  after  appropriate  treatment  with 
silver  nitrate  and  carmine  that  the  outlines 
of  the  cells  composing  it,  with  their  nuclei, 
become  apparent.  The  length  of  the  ca- 
pillary— that  is,  the  distance  between  the 
end  of  the  artery  and  the  beginning  of 
the  vein — varies,  on  an  average,  between 
the  \  and  Ath  of  a  mm.  (-^th  and  y^  th  of 
an  inch),  the  average  diameter  varying  be- 
tween 


the  s^th 


and  the  yyo-th   of  a  mm. 


Fine   capillaries  from   the   mesentery. 
(Carpenter  ) 


(2o1oo^   an(^    3  -}q  o tn    °f  an  mcn)-     The 

smallest  capillaries  are  found  in  the  nervo- 

muscular  tissues,  retina,  and  patches  of  Peyer,  having  there  a  diameter 

of  yloth  to  the  2T¥th  of  a  mm.  (y^W11  to  6Wotn  of  an  inch)  '■>  the 

largest  in  the  glands  and  bones  with  a  diameter  of  -g^th  to  the  y-5-jjth 

of  a  mm.  (^  ^  0   to   s-jjoT^i   of  an  inch) ;    the  capillaries  of   the  skin 


1 
vary  between  these  two  extremes,  having  a  diameter  of  from  the  -rrg-th  to 

the  y-^th  of  a  mm.  (j^th  to  TirV otn  of  an  incn)-  ^ie  wal1  of  tlie 
capillary  varies  between  the  4^5-th  to  1010oth  of  a  mm.  (^-A-^-Ah 
and  ,tinctli  of  an  inch)  in  thickness. 


2500' 


1 


a  mm.   (y^r. 
th  of  an  inch,  from  the 


After  deducting  this  thickness,  say  the  T 
diameter,  it  will  be  observed  that  the  calibre  of  the  vessel  is  reduced  to 
the  3  0\  0  th  of  an  inch,  so  that  the  blood  corpuscles  can  move  only  in  a 
single  row,  and  in  many  cases  even  the  corpuscle  must  change  its  shape 
in  order  to  pass  into  the  vessel ;  this  is  possible  through  its  elasticity. 

The  small  size  of  the  capillaries,  both  as  regards  their  length  and 
breadth,  has  an  important  significance  in  reference  to  the  amount  of 
blood  flowing  from  them  into  the  veins.  Thus  it  is  well  known,  from 
the  researches  of  Poisseuille,1  that  the  amount  of  fluid  discharged  by  a 
tube  the  yfg-th  of  a  millimetre  in  diameter  (^th  of  an  inch)  will  be 
sixteen  times  that  discharged  by  a  tube  the  -j 3-g-th  of  a  mm.  (5C/00th  of 
an  inch),  the  amounts  discharged  being  proportional  to  the  fourth 
powers  of  the  diameters — that  is,  1  :  x  :  :  2T0~tn  :  TTo  th>  or  x  e(luals  2 
and  24  equals  10.  On  the  other  hand,  the  amount  discharged  by  tubes 
of  the  length  of  the  capillaries  will  be  inversely  as  their  lengths — that 
is,  of  two  capillaries  of  different  lengths  more  fluid  will  be  discharged 
from  the  short  vessel  than  the  long  one.  It  will  be  seen,  therefore,  that 
any  change  in  the  length  or  breadth  of  a  capillary  will  influence  greatly 
the  amount  of  blood  delivered  to  the  veins,  and  so  increase  or  diminish 
the  resistance  offered  by  the  capillary  system  to  the  arterial  flow ;  the 
significance  of  which  we  have  seen  in  considering  the  velocity  of  the 


1  Mem.  de  l'Acad.  dea  Si  iei  i  is  Savant  Etramr,  tome  i\.  p.  513. 


348 


THE    CAPILLARIES. 


blood  and  its  pressure  in  the  arteries.  The  cell-like  structure  of  the 
capillaries  just  referred  to  makes  perfectly  clear  how  it  is  possible  for 
the  white  and  red  corpuscles  to  pass  from  the  capillary  into  the  sur- 
rounding tissues.  The  capillaries,  unlike  the  arteries  and  veins,  con- 
stitute a  true  plexus  of  vessels  of  nearly  uniform  diameter,  branching 
and  inosculating  in  every  direction.  This  inosculation  is  characteristic 
of  the  capillaries  and  the  plexus  is  developed  in  proportion  to  the 
functional  activity  of  the  part.  Thus  the  capillaries  are  very  numerous 
and  close  set  in  the  nervo-muscular  and  glandular  tissues,  absorbing 
surfaces,  etc.,  structures  in  which  the  molecular  changes  incident  to 
nutrition  are  peculiarly  active. 

While  the  general  character  of  the  capillaries  throughout  the  system 
is  the  same,  the  difference  in  their  disposition  as  regards  their  closeness 
and  the  form  of  the  network  is  often  so  marked  that  the  histologist  can 
frequently  tell  from  what  part  of  the  body  a  tissue  has  been  taken  by 
an  examination  of  the  capillaries  alone.  No  one  can  fail  to  recognize 
the  difference  in  the  arrangement  of  the  capillaries  in  the  skin  (Fig. 
200),  as  compared  with  that  in  muscle  or  mucous  membrane  (Figs.  201, 
202).      While  capillaries  are  found  almost  everywhere  in  the  human 


Fig.  200. 


Fig.  201. 


Distribution  of  capillaries  on  the  surface  of  th 
skin  of  tbe  finger.     (Carpenter.) 


Distribution  of  capillaries  in  muscle. 
(Carpenter.) 


Fig.  202 


body,  it  has  been  shown  by  Suquet1  that  in  certain  parts  of  the  head 
and  in  the  extremities  the  blood  passes  directly  from  the  arteries  into 
veins  without  the  intervention  of  capillaries.  Capillaries  are  absent  in 
certain  structures  like  cartilage,  hair,  nails,  etc.,  and  hence  such  parts 

are  often  called  extravascular.  This  name  is 
apt,  however,  to  mislead  and  is  inappropriate, 
since  all  tissues  are  extravascular  in  so  far 
as  they  lie  outside  of  the  vessel  carrying  the 
blood  that  nourishes  them.  In  the  vascular 
tissues  the  nutriment  osmoses  through  the 
wall  of  the  capillary  into  the  tissue  imme- 
diately surrounding  the  vessel  and  thence 
into  parts  more  and  more  remote  from  it. 
In  the  so  -  called  extravascular  tissue  the 
nutriment  comes  from  the  blood  of  a  capil- 
lary, as  in  the  vascular  tissue,  though  the 
capillary  may  be  situated  at  a  considerable 
distance  from  the  tissue  that  it  nourishes.  The  only  difference  between 
the  vascular  and  extravascular  tissue  is  that  the  nutriment  is  conveyed 


Distribution  ol  capillaries  around 
follicles  of  mucous  membrane.  (Car 
penter.) 


1   De  la  Circulation  du  Sans  dans  les  membres  et  dans  la  tete  de  1' Homme.     Paris,  1800. 


CAPACITY    OF    CAPILLARY    SYSTEM.  3-19 

a  longer  distance  in  the  one  case  than  the  other ;  the  difference,  there- 
fore,  is  one  of  degree,  not  of  kind.  There  are  no  capillaries  in  the 
spleen,  erectile  tissues,  and  maternal  part  of  the  placenta,  their  place 
being  supplied  by  blood  sinuses.  When  we  come,  however,  to  the  study 
of  the  development  of  these  organs,  we  shall  see  that  these  blood  sinuses 
are  probably  enormously  dilated  capillaries.  It  will  be  remembered 
that  the  arterial  system  was  likened  to  a  cone,  of  which  the  heart  is  the 
apex  and  the  capillaries  the  base,  and  that  the  area  of  the  branches  of 
an  artery  is  usually  greater  than  that  of  the  artery  itself.  We  should 
expect,  therefore,  to  find  that  the  capacity  of  the  capillary  system  is  far 
greater  than  that  of  the  arterial.  Indeed,  the  microscopical  examina- 
tion of  the  skin,  mucous  membrane,  muscle,  etc.,  in  which  the  capillary 
vessels  have  been  injected  gives  the  impression  that  such  tissues  consist 
of  nothing  but  capillaries.  This  is  also  true  almost  to  the  same  extent 
in  living  animals  under  certain  conditions,  thus  during  digestion  the 
surface  of  the  mucous  membrane  lining  the  alimentary  canal  presents  a 
light  red  appearance  through  the  distention  of  its  capillaries  with  blood. 
The  capacity  of  the  capillary  system  must  be  immense — indeed,  accord- 
ing to  Vierordt,1  it  is  800  times  that  of  the  arterial.  This  estimate, 
though  only  approximative,  cannot  be  very  far  from  the  truth,  being 
deduced  from  the  law  that  the  velocity  with  which  a  fluid  flows  through 
a  tube  is  inversely  as  the  diameter  of  the  tube  We  shall  soon  see,  as 
an  illustration  of  this  law,  that  the  blood  flows  much  more  slowly  in  the 
capillaries  than  in  the  aorta,  the  total  area  of  the  capillaries  being 
far  greater  than  that  of  the  aorta.  The  sectional  area  of  the  capillary 
system  being  then  to  the  sectional  area  of  the  aorta  as  the  velocity  of 
the  blood  in  the  aorta  is  to  the  velocity  of  the  blood  in  the  capillaries, 
the 

f        .11     •  sec.  area  of  aorta  X  vel.  of  blood  in  aorta 

sec.  area  or  capillaries  =  ^— : : 

vel.  of  blood  in  capillaries 

Donders's2  estimate  of  the  capillary  system  being  500  times  that  of 
the  arterial — rather  too  low — is  based  upon  the  observations  of  Volkmann. 

By  dividing  the  total  sectional  area  of  the  capillaries  by  the  area  of  one 
capillary  an  approximate  estimate  of  the  number  of  capillaries  can  be 
obtained.  It  was  in  this  way  that  Hales3  calculated  that  there  were 
over  eight  millions  of  capillaries  in  the  human  body.  The  general  struc- 
ture, distribution,  etc.,  af  the  capillaries  having  been  described,  let  us 
now  consider  the  manner  in  which  the  blood  flows  through  them. 

As  the  phenomenon  of  the  flow  of  the  blood  through  the  capillaries, 
as  viewed  by  the  microscope,  is  one  of  the  most  beautiful  and  striking 
spectacles  in  nature,  a  few  words  as  to  the  most  convenient  method  by 
which  it  can  be  observed  appear  necessary.  For  this  purpose  we  gener- 
ally make  use  of  the  mesentery  of  the  frog,  on  account  of  it  being  so 
easily  exposed  and  readily  arranged  on  the  apparatus  supporting  it, 
which  is  a  very  simple  one,  consisting  of  a  thin  piece  of  cork  with  an 
opening  in  it  through  which  the  light  can  pass,  and  upon  which  rests, 
slightly  elevated,  a  glass  slide,  over  which  is  placed  the  mesentery,  the 

1  Die  ErscheinuDgen  und  Oesetze  der  Stromgeschwiudigkeiten  des  Blntes,  S.  35 

2  Phjsiologie,  Band  i.  S.  131.  3  Statistical  Essays,  vol.  ii.  p.  69 


350  THE    CAPILLARIES. 

loop  of  intestine  drawn  out  of  the  body  to  wliich  the  mesentery  is  at- 
tached resting  in  a  little  gutter  or  groove  on  the  glass  slide  surrounding 
the  opening.  A  few  drops  of  a  solution  of*  sodium  chloride  (3  per  cent.) 
being  placed  upon  the  mesentery  and  a  slide  cover  placed  over  it,  and 
the  cork  placed  on  the  stage  of  the  microscope,  the  circulation  can  be 
observed  for  a  considerable  time  before  inflammation  sets  up.  The  web 
of  the  frog's  foot,  its  lung  and  tongue,  may  also  be  used  for  the  demon- 
stration of  the  circulation.  The  tongue  of  the  frog,  on  account  of  its 
being  attached  to  the  anterior  part  of  the  lower  jaw  and  free  posteriorly, 
and  therefore  being  easily  drawn  out  of  the  mouth  and  through  its  great 
vascularity,  is  also  a  favorite  subject  of  study  with  physiologists.  When 
the  tongue  is  used  it  is  best,  however,  to  innate  it  first  and  then  slit  it 
open,  when  a  magnificent  view  of  the  circulation  is  obtained.  The  tail 
of  tadpoles,  of  little  fish,  and  the  gills  of  the  salamander,  are  also  ser- 
viceable objects  for  the  study  of  the  circulation.  When  the  salamander 
is  used  it  should  be  placed  in  a  Holman's  life  slide,  by  means  of  which 
the  animal  is  firmly  secured  without  injuring  it,  while  the  water  is  con- 
stantly renewed.  When  the  fish  is  used,  Caton's  fish-trough  will  be 
found  serviceable.  This  consists  of  an  oblong  box,  one  end  of  which 
transmits  the  light  through  an  opening  in  the  piece  of  glass  upon  which 
the  tail  of  the  fish  in  which  the  capillaries  are  to  be  examined  is  secured, 
the  head  and  body  of  the  fish  resting  at  the  other  end  of  the  box.  By 
means  of  a  cistern  and  tube,  a  constant  current  of  water  passes  through 
the  box. 

The  study  of  the  capillary  circulation  in  mammals  is  more  difficult 
than  in  any  of  the  animals  just  referred  to,  since,  with  the  exception  of 
the  wing  of  the  bat,  there  is  no  external  part  transparent  enough  to  be 
observed  with  the  high  power  of  the  microscope,  and  if  any  of  the  inter- 
nal parts  are  used  the  effects  of  exposure  are  far  more  injurious  than  in 
the  frog,  for  example.  The  mesentery  and  omentum  of  small  rodents, 
like  rats  and  mice,  etc.,  have  been  often  made  use  of  in  demonstrating 
the  capillary  circulation  in  the  mammalia ;  but  the  omentum  of  the 
guinea-pig  is  preferable  for  many  reasons,  on  account  of  its  transparency 
and  of  its  delicate  and  simple  structure,  consisting,  to  a  great  extent,  of 
only  two  layers,  of  being  attached  to  only  one  side  of  the  stomach,  and  little 
or  no  fat  being  present.  The  great  difficulty  experienced  in  observing 
the  capillaries  in  the  peritoneum  of  the  mammalia  is  due  to  the  injurious 
effects  of  exposing  the  membrane  to  the  atmosphere  and  the  risk  of 
wounding  it.  To  avoid  this,  the  omentum,  wliich  is  the  part  we  shall 
use,  is  floated  into  a  glass  trough  containing  either  serum  or  a  solution 
of  sodium  chloride  (3  per  cent.),  wliich  is  kept  at  the  temperature  of  the 
body  by  means  of  the  warm  stage,  which  we  have  already  described. 
The  guinea-pig  used  should  be  put  under  the  influence  of  chloral,  three 
grains  injected  under  the  skin  being  sufficient  for  an  animal  weighing 
one  pound,  and  then  placed  upon  a  support  on  a  level  with  the  stage  of 
the  microscope.  The  incision  being  made  a  little  below  the  ensiform 
cartilage,  and  extending  outward  from  the  rectus  muscle,  about  an  inch 
from  the  edge  of  the  omentum  is  carefully  seized  and  drawn  out  into 
the  trough.  It  is  well  to  cover  the  parts  of  the  membrane  not  imme- 
diately under  the  microscope  with  pieces  of  blotting-paper,  in  this  way 


PHENOMENA    OF    CAPILLARY    CIRCULATION.  351 

avoiding  unnecessary  exposure,  and  at  the  same  time  keeping  the 
omentum  steadier  than  it  otherwise  would  be.  With  all  the  above  pre- 
cautions, however,  the  view  of  the  capillary  circulation  thus  obtained  is 
far  from  satisfactory,  and  not  comparable  to  that  observed  in  the  mesen- 
tery of  the  frog. 

Since  the  time  of  Malpighi,  the  phenomena  of  the  capillary  circulation 
have  been  often  described  :  but  language  is  inadequate  to  give  one  any 
idea  of  the  beauty  of  the  spectacle,  and  to  be  appreciated  it  must  be  seen. 

We  will  suppose  the  mesentery  of  the  frog  disposed  within  the  field 
of  the  microscope  as  just  described.  Here  may  be  seen  the  arterioles  of 
the  mesenteric  artery  through  which  the  blood  flows  with  apparently 
amazing  rapidity,  dividing  and  subdividing  until  the  blood  is  carried  to 
an  exquisite  network  of  delicate  tubes  resembling  a  web  of  fine  spun 
glass,  the  capillaries,  in  which  the  blood  is  separated  from  the  tissues  by 
a  thickness  varying  between  the  ^g-th  and  the  -^jth  of  a  mm.  (j2 o"Fotn 
and  2  5  o  o  o *h  °f  an  inch)  only. 

It  will  be  readily  appreciated,  therefore,  with  what  rapidity  the  nutri- 
tive elements  can  osmose  into  the  tissues  and  the  effete  matters  be  taken 
up  by  the  blood.  Indeed,  the  capillaries  are  the  seat  of  all  physiological 
and  pathological  nutrition  processes.  The  arteries  and  veins  are  only 
means  toward  an  end,  the  one  set  of  vessels  carrying  the  blood  to  the 
part  to  be  nourished,  the  other  carrying  it  away  laden  with  the  waste 
products.  It  will  be  observed  that  the  true  capillaries  are  of  uniform 
diameter,  and  are  so  small  that  they  admit  but  a  single  row  of  cor- 
puscles, and  these  are  seen  moving  in  the  middle  of  the  stream,  flowing 
along  in  the  clear  plasma  which  forms  a  distinct  layer,  and  which  ad- 
heres to  such  an  extent  to  the  walls  of  the  capillary  that  it  appears 
immovable,  and  for  this  reason  is  called  the  still  layer.  The  presence 
of  this  still  layer  is  due  to  the  capillary  attraction  existing  between  the 
liquor  sanguinis  and  the  wall  of  the  capillary,  and  in  proportion  as  the 
diameter  of  the  capillary  is  diminished  this  force  is  relatively  increased, 
since  a  greater  surface  of  the  capillary  wall  is  exposed  to  the  liquor 
sanguinis ;  there  being  little  or  no  affinity  between  the  red  blood-cor- 
puscles and  the  wall  of  the  capillary,  the  corpuscles  meeting  with  no 
obstacle  to  their  flow  consequently  move  with  great  rapidity  through 
the  middle  of  the  stream.  A  red  corpuscle  is  sometimes  caught  in  the 
still  layer,  where  it  moves  slowly  for  a  time,  turning  over  and  over; 
sooner  or  later,  however,  it  passes  again  with  the  central  stream  and  in 
an  instant  is  whirled  out  of  sight.  The  white  corpuscles,  on  the  con- 
trary, through  their  adhesiveness,  stick  either  to  the  still  layer  or  to  the 
capillary  wall,  and  being  quite  numerous  in  the  frog  (1  white  to  8  red) 
a  number  are  often  seen  at  one  time  in  the  same  capillary. 

It  is  an  interesting  illustration  of  the  uniformity  of  the  laws  of  nature 
that  the  same  phenomenon  of  the  rapidity  of  the  flow  of  a  stream  being 
greater  in  the  middle  than  at  the  sides  is  seen  on  a  magnificent  scale  in 
the  motion  of  a  glacier.  It  has  been  a  matter  of  daily  observation  to 
those  passing  any  time  on  a  glacier  to  notice  that  the  stones,  debris,  etc., 
move  more  rapidly  in  the  middle  of  the  glacier  than  those  at  the  sides. 
It  was  Poisseuille1  who  first  showed  that  the  law  regulating  the  flow  of 

1  Becherches  sur  la  cause  dn  Mouvenu  ut  <ln  Sang  dans,  les  vaisseaux  capillaire.". 


352  THE     CAPILLARIES 

liquids  in  tubes  was  applicable  to  such  having  as  small  a  diameter  as 
those  of  the  capillaries.  The  corpuscles  often  move  in  such  a  manner 
that  they  appear  as  if  they  were  endowed  with  consciousness  and  voli- 
tion. Thus  when  the  single  rows  of  corpuscles  flowing  in  two  capillaries 
reach  a  third  vessel,  formed  through  the  union  of  the  other  two  and  only 
large  enough  to  admit  one  row,  one  row  will  hold  back  until  the  other 
one  has  passed  into  the  capillary  and  then  will  follow  in  its  turn.  Fre- 
quently the  corpuscles  will  flow  in  one  direction  and  meeting  some 
obstacle  will  entirely  reverse  their  course.  A  corpuscle  is  often  retarded 
for  some  time  by  the  angle  formed  by  the  division  of  a  capillary  into 
two,  and  may  be  observed  turning  over  and  over  and  changing  its  shape 
according  to  the  pressure  of  the  current  until  it  is  swept  finally  into  the 
main  stream. 

Certain  capillaries  will  be  for  a  time  quite  empty,  while  others  near  by 
are  filled  with  corpuscles,  then  one  or  two  corpuscles  will  float  into  the 
empty  capillary,  in  a  moment  or  so  a  few  more,  and  soon  a  current  is 
established,  while  in  the  same  gradual  way  a  distended  capillary  may 
become  empty.  One  of  the  most  striking  facts  in  the  phenomena  of  the 
capillary  circulation  is  the  uniformity  with  which  the  blood  flows  through 
these  vessels.  The  motion  is  here  perfectly  continuous ;  we  no  longer 
observe  either  the  intermittent  or  remittent  action  so  characteristic  of 
the  heart  and  arteries.  We  observe  that  the  flow  of  the  blood  in  the 
capillaries  is  never  the  same  for  any  length  of  time — indeed,  one  of  its 
most  interesting  peculiarities  is  the  constant  manner  in  which  the  scene 
varies — influenced  as  it  is  by  so  many  conditions.  In  endeavoring 
to  follow  the  course  of  the  corpuscles  as  they  flow  through  the  capilla- 
ries, one's  first  impression,  seeing  them  often  swept  along  as  if  in  a 
torrent,  is  that  the  velocity  of  the  flow  must  be  very  great.  Reflection 
at  once  suggests  to  us,  however,  that  in  proportion  to  the  power  of 
the  microscope  used  the  velocity  is  magnified.  According  to  Milne 
Edwards,1  Hales  was  the  first  who  endeavored  to  determine  by  observa- 
tion the  velocity  of  the  blood  in  the  capillaries.  Hales2  does  not  tell 
us,  however,  the  manner  in  which  he  accomplished  this,  simply  stating 
that  on  comparing  the  different  velocities  of  the  blood  in  the  muscles 
and  in  the  lungs  of  a  frog,  he  found  that  the  blood  moves  in  the  parallel 
cylindrical  arteries  in  the  straight  muscles  of  its  abdomen  at  the  rate  of 
one-tenth  of  an  inch  in  nine  seconds  of  time — that  is,  at  the  rate  of  an 
inch  in  ninety  seconds  or  one  minute  and  a  half.  The  simplest  way  of 
determining  the  velocity  of  the  blood  in  the  capillaries  is  to  substitute 
for  the  ordinary  eye-piece  of  the  microscope  an  ocular  micrometer,  and 
with  a  reliable  watch  held  close  to  the  ear  to  determine  the  time  that  it 
takes  a  blood  corpuscle  to  pass  across  the  field  of  the  microscope,  or  the 
interval  of  space  included  between  two  or  more  divisions  of  the  microm- 
eter. Weber3  was  the  first,  we  believe,  to  make  use  of  this  method.  It 
was  in  this  way  that  he  determined  the  velocity  of  the  blood  in  the 
capillaries  of  the  tail  of  the  tadpole  to  be  about  the  J  of  millimetre  in  a 
second  (the  -jV^1  °f  an  mcn)-     Valentin4  estimated  the  velocity  in  the 

1  Physiologic,  tome  iv.  p.  286.  2  Op.  cit.,  vol.  ii.  p.  66. 

3  Miiller's  Archiv,  1838,  S.  467.  4  Physiologie,  Band  i.  S.  482. 


VELOCITY    OF    BLOOD     IN     CAPILLARIES.  353 

capillaries  of  the  web  of  the  frog's  foot  was  about  the  same — in  round 
numbers,  about  2.5  cm.  (one  inch)  in  a  minute.  According  to  Volk- 
mann,1  the  velocity  of  the  blood  in  the  capillaries  of  the  gills  of  the  tad- 
pole is  ith  of  a  mm.,  in  the  tail  of  a  little  fish  -j^th  of  a  mm.,  and  in 
the  capillaries  of  the  mesentery  of  a  dog  yg-th  of  a  millimetre  in  a 
second — in  round  numbers,  about  5  cm.  (2  inches)  in  a  minute. 

Yierordt2  makes  use  of  an  apparatus  for  measuring  the  velocity  of  the 
blood  in  the  capillaries,  which  is  based  upon  the  fact  that  a  body  moving 
at  a  certain  rate  and  illuminated  but  for  a  very  short  instant  appears 
immovable.  By  placing  between  the  mirror  of  the  microscope  and  the 
object-glass  a  movable  disk  pierced  with  holes  through  which  the  light  is 
transmitted,  the  object  viewed  is  only  seen  when  one  of  the  holes  passes 
across  the  axis  of  vision.  If  the  length  of  time  the  blood  corpuscle  is 
illuminated  be  known  and  the  blood  corpuscle  appear  immovable,  then 
the  rate  at  which  it  is  moving  can  be  inferred.  This  physiologist  has 
also  calculated  the  velocity  of  the  blood  in  the  capillaries  of  the  human 
retina.  As  is  well  known,  the  eye  after  a  time  becomes  fatigued  when 
exposed  to  a  strong  white  light :  if  the  eye  be  now  compressed,  one  sees 
the  image  of  a  current  in  the  form  of  a  network.  This  appears  to  be 
due  to  the  passage  of  the  blood  corpuscles  through  the  capillaries  of  the 
retina.  By  calculating  the  space  passed  over  in  a  given  time  by  the 
image,  Vierordt3  estimates  the  velocity  in  this  situation  to  vary  between 
the  yVth  and  yVtn  of  a  millimetre  in  a  second.  Assuming  that  the 
rapidity  of  the  motion  of  the  white  corpuscles  can  be  accepted  as  a  means 
of  estimating  the  velocity  of  the  still  layer,  it  can  be  stated  that  on  an 
average  the  latter  moves  9  to  17  times  more  slowly  than  the  current  in 
the  middle.  Inasmuch  as  the  amount  of  blood  required  by  the  tissues 
varies  very  much  from  time  to  time,  we  should  expect  to  find  also  great 
variations  in  the  state  of  the  capillaries  in  this  respect.  Thus  at  one 
time  the  capillaries  supplying  a  tissue  may  be  entirely  empty  or  almost 
so,  at  another  gorged  with  blood.  It  becomes  important,  therefore,  to 
study  the  effects  of  such  agents  as  will  modify  the  calibre  of  these  vessels 
or  accelerate  or  retard  the  flow  of  the  blood  through  them. 

Among  the  most  important  of  these  may  be  mentioned  the  effects  of 
cold,  heat,  electricity,  certain  local  irritants,  and  changes  in  the  physical 
and  chemical  composition  of  the  blood.  Thus  a  low  temperature  dimin- 
ishes the  quantity  of  blood  in  the  capillaries  and  retards  the  circulation, 
while  a  high  temperature,  on  the  contrary,  increases  the  amount  and 
accelerates  its  velocity.  The  effect  of  cold  upon  the  capillary  circulation 
can  be  readily  demonstrated  by  placing  a  piece  of  ice  upon  the  part 
examined,  the  web  of  a  frog's  foot,  for  example,  or  the  mesentery.  The 
circulation  will  at  once  be  observed  to  become  much  slower,  stagnate, 
and  often  cease  entirely,  the  capillaries  are  emptied  and  the  small  arte- 
rioles, those  carrying  usually  two  or  three  rows  of  blood  corpuscles,  will 
now  admit  only  one  row.  If  the  ice  be  removed,  the  circulation  will 
become  normal  again.     If  now  the  part  examined  be  covered  with  water, 

»  Die  Hsemodynamik,  S.  184.  *  Op.  cit.,  S.  35. 

»  Op.  cit.,  S.  112. 

23 


354  THE    CAPILLARIES. 

say  at  a  temperature  of  40°  C.  (104°  F.)  or  placed  upon  the  warm  stage 
at  the  same  temperature,  the  quantity  of  blood  in  the  capillaries  will  be 
greatly  increased  and  the  velocity  so  much  accelerated,  that  it  is  with 
difficulty  the  corpuscles  can  be  distinguished.  The  circulation  can  be 
at  once  arrested  by  the  stimulus  of  electrical  currents,  the  greatest  effect 
being  obtained  when  individual  currents  are  used.  The  effect  of  the  appli- 
cation of  a  local  irritant,  like  a  solution  of  common  salt,  when  applied  to 
the  arterioles,  and  possibly  also  to  the  true  capillaries,  is  at  first  to  pro- 
duce a  constriction  and  a  diminution  in  the  velocity  of  the  current.  The 
constriction  is,  however,  soon  followed  by  a  dilatation  and  the  velocity 
is  accelerated.  This  condition,  however,  lasts  but  a  moment,  an  oscilla- 
tion of  the  current  begins,  the  velocity  is  diminished  again,  stagnation 
follows,  the  capillary  becomes  gorged  with  blood,  the  white  corpuscles 
increase  in  number,  and  an  inflammatory  state  is  set  up.1 

Since  the  experiments  of  Poisseuille,  it  is  well  known  that  the  com- 
position of  a  fluid  will  influence  the  rapidity  with  which  it  flows  through 
tubes  of  small  diameter.  Thus,  solutions  of  potassium  iodide  and  bro- 
mide, etc.,  flow  more  rapidly  than  solutions  of  sodium,  calcium,  and 
magnesium  chloride,  of  sodium  phosphate  and  carbonate.  One  would 
naturally  infer  then  that  the  presence  or  absence  of  certain  salts  in  the 
blood  would  influence  the  rapidity  with  -which  it  flows  in  the  capillaries. 
Such  was  experimentally  proven  to  be  the  case  by  Poisseuille,2  the 
rapidity  of  the  circulation  in  the  horse  being  diminished  by  the  intro- 
duction into  the  blood  of  ammonium  acetate  and  sodium  chloride.  The 
influence  of  respiration  upon  the  capillary  circulation  will  be  considered 
when  the  subject  of  asphyxia  is  taken  up ;  while  the  effect  of  the  vaso- 
motor nerves  in  modifying  the  calibre  of  the  arteries,  and  thereby  affect- 
ing the  quantity  of  the  blood  delivered  to  the  capillaries,  will  be  deferred 
until  we  study  the  nervous  system. 

In  speaking  of  the  effect  of  irritants  when  applied  to  the  capillaries, 
it  was  just  stated  that  a  constriction  of  the  arterioles,  and  probably  also 
of  the  capillaries,  was  the  first  effect.  It  has  long  been,  however,  a 
subject  of  discussion  as  to  whether  the  capillaries  are  really  contractile 
in  the  same  sense  as  the  arteries.  It  is  possible  that  the  cause  of  the 
difference  of  opinion  that  still  prevails  in  reference  to  this  matter,  may 
be  due  to  the  fact  of  one  physiologist  regarding  as  a  capillary  what 
another  would  consider  an  arteriole.  The  arterioles  are,  undoubtedly, 
contractile,  their  walls  containing  muscular  fibres,  and  since  the  layer  of 
nucleated  cells  of  which  the  capillary  wall  consists  is  continuous  with 
the  contractile  tunic  of  the  arteriole,  the  capillary  may  possess  true  con- 
tractility. This  seems  to  be  the  case,  at  least  in  the  capillaries  of  the 
embryo,  as  shown  by  llouget,3  where  the  nuclei  of  the  cells  stand  out 
through  the  contraction  of  the  capillaries.  On  the  other  hand,  the 
diminution  in  the  calibre  of  the  capillary,  often  supposed  to  be  an  evi- 
dence of  its  contractility,  is  really  due  to  a  diminution  in  the  pressure 
of  the  blood,  the  wall  of  the  capillary  recoiling  upon  its  contents  through 
its  elasticity,  from  a  previous  state  of  distention. 

1  Thompson  :  Lectures  on  Inflammation,  Edinburgh,  1813.     Wilson  Philip  :  Med.  Chir   Trans.,  182.% 
vol    xii.     Wharton  Jones  :   Guy's  Hospital  Reports. 

2  Comptes  Itendus  de  l'Acad.  des  Sciences,  1843,  tome  xvi.  p.  60.  3  Ibid.,  1879. 


PLETHYSMOGRAPH, 


355 


When  a  tissue  which  has  been  thoroughly  injected,  is  seen  under  the 
microscope,  it  appears  as  if  it  consisted  almost  entirely  of  capillaries. 
It  will  be  readily  understood  that  any  change,  however  slight,  in  the 
calibre  of  the  capillaries  will  considerably  influence  the  volume  of  the 
organ  containing  them.  The  changes  in  the  volume  of  an  organ  will 
serve  then  as  a  measure  of  the  amount  of  the" contraction  and  relaxa- 
tion of  its  capillaries.  Physiology  is  indebted  to  Mosso1  more  particu- 
larly for  the  employment  of  this  method  as  a  means  of  determining 
changes  in  the  volume  of  the  capillaries.  For  example,  an  isolated 
kidney  in  which  the  circulation  is  maintained  artificially,  is  placed  in  a 
vessel  filled  with  oil,  the  latter  communicates  with  a  second  vessel. 
With  an  increase  in  the  pressure,  the  volume  of  the  kidney  expands, 
and  the  oil  is  driven  out  of  the  vessel,  with  a  diminution  of  the  pressure, 
the  organ  contracts,  and  the  oil  is  drawn  back.  The  plethysmograph 
of  Mosso2  is  an  instrument  based  upon  the  principle  of  the  experiment 

Fig.  203. 


PlSthysmograph  of  Mosso.     (Marey.) 

just  described,  having  for  its  object  the  measurement  of  slow  volumetric 
variations  in  the  capillaries  of  man,  depending  upon  either  changes  in 
the  blood  pressure,  or  variations  in  the  state  of  contraction  or  relaxation 
in  the  vessels  themselves.  It  consists  essentially  of  a  large  glass  jar  (A, 
Fig.  203),  in  which  an  arm  is  enclosed,  for  example,  and  communi- 
cating by  a  tube  with  a  small  glass  jar  (B),  which  is  suspended  in  the 
water  of.  the  jar  C  by  means  of  the  pulley  and  weight.  The  jar  A 
enclosing  the  arm  is  filled  with  water.  With  each  increase  in  the 
volume  of  the  arm  the  water  is  driven  out  of  the  jar  A  through  the  tube 
into   the  jar  B,  sinking  it  deeper  in  the   water  of  the  jar  C.     With 


1  Sopra  alcime  nuove  proprieta  delle  pareti  dei  vasi  sanguigne,  Recherche  di  fiselogia,  etc.    Torino,  1875. 

2  Reale  :  Acad   delle  scienze  di  Torino,  xi.,  1875. 


356 


THE    CAPILLARIES. 


each  diminution  in  the  volume  of  the  arm,  the  water  is  drawn  back  into 
the  jar  A,  the  jar  rising  out  of  the  water  in  C.  A  pen  adapted 
to  the  weight,  records  graphically  upon  a  cylinder  the  elevation  and 
depression  of  the  jar  B — that  is,  the  changes  in  the  volume  of  the  arm 
examined.  From  the  results  of  his  experiments,  Mosso  concludes  that 
the  changes  in  the  volume  of  an  organ  are  due  not  only  to  variations  in 
the  blood  pressure,  but  also  to  changes  in  the  calibre  of  the  vessels  as 
well. 

It  will  be  remembered,  that  in  speaking  of  the  pressure  of  the  blood 
in  the  arteries,  an  experiment  was  performed,  by  which  it  was  shown 
that  the  pressure  of  a  fluid  gradually  diminished  as  it  receded  from  the 
source  of  the  supply  to  the  outlet,  the  diminution  being  shown  by  the 
different  heights  to  which  the  fluid  rose  in  the  vertical  tubes.  Let  us 
now  see  what  takes  place  when  the  fluid  flows  out  of  the  apparatus 
(Fig  204),  which  is  almost  the  same  as  that  just  referred  to,  with  the 

Fig.  '204. 


r 

p 

6 

• 

■„^ 

4 

.5 

a>-~ 

E  "~~::i,^ 



""""■-.       | 

L/v- 

-6 


Apparatus  to  show  decrease  of  pressure  in  tubes  of  unequal  calibre.     (Marey.) 


difference  only  that  the  diameter  of  the  horizontal  tube  instead  of  being 
the  same  throughout  its  entire  length,  for  a  short  distance  in  the  middle 
(r),  is  very  much  diminished.  We  will  consider  this  part  as  represent- 
ing the  capillaries,  the  horizontal  portion  of  the  tube  on  the  left,  the 
arteries,  that  on  the  right,  the  veins.  It  will  be  observed,  as  in  the 
previous  experiment,  that  the  pressure  diminishes  very  gradually  and 
regularly  in  the  tubes  1,  2,  3,  corresponding  to  the  arterial  system,  but 
that  the  pressure  in  the  tubes  4,  5,  6,  representing  the  veins,  is  very  low, 
the  blood  passing  from  the  arteries  into  the  capillaries  with  difficulty, 
but  readily  passing  out  of  the  capillaries  into  the  veins.  Indeed,  in  the 
living  animal  at  times,  while  the  arterial  pressure  amounts  to  150  to 
200  mm.  of  mercury,  the  venous  pressure  is  almost  nothing.  Such  a 
difference  in  the  pressure  implies  that  the  capillary  offers  great  -obstacles 
to  the  flow  of  the  arterial  blood.  We  have  just  seen  that  the  adhesive- 
ness between  the  liquor  sanguinis  and  the  walls  of  the  vessels  is  so  great 
as  to  give  rise  to  the  "still  layer,"  and  so  retard  the  flow  of  a  great  por- 
tion of  the  blood,  and  the  presence  of  this  still  layer  must  affect,  to  a 


PRESSURE    OF    BLOOD    IN    CAPILLARIES.  357 

certain  extent,  the  flow  of  the  rest  of  the  blood  as  well.  Let  us  modify 
now  the  experiment  a  little,  by  substituting  a  somewhat  larger  tube  for 
the  one  representing  the  capillaries  in  the  last  experiment.  The  effect 
Of  this  dilatation  of  the  capillary,  it  will  be  observed,  is  that  the  pres- 
sure in  the  artery,  and  in  the  arterial  end  of  the  capillary,  is  diminished, 
while  the  pressure  in  the  venous  end  of  the  capillary,  and  in  the  veins, 
is  increased.  Any  influence,  therefore,  that  favors  the  retention  of  the 
blood  in  the  arteries,  will  diminish  the  quantity  of  blood  in  the  veins, 
and  vice  versa.1  The  dotted  line  (Fig.  204)  represents  the  effect  of 
substituting  the  large  tube. 

Hales  was  the  first,  so  far  as  I  have  been  able  to  learn,  who  endeavored 
to  determine  the  pressure  of  the  blood  in  the  capillaries.  His  method2 
of  calculating  this  was  as  follows:  Assuming  the  diameter  of  a  capil- 
lary to  be  double  that  of  a  red  corpuscle,  "viz.,  YT2irtn  part  of  an  inch, 
or  0.000617;  the  periphery,  therefore,  of  this  vessel  will  be  0.000939, 
and  its  area  0.000000298;  which,  multiplied  by  80,  the  number  of 
inches  to  which  the  blood  rose  in  the  tube  when  fixed  to  the  artery  of 
the  dog  No.  1,  gives  0.000239  part  of  80  cubic  inches  of  blood,  or 
21416  grains,  equal  to  0.515  part  of  a  grain.  But  the  resistance  of 
the  blood  in  the  veins  of  the  same  dog  being  found  equal  to  six  inches 
height,  or  x  3133d,  or  0.075  part  of  80  inches,  this  13133d  part  equals 
0.03039  grain,  which  being  deducted  from  0.5118  grain,  the  remainder, 
0.4737  grain,  is  the  force  with  which  the  blood  would  be  impelled 
into  such  a  capillary  by  a  column  of  blood  of  eighty  inches  height." 

It  is  an  everyday  observation  that  when  one  compresses  the  skin  with 
the  finger,  the  part  becomes  pale,  regaining  its  natural  color,  however, 
as  soon  as  the  compression  ceases,  the  blood  returning  then  to  the  capil- 
laries. In  order  that  the  blood  should  be  driven  out  of  the  vessels  of 
the  skin,  the  external  compression  force  must  be  superior  to  the  internal 
one,  or  the  pressure  of  the  blood.  If  we  know  the  amount  of  compres- 
sion used,  then  we  can  estimate  approximately  the  internal  force,  or  the 
pressure  of  the  blood  in  the  capillaries.  By  means  of  a  piece  of  glass, 
through  which  any  changes  in  the  color  of  the  skin  can  be  observed, 
and  by  gradually  placing  weights  upon  it,  so  that  the  amount  of  pres- 
sure used  could  be  learned,  Kries3  has  endeavored  to  calculate  the 
pressure  of  the  blood  in  the  capillaries  of  a  given  surface.  In  this 
experiment,  however,  no  account  is  taken  of  the  resistance  to  be  over- 
come otherwise  than  that  of  the  blood.  More  recently,  Roy4  and 
Brown  have  used  an  apparatus  for  determining  the  pressure  of  the  blood 
in  the  capillaries,  which  consists  essentially  of  a  cylinder  closed  infe- 
riorly  by  glass,  and  superiorly  by  a  transpai-ent  membrane  covered  with 
glass,  which  is  placed  within  the  field  of  the  microscope.  The  air  in 
the  cylinder  being  compressed  by  a  connecting  tube,  the  membrane  is 
pressed  against  the  tissue  containing  the  capillaries  to  be  examined.  As 
the  compression  is  increased  the  circulation  disappears  in  the  capillaries, 
veins,  and  arteries.  It  would  seem  from  the  results  of  this  kind  of 
investigation  that  it  is  impossible  to  assign  any  absolute  value   to  the 

1   Marev,  op.  cit.,  p.  357.  2  Op.  cit.,  vol.  ii.  p.  55. 

3  LudVig's  Arbeiten.     Leipzig,  1875.  *  Journal  of  Physiology,  1880,  vol.  ii.  p.  223. 


358  THE    CAPILLARIES. 

pressure  of  the  blood  in  the  capillaries,  but  that  the  pressure  varies 
according  to  the  volume  of  the  capillaries. 

While  there  can  be  no  doubt  that  the  heart  is  the  main  cause  of  the 
circulation,  there  are  also  good  reasons  for  believing  that  there  are  other 
conditions  than  the  contractile  force  of  the  heart  and  the  arteries  which 
influence  the  flow  of  the  blood  through  the  capillaries.  As  is  well 
known,  in  plants,  and  in  many  of  the  lower  animals,  the  nutrient  fluid 
is  carried  to  all  parts  of  the  system  in  the  absence  of  a  heart ;  analogy 
would  lead  us  to  expect,  therefore,  that  there  must  exist  in  the  higher 
animals  a  similar  force,  a  capillary  power,  so  to  speak,  which  may  be 
masked  by  the  influence  of  a  centralized  powerful  heart.  This  so-called 
capillary  force  appears  to  be  inseparably  connected  with  the  nutritive 
and  secretory  processes,  since  what  increases  or  diminishes  the  one  influ- 
ences in  the  same  way  the  other.  The  idea  of  such  a  force  is  not  a  new 
one,  it  is  embodied  in  the  ancient  aphorism  of  TJbi  stimulus  ibi  fluxus. 
That  some  such  power  exists  in  the  capillaries  of  the  higher  animals, 
independent  of  the  action  of  the  heart,  is  shown  by  the  fact  that  the 
blood  will  still  continue  to  flow  in  the  capillaries  after  the  heart  has 
ceased  beating,  while,  on  the  other  hand,  the  heart  may  still  be  acting, 
and  yet  the  circulation  will  entirely  cease  in  the  capillaries  of  certain 
parts.  Local  variations  in  the  volume  of  the  blood  flowing  through  the 
capillaries,  the  reversal  of  the  current  in  the  vessels,  changes  in  their 
diameter,  so  often  observed  in  the  healthy  living  animal,  cannot  be 
attributed  to  the  action  of  the  heart,  but  are  evidently  due  to  an  influ- 
ence engendered  in  the  walls  of  the  capillaries  themselves,  or  in  the  sur- 
rounding tissues. 

Many  pathological  facts  might  be  mentioned  as  illustrations  of  such 
local  variations.  Thus,  in  cases  of  spontaneous  gangrene  of  the  lower 
extremities,  although  the  heart  may  be  beating,  and  the  arteries  and  the 
capillaries  entirely  pervious,  nevertheless  the  blood  will  not  flow  through 
the  capillaries,  the  stopping  of  the  circulation  being  due  to  a  difference 
in  the  capillaries  themselves,  and  the  surrounding  tissues.  Again,  it 
has  often  been  demonstrated,  at  least  in  cold-blooded  animals,  that  the 
flow  of  blood  through  the  capillaries  will  continue  even  after  the  heart 
has  been  completely  excised.  While  this  cannot  be  shown  experiment- 
ally upon  a  hot-blooded  animal,  the  shock  experienced  being  so  great 
from  so  severe  an  operation,  nevertheless  nature  often  does  in  a  gradual 
way  what  we  cannot  show  by  experiment.  Thus,  as  is  well  known,  after 
the  general  death  of  the  body,  urine  has  flowed  from  the  ureters,  sweat 
exuded  from  the  skin,  and  glands  have  secreted.  Such  phenomena  can 
only  be  explained  on  the  supposition  that  the  blood  has  continued  to 
flow  through  the  capillaries  after  the  heart  has  ceased  to  beat.  It  is 
well  known,  since  the  observations  of  Dr.  Bennett  Dowler1  upon  the 
bodies  of  individuals  who  have  died  of  yellow  fever,  that  the  veins  often 
become  so  distended  with  blood  within  a  few  minutes  after  death  that 
when  opened  the  blood  will  spurt  from  them  a  foot  or  more.  The  tonicity 
of  the  arteries  can  hardly  be  supposed  to  account  for  this  venous  jet,  or 
for  the  empty  condition  in  which  the  arteries  are  almost  always  found 

l  Researches  on  the  Capillary  Circulation,  New  Orleans  Med.  and  Surg.  Journal,  1849. 


CAPILLARY    FORCE.  359 

after  death — but  to  some  additional  force  in  the  capillaries  themselves. 
Further,  we  shall  see,  when  we  come  to  study  the  development  of 
the  circulation  in  the  embryo,  that  the  blood  begins  to  move  first  in  the 
area  vasculosa,  that  is,  toward  the  heart,  not  from  it,  and  that  the  heart 
itself  consists  of  cells  so  loosely  attached  together  that  it  can  be  scarcely 
supposed  to  contract  with  force  enough  to  account  for  the  primitive  circu- 
lation. Indeed,  in  the  case  of  twins,  it  has  been  noticed  that  the  heart 
in  one  of  the  two  has  even  never  been  developed  during  the  whole  period 
of  embryonic  life,  and  yet  the  greater  part  of  the  organs  were  well 
formed.  It  might  be  supposed  that  the  circulation  in  the  twin  in  which 
the  heart  was  absent  was  maintained  by  the  heart  of  the  one  in  which 
it  was  present,  the  blood  from  the  one  twin  passing  to  the  other  through 
the  vessels  of  the  placentas,  which  were  more  or  less  in  contact.  This 
was  shown  by  Dr.  Houston1  to  be  impossible,  at  least  in  the  case  reported 
by  him. 

In  this  connection  the  researches  of  Hvrtl2  are  interesting,  this  emi- 
nent  anatomist  having  shown  that  the  placental  vessels  do  not  commu- 
nicate in  those  cases  where  the  twins  are  of  the  opposite  sex.  The 
facts  of  comparative  anatomy,  experiment,  pathology,  embryology,  all 
harmonize  in  showing  that  there  exists  in  the  capillaries  some  force  inde- 
pendent of  the  heart's  action,  which  aids  the  flow  of  the  blood  through 
them.  It  has  often  been  supposed  that  the  contractility  of  the  capil- 
laries aids  the  flow  of  blood  through  them.  Admitting  that  the  capil- 
laries are  contractile,  this  force  could  only  be  exerted  in  a  rhythmical 
manner  by  alternate  contractions  and  dilatations,  a  kind  of  peristalsis; 
but  no  such  movement  is  observed,  the  blood  flowing  through  the  capilla- 
ries as  if  they  were  glass  tubes.  Further,  it  can  be  experimentally  demon- 
strated that  a  diminution  in  the  diameter  of  the  capillaries,  whether  it 
be  due  to  true  contractility,  or  simply  to  elasticity,  retards  the  flow  of  the 
blood,  the  blood  pressure  rising.  The  capillary  force  cannot,  therefore, 
be  of  such  a  kind.  On  the  other  hand,  the  experiments  of  Weber  and 
Wharton  Jones  have  shown  that  electrical  and  chemical  stimuli  modify 
the  capillary  circulation,  retarding  the  flow  of  the  blood,  and  even  pro- 
ducing complete  stagnation,  and  yet  no  alterations  in  the  diameter  of 
the  capillaries  are  observed,  the  change  being  evidently  of  a  physico- 
chemical  nature.  Such  facts,  as  well  as  those  already  referred  to,  show 
that  there  exists  some  mutual  relation  between  the  blood,  on  the  one 
hand,  and  the  walls  of  the  capillaries  and  the  surrounding  tissues  on 
the  other. 

It  appears,  then,  that  while  the  heart  forces  the  blood  into  and 
through  the  capillaries,  the  rate  at  which  it  flows  through  these  vessels 
will  depend  upon  the  general  nutritive  condition  of  the  parts  supplied 
by  the  capillaries,  and  that  this  capillary  force  can,  under  certain  con- 
ditions, maintain  the  circulation  independently  of  the  heart. 

Prof.  Draper3  suggests  that  the  capillary  force  just  referred  to,  may 
be  of  the  same  character  as  the  force  of  capillary  attraction,  illustrating 
this  view  by  the  following  experiment :  "if  two  liquids  communicating 

1  Dublin  Medical  Journal,  1837.  -  Die  Blutegefasse  der  Menschlichen  Naohgeburt.     Wien,  1870. 

3  Treatise  on  the  Forces  which  produce  the  Organization  of  Plants,  pp.  22,  41.    Physiology,  1878,  p.  131. 


360  THE    CAPILLARIES. 

with  one  another  in  a  capillary  tube,  or  in  a  porous  structure,  have  for 
that  tube  or  structure  different  chemical  affinities,  movements  will  ensue, 
that  liquid  which  has  the  most  energetic  affinity  will  move  with  the 
greatest  velocity,  and  may  even  drive  the  other  liquid  before  it."  Thus, 
it  will  be  noticed  that  if  a  capillary  tube,  containing  gum,  be  immersed 
in  a  vessel  filled  with  water,  that  the  gum  will  rise  in  the  tube,  being 
displaced  by  the  water,  the  water  having  a  greater  affinity  for  the  walls 
of  the  tube  than  the  gum.  These  experimental  conditions  are  realized 
in  the  living  body,  the  fresh  arterial  blood,  on  account  of  its  oxygen 
and  other  nutritive  elements  having  a  greater  affinity  for  the  tissues 
than  the  effete  venous  blood,  hence  the  arterial  blood  will  push  forward 
the  venous  blood  from  the  systemic  capillaries  toward  the  veins.  On 
the  other  hand,  in  the  pulmonary  capillaries  just  the  reverse  obtains, 
the  venous  blood  drives  forward  the  arterial,  since  the  former  has  a 
greater  affinity  for  the  inspired  oxygen  than  the  latter,  in  which  the 
blood  is  already  oxygenated.  According  to  the  same  physical  principle, 
the  portal  blood,  containing  the  same  elements  out  of  which  the  bile  is 
elaborated,  having  a  greater  attraction  for  the  hepatic  cells  than  the 
blood  of  the  hepatic  vein,  the  latter  will  be  driven  out  of  the  hepatic 
capillaries  into  the  hepatic  veins.  Indeed,  there  must  be  a  continual 
movement  going  on  in  every  part  of  the  economy,  each  cell  having  a 
greater  attraction  for  the  blood  containing  its  nourishment  than  for  that 
blood  which  has  nourished  it.  Such  a  movement  undoubtedly  supple- 
ments the  force  of  the  heart. 

The  consideration  of  the  influence  of  the  nervous  system  upon  the 
capillary  circulation,  whether  as  modifying  through  the  vasomotor 
nerves  the  calibre  of  the  arteries,  or  acting  directly  by  changing  the 
nutrition  of  the  parts,  will  be  deferred  for  the  present.  In  concluding 
our  account  of  the  circulation  of  the  blood  it  remains  for  us  now  to  de- 
scribe the  flow  of  the  blood  from  the  capillaries  back  to  the  heart 
through  the  veins. 


CHAPTEK   XXIY. 

THE  VEINS. 

In  observing  the  flow  of  the  blood  through  the  capillaries,  it  will  be 
seen  that  these  vessels  gradually  pass  into  larger  ones,  the  venous  radi- 
cles, which  in  turn  transmit  the  blood  to  the  veins,  the  latter  gradually 
uniting  form  two  large  trunks,  the  venae  cavse,  which,  together  with  the 
coronary  vein,  transmit  the  blood  to  the  right  side  of  the  heart  and  the 
pulmonary  veins  return  it  to  the  left. 

The  venous  system  may  be  regarded  as  consisting  of  two  sets  of  veins, 
a  superficial  set  returning  the  blood  from  the  skin  and  surface  generally, 
and  a  deep  set  which  accompanies  the  arteries. 

The  veins  diifer  in  their  structure  from  the  arteries  rather  in  degree 
than  in  kind,  consisting  essentially  like  the  latter  of  three  coats,  an 
internal  epithelial,  a  middle  elastic  muscular,  and  an  external  fibrous. 
The  internal  coat,  consisting  of  subepithelial  and  elastic  layers,  is  a  con- 
tinuation of  the  capillary,  which  we  have  seen  is  a  prolongation  of  the 
internal  coat  of  the  artery.  Indeed,  it  is  practically  impossible  to  say 
exactly  where  the  artery  ends  and  the  capillary  begins,  or  where  the 
capillary  ends  and  the  vein  begins,  the  transition  from  the  one  set  of 
vessels  to  the  other  is  so  gradual. 

The  middle  coat,  containing  the  vasa  vasorum,  consists  principally  of 
fibrous  tissue  disposed  in  a  longitudinal  direction  with  some  elastic 
fibres,  and  of  a  circular  coat  of  elastic  and  muscular  fibres  mingled  with 
some  fibrous  tissue.  The  external  coat,  like  that  of  the  artery,  consists 
of  white  fibrous  tissue,  and  in  the  largest  veins,  particularly  in  those  of 
the  abdominal  cavity,  there  are  a  few  unstriped  muscular  fibres  arranged 
in  a  longitudinal  direction.  In  the  veins  near  the  heart  a  few  striated 
muscular  fibres  are  present,  derived  principally  from  those  of  the  auricle. 
These  fibres  are  particularly  well  developed  in  the  turtle.  In  certain 
situations  in  the  cerebral  sinuses,  etc.,  the  veins  consist  of  little  more 
than  the  internal  coat  with  a  few  longitudinal  fibres.  Generally  the 
veins  adhere  much  more  closely  to  the  surrounding  tissues  than  the 
arteries.  Were  such  not  the  case,  in  many  instances  the  vessels  would 
collapse,  the  walls  not  being  strong  enough  to  resist  external  pressure. 
Bernard  has  called  attention  to  the  importance  of  this  physiologically, 
showing  that  it  is  through  the  intimate  adhesion  of  the  wall  of  the 
superior  vena  cava,  jugular,  subclavian,  etc.,  to  the  surrounding  apon- 
eurotic layers  that  these  vessels  are  kept  open  during  inspiration. 

Many  of  the  larger  veins  are  provided  with  valves  resembling  those 
of  the  aorta  and  pulmonary  artery  (Fig.  205).  They  are  usually  found 
in  pairs,  and  consist  of  crescentic  semilunar  doublings  or  folds  of  the 
internal  coat  or  lining  membrane  of  the  vein  strengthened  with  some 
included  fibro-elastic  tissue.     These  valves  are  usually  situated  opposite 


362 


THE    VEINS. 


Fig.  205. 


Diagrams  showing  valves  of  veins  A. 
Part  of  a  vein  laid  open  and  spread  out,  with 
two  pairs  of  valves.  B.  Longitudinal  section 
of  a  vein,  showing  the  apposition  of  the  edges 
of  the  valves  in  their  closed  state  C.  Portion 
of  a  distended  vein,  exhibiting  a  swelling  in 
the  situation  of  a  pair  of  valves.     (Quain.) 


each  other  and  project  obliquely  into  the  cavity  of  the  vein  or  in  the 
direction  of  the  current.  The  convex  portion  of  each  valve  is  attached 
to  the  side  of  the  vein,  the  concave  edge  is  free  and  points  toward  the 
heart.      Behind  each  valve  the  vein  is  dilated  into  a  sort  of  pouch  or 

sinus  (Fig.  205)  which  prevents  the 
valves  adhering  to  the  sides  of  the  vein 
as  the  blood  passes  between  them  to- 
ward the  heart.  When,  however,  the 
blood  passes  backward  toward  the  per- 
iphery, as  we  shall  see  it  does  under  cer- 
tain circumstances,  it  enters  the  sinus 
and  getting  behind  the  valves  presses 
them  toward  each  other  and  together 
and  so  prevents  any  further  reflux. 

The  valves  are  so  disposed,  there- 
fore, that  while  they  offer  no  obstacle 
to  the  flow  of  the  blood  toward  the 
heart  they  effectually  prevent  to  any 
extent  motion  in  the  reverse  direction. 
The  valves  are  most  abundant  in  the 
upper  and  lower  extremities ;  the  sig- 
nificance of  this  we  shall  see  presently. 
The  importance  of  the  valves  in  the 
veins,  though  great  physiologically, 
must  not  be  exaggerated,  since  many  veins  have  no  valves.  Thus  in 
man  at  least,  however  it  may  be  in  other  mammals,  there  are  no  valves 
in  the  vena3  cavse,  in  the  innominate,  pulmonary,  portal,  hepatic,  renal, 
uterine,  ovarian,  spinal,  and  iliac  veins.  Further,  there  are  very  few 
valves  in  the  veins  of  birds,  reptiles,  and  fishes,  and  with  the  exception 
of  that  in  the  aorta,  so-called,  of  the  eolis,  a  small  nudibranchiate  mol- 
lusk,  there  are  none  in  the  veins  of  the  invertebrata.  It  is  evident, 
therefore,  that  the  valves  are  not  indispensable  in  the  maintenance  of 
the  circulation. 

The  veins  possess  a  considerable  amount  of  elasticity.  This  is  shown 
by  the  jet  of  blood  which  follows  the  puncture  of  a  distended  vein  made 
in  a  portion  of  the  vessel  between  two  ligatures.  The  veins  through 
their  unstriped  muscular  fibres  are  also  contractile,  their  calibre  being 
slowly  and  gradually  diminished  through  the  application  of  electrical 
and  other  stimuli.  The  contractility  of  the  veins  can  be  more  readily 
demonstrated  in  the  frog  and  other  batrachians  than  in  mammals.  The 
veins,  like  the  arteries,  are  supplied  and  influenced  by  the  vasomotor 
nerves  though  not  to  the  same  extent.  The  veins,  though  much  thinner 
and  apparently  weaker,  will  usually  resist  a  greater  pressure  than  the 
arteries.  Thus  it  was  shown  in  the  last  century  by  Wintringham1 
that  a  greater  force  was  required  to  rupture  the  vena  cava  and  portal 
vein,  for  example,  than  the  aorta.  The  method  by  which  this  was  de- 
termined is  as  follows  :  An  iron  siphon  containing  a  sufficient  quantity 
of  mercurv,  to  which  was  screwed  a  glass  gauge,  and  which  communi- 


1  An  Experimental  Inquiry  on  some  parts  of  the  animal  structure,  pp.  49,  73,  179,  212.    London,  1740. 


CAPACITY    OF    VENOUS    SYSTEM.  363 

cated  freely  with  a  condensing  syringe,  was  adapted  to  the  artery  or 
vein  whose  strength  was  to  be  tested.  When  the  air  in  the  sealed  top 
of  the  gauge  was  compressed  with  a  pressure  equal  to  138  pounds,  the 
aorta  in  the  ram,  for  example,  burst,  the  vena  cava  of  the  same  animal, 
however,  resisting  until  the  pressure  amounted  to  176  pounds,  or  about 
4.8  atmospheres.  The  strength  of  the  portal  vein  was  even  greater 
than  that  of  the  vena  cava,  a  pressure  of  nearly  5  atmospheres  being 
required  to  rupture  it.  Wintringham,  however,  notices  that  the  arteries 
of  glands  are  stronger  than  the  corresponding  veins.  Thus  the  splenic 
vein  burst  under  a  pressure  of  about  1  atmosphere,  equal  to  a  pressure  of 
about  34  pounds,  the  artery  supporting  a  pressure  of  6  atmospheres,  or 
150  pounds.  These  experiments  of  Wintringham  were  very  numerous 
and  extended,  being  made  upon  the  vessels  of  men,  pigs,  sheep,  dogs, 
etc.,  and  in  the  main  have  been  confirmed  by  the  later  ones  of  Davy.1 
The  significance  of  the  greater  strength  of  the  veins,  as  compared  with 
that  of  the  arteries,  usually  observed,  becomes  at  once  apparent  when 
we  reflect  upon  the  different  amounts  of  pressure  to  which  the  two  sets 
of  vessels  are  subjected.  We  have  seen  that  the  pressure  all  throughout 
the  arterial  system  is  about  the  same,  that  the  force  of  the  heart  is 
practically  constant,  and  that  the  arterial  pressure  is  being  constantly 
relieved  by  the  flow  into  the  capillaries.  On  the  other  hand,  the  pressure 
into  the  veins  varies  according  to  the  amount  of  blood  delivered  to 
them  by  the  capillaries,  regurgitation  to  any  extent  is  impossible  through 
the  presence  of  the  valves,  while  the  heart  offers  a  very  restricted  outlet. 
Thus  portions  of  the  venous  system,  from  pressure  in  the  veins,  absorp- 
tion of  fluid,  accumulation  through  gravity,  etc.,  are  subject  to  very  great 
variations  in  pressure  which  the  tenacity  of  their  Avails  usually  enables 
them  to  resist  without  injury.  The  ill  effects  of  over-distention  are, 
nevertheless,  seen  only  too  frequently  in  varicose  veins,  etc.  The  capacity 
of  the  venous  svstem  is  much  Greater  than  that  of  the  arterial — according 
to  Haller,2  in  the  ratio  of  2.2  to  1.  Usually  a  vein  when  distended 
contains  more  blood  than  the  adjacent  artery;  the  pulmonary  arteries, 
however,  about  equal  the  corresponding  veins  in  capacity.  Many 
arteries,  like  those  of  the  extremities,  are  accompanied  by  more  than 
one  vein,  and  some,  like  the  brachial  and  spermatic,  have  more  than  two; 
the  superficial  veins,  further,  have  no  corresponding  arteries.  Never- 
theless, any  estimate  of  the  capacity  of  the  venous  system  as  compared 
with  that  of  the  arterial  can  be  only  approximate,  since  the  quantity  of 
blood  flowing  through  the  veins  must  vary  according  to  the  pressure  and 
velocity  of  the  flow,  the  amount  passing  through  the  capillaries,  the  state 
of  the  digestion  and  respiration,  etc.  Indeed,  the  most  striking  char- 
acteristic of  the  venous  system  is  the  variability  of  the  amount  of  blood 
it  contains. 

One  of  the  most  important  features  of  the  venous  system  is  the 
numerous  anastomoses  between  the  veins,  which,  it  will  be  remembered, 
are  exceptional  in  the  case  of  the  arteries.  There  are  always  numer- 
ous such  channels  by  which  the  blood  finds  a  ready  route  back  to  the 

1   Iti'si'tiivhi's,  Physiological  and  Anatomical,  vol.  i    ]>.  441. 
-  Elementa  Physiologice,  tonms  1.  p    133. 


364 


THE    VEINS 


heart,  so  that,  if  the  flow  be  obstructed  in  one  vein,  an  equally  easy 
way  is  offered  by  another.  The  anastomoses  between  the  veins  are  very 
important,  enabling  these  vessels  to  accommodate  themselves  to  the 
great  variation  in  the  quantity  of  blood  flowing  into  them  to  which  they 
are  subject.  The  anastomoses,  together  with  the  valves,  serve  to  pro- 
vide against  any  obstacle  to  the  freedom  of  the  capillary  How.  the  im- 
portance of  which  we  have  already  seen.  In  addition  to  the  anasto- 
motic branches  usually  described  may  be  mentioned  others  less  well 
known,  such  as  those  connecting  the  vena  cava  and  portal,  like  the 
subperitoneal  vessels,  the  oesophageal  and  hemorrhoidal,  the  diaphrag- 
matic connecting  the  hepatic  circulation  with  the  vena  cava.  The 
importance  of  these  anastomotic  vessels  becomes  evident  when  the  veins 
usually  returning  the  blood  to  the  heart  are  obstructed.  Under  such 
circumstances,  they  become  greatly  enlarged,  as  is  well  known  to  the 
pathological  anatomist. 

When  it  is  remembered  that  the  arterial  pressure  gradually  diminishes 
as  we  recede  from  the  heart  to  the  periphery,  it  might  be  expected  by 
the  time  that  the  blood  has  passed  through  the  capillaries  and  reached 
the  veins,  that  it  would  exert  but  little  pressure  on  the  latter.  This 
has  been  experimentally  shown  to  be  the  case.  Thus,  according  to 
Volkmann,1  while  the  pressure  in  the  carotid  artery  of  the  calf  amounts 
to  165  mm.  (6.6  inches),  and  that  of  the  metatarsal  to  146  mm.  (5.8 
inches),  the  pressure  in  the  metatarsal  vein  was  only  27.5  mm. 
(1.1  inch).  Indeed,  at  times,  the  pressure  in  the  vein  is  actually  less 
than  that  of  the  atmosphere.  This  is  well  seen  in  the  experiment  of 
Barry,2  which  consists  in  introducing  into  the  jugular  vein  of  a  horse 
or  dog  a  bent  tube,  of  which  the  opposite  end  is  immersed  in  a  vase 
of  colored  liquor.  With  each  inspiration  the  liquid  rises  in  the  tube, 
falling  again  with  each  expiration.  While  the  pressure  is  diminished  in 
the  jugular  and  hepatic  veins  during  inspiration,  on  the  other  hand,  in  the 
remaining  abdominal  veins  it  is  increased ;  the  latter  being  compressed  by 
the  viscera  through  the  falling  of  the  diaphragm,  an  obstacle  is  offered  to 
the  flow  of  the  blood,  and  the  pressure  rises.  The  lowering  of  the  thoracic 
pressure  during  inspiration  is  shown  graphically  by  Fig.  206,  in  which  the 

Fig.  20fi. 


Trace  of  blood  pressure  in  hepatic  vein.     E.  Trace  of  respiration,  taken  with  pneumograph. 

(3IAEF.Y  ) 

depression  of  the  upper  trace  Pr.V.  H,  representing  the  blood  pressure, 
coincides  with  that  of  the  lower  trace  R,  representing  the  respiratory 

i  Die  Haemodynamik,  S.  173. 

-  Recherches  experimeutalea  sur  les  causes  du  mouvement  du  sang  dans  lea  veines.     Paris,  1825. 


VENOUS   PRESSURE. 


365 


movement.     The  increase  in  the  pressure  in  the  abdominal  vein  during 
inspiration  is  well  shown  by  Fig.  207,  in  which  the  depression  in  the 


Fig.  207. 


Pr  V.  P. 


Trace  of  blood  pressure  in  port.il  vein.     R.  Trace  of  respiration,  taken  with  pneumograph. 
(Marey.) 


lower  trace  R,  due  to  inspiration,  coincides  with  the  elevation  of  the 
upper  trace  Pr.V.  P.,  due  to  the  increase  in  the  blood  pressure.  On  the 
other  hand,  during  the  expiration,  the  pressure  in  the  abdominal  veins 
is  diminished,  the  viscera  no  longer  compressing  these  vessels,  the 
diaphragm  being  elevated.  If,  however,  the  expiration  be  violent,  then 
the  contraction  of  the  abdominal  walls  compressing  the  viscera  and  the 
veins  will  increase  the  pressure. 

The  weight  of  the  blood  influences  the  pressure  in  the  veins.  Thus, 
the  blood  flows  more  readily  to  the  heart  in  the  veins  of  the  upper 
extremity  when  the  limb  is  elevated  than  when  hanging  down.  The 
varicose  condition  often  observed  in  the  veins  of  the  lower  extremities 
illustrates  the  effect  of  the  venous  pressure  due  to  the  weight  of  the 
blood.  While  the  pressure  in  the  veins  is  ordinarily  very  slight,  at 
times  it  is  so  much  increased  as  to  give  rise  to  a  pulsation — the  venous 
pulse.  This  may  be  due  to  an  obstruction  in  the  veins,  or  to  an  in- 
crease in  the  quantity  of  blood  flowing  in  these  vessels.  Thus,  if  all 
the  venous  blood  in  a  part  be  forced  to  return  to  the  heart  by  a 
single  vein,  as  can  be  effected  by  ligating  all  the  adjacent  veins,  as  in 
the  experiment  of  Poisseuille,1  the  pressure  on  the  vein  will  be  so  much 
increased  as  to  equal  that   of  an  artery  of  like  size,  the  force  of  the 

Fig.  208. 


f.O 


•         E 

O.  Trace  uf  auricl 


E 

V.  Trace  of  ventricle.     &'  0.  Systole  of  auricle, 
by  abdominal  irritation  and  elevation  of  pressure 


E.  Arrest  of  heart  in  diastole 
(Marey.) 


heart  being  exerted  upon  the  blood  of  a  single  vein,  and  therefore 
concentrated  instead  of  as  ordinarily  upon  several  and,  therefore,  dif- 
fused and  dissipated.  During  the  ventricular  systole,  and,  therefore, 
when  the  tricuspid  valve  is  closed,  the  flow  of  the  blood  through  the 
auricle  into  the  ventricle  is,  for  the  instant,  stopped,  the  pressure  in  the 

1  Magendie  :  Lecons  sur  les  phenomenee  physique  de  la  vie,  tome  iii.  p.  181.     Paris,  1837. 


366  THE     VEINS. 

auricle  and  vena  cava  is  then  momentarily  increased.  If,  however,  the 
beating  of  the  heart  cease  in  diastole,  as  is  the  ease  utter  excitation  of  the 
pneumogastric  nerve,  the  blood  flows  into  the  ventricle,  which,  being  filled, 
receives  then  no  more  blood  from  the  auricle;  the  blood  continuing  to  flow 
will  iill  the  auricle  and  other  vena  cava  until  these  parts,  being  dis- 
tended, the  pressure  will  be  very  much  increased.  This  can  be  experi- 
mentally shown  in  the  frog  by  means  of  the  double  myograph.  By 
comparing  the  traces  (Fig.  208)  of  the  auricle  and  ventricle,  taken 
simultaneously,  it  will  be  observed  that  the  pressure  in  the  auricle  is 
increased  during  the  arrest  in  diastole  of  the  heart's  action  through 
stimulation  of  the  pneumogastric  nerve. 

There  is  also  observed  at  times  in  certain  veins,  the  external  jugular, 
for  example,  a  regurgitant  venous  pulse.  This  is  due  to  a  reflux  of 
blood  from  the  right  side  of  the  heart,  and  is  synchronous  with  the 
movement  of  expiration,  there  being  no  obstacle  at  the  mouth  of  the 
vein  to  the  return  of  the  blood  if  the  expiratory  movement  be  exagger- 
ated. The  regurgitant  venous  pulse  can  be  often  noticed,  however.  It 
is  usually  evidence  of  insufficiency  of  the  tricuspid  valve,  or  some  other 
pathological  condition.  We  have  seen  that  the  veins  are  both  larger 
and  more  numerous  than  the  arteries,  and  as  the  volume  of  blood 
wdiich  passes  in  a  given  moment  through  any  part  of  the  vascular  sys- 
tem is  the  same,  it  follows  that  the  blood  ought  to  flow  more  slowly 
through  the  veins  than  the  arteries.  If  the  venous  system  be  con- 
sidered twice  as  capacious  as  the  arterial,  then  the  blood  should  flow 
half  as  slowly  through  the  veins  as  the  arteries.  Experiment  is  in 
harmony  with  theoretical  considerations,  it  having  been  shown  by 
Volkmann1  that  the  blood  flows  in  the  jugular  vein  of  the  dog  at  the 
rate  of  225  mm.  (9  inches)  in  a  second,  that  of  the  carotid  artery  in 
the  same  animal  being  329  mm.  (13  inches).  The  conditions  that  ii>- 
fluence  the  rapidity  of  the  flow  in  the  veins,  however,  vary,  so  that  it 
is  impossible  to  fix  upon  any  average  rate. 

There  can  be  no  doubt  that  the  flow  of  the  blood  in  the  veins  is  essen- 
tially due  to  the  contractile  force  of  the  heart.  Thus,  according  to 
Sharpey,2  the  hepatic  veins  can  be  filled  with  an  injection  of  defibri- 
nated  blood  thrown  into  the  aorta  under  a  pressure  of  3.6  cm.  (3.5  in.) 
of  mercury,  which  is  only  about  half  that  of  the  normal  arterial  pressure. 
The  experiment  of  Magendie,3  in  which  the  femoral  vein  was  ligated 
and  opened,  the  blood  jetting  forth,  the  jet  and  flow  gradually  ceasing 
with  compression  of  the  femoral  artery,  proved  the  competency  of  the 
heart  to  force  the  blood  through  the  capillaries  into  the  veins,  the  force 
of  the  artery  causing  the  jet  from  the  vein  being,  as  we  have  seen,  only 
the  reaction  from  its  previous  distention,  due  to  the  preceding  ventricular 
systole.  While  the  heart  is  the  main  cause  of  the  venous  flowT,  as  in 
the  case  of  the  capillaries,  there  are  other  causes  which  assist  in  pro- 
moting this  movement.  Thus,  muscular  contraction,  by  compressing 
the  veins,  forces  the  blood  in  these  vessels  toward  the  heart,  regurgita- 
tion being  impossible  through  the  action  of  the  valves.     Hence,  the 

i  Op.  cit.,  S    195.  -  Todd  and  Bowman  :   Phys.  Anat,  1856,  vol.  ii.  p.  350. 

3  Journal  de  Physiologie,  1821,  t.  i.  3. 


CAUSES    OF    FLOW    OF    BLOOD    IN    VE1XS.  367 

significance  of  the  fact  of  valves  being  so  much  more  numerous  in  the  veins 
of  the  muscles  than  in  the  cavities  of  the  body,  the  veins  .in  the  latter 
situation  not  being  subjected  to  the  same  kind  of  compression  as  those 
between  and  within  the  muscles.  It  must  be  mentioned,  however,  in 
order  that  too  much  stress  be  not  laid  upon  this  connection  between  mus- 
cular action  and  the  presence  or  absence  of  valves,  that  in  some  cases,  as 
in  the  portal  vein  of  the  horse  and  in  the  mesenteric  veins  of  the  reindeer, 
for  example,  valves  do  exist.  In  order  that  muscular  contraction  shall 
assist  the  flow  of  the  blood  through  the  veins,  not  only  must  valves  exist 
to  prevent  regurgitation,  but  the  contractions  of  the  muscles  must  be  inter- 
mittent, as  during  the  period  of  repose  after  a  contraction  the  vein  has 
time  to  fill  up  again  with  blood'that  will  be  forced  forward  with  the  fol- 
lowing contraction.  This  alternate  filling  up  and  emptying  of  the  mus- 
cular veins  i<  also  of  advantage  from  a  nutrition  point  of  view,  since,  as 
we  shall  see,  the  activity  of  the  muscle  depends  upon  the  free  and  rapid 
circulation  of  the  blood  through  its  substance.1  The  influence  of  mus- 
cular contraction  in  accelerating  the  venous  flow  is  well  known  to  every 
surgeon,  the  jet  from  a  vein  increasing  in  force  with  the  contraction  of 
the  muscles  below  the  opening.  The  amount  of  increase  of  pressure  in 
the  veins,  due  to  muscular  contraction,  can  be  experimentally  deter- 
mined by  placing  a  vein  in  communication  with  a  mercurial  manometer, 
and  observing  the  variations  in  the  height  of  the  mercury  due  to  mus- 
cular contraction,  whether  produced  naturally  or  by  movements  of  the 
animal,  or  induced  by  stimuli.  In  the  experiments  of  Magendie2  and 
Bernard3  the  mercury  rose  50  mm.  (2  in.)  above  the  normal  venous 
pressure  after  a  general  muscular  contraction.  However  important 
muscular  action  may  be  in  promoting  the  flow  of  venous  blood,  that  it 
is  not  indispensable,  is  shown  by  the  fact  that  the  blood  flows  through 
the  veins  in  parts  that  are  paralyzed.  When  we  come  to  study  the 
mechanism  of  respiration  we  shall  see  that  the  thoracic  walls  alternately 
recede  and  approach  synchronously  with  the  rise  and  fall  of  the  dia- 
phragm in  the  production  of  the  inspiratory  and  expiratory  movements. 
It  will  become  apparent,  then,  that  the  rarefaction  of  the  air  within 
the  thorax  during  its  dilatation,  which  causes  the  entrance  of  the 
external  air  into  the  trachea  and  the  lungs  in  inspiration,  must  exercise 
a  similar  suction  influence  upon  the  blood  flowing  in  the  large  and 
extensible  veins  emptying  into  the  heart.  This  action  of  the  thoracic 
Avails  will  have,  however,  little  or  no  influence  upon  the  blood  of  the 
aorta,  its  walls  being  too  resisting  to  give  to  any  extent.  The  suction 
force  thus  exerted  by  the  thorax  during  inspiration  upon  the  venous 
blood  flowing  toward  the  heart  extends  also,  to  a  certain  extent,  to  the 
veins  situated  outside  of  the  thorax.  The  fact  already  alluded  to,  and 
noticed  particularly  by  Bernard,4  of  the  walls  of  the  superior  vena  cava, 
jugular,  subclavian,  etc.,  adhering  to  the  surrounding  tissues  by  apo- 
neurotic layers,  and  so,  being  kept  open,  evidently  favors  the  flow  of 
blood  through  these  veins  toward  the  heart  during  inspiration.  Were 
it  not  for  such  a  disposition  the  veins  would  entirely  collapse  through 

1  ililne  Edwards:  Pbysiologie,  tome  iv.  p.  310.  -  Op.  cit.,  tome  iii.  p.  162. 

3  Lecons  sur  la  Phys.  et  Path   du  S.vsteme  Veueux,  tome  i.  p.  285.     Paris,  1858. 

4  Pbysiologie,  tome  iv.  p.  9. 


368  THE    VEINS. 

atmospheric  pressure.  The  hepatic  veins  also  adhere  to  such  an  extent 
to  the  tissue  of  the  liver  that  when  divided  they  remain  open,  and  the 
inferior  vena  cava,  in  which  these  veins  terminate,  is  further  surrounded 
by  fibrous  expansions,  which  fix  it  to  the  margin  of  the  diaphragm 
through  which  it  passes  on  its  way  to  the  heart.  The  anatomical  rela- 
tions of  the  parts  are  such,  therefore,  as  to  favor  the  flow  of  the  venous 
blood  from  the  liver  toward  the  heart  during  the  contraction  and 
consequent  fall  of  the  diaphragm  incidental  to  inspiration.  That  such 
a  suction  force  is  really  exerted  upon  the  venous  blood  during  inspi- 
ration by  the  thorax  is  seen  whenever  a  violent  inspiratory  effort  is 
made.  At  such  times  the  veins  at  the  lower  pari  of  the  neck  are  seen 
to  empty  themselves  completely.  The  experiment  of  Barry,  already 
described,  illustrates  the  power  of  this  suction  force,  the  fluid  being 
sucked  up  into  the  glass  tube  introduced  into  the  jugular  vein  with 
each  inspiration.  Barry,  however,  exaggerated  the  influence  of  this 
suction  force.  That  it  does  not  ordinarily  extend  much  beyond  the 
thorax  can  be  proved  by  introducing  the  glass  into  the  anterior  end  of 
the  jugular  vein,  when  little  or  no  variation  will  be  observed  in  the 
level  of  the  liquid  with  the  inspiratory  effort. 

Death  from  the  entrance  of  air  into  the  veins  is  due  to  the  suction 
force  exerted  by  the  thorax  during  inspiration.  The  consideration  of 
such  cases  belongs  to  pathology,  but  it  may  be  mentioned  here  inci- 
dentally that  the  cause  of  death  is  due  to  the  blood  becoming  frothy  or 
spumous  when  mixed  with  air,  and  in  that  condition  will  not  circulate 
through  the  pulmonary  capillaries,  hence  the  left  side  of  the  heart  is 
found  on  post-mortem  examination  empty. 

It  might  naturally  be  supposed  that,  as  inspiration  favors  the  flow  of 
the  venous  blood  toward  the  heart,  the  expiration  would  oppose  it. 
Were  expiration  due  solely  to  the  contraction  of  the  thoracic  walls, 
such  would  be,  at  least  to  a  certain  extent,  the  case,  but,  as  we  shall  see, 
the  air  is  expelled  during  expiration  from  the  lungs  to  a  great  extent 
through  the  elasticity  of  the  organs  themselves,  and,  as  Milne  Edwards1 
suggests,  this  action  of  the  lungs,  so  far  from  compressing  the  veins 
near  the  heart,  tends  to  dilate  them.  A  part  of  the  pressure  due  to 
contraction  of  the  thoracic  walls  that  would  otherwise  compress  the 
veins  is,  therefore,  neutralized  by  the  elasticity  of  the  lungs.  It  can 
be  shown  experimentally  by  the  manometer,  as  the  above  considera- 
tion would  lead  us  to  expect,  that  the  effect  due  to  inspiration  upon  the 
flow  of  the  venous  blood  far  exceeds  that  of  expiration.  The  valves, 
further,  while  offering  no  obstacle  to  the  flow  of  the  blood  during 
inspiration,  prevent,  to  any  extent,  regurgitation  during  expiration. 
Thus,  if  the  manometer  be  placed  in  the  internal  jugular  vein  above 
the  valves,  the  effect  of  inspiration  is  the  same  as  when  placed  below 
them,  but  in  the  first  case  the  reflux  during  expiration  amounts  to 
nothing.  If  expiration  be  violent,  however,  then  the  reflux  may  be 
considerable,  thus  the  veins  of  the  neck  during  singing  or  prolonged 
speech  are  seen  to  swell  up,  and  when  any  effort  is  made  in  which  the 
glottis  is  closed.     The  dilatation  of  the  thorax    has    but  little  effect 

1  Op.  cit.,  tome  iv.  p.  419. 


RAPIDITY    OF    THE    CIRCULATION.  o69 

upon  the  blood  flowing  in  the  great  veins  of  the  abdomen  on  account  of 
the  flaccidity  of  their  walls,  but  the  diaphragm  falling  during  inspiration 
compresses  the  viscera,  and  they  in  turn  pressing  upon  the  vena  cava 
and  its  branches,  force  the  blood  toward  the  heart,  regurgitation 
toward  the  extremities  being  prevented  through  the  closing  of  the 
valves.  With  the  rise  of  the  diaphragm  the  pressure  upon  the  vena 
cava  will  be  relieved,  and  the  blood  will  rapidly  flow  into  it  again  from 
the  extremities.  Should  the  expiration,  however,  be  labored  or  violent, 
and  the  abdominal  walls  contract,  then  the  pressure  exerted  upon  the 
viscera  would  be  an  obstacle  to  the  flow  of  the  venous  blood  from  the 
extremities.  In  order  to  appreciate  the  influences  of  respiration  upon 
the  flow  of  the  venous  blood,  as  seen  from  what  has  just  been  said,  we 
must  carefully  consider  the  conditions  of  the  inspiration  and  expiration, 
as  the  same  cause  may,  under  different  circumstances,  produce  exactly 
the  opposite  effect.  On  the  whole,  respiration  favors  the  flow  of  the 
venous  blood  from  the  periphery  to  the  heart,  and,  as  we  shall  see  here- 
after, the  flow  of  the  arterial  blood  from  the  heart  to  the  periphery. 

The  contractility  with  which  the  veins  are  endowed  assists  somewhat 
in  the  lower  animals  the  flow  of  the  blood.  This  influence  is  limited 
in  man.  however,  to  the  large  veins  near  the  heart,  and  is  even  there 
very  slight.  Gravity,  while  favoring  the  flow  of  the  venous  blood  from 
parts  above  the  heart,  opposes  that  from  below.  While  muscular  action, 
respiration,  contractility,  gravity,  etc..  no  doubt  at  times  favor  the  flow 
of  the  venous  blood  toward  the  heart,  it  must  not  be  forgotten  that  all 
these  conditions  are  only  supplementary  to  the  force  of  the  heart,  this 
being  sufficient  to  force  the  blood  throughout  the  entire  vascular  system. 
Having  described  the  general  manner  in  which  the  blood  flows  through 
the  system,  we  might  now  consider  the  peculiarities  presented  by  the 
circulation  in  the  lungs,  liver,  brain,  erectile  tissues,  etc.  We  will  defer, 
however,  our  account  of  the  circulation  in  these  organs  until  we  take  up 
their  functions.  We  have  seen  that  the  velocity  of  the  blood  varies 
considerably  in  the  different  parts  of  the  vascular  system,  being  greatest 
in  the  large  arteries,  least  in  the  capillaries,  and  intermediate  between 
these  extremes  in  the  veins,  so  far  as  can  be  estimated. 

It  remains  for  us  nowT  to  determine  if  possible,  the  general  rapidity 
of  the  circulation ;  that  is,  the  period  necessary  to  complete  the  entire 
circuit,  or  the  time  that  elapses  during  which  a  particle  of  blood  passing 
out  of  the  left  ventricle  traverses  the  arterial  capillary  and  venous  sys- 
tems, returning  by  the  right  side  of  the  heart  and  lungs  to  the  point 
from  which  it  started. 

The  general  rapidity  of  the  circulation  can  be  easily  and  satisfactorily 
determined  experimentally  in  a  living  animal  in  the  following  manner, 
as  was  first  done  by  Ilering:1  A  harmless  substance,  and  easily  recog- 
nized, is  injected  into  the  jugular  vein,  and  blood  is  drawn  as  quickly 
as  possible,  and  at  intervals,  from  the  corresponding  vein  of  the  oppo- 
site side  of  the  head,  the  time  being  carefully  noted  when  the  substance 
injected  can  be  detected.     Suppose,  for  example,  that  a  solution  of  ferro- 

1  Zeitschrift  fiir  Phvsiologie  Treviranus,  1829,   Baud   iii.  p.  85.     Arcbiv  f.  physiol.  Heilkundi-,  i  -  ,  .. 
Baud  xii.  S.  112;  1832,  Band  v.  S.  58. 

24 


<J7<>  THE     VEINS. 

cyanide  of  potassium  be  injected  into  the  jugular  vein  of  a  rabbit,  the 
salt  can  be  recognized  in  the  blood  of  the  opposite  vein  in  about  seven 
seconds.  In  this  experiment  the  blood  carrying  the  salt  passes  to  the 
right  side  of  the  heart,  then  through  the  lungs  to  the  left  side,  from 
there  into  the  aorta,  and  traversing  the  capillaries  of  the  head  and  face 
returns  back  by  the  jugular  vein  on  the  opposite  side.  If  the  substance 
be  injected  into  the  femoral  vein  the  period  elapsing  is  slightly  longer, 
the  vessels  through  which  the  blood  flows  being  somewhat  longer.  This 
is  more  evident,  however,  in  a  large  animal  like  a  horse,  than  in  a  small 
one  like  a  rabbit.  Ferrocyanide  of  potassium  is  not  only  used  in  this 
experiment  on  account  of  it  being  harmless,  but  from  the  readiness  with 
which  its  presence  can  be  determined  in  the  blood.  Vierordt1  improved 
somewhat  Hering's  method  by  collecting  the  blood  as  it  flowed  at  small 
intervals  in  little  vessels  that  Avere  fixed  to  a  disk  which  revolved  at  a 
fixed  rate,  the  time  being  determined  a  little  more  accurately-  The 
results  of  the  experiments  of  both  these  observers,  however,  agree 
essentially.  According  to  Hering,  the  rapidity  of  the  circulation  in  an 
animal  is  inversely  as  its  size,  and  directly  as  the  rapidity  of  the  action 
of  its  heart.  Thus,  while  in  the  rabbit  we  have  seen  that  the  circula- 
tion from  jugular  to  jugular  is  accomplished  in  6.9  seconds,  in  the  goat, 
dog,  and  horse,  12.8,  15.2,  and  27.3  seconds  are  required  respectively. 

Table  LV. — Rapidity  of  Circulation. 

Ventricle  contracts  in  a  minute 72  times. 

Amount  of  blood  expelled  at  each  contraction     .         .       4  oz. 

Amount  of  blood  passing  through  ventricle  in  a  minute  288  oz. 

16  lbs.  of  blood  in  the  body. 
16  oz.  to  lb. 

256  oz. 

60  :  288  oz.  of  blood  ::  x   sec.  :  256  oz.  of  blood. 
288  x       256  X  60       15360 
15360  =  53_3  seconds_ 


288 


The  general  rapidity  of  the  circulation  in  man  can  be  deduced,  at 
least  approximately,  from  these  experiments,  about  thirty-two  seconds 
probably  being  required  for  the  blood  to  pass  from  jugular  to  jugular. 
On  the  supposition  that  the  heart  beats  seventy-two  times  in  a  minute, 
and  that  at  each  ventricular  systole  four  ounces  of  blood  are  forced  into 
the  aorta,  it  is  evident  that  288  ounces  of  blood  (72  X  4  equals  288) 
pass  through  the  heart  in  one  minute;  but  we  have  seen  that  there  are 
probably,  on  an  average,  only  256  ounces  (16  pounds)  of  blood  in  the 
body.  It  follows,  therefore,  that  less  time  than  one  minute,  or  about 
fifty-three  seconds,  would  be  required  for  the  whole  mass  of  the  blood 
to  pass  through  the  heart.  Table  LV.  shows,  synoptically,  the  calcu- 
lation by  which  this  estimate  is  made.  The  only  objection  to  this 
manner  of  determining  the  time  required  for  the  whole  mass  of  the 
blood  to  pass  through  the  heart  is  the  uncertainty  as  regards  the  exact 

i  Die  Erscheiuungen  und  Gesetze  der  Stromgeschwindigkeiten  des  Blutes,  etc.,  S.  65. 


RAPIDITY    OF     THE     CIRCULATION.  371 

amount  of  blood  in  the  body,  and  of  the  quantity  expelled  with  each 
ventricular  systole.  From  the  nature  of  the  case  these  data  must  be 
variable ;  the  estimate  will  be  true,  however,  within  limits. 

In  confirmation  of  what  has  just  been  said  in  reference  to  the  rapidity 
of  the  general  circulation,  etc.,  it  may  be  mentioned  that  the  time 
elapsing  between  the  introduction  of  a  poison  into  the  blood  and  its 
characteristic  effects  is  about  the  same  as  that  observed  in  the  experi- 
ment of  Hering.  The  influence  of  the  frequency  of  the  heart's  action 
upon  the  rapidity  of  the  general  circulation  must  not  be  lost  sight  of, 
and  this  was  taken  into  consideration  also  by  Hering.  It  was  shown  by 
this  observer,  contrary  to  what  might  have  been  expected,  that  an 
increase  in  the  number  of  the  beats  of  the  heart,  whether  induced  phy- 
siologically or  pathologically,  diminished  the  rapidity  of  the  circulation 
instead  of  increasing,  the  force  of  the  heart  being  diminished  as  the 
number  of  its  beats  was  increased. 


CHAPTER     XXV. 

HISTORY  OF  THE  DISCOVERY  OF  THE  CIRCULATION 
OF  THE  BLOOD. 

In  the  minds  of  every  one  the  circulation  of  the  blood  is  invariably 
and  justly  associated  with  the  name  of  Harvey.  The  discovery  of  the 
circulation,  however,  like  all  other  great  discoveries,  was  not  made 
by  Harvey  alone.  Indeed,  the  discovery  of  the  circulation  of  the 
blood,  in  the  widest  acceptation  of  the  term,  cannot  be  attributed  to  any 
one  person,  age,  or  country.  With  the  name  of  Harvey  must  be  asso- 
ciated those  of  Erasistratus,  Galen,  Servetus,  Csesalpinus,  Malpighi, 
Aselli,  Pecquet,  Rudbeck,  and  Bartholinus.  The  history  of  the  circula- 
tion extends,  therefore,  over  a  period  of  2000  years,  from  the  epoch  of  the 
Egyptian  Ptolemies  to  the  latter  part  of  the  seventeenth  century,  and 
even,  in  some  respects,  to  the  present  day.  The  general  structure  of 
the  heart,  its  cavities,  the  play  of  its  valves,  the  passage  of  the  blood 
from  its  right  side  to  the  lungs  and  back  to  its  left  side,  thence  through 
the  arteries  to  all  parts  of  the  body  ;  the  valves  in  the  veins  ;  the  flow 
of  the  venous  blood  toward  the  heart,  had  been  demonstrated,  in  an 
isolated  way,  by  this  or  that  person,  before  Harvey's  time  ;  while  it  was 
not  until  after  the  appearance  of  his  great  work  that  the  discovery  of 
the  capillaries  made  intelligible  the  manner  in  which  the  blood  passed 
from  the  arteries  to  the  veins;  and  the  demonstration  of  the  lymphatics 
completed  our  otherwise  imperfect  knowledge  of  the  circulation.  If, 
however,  the  great  generalizations  as  regards  the  circulation,  just  re- 
ferred to,  were  made  either  before  or  after  the  time  of  Harvey,  natu- 
rally, it  might  be  asked,  What  was  there  left  for  Harvey  to  discover? 
In  what  does  the  merit  of  his  great  work  consist  ?  In  that  he  Avas 
the  first  to  describe  accurately  the  motions  of  the  heart,  and  both  the 
pulmonary  and  systemic  circulations  correctly.  Without  doubt,  Harvey 
was  the  first  who  described  correctly  the  entire  circulation  of  the  blood, 
understanding  by  the  word  circulation  the  flowing  of  the  blood  from 
the  heart  to  the  lungs,  back  to  the  heart,  thence  through  the  arteries  to 
the  periphery,  and  from  the  periphery,  through  the  veins,  back  to  the 
heart.  That  is,  the  flowing  of  the  blood  in  a  circle.  It  must  be  re- 
membered, however,  that  Harvey  saw  this  circulation  only  in  his  mind's 
eye,  as  the  capillaries  or  connecting  links  between  the  arterial  and 
venous  systems  were  not  discovered  by  Malpighi  until  after  Harvey's 
death.  The  history  of  the  discovery  of  the  circulation  of  the  blood  has 
often  been  told ;  but  the  subject  is  one  of  such  interest,  extending  as 
it  does  over  a  very  long  period,  illustrating  so  forcibly  how  slowly  truth 
is  attained,  that  fact  after  fact  must  be  first  established  before  any 
generalization  can  be  arrived  at ;  how  the  isolated,  unconnected  labors 


KNOWLEDGE    OF    THE     ANCIENTS.  373 

of  generations  finally  culminate,  in  the  hands  of  a  genius,  in  a  grand 
discovery  ;  that  I  trust  it  will  not  be  considered  superfluous  if  I  rapidly 
tell  the  story  of  the  discovery  of  the  circulation  of  the  blood  once 
more.  Although  no  mention  is  made  of  bleeding  in  the  Iliad,  that 
encyclopaedia  of  the  knowledge  possessed  by  the  Greeks  in  Homer's 
day,  vet  there  is  no  reason  to  doubt  that  Podalirius,  who  attended,  as 
surgeon,  the  hosts  of  Agamemnon,  made  use  of  this  practice  ;  as  we 
learn  from  later  sources1  that,  by  bleeding  the  daughter  of  the  King  of 
Caria,  he  effected  a  cure,  the  reward  of  which  was  her  hand  in  mar- 
riage, and,  as  dowry,  the  Chersonesus.  While  the  Greeks  and  the 
ancients  generally  were  aware  that  the  blood  of  man  and  animals 
coursed  in  a  vast  system  of  tubes,  their  knowledge  of  the  circulation  of 
the  blood  extended  but  a  little  beyond  this.  Indeed,  their  views  on 
this  subject  were  of  the  most  imperfect  or  erroneous  character.  That 
the  blood  flowed  in  certain  veins :  that  there  were  additional  vessels 
erroneously  called  arteries,  because  they  were  supposed  to  contain  air  ; 
that  the  heart  was  a  hollow,  muscular  organ,  constituted  about  all  their 
knowledge  of  the  circulation.2  This  is  not  to  be  wondered  at,  however, 
since  the  superstitious  respect  paid  to  their  dead  by  the  Greeks  made 
dissection  an  impossibility,  the  little  anatomical  knowledge  existing  in 
the  days  of  Hippocrates  having  been  derived  from  the  rapid  inspection 
of  the  viscera  of  animals  sacrificed  upon  the  altar  on  the  occasion  of 
some  religious  ceremony.  Even  Aristotle,3  whose  anatomical  knowledge 
far  exceeded  that  of  Hippocrates,  advanced  but  little  our  knowledge  of 
the  vascular  system.  Aristotle  taught  that  the  veins  communicate  with 
the  heart ;  that  vessels  pass  from  the  heart  to  the  lungs,  and  that  the 
heart  and  veins  are  filled  with  blood.  Such  was  the  limited  knowledge 
of  the  circulation  of  the  blood  as  known  to  the  most  celebrated  of  the 
Greeks.  A  great  advance,  however,  was  soon  to  be  made,  not  only  in 
anatomy,  but  in  all  branches  of  science.  The  wonderful  campaigns  and 
victories  of  Alexander,  Aristotle's  patron,  resulting  in  the  conquering 
of  Egypt  and  the  establishing  of  the  Macedonian  dynasty  of  kings,  and 
the  building  of  Alexandria  not  only  revolutionized  the  political  and 
social  Avorld,  but  influenced  all  branches  of  knowledge  in  a  way  and  to 
an  extent  that  modern  Europe  is  only  now  beginning  to  appreciate. 
Under  the  magnificent  patronage  of  the  Ptolemies,  the  Macedonian 
kings  of  Egvpt,  there  arose  at  Alexandria  that  famous  school,  the 
Museum,  a  centre  of  learning  for  the  organization  and  development  of 
all  kinds  of  knowledge,  the  like  of  which  has  never  been  seen  since. 
There  were  associated  under  the  hospitable  roof  of  the  Egyptian  kings 
some  of  the  most  learned  and  wonderful  men  the  world  has  ever  seen. 
The  astronomers,  Hipparchus  and  Ptolemy  ;  geometers  like  Euclid  and 
Archimedes ;  the  engineers  and  geographers,  Apollonius,  Erastosthenes ; 
historians  like  Manetho  ;  the  theologian,  Cyril ;  learned  women  like 
Hypatia  :  the  celebrated  anatomists  and  physicians,  Herophilus  and 
Erasistratus.     For  the  practical  study  of  astronomy  there  were  placed 

1  Stephani  Byzantini  :  De  TTrbibns.  p.  G80.     Lugd.  Bat.,  1694. 

2  Hippocratis'  Opera  Omnia,  p.  275     Lugd.  Bat.,  1G65.   (Euvres  completes  d'Hippocrate,  par  E.  Littre. 
Tomes  viii.     Paris,  18  59-1853.     Introduction,  tome  i   p.  211. 

8  '  \.plOTOTe%OVg  TLep't  Z&urv  'laropla,  Lib.  iii.  Cap.  2,  3,  4.     Lipsa?,  1869. 


374    HISTORY    OF    THE    DISCOVERY    OF    THE    CIRCULATION. 

beneath  the  Porch  equinoctial  and  solstitial  armils,  quadrants,  dioptras, 
astrolabes  and  meridian  lines ;  a  botanical  garden  offered  opportunity 
to  those  who  wished  to  study  plants  ;  a  zoological  menagerie  offered 
facilities  to  those  interested  in  the  dissection  of  animals.  The  library, 
containing  nearly  a  million  volumes,  was  open  daily  to  those  desirous  of 
making  themselves  acquainted  with  the  knowledge  of  the  day  or  of 
that  of  antiquity.  A^ast  collections  of  all  kinds  of  natural  objects  had 
been  brought  there,  from  every  part  of  the  known  world,  by  the  Mace- 
donian conquerors,  for  the  use  and  benefit  of  the  student.  At  the 
Museum,  in  Alexandria,  the  student  found  everything  that  would  assist, 
develop,  and  refine  the  intellect — the  calm,  the  leisure,  the  means  of 
living  and  of  study.  The  usages  of  that  wonderful  country,  Egypt, 
where  death  perpetuates  itself  in  a  thousand  embalmed  forms,  had, 
from  time  immemorial,  familiarized  the  vulgar  and  uneducated  with 
autopsies  and  dissections.  The  study  of  anatomy  by  the  only  means 
possible,  the  dissection  of  the  dead  body,  was  no  longer  regarded  with 
superstitious  horror  and  considered  as  sacrilege.  Pliny  tells  us  that 
those  intelligent  and  magnificent  princes,  the  Greek  kings  of  Egypt, 
not  only  lavished  their  treasure  in  the  interests  of  science,  but  per- 
sonally attended  the  dissections  that  were  daily  conducted  at  the 
Museum.  The  Medical  School  of  Alexandria  gave  to  the  world  those 
famous  anatomists,  Herophilus  and  Erasistratus.  With  them  began  the 
study  of  the  structure  and  use  of  the  heart  and  its  great  bloodvessels, 
by  means  of  actual  dissection. 

The  name  of  Herophilus  ought  to  be  familiar  to  all  students  of  anat- 
omy, as  many  parts  of  the  human  body,  such  as  the  choroid  plexus,  the 
torcular  Herophili,  the  calamus  scriptorius,  the  duodenum,  etc.,  were 
first  described  by  him.  The  most  important  contribution  that  he  made 
to  our  knowledge  of  the  vascular  system  was  the  demonstration  of 
the  isochronism  of  the  pulsations  of  the  arteries  and  of  the  beating  of 
the  heart,  and  of  the  latter  being  the  cause  of  the  former,  a  phenomenon 
that  had  already  been  imperfectly  referred  to  by  Hippocrates  and  Aris- 
totle. Herophilus  noticed  also  the  difference  in  the  thickness  of  the 
walls  of  the  arteries  and  of  the  veins,  and  described  the  vessels  connect- 
ing the  heart  and  the  lungs,  distinguishing  the  pulmonary  artery  from 
the  pulmonary  vein,  designating  the  former  as  the  arterial  vein  and  the 
latter  as  the  venous  artery. 

To  Erasistratus,  one  of  the  most  distinguished  of  the  anatomists  of 
the  Alexandrian  school,  and  one  of  the  most  celebrated  physicians  of 
antiquity,  science  is  indebted  for  the  discovery  of  the  valves  of  the 
heart,  and  their  function  in  the  circulation.  It  was  stated  in  a  pre- 
vious chapter  that  there  is  reason  to  believe  that  Erasistratus  had  seen 
the  lacteals  a  dependence,  so  to  speak,  of  the  vascular  system,  even 
though  he  had  misunderstood  their  use,  and  we  shall  see  hereafter  that 
he  appears  also  to  have  distinguished  the  sensory  from  the  motor  nerves. 
While  there  is  no  doubt  that  the  anatomists  and  physiologists  of  an- 
tiquity distinguished  two  kinds  of  vessels,  arteries  and  veins,  their  very 
name,  artery,  from  the  Greek  ayp,  air,  and  T/ipeu,  I  guard  or  keep,  con- 
clusively proves  how  absolutely  ignorant  they  were  of  the  two  functions 
of  these  vessels.   Hippocrates,  Aristotle,  and  more  especially  Erasistratus, 


DEMONSTRATION    OF    THE    FUNCTION    OF    ARTERIES.       875 

believed  that  the  arteries,  as  their  name  implies,  carried  air.  This  error 
was  due.  no  doubt,  to  the  fact  that  when  a  dead  body  is  opened  the 
arteries  are  usually  found  empty;  and  to  the  theory  that  the  air  in  these 
vessels  came,  originally,  from  the  trachea,  hence  the  name  of  tracheal 
artery,  by  which  it  is  designated  by  the  French,  even  at  the  present 
day.  Erasistratus1  supposed  the  air  passed  from  the  trachea  into  the 
pulmonary  veins  (his  venous  artery),  from  there  to  the  left  side  of  the 
heart,  and  thence,  by  the  arteries,  to  all  parts  of  the  body.  Substitute 
for  the  air  oxygen,  and  for  his  venous  artery  pulmonary  capillaries,  and 
the  much-abused  theory  of  Erasistratus  becomes  the  modern  one  of 
respiration.  Although  during  the  four  centuries  that  followed  the  bril- 
liant epoch  of  the  Alexandrian  school  just  described,  dissection  had 
gradually  fallen  into  disuse,  nevertheless  the  most  famous  anatomist  of 
antiquity,  Galen,  learned  his  anatomy  in  Egypt,  where  he  devoted  many 
years  to  anatomical  studies.  His  dissections,  however,  appear  to  have 
been  limited  to  animals.  By  ligating  in  a  living  animal,  an  artery  in 
two  places,  and  opening  the  vessel  between  the  ligatures,  Galen2  demon- 
strated that  the  vessel  contained  blood.  Thus,  by  an  experiment  upon 
a  living  animal,  a  vivisection,  the  first  great  source  of  error,  that  of 
supposing  that  the  arteries  contained  air,  was  removed,  the  true  nature 
of  an  artery  demonstrated,  and  the  modern  theory  of  the  circulation  of 
the  blood  made  possible.  Too  much  importance  cannot  be  attached  to 
this  cardinal  experiment  of  Galen.  It  is  evident  that  as  long  as  it  was 
believed  that  the  veins  alone  carried  blood,  and  that  the  arteries  only 
contained  air,  the  discovery  of  the  circulation  was  an  impossibility. 

For  1300  years,  in  anatomical  and  physiological  matters,  the  authority 
of  Galen  was  supreme.  With  the  truths  discovered  by  this  most  de- 
servedly famous  physician,  were  perpetuated  errors,  among  which  was 
Galen's  theory  that  the  air  inspired  did  not  enter  into  the  body  to  any 
extent,  as  Erasistratus  supposed,  but  was  at  once  rejected  after  having 
performed  its  office,  which  was  that  of  cooling  the  body,  and  that  the 
cavity  of  the  right  ventricle  of  the  heart  communicated  with  that  of  the 
left  ventricle  by  means  of  holes  in  the  septum.3  It  is  true  that  no  one 
had  seen  these  holes  in  the  septum,  separating  the  ventricle ;  even  Galen 
himself  did  not  .claim  that  he  actually  saw  them;  but  the  theory  in 
Galen's  time,  and  many  a  day  afterward,  was.  that  the  spirituous  blood 
of  the  left  ventricle  must  be  mixed  with  the  coarser  blood  of  the  right 
ventricle,  that  the  latter  should  fulfil  its  function  in  nutrition.  Now  the 
only  way  that  theory  could  account  for  this  mixing  of  the  two  kinds 
of  blood  was  on  the  supposition  that  the  septum  of  the  ventricle  was 
perforated  with  holes,  through  which  part  of  the  blood  passed  from  one 
ventricle  to  the  other,  the  rest  of  the  blood  passing  through  the  pulmo- 
nary artery  to  the  lungs. 

Men  saw,  or  believed  they  saw.  what  theory  demanded  they  ought  to 
see.  As  has  been  too  often  the  case,  as  the  history  of  science  teaches 
us,  the  theory  did  not  follow  from  the  facts,  but  the  facts  were  made  to 
-\ut  the  theory.     Further,  when  it  is  remembered  that  for  sixteen  cen- 

1  Galenus  edit,  .it  -  Galenus,  edit  i  it.  an  sanguis  in  arteriis  aatara  contineatur,  Cap.  >'>■ 

4  Galenus,  edit   cit.     De  usu  partium,  Lib.  vi.  Cap.  IT. 


376    HISTORY    OF    THE    DISCOVERY    OF    THE' CIRCULATION. 

turics,  during  the  period  extending  from  the  epoch  of  the  Alexandrian 
Museum  to  that  of  the  School  of  Salerno,  in  1-24, '  or  more  probably 
to  that  of  Mundini,  in  1306,2  the  human  body  had  never  been  dissected, 
it  is  not  to  be  wondered  at  that  the  grossest  ignorance  of  anatomy 
should  have  universally  prevailed.  The  horror  with  which  dissection 
was  regarded,  and  the  limited  number  of  subjects  obtainable  for  study, 
will  be  appreciated  from  the  fact  that  Mundini,  who  was  Professor  of 
Anatomy  at  Bologna  during  the  latter  part  of  the  thirteenth  and 
beginning  of  the  fourteenth  century,  had  dissected  in  eleven  years  only 
three  human  bodies.  Berenger  de  Carpi,  who  also  occupied  the  Chair 
of  Anatomy  in  Bologna  a  century  later,  had  butter  opportunities  of 
study  than  Mundini,  whose  works  he  commentated,  he  having  dissected 
a  hundred  bodies ;  and  yet  the  authority  of  Galen  had  such  weight 
with  De  Carpi,  that  he  states  that  there  are  certainly  holes  in  the 
septum  separating  the  ventricles.  He  adds,  however,  as  if  he  had  an 
uneasy  suspicion  as  to  the  truth  of  the  statement,  that  these  holes  are 
seen  in  man  with  great  difficulty.3 

A  short  time,  however,  after  the  publication  of  De  Carpi's  work, 
viz.,  in  1553,  there  appeared  the  Christianismi  Restitutio  of  the  Span- 
iard, Michael  Servetus,  whose  career  reads  rather  like  that  of  the  hero 
in  some  romance  than  of  a  real  historical  personage.  Educated  for 
the  priesthood  at  Saragossa,  relinquishing  such  studies  for  that  of  the 
law,  at  Toulouse ;  accompanying,  as  secretary,  Quintana,  Confessor  to 
Charles  V.,  upon  the  occasion  of  the  imperial  coronation  at  Bologna; 
and  going  afterward  to  the  Diet  of  Augsburg ;  giving  up  the  prospect 
of  a  diplomatic  career  for  that  of  a  theologian  ;  leaving  Switzerland 
and  changing  his  name  to  Villanovus,  to  avoid  persecution  ;  supporting 
himself  as  a  proof-reader  and  editor  of  learned  books  while  a  student 
of  medicine  in  Paris ;  receiving  his  degree  of  doctor  in  medicine ; 
writing  works  on  medical  subjects,  and  practising  medicine  with  great 
success  for  a  number  of  years ;  returning  to  the  study  of  theology 
again,  his  career  of  usefulness  is  suddenly  cut  short  by  death  at  the 
stake ;  Servetus,  as  is  well  known,  being  burned  alive,  in  1553,  at 
Geneva,  for  heresy,  as  the  author  of  the  Christianismi  Restitutio. 
This  work,  as  its  name  implies,  is  a  theological  treatise,  but  it  is  also 
of  the  greatest  interest  to  the  physiologist,  as  in  discussing  the  nature 
of  the  vital  spirit,  and  the  manner  in  which  it  is  elaborated,  Servetus 
describes  the  flow  of  the  blood  from  the  right  ventricle  of  the  heart,  by 
the  pulmonary  artery,  through  the  lungs,  and  by  the  pulmonary  veins 
to  the  left  ventricle ;  distinctly  stating  that  the  blood  does  not  pass 
from  the  right  ventricle  to  the  left  through  the  septum  of  the  heart, 
as  is  commonly  believed,  but  by  a  long  passage  through  the  lungs, 
from  the  right  ventricle,  and  that  it  is  in  the  lungs  that  the  blood 
is  agitated,  prepared,  and  changes  its  color,  thence  passing  to  the  left 
ventricle  by  the  pulmonary  veins.  Servetus  was  not  only  the  first  to 
describe,  therefore,  the  flow   of  the  blood  from  the   right  side  of  the 

i  Hseser  :   Geschichte  der  Hedicin,  S.  733-738.      Jena,  1875.     Corradi:   Eendiconde  del  R.  Institut. 
Lombardo,  Ser.  ii.  vol.  vi. 

2  Hyrtl :  Das  Arabische  und  Hebraische  in  der  Anatomie,  p.  11.     Wien,  1879. 

3  Berenpcer  de  Carpi.     Commentarii  cum  amplissiimia  additionibua  super  anatomia  Mundini.   Pp.341. 
Bologna,  1521. 


DISCOVERY    OF    PULMONAEY    CIRCULATION.  377 

heart,  through  the  lungs,  to  the  left,  and  the  imperviousness  of  the 
septum  of  the  heart,  hut  was  also  the  first  to  point  out  the  place  where 
tlir  venous  was  changed  into  arterial  blood,  the  significance  of  which 
discovery  was  neither  understood  nor  appreciated  for  more  than  a 
century  afterward.  Further,  Servetus  adds  that  the  left  ventricle  is 
not  sufficiently  capacious  for  so  copious  a  mixture,  nor  will  it  suffice 
for  the  elaboration  of  the  color ;  and  that  the  septum  is  neither  fit 
for  the  communication  nor  the  elaboration  of  the  blood,  even  if  any 
may  exude  through  ir.  Servetus  evidently  does  not  consider  that  any 
blood  passes  through  the  septum  of  the  heart,  for  he  most  distinctly 
says  that  none  does  so,  and  in  confirmation  of  his  view  adds  that  even 
if  any  blood  does  pass  through  the  septum,  the  left  ventricle  is  not 
adapted  to  its  elaboration.  That  Servetus  did  not  hold  the  view  of 
Galen,  of  part  of  the  blood  passing  through  the  pulmonary  artery  and 
part  through  the  septum,  is  evident  from  what  Servetus  says,  that  if 
any  one  compares  his  views  with  Galen's  (and  no  one  understood  Galen 
better  than  Servetus),  he  will  perceive  clearly  the  truth  not  observed 
by  Galen  himself.  The  celebrated  passage  upon  the  pulmonary  circu- 
lation, in  the  Restitutio,  is  found  in  Liber  Quintus,  De  Trinitate 
Divina,  In  quo  agitur  de  Spiritus  Sancto,  p.  170.     It  is  as  follows : 

"  For  which  purpose  the  substantial  generation  of  the  vital  spirit 
itself  is  first  to  be  understood,  which  is  composed  of  and  nourished  by 
the  inspired  air  and  most  subtile  blood.  The  vital  spirit  has  its  origin 
in  the  left  ventricle  of  the  heart,  the  lungs  aiding,  to  the  highest  degree, 
in  its  generation.  The  spirit  is  subtile,  elaborated  by  the  force  of  heat, 
of  a  yellowish  color,  with  the  power  of  fire,  to  the  end  that  it  may  be, 
as  it  were,  a  bright  vapor  from  the  purer  blood,  containing  in  itself  the 
substance  of  water,  air,  and  of  fire.  It  is  generated,  in  fact,  in  the 
lungs,  with  the  mixture  of  inspired  air  with  the  elaborated,  subtile 
blood  which  the  right  ventricle  of  the  heart  communicates  to  the  left. 
Yet  this  communication  is  made,  not  by  the  middle  wall  of  the  heart, 
as  is  commonly  believed,  but  the  subtile  blood  is  driven,  by  a  great 
plan  or  device,  from  the  right  ventricle  of  the  heart,  by  the  long  passage 
through  the  lungs ;  is  prepared  in  the  lungs ;  the  yellow  color  is  made, 
and  it  is  poured  out  from  the  arterial  vein  (vena  arteriosa),  or  pulmonary 
artery  into  the  venous  artery  (arteria  venosa  or  pulmonary  vein)  ;  there 
is  mixed  in  the  venous  artery  itself  with  the  inspired  air  ;  is  purged  by 
expiration  of  its  fuliginous  matter ;  and  so,  at  length,  the  whole  mix- 
ture is  attracted  by  the  diastole  from  the  left  ventricle  of  the  heart,  a 
fit  stuff  out  of  which  to  make  vital  spirit.  The  various  connection  and 
communication  of  the  arterial  vein  with  the  venous  artery  teaches  that 
the  communication  and  preparation  is  made  by  the  lungs  in  this  manner. 
The  remarkable  size  of  the  pulmonary  artery  confirms  this,  which  would 
be  neither  made  in  such  a  way  nor  so  large,  nor  would  there  be  emitted 
so  great  a  mass  of  blood  from  the  heart  itself  into  the  lungs,  if  for  the 
nourishment  of  these  alone,  nor  would  the  heart  serve  the  lungs  in  this 
manner,  since,  especially  before,  in  embryo,  the  lungs  themselves  are 
accustomed  to  be  nourished  from  elsewhere,  on  account  of  those  little  mem- 
branes, or  valves  of  the  heart,  not  yet  being  open  until  the  hour  of  birth, 
as  Galen  teaches.     Therefore  the  blood  is  poured  forth,  and  so  copiously. 


378    HISTORY    OF    THE     DISCOVERY    OF     THE     CIRCULATION. 

from  the  hear!  into  the  lungs  at  the  hour  of  birth,  for  another  use. 
The  air  also  is  sent  from  the  lungs  to  the  heart  by  the  venous  artery, 
not  pure,  but  mixed  with  blood;  therefore  the  mixture  is  made  in  the 
lungs.  That  yellow  color  is  given  to  the  blood  by  the  lungs,  not  by 
the  heart.  The  space  in  the  left  ventricle  is  not  capable  of  holding  so 
great  and  so  capacious  a  mixture,  nor  is  sufficient  for  that  elaboration 
of  color.  Finally,  that  middle  wall,  as  it  is  wanting  in  vessels  and 
power,  is  not  fit  for  that  communication  and  elaboration,  even  if  some 
might  sweat  through.  By  the  same  plan  by  which  the  transfusion  is 
made  from  the  vena  porta  to  the  vena  cava,  with  reference  to  the  blood, 
so  the  transfusion  from  the  arterial  vein  to  the  venous  artery  is  made  in 
the  lungs,  with  reference  to  the  spirit.  If  any  one  compares  this  with 
that  which  Galen  writes,  Lib.  vi.  et  vii.,  on  the  use  of  the  parts,  he 
easily  perceives  the  truth,  not  observed  by  Galen  himself.  And  so  the 
vital  spirit  from  the  left  ventricle  of  the  heart  is  thence  poured  out  into 
the  arteries  of  the  whole  body." 

The  Christianismi  Restitutio  is  a  very  rare  work.  At  the  present 
moment  there  are,  indeed,  only  three  original  copies  known  to  exist — 
one  in  the  National  Library  at  Paris,  one  in  the  Imperial  Library  at 
Vienna,  and  one  in  the  Library  of  the  University  of  Edinburgh.  The 
copy  in  Paris  probably  belonged  to  Colladon,  Calvin's  lawyer,  since  his 
name  is  in  it,  and  wTas  in  the  possession  of  the  celebrated  Dr.  Mead,  of 
London,  in  the  early  part  of  the  eighteenth  century,  from  whose  hands 
it  passed  successively  through  those  of  de  Boze,  de  Cotte,  Gaignat,  la 
Vaillere,  finally  becoming  the  property  of  the  National  Library.  There 
is  not  the  slightest  reason  to  suppose  that  the  Paris  copy  of  the  Resti- 
tutio was  ever  in  the  flames  that  enveloped  its  author,  as  is  picturesquely 
described  by  Flourens,1  the  blackness  on  the  pages  being  due,  not  to 
fire,  but  possibly  to  dampness.2 

In  the  year  1555,  two  years  after  the  printing  of  the  Christianismi 
Restitutio,  there  appeared  the  second  edition  of  the  magnificent 
Anatomy  of  Vesalius,  which  differed  in  many  important  respects  from 
the  first  edition  of  1543 ;  among  others,  as  regards  the  description  of 
the  heart.  In  the  1555  edition,  Vesalius  begins  by  saying  that,  influ- 
enced by  the  views  of  Galen,  he  considered  that  the  blood  passed  from 
the  right  to  the  left  ventricle  of  the  heart,  through  the  septum,  by 
means  of  the  pores.  He  immediately  adds,  however,  that  the  septum 
of  the  heart  is  as  thick,  dense,  and  compact  as  the  rest  of  the  heart, 
and  not  the  smallest  quantity  of  the  blood  passes  through  the  septum. 
There  can  be  no  doubt  that  Vesalius  held  that  the  septum  of  the  heart 
was  imperforate,  in  this  (the  1555)  edition,  but  the  passage  in  which 
he  maintains  this  view  is  not  to  be  found  in  the  1543  edition  ;  and  yet, 
in  all  of  the  accounts  of  the  history  of  the  circulation  with  which  I  am 
familiar,  that  of  Tollin3  excepted,  the  views  of  Vesalius  in  reference  to 
the  imperviousness  of  the  septum  of  the  heart  (printed  in  1555), 4  are 
said  to  have  preceded  those  of  Servetus  (printed  in  1553).     The  only 

1  Histoire  de  la  deconv  -rte  de  la  Circulation  du  Sane,  p.  155.     Paris,  1857. 

2  Henri  Tollin  :  Die  Entdecknng  des  Blutkreislaufs,  dnrch  Michael  Servet,  p.  69.     Jena,  1876. 
»  Die  Entdeckung  dea  Blutkreislaufs,  etc.,  p   26      Jena,  1876. 

4  Audrese  Vesalii :  De  Humaui  corporis  fabrica  Libri  septem.     Basilea;,  1555 


DISCOVERY    OF     PULMONARY    CIRCULATION.  379 

way  in  which  I  can  account  for  this  error  is  by  supposing  that  the  his- 
torians of  the  circulation,  in  quoting  Aresalius,  have  made  use  of  the 
1555  or  1725  editions,  and  not  that  of  1543.  Certainly  Servetus  did 
not  learn  his  anatomy  from  Vesalius,  since  they  were,  at  the  same  time, 
prosectors  for  Guntherus,  Professor  of  Anatomy  in  the  Medical  School 
of  Paris:  and  as  to  Servetus's  knowledge  of  practical  anatomy  there 
can  be  no  doubt,  Guntherus  testifying  to  that.1  On  the  other  hand, 
Vesalius  was  probably  entirely  ignorant  of  what  his  former  associate  in 
the  dissecting-room  had  published  about  the  heart. 

While,  to  my  mind,  there  is  no  doubt  that  the  pulmonary  circulation 
was  correctly  described  by  Servetus,  beyond  statements  like  that  of  the 
blood  being  transmitted  by  the  left  ventricle  to  the  aorta,  and  thence 
through  the  arteries  to  the  whole  system,  and  of  the  blood  flowing  from 
the  vena  porta  through  the  liver  to  the  hepatic  vein,  etc.,  I  can  find 
nothing  in  his  work  to  warrant  the  view  that  Servetus  had  any  idea  of 
the  so-called  systemic  or  general  circulation.  Further,  it  is  not  to  be 
supposed  that  Servetus  understood  the  exact  manner  in  which  the  blood 
passed  from  the  pulmonary  arteries  to  the  veins,  since  the  capillaries 
were  not  discovered  by  Malpighi  for  more  than  a  century  afterward. 

Six  years  after  the  death  of  Servetus — that  is,  in  1559 — the  pulmo- 
nary circulation  was  re-described  by  Colombo,  who  taught  anatomy  at 
Padua,  Pisa,  and  Rome.  In  a  work  on  anatomical  subjects,  Colombo, 
in  speaking  of  the  heart,  observes  that  between  the  ventricles  a  septum 
is  present,  through  which  almost  every  one  believes  that  the  blood  passes 
from  the  right  ventricle  of  the  heart  to  the  left,  but  that  really  the 
blood  goes  through  the  pulmonary  artery  to  the  lungs,  and  is  then 
carried,  with  the  air,  by  the  pulmonary  vein,  to  the  left  ventricle  of 
the  heart,  and  that  no  one  had  previously  observed  or  described  this.2 
Colombo,  however,  is  evidently  wrong  when  he  says  no  one  had  pre- 
viously observed  or  described  this.  It  is  possible  that  Colombo  was 
ignorant  of  what  Servetus  had  written  in  his  Christianismi  Resti- 
tutio, but  it  certainly  appears  to  me  very  extraordinary,  if  such  was  the 
case,  for  Colombo  was  the  pupil  of  Vesalius,  and  taught,  as  prosecter 
and  professor,  for  years,  in  Padua,  the  very  city  where  Servetus  had 
sent  one  of  the  manuscript  copies  of  his  work,  and  where  his  views 
were  well  known.  Whether  Colombo  was  acquainted  with  the  writings 
or  the  views  of  Servetus  may  be  a  question,  but  there  can  be  no  doubt 
that  he  understood  and  described  the  pulmonary  circulation.  This  able 
anatomist,  however,  held  entirely  erroneous  views  as  regards  the  general 
or  systemic  circulation,  for,  in  speaking  of  the  liver  and  veins,  in  the 
same  work  that  we  have  just  referred  to,  he  distinctly  states  that  the 
liver  is  the  head,  the  fountain,  the  origin  of  all  the  veins.3  It  is  evi- 
dent that  one  who  held,  with  Galen,  that  the  veins  originated  in  the 
liver,  the  venous  blood  being  transmitted  thence  to  the  periphery,  could 
have  no  idea  of  the  general  circulation. 

In  1571,  eighteen  years  after  the  death  of  Servetus,  there  appeared 

1   ECaller  Bibliotheca  Anatomies,  tomiis  i.    Tiguri,  1774. 

-  Realdi  Columbi  Cremonenaia  in  aliuo  Gyninaso  Romano  Anatomici  celeberiinmi  de  re  Anatomica, 
Libri  xv.;  Lib.  vii.  de  corde  et  Arteriis,  p.  177.     Venetiis,  1559. 
1  l»r-  jecore  et  venis,  p.  164,  op.  cit . 


380     HISTORY    OF    THE    DISCOVERY    OF    THE    CIRCULATION. 

the  QucBstionum  Peripateticarum  of  Caesalpinus,1  one  of  the  most  distin- 
guished of  the  many  celebrated  men  thai  Italy  produced  in  the  six- 
teenth century.  Caesalpinus  taught  medicine  al  Pisa,  and  was  afterward 
physician  to  Pope  Clement  VIII.  at  Rome,  and  was  as  distinguished  a 
botanist  as  a  physician,  being  the  first  to  classify  plants  according  to  a 
natural  method,  and  may  be  justly  regarded  as  the  father  of  vegetable 
anatomy.  Csesalpinus  described  the  pulmonary  circulation,  observing 
that  the  circulation  of  the  blood  from  the  right  ventricle  of  the  heart, 
by  the  lungs,  to  the  left  ventricle  of  the  same,  agrees  best  with  what 
appears  from  dissection.  One  can  hardly  believe  that  such  a  learned 
man  as  Csesalpinus  was  unaware  of  the  views  of  Servetus  or  Colombo: 
certainly,  at  least,  of  the  existence  of  the  De  re  Anatomica,  published 
so  recently  as  1559,  and  by  an  anatomist  who  taught  in  the  neighboring 
city  of  Padua :  and  yet  he  mentions  neither. 

It  is  strange,  however,  that  if  Cnesalpinus's  views  upon  the  pulmonary 
circulation  were  derived  from  either  the  works  of  Servetus  or  Colombo, 
he  should  have  held,  with  Galen,  as  he  undoubtedly  did,  that  the  septum 
of  the  heart  wras  pervious,  part  of  the  blood  passing  directly  from  the 
right  to  the  left  ventricle,  which  both  Servetus  and  Colombo  showed 
was  not  the  case.  Had  Caesalpinus  published  nothing  more  than  his 
Qucestionum  Peripateticarum,  there  would  have  been  no  necessity  for 
my  referring  to  that  philosopher  in  connection  with  the  history  of  the 
discovery  of  the  circulation  of  the  blood.  Twelve  years  afterward  (1583), 
however,  the  De  Plantis,2  by  the  same  author,  appeared,  and  this  work 
has  the  greatest  interest  for  us,  as  for  the  first  time  the  general  or  sys- 
temic circulation,  with  the  exception  of  the  capillaries,  is  described, 
though  it  must  be  admitted  that  the  description  is  very  brief,  and  sup- 
ported by  little  or  no  experimental  evidence.  In  this  work  Caesalpinus 
distinctly  says  that  the  food  is  carried  by  the  veins  to  the  heart,  and 
thence,  by  means  of  the  arteries,  is  distributed  to  all  parts  of  the  body. 
Caesalpinus  not  only  understood  the  way  in  which  nutriment  is  distrib- 
uted throughout  the  economy,  but,  with  the  exception  of  the  capillaries, 
the  manner  in  which  the  blood  flows  through  the  system.  For  in  his 
Quoestionum  Medicarum  (p.  234)  Caesalpinus  calls  attention  to  the  fact 
that  when  the  veins  in  the  neck  are  compressed  the  swelling  of  the  veins 
is  between  the  brain  and  ligature,  not  between  the  ligature  and  the 
heart,  and  draws  the  conclusion  that  just  the  opposite  ought  to  happen 
— that  is,  the  swelling  ought  to  be  between  the  ligature  and  the  heart, 
if  the  motion  of  the  blood  in  the  veins  is  from  the  heart  and  other  vis- 
cera to  the  periphery  of  the  system,  as  was  the  general  opinion  at  that 
time.  Caesalpinus  continues,  in  the  same  page,  by  saying  that  there  is 
a  perpetual  motion  of  the  blood  from  the  vena  cava,  through  the  heart 
and  lungs,  to  the  aorta,  and  that  the  arteries  communicate  with  the 
veins  by  what  are  called  anastomoses ;  that  the  blood  flows  to  the  upper 
parts  and  returns,  Euripus-like,  to  the  lower  ones,  is  perfectly  evident, 
both  when  one  is  asleep  and  awake,  and  that  this  motion  is  not  obscure 
in  any  part  of  the  body  when   you   experiment  by  binding  veins  or 

1  Andrea  Cassalpini  Aretini  Qiifestionum  Peripateticarum,  Lib.  v.  Qusestio  iv.  p.  125.     Venetiis,  1593, 

2  De  Plantis  Libri.  xvi.  Lit'.  1,  Cap.  ii.  p   3.     Flurentiie,  1583. 


DISCOVERY    OF    SYSTEMIC     CIRCULATION.  381 

occluding  them  in  any  other  manner.  The  above  distinct,  concise  state- 
ments appear  to  me  to  prove  that  Caesalpinus  understood  the  systemic 
circulation,  as  far  as  was  possible  for  one  who  had  never  seen  the  capil- 
laries ;  as  regards  the  pulmonary  circulation  he  undoubtedly  also  states 
that  the  blood  passed  from  the  right  side  of  the  heart  to  the  left,  by  the 
lungs;  but,  as  we  have  seen  that,  in  the  Qucestionum  Peripateticarum, 
he  says  that  part  of  the  blood  passes  through  the  septum,  and  as  he 
does  not  contradict  this  statement,  but  refers  to  this  work  as  containing 
his  views,  he  could  only  have  understood  the  pulmonary  circulation 
imperfectly.  By  most  of  those  who  have  written  on  the  discovery  of 
the  circulation,  a  very  different  interpretation,  however,  is  offered  of 
the  views  of  Caesalpinus  from  that  just  given.  By  such,  it  is  stated 
that  Caesalpinus  held  that  there  was  a  to-and-fro  motion  of  the  blood  in 
the  veins,  Euripus-like  ;  that  the  arteries  communicated  with  the  veins 
only  during  sleep  ;  that  the  blood  only  irrigated  the  tissues,  but  did  not 
circulate  through  them,  etc.  If  these  are  the  views  of  Caesalpinus, 
then  he  certainly  did  not  understand  the  circulation  in  any  part  of  its 
course. 

In  order  that  the  reader  may  judge  for  himself,  as  to  what  the  views 
of  Cresalpinus  really  were,  I  will  give  the  passage  from  his  Quces- 
tionum  Medicarum1 — to  which  I  have  referred,  and  will  say  but  a  word 
further  concerning  it. 

But  that  appears  worthy  of  observation,  for  the  reason  that  the  veins 
swell  up  from  a  bandage  on  the  other  side  of  the  seat  of  application, 
not  this  (toward  heart),  which  those  know  from  experience  who  bleed, 
for  they  apply  the  bandage  this  side  of  the  position  of  section,  not 
on  the  other  side,  because  the  veins  swell  up  on  the  other  side  of  the 
bandage,  not  this  side.  But  the  opposite  way  ought  to  happen  if  the 
motion  of  the  blood  and  spirit  is  made  from  the  viscera  into  the  whole 
body,  for  the  canal  being  intercepted,  progression  is  not  given,  therefore, 
the  swelling  of  the  veins  ought  to  be  made  on  this  side  of  the  bandage. 
Or,  indeed,  our  doubt  is  solved  from  that  which  Aristotle  writes  of 
sleep,  Chap.  3,  where  he  says,  "Necessarily  what  is  evaporated, 
impelled  continually  elswhere,  is  then  turned  back  and  changed,  like 
the  Euripus ;  for  the  heat  of  any  animal  is  intended  by  nature  to  be 
carried  to  the  higher  parts,  much,  at  the  same  time,  on  the  other 
hand,  is  turned  back  and  carried  downward."'  So,  Aristotle.  For 
the  explanation  of  this  passage,  we  must  know  this.  That  the  cavities 
of  the  heart  are  so  prepared  by  nature  that  there  is  an  opening  made 
from  the  vena  cava  into  the  right  ventricle  of  the  heart,  when  an  exit 
into  the  lungs  is  opened.  Further,  from  the  lungs  there  is  another 
opening  into  the  left  ventricle  of  the  heart,  from  which,  finally,  an 
exit  is  open  into  the  arterial  aorta,  the  valves  of  which  are  placed  at 
the  mouths  of  the  vessels,  in  order  to  impede  retrogression.  For  thus 
there  is  a  perpetual  motion  from  the  vena  cava,  through  the  heart  and 
lungs,  to  the  arterial  aorta,  as  we  have  explained  in  the  peripatetic 
questions.  But  since,  when  we  are  awake,  the  motion  of  the  native 
heat  is   outward,  that  is,  toward   the   sensorium,  but  in  sleep   inward, 

1  Andreas  Caesalpini  Arotini,  Quaestionum  Medicarura,  Libri  ii.  ]>p.  233,  234.    Venetiis,  1593. 


382     HISTORY    OF    THE     DISCOVERY    OF    THE    CIRCULATION. 

that  is,  toward  the  heart,  we  must  be  led  to  think  that  while  Ave  are 
awake  uiiicli  spirit  and  blood  are  carried  to  the  arteries,  for  thence 
is  the  way  to  the  nerves.  But  in  sleep  the  same  heat  reverts,  by  the 
veins,  to  the  heart,  not  by  the  arteries,  for  the  natural  entrance  to  the 
heart  is  given  by  the  vena  cava,  not  by  the  artery.  The  evidence  of 
this  is  the  pulses,  which,  while  we  are  awake,  are  made  great,  vehement, 
rapid,  swift,  with  each  vibration,  but  in  sleep  small,  languid,  slow, 
infrequent  (;5  de  can.  pul.  9  and  10).  For  in  sleep  the  native  heat 
tends  less  toward  the  arteries,  it  bursts  forth  into  the  same  most 
vehemently  when  they  are  awake.  But  the  veins  have  a  contrary 
habit,  for  in  sleep  they  become  more  swollen,  and  when  we  are  awake 
more  empty,  as  is  evident  by  observing  those  which  are  in  the  hand. 
For  the  native  heat  in,  sleep,  passes  from  the  arteries  to  the  veins  by 
their  common  mouths,  which  they  call  anastomoses,  and  thence  to  the 
heart.  But  the  pouring  out  of  the  blood  to  the  higher  parts  and  its 
retrocession  to  the  inferior  ones,  like  that  of  the  Euripus,  is  manifest 
in  sleep  and  when  we  are  awake,  for  this  kind  of  motion  is  not  obscure 
in  whatever  part  of  the  body  the  bandage  is  applied,  or  by  whatever 
other  means  the  veins  are  closed  up.  For  when  the  permeation  is 
allowed,  the  rivulets  swell  up  in  parts  by  which  they  are  accustomed 
to  flow.  The  blood  recurs  powerfully  at  that  time  to  its  source,  lest, 
having  been  cut  off,  it  be  extinguished. 

It  will  be  observed  that  in  this  passage  the  word  Euripus  occurs 
twice.  In  the  first  instance,  however,  it  is  Aristotle  that  uses  it, 
expressing  by  it  in  a  metaphorical  way,  his  view  as  to  the  ebb  and 
flow  of  the  heat  of  an  animal ;  Euripus  being  a  narrow  sea  between 
Boeotia  and  Euboea,  which,  according  to  the  ancients,  ebbed  and 
flowed  several  times  a  day.  Hence,  we  find  several  writers  using  the 
word  Euripus  to  express  an  oscillation  of  any  kind.  As  we  are  not 
concerned  at  present  with  what  Aristotle  or  (Jiesalpinus  thought  of 
animal  heat,  it  is  not  necessary  to  dwell  further  upon  this  part  of  the 
passage,  simply  mentioning  that  Csesalpinus  says  nothing  as  regards 
the  heat  as  evidenced  by  the  pulse,  etc.,  which  is  inconsistent  with 
what  is  known  at  the  present  day,  the  heat  going  to  the  heart  by  the 
veins,  not  by  the  arteries.  In  the  second  instance  where  the  word 
Euripus  occurs,  (Jiesalpinus  uses  it  metaphorically,  in  the  sense  of  an 
oscillation ;  but  in  this  case,  as  applied  to  the  blood.  It  is  distinctly 
stated  that  the  blood  is  poured  out  toward  the  superior  parts,  and 
retrogrades  to  the  inferior  ones,  both  asleep  and  awake.  The  ebb  and 
flow  is  from  the  heart  to  the  head  and  back  again,  by  the  arteries  to  the 
head,  by  the  veins  to  the  heart,  there  being  a  perpetual  motion  from 
the  vena  cava  to  the  heart,  through  the  lungs  back  to  the  heart,  and  so 
to  the  arteries ;  thence  the  way  to  the  nerves,  the  nerves  being  nour- 
ished by  arterial  blood,  like  all  the  other  structures.  Not  a  word  is 
said  of  there  being  an  ebb  and  flow,  a  Euripus-like  motion,  in  the 
veins;  on  the  contrary,  it  is  distinctly  said  that  blood  flows  in  the 
veins  toward  the  heart,  as  can  be  proved  by  binding  up  a  vein  any- 
where. It  will  be  observed  that  Csesalpinus  says  that  the  natural 
heat  passes,  only  during  sleep,  from  the  arteries  to  the  veins,  by 
anastomoses.     This  statement,  however,  is  a  totallv  different  one  from 


KNOWLEDGE    AT    THE    END    OF    THE    16TH     CENTUEY.       383 

saying  that  the  arteries  anastomose  only  with  the  veins  during  sleep. 
If  there  are  anastomoses  during  sleep,  there  are  anastomoses  during 
the  wakeful  condition.  More  heat  may  be  generated  and  transmitted 
through  the  economy  at  one  time  than  another,  but  the  absence  of  all 
heat  would  not  affect  the  existence  of  the  anastomoses.  Csesalpinus, 
so  far  from  saying  that  the  blood  passes  from  the  arteries  to  the 
veins  only  during  sleep,  says  that  the  motion  of  the  blood  is  perpetual, 
during  both  the  sleeping  and  waking  conditions.  That  Csesalpinus 
understood  that  the  blood  circulated,  and  did  not  simply  irrigate  the 
system,  seems  to  be  proved  by  the  fact  of  his  saying  that  the  blood 
circulates  in  one  work,  in  another  that  the  blood  is  carried  by  the  veins 
to  the  heart,  and  from  the  heart  by  the  arteries,  and  that  the  arteries 
anastomose  with  the  veins,  and  that  the  motion  is  perpetual  from  the 
vena  cava  to  the  heart  and  lungs  to  the  aorta.  It  is  not  to  be  implied, 
however,  that  he  understood  the  exact  manner  in  which  the  blood 
passed  from  the  arteries  to  the  veins  because  he  uses  the  word 
anastomoses.  Galen  and  Servetus  used  the  same  word  in  this  connec- 
tion, as  also  afterward  Harvey,  although  there  is  no  reason  to  suppose 
that  these  writers  ever  meant,  by  the  word  anastomosis  the  capillaries, 
and  yet,  without  a  knowledge  of  these  vessels,  the  systemic,  no  more 
than  the  pulmonary  circulation,  could  be  thoroughly  understood. 

It  will  be  seen,  from  this  brief  resume  of  the  views  of  Servetus, 
Colombo,  and  Csesalpinus,  that  while  the  pulmonary  circulation  (with 
the  exception  of  the  capillaries)  was  understood  by  Servetus  and 
Colombo,  they  had  but  little  or  no  idea  of  the  general  or  systemic 
circulation  ;  on  the  other  hand,  while  the  general  circulation  (with  the 
exception  of  the  capillaries)  was  correctly  described  by  Csesalpinus,  he 
understood  the  pulmonary  circulation  only  imperfectly.  It  cannot  be  said, 
therefore,  that  any  one,  up  to  the  end  of  the  sixteenth  century,  under- 
stood the  entire  circulation  of  the  blood,  using  the  word  circulation  in 
the  sense  that  we  do  at  the  present  day.  Isolated  portions  of  the  circu- 
lation only  had  been  described.  It  remained  now  for  some  one  to  show 
the  connection  between  the  facts  already  established,  to  add  important 
new  ones,  to  offer  a  view  based  upon  observation  and  experiment  that 
would  explain  all  the  facts.  In  a  word,  to  demonstrate  that  the  blood 
actually  circulates. 

It  is  claimed  by  some  writers  that  this  honor  should  be  accorded  to 
Carlo  Ruini,  of  Bologna,  it  having  been  asserted  that  Ruini  discovered 
both  the  pulmonary  and  systemic  circulations.  Even  if  Ruini  had 
described  both  the  circulations  correctly,  that  would  not  have  entitled 
him  to  be  called  their  discoverer,  since  the  pulmonary  circulation 
had  been  previously  described  by  Servetus  and  Colombo,  and  the 
systemic  circulation  by  Csesalpinus.  Ruini  does  not  appear  to  me, 
however,  to  have  thoroughly  understood  either  the  systemic  or  pulmo- 
nary circulations,  since  he  states  that  the  veins  carry  the  nourishment, 
as  well  as  the  arteries,  to  the  viscera,  and  that  the  pulmonary  arteries 
nourish  the  lungs.  There  can  be  no  possible  misunderstanding  of 
Ruini's  views  as  to  the  systemic  circulation,  as  in  his  Anatomy  of  the 
Horse,1  he  says  the  vein  that  carries  nutriment  to  the  eye,  and  gives  a 

1  Anatoniia  del  Cavallo,  in  Venetia,  1599,  Lib.  i.  p.  65. 


384     HISTORY   OF    THE    DISCOVERY    OF    THE    CIRCULATION. 

figure  illustrating  this  view.  In  speaking  of  the  arteries  and  veins,  we 
find  that  they  appear  to  be  made  solely  to  carry  nutriment  to  parts  as 
noble  as  the  spinal  medulla  ;  and  they  give  nutriment,  life,  and  motion  to 
all  these  parts — a  branch  of  the  vein  and  artery.  That  Ruini  bad  but 
an  imperfect  idea  of  the  pulmonary  circulation  is  evident  from  the 
manner  in  which  he  describes  it,  p.  108  : 

"The  office  of  these  ventricles  is.  for  the  right  one,  to  prepare  the 
blood,  that  the  spirits  of  life  can  be  generated  from  it  and  the  lungs 
nourished;  of  the  left  to  receive  this  blood  already  prepared,  and  to 
convert  a  part  into  spirits,  which  give  life,  and  to  send  the  rest,  together 
with  the  spirits,  by  means  of  the  arteries,  to  all  parts  of  the  body.  In 
both  the  ventricles  are  two  mouths  or  chinks  ;  by  that  of  the  right  the 
blood  of  the  great  vein,  or  cava,  enters,  and  goes  out  by  the  arterial 
vein  ;  by  that  of  the  left  ventricle,  the  blood  enters,  accompanied  by 
the  air  prepared  in  the  lungs  from  the  venous  artery  ;  this  being  en- 
tirely spiritualized  and  perfected  in  the  left  ventricle,  goes  out  (guided 
by  the  great  arteria)  through  all  parts  of  the  body,  except  that  for  the 
lungs,  to  impart  it  that  heat  which  give's  life." 

During  the  middle  of  the  sixteenth  century  the  fame  of  the  medical 
schools  of  Italy  had  spread  far  and  wide.  Students  from  all  parts  of 
Europe  crowded  to  listen  to  the  eloquent  lectures  of  Vesalius,  Eus- 
tachius,  and  Fallopius,  to  attend  the  anatomical  demonstrations  given 
in  the  amphitheatres  at  Padua,  Pisa,  and  Bologna.  At  the  end  of  the 
sixteenth  century,  with  other  foreigners,  William  Harvey  came  to  Padua 
and  studied  with  the  celebrated  Fabricius,  of  Aquapendente,  the  first 
anatomist  to  describe  thoroughly  in  his  Be  venarum  ostiolis,  Patav, 
1603,  the  valves  in  the  veins.1  Fabricius  is  often  said  to  have  first 
discovered  these  valves :  indeed,  he  says  so  himself ;  but  the 
presence  of  valves  in  the  veins  had  been  previously  noticed  by  several 
anatomists ;  among  others,  by  Cannanus,2  Sylvius,3  Eustachius,4  and 
Piccolhominus.5  At  this  moment,  however,  that  which  interests  us 
particularly  in  reference  to  these  valves  is,  that  Fabricius  demonstrated 
them  to  Harvey,  and  that  the  latter  made  such  good  use  of  that  knowl- 
edge that  the  names  of  pupil  and  master  have  ever  since  been  asso- 
ciated ;  for,  undoubtedly,  it  was  reflection  upon  what  might  be  the  use 
of  the  valves,  as  well  as  other  anatomical  considerations,  that  first  led 
Harvey  to  investigate  the  manner  in  which  the  blood  flows  through  the 
system.  Harvey  studied  about  five  years  at  Padua  (1598-1602). 
Naturally,  during  that  time,  he  became  thoroughly  acquainted,  not 
only  with  the  views  of  his  teachers,  Fabricius,  Rudio,  etc.,  but  also 
with  those  of  Colombo,  and  probably  of  Caesalpinus  and  others  who 
had  taught  and  written  concerning  the  manner  in  which  the  blood  was 
supposed  to  flow.  Perfectly  familiar  with  the  anatomical  views  and 
methods  of  the  school  of  Padua,  dissatisfied  with  the  prevailing  imperfect 

1  Hieronymi  Fabrici  ;tl>  Aipiapendente  Opera  Omnia  Lipsiae,  1G87,  De  Venarum  Ostiolis,  p.  150. 

2  Amati  Lusitani  Medici  Physici  Prsestantio  Curationum  Medicinalium,  Lugduni,  1567. 

<*  In  Hippocrates  et  Galeni  Pnysiologiaa  partem  anatomicam  Isagoge  a  Jacobo  Sylvio-Parisiis,  1555. 

*  Bartholmasi  Bustachii  Opuscnla  Anatomica  Venetiis,  1584. 

6  Anatomica;  Prselectiones  Archangel  Piccolhomini  Romas,  158(5.  By  most  writers  tlie  French  ana- 
tomist, Etienne,  is  considered  to  have  described  the  valves  in  the  veins  even  before  Cannanus  or  Sylvius. 
— De  dissectione  partium  corporis  humani  Iibri  tres  a  Carolo  Stephano.  Parisiis,  1545.  Lib.  ii.  llepar, 
Cap.  ix.  p.  182. 


APPEARANCE    OF    HARVEY'S    WORK.  385 

physiological  theories  of  the  circulation,  on  his  return  to  England 
Harvey  began  anew  the  study  of  the  flow  of  the  blood.  The  results  of 
his  reflection  upon  the  knowledge  gained  in  Italy,  of  his  studies  upon 
his  return,  by  numerous  vivisections,  of  extended  comparisons  of  the 
structure  of  the  heart  and  bloodvessels  in  the  animal  kingdom,  of 
pathological  observations  upon  man  and  beast,  were  embodied  in  his 
classical  treatise,  An  Anatomical  Exercise  on  the  Motion  of  the 
Heart  and  Blood  in  Animals.1  This  deservedly  famous  work  will 
always  serve  as  a  model  for  physiological  investigation.  Thus  Harvey 
shows  the  necessity  of  making  vivisections2  in  the  study  of  the  circula- 
tion, and  too  much  stress  cannot  be  laid  upon  this  statement,  as  it  is 
often  said  that  the  circulation  of  the  blood  was  discovered  without  re- 
course to  experiments  upon  living  animals.  The  importance  of  compara- 
tive anatomy  as  an  aid  to  the  study  of  physiology  is  well  shown  by  the 
use  that  Harvey  made  of  his  knowledge  of  the  structure  and  functions 
of  the  heart  in  the  lower  animals,  in  his  researches  upon  the  circulation. 
Indeed,  Harvey  says,3  had  anatomists  only  been  as  familiar  with  the 
dissection  of  the  lower  animals  as  they  are  with  that  of  the  human 
body,  matters  that  have  been  a  source  of  doubt  would  be  free  from  all 
difficulty.  Unfortunately,  comparative  anatomy  is  too  much  neglected 
by  physiologists  at  the  present  day.  That  the  value  of  pathological 
anatomy  in  throwing  light  upon  the  normal  functions  of  the  body  was 
thoroughly  appreciated  by  Harvey  is  evident  from  the  cases  he  refers  to4 
in  connection  with  his  study  of  the  circulation.  Harvey,  therefore,  did 
not  confine  himself  to  any  one  method  of  investigation,  but  availed  him- 
self of  vivisection,  comparative  anatomy,  and  pathology  in  his  researches. 
It  may  be  seen  by  referring  to  the  writings  of  the  great  predecessors  of 
Harvey,  that,  with  the  exception  of  Cfesalpinus,  it  was  always  assumed 
that  the  venous  blood  flowed  from  the  viscera  to  the  periphery.  Un- 
doubtedly, Harvey  demonstrated  far  more  thoroughly,  by  experiment 
and  argument,  than  Gsesalpinus,  the  true  course  of  the  venous  blood, 
and  this  he  proved  in  many  different  ways.  Thus,  in  his  thirteenth 
chapter,5  after  referring  to  the  discovery  of  the  valves  of  the  veins  by 
Fabricius,  and  the  different  uses  that  had  been  assigned  to  them,  Har- 
vey proceeds  to  show  that  the  valves  are  disposed  in  such  a  way  that 
they  permit  the  blood  to  pass  through  them  in  only  one  direction,  and 
that  is  toward  the  heart,6  demonstrating  this  by  calling  attention,  as 
Csesalpinus  had  done  before  him,  to  the  condition  of  the  veins  when 
compressed  as  if  for  bleeding.  At  intervals  in  the  course  of  the  veins, 
under  such  circumstances,  large  knots  are  visible,  which  are  due  to  the 
distended  valves,  which  thus  show  themselves  externally.  By  pressing 
upon  these  veins  above  or  below,  or  between  the  valves,  Harvey  showed 
that  the  venous  blood  ahvays  passed  in  the  same  direction — that  is, 
toward  the  heart — and  concluded  that  the  functions  of  the  valves  were 

1  Exercitatio  anatoniica  de  motu  cordis  et  sanguinis  in  animalibus.     Francofurti  MDCXXVIII. 

-  Op.  cit.,  Cap.  ii.  p.  21  ;  Cap.  iv.  p.  25.  3  Cap.  vi.  p.  32. 

4  Cap.  iii    p.  :U.  5  Cap.  xiii.  p.  54. 

6  It  must  not  be  forgotten  that  Piccoltaominus  had  already  described  the  valves  in  the  jugular  vein, 
ami  drew  the  conclusion  that  these  valves  prevented  regurgitation  to  the  head  and  extremities  respec- 
tively. It  is  to  be  regretted  that  Harvey,  in  his  description  of  the  valves  and  the  flow  of  blood  through 
the  veins,  should  never  have  mentioned  either  Piccolhominus  or  Ciesalpinus,  as  it  is  probable  that  he 
was  acquainted  with  the  writings  of  these  anatomists,  both  teaching  at  Rome  about  the  same  time. 

25 


386     HISTORY    OF    THE    DISCOVERY    OF    THE    CIRCULATION. 

like  those  of  the  semilunar  valves  of  the  pulmonary  artery  and  aorta,  to 
prevent  all  reflux.1  Excellent  figures  are  given  in  this  chapter  to 
illustrate  the  experiments  by  which  the  functions  of  the  valves  were 
demonstrated.  Further,  that  the  blood  flowed  toward  the  heart  in  the 
veins  and  from  the  heart  in  the  arteries,  was  beautifully  demonstrated 
by  an  experiment  upon  a  living  snake,  so  clearly  described  by  Harvey 
in  <  'hapter  X.  After  noticing  the  pulsating  heart  in  the  snake  as  it 
appeared  after  the  animal  had  been  opened,  Harvey  calls  attention  to 
the  fact  that  if  the  vena  cava  be  compressed  it  gradually  empties  itself 
between  the  point  of  compression  and  the  heart ;  whereas,  if  the  aorta 
be  compressed,  it  becomes  distended  between  the  heart  and  the  point  of 
compression,  showing  conclusively  that  the  blood  in  the  vena  cava  flows 
toward  the  heart,  while  that  in  the  aorta  flows  from  the  heart.  In  his 
second  answer  to  Riolan,  Harvey2  gives  further  proof  of  the  circula- 
tion in  noticing  that  in  a  divided  artery  the  blood  flows  from  the  end  of 
the  vessel  that  is  still  in  connection  with  the  heart,  whereas,  in  the 
divided  vein  the  blood  flows  from  that  part  of  the  vessel  separated  from 
the  heart.  One  of  the  most  remarkable  proofs  of  the  circulation  of  the 
blood  advanced  by  Harvey3  is,  that  more  blood  passes  through  the  heart 
in  a  given  time  than  can  be  accounted  for  by  the  ingesta  or  by  the  quantity 
of  the  blood  in  the  vessels  ;  hence  the  blood  must  pass  and  repass 
throug-h  the  heart,  and  in  estimating  the  amount  of  blood  flowing  from 
the  left  ventricle  into  the  aorta  during  a  short  period  of  time  even,  we 
necessarily  count  the  same  blood  over  and  over  again.  Harvey  was 
not  only  the  first  to  describe  correctly  the  entire  circulation,  but  in  the 
great  work4  we  have  so  often  referred  to  is  found  the  first  accurate 
account  of  the  movements  of  the  heart,  the  successive  dilatations  and 
contractions  of  the  auricles  and  ventricles,  the  contraction,  hardening, 
and  elevation  of  the  heart  against  the  chest,  etc.  An  excellent  descrip- 
tion, as  may  be  supposed,  is  also  given  of  the  pulmonary  circulation, 
etc.  Further,  though  from  the  day  of  Aristotle  it  was  known  that  there 
was  some  connection  between  the  beating  of  the  heart  and  the  pulse, 
Harvey5  showed  clearly  that  the  dilatation  of  the  artery,  or  the  pulse, 
was  the  effect  of  the  contraction  of  the  ventricle.  Harvey  was  not  the 
first,  however,  to  show  this,  since  in  an  ancient  work,  Synopsis  peri 
Sphugmon,  by  an  unknown  author,  the  pulse  in  this  respect  was 
correctly  described.  When  this  work  was  first  discovered,  according 
to  d'Aremberg,  it  was,  without  any  reason,  attributed  to  Rufus,  of 
Ephesus.     The  description  I  refer  to  is  to  be  found  at  page  20  :6 

"  How  is  the  pulse  generated  ?  The  pulse  is  produced  as  follows  : 
The  heart,  after  having  drawn  in  the  air  from  the  lung,  first  receives  it 
in  its  left  cavity,  then  falling  back  upon  itself  immediately  distributes  it 

1  The  importance  of  the  valves  in  the  veins,  either  functionally  or  as  leading  to  the  discovery  of  the 
circulation,  must  not  be  exaggerated,  since  in  many  veins  there  are  no  valves.  Thus  in  man,  at  least, 
however  it  may  be  in  other  mammals,  valves  are  not  found  in  the  vena?  cava;,  the  innominate,  pulmonary, 
portal,  hepatic,  renal,  uterine,  ovarian,  iliac,  and  spinal  veins.  Further,  there  are  tew  valves  in  the  veins 
of  birds,  reptiles,  or  fishes,  and  none  in  the  veins  of  in  vertebra  ta,  and  yet  the  blood  circulates  in  all  these 
animals.  It  is  evident,  therefore,  that  the  valves  in  the  veins  are  not  indispensable  in  the  maintenance 
of  the  circulation. 

2  Opera  Omnia  Edita,  17(16,  p.  120.     Exercitatio  altera  ad  J.  Eiolanum. 

3  Cap.  ix.  p.  42.  4  Cap.  ii.  iii.  iv.  v.  vi.  5  Cap.  iii.  p.  24. 

<-.  Sbvoipig  T£pl  a<pvy/iuv,  Traite  sur  le  Pouls  attribue  a  Kufus  d'Ephese,  par  le  Dr.  Ch.  Dareniberg, 
Paris,  184ti,  p   20. 


DISCOVERY    OF    THE    CAPILLARIES.  387 

to  the  arteries  ;  it  follows,  then,  that  during  the  collapse  of  the  heart, 
the  arteries  of  the  body  being  filled,  their  pulse  is  produced,  and  when 
empty,  their  systole.  As  I  was  saying,  the  pulse  is  produced  in  the 
arteries  when  full  and  receiving  the  air,  and  in  the  heart  when  empty, 
as  we  shall  establish  below." 

In  his  view  of  the  contraction  of  the  ventricle  being  the  cause  of  the 
dilatation  of  the  artery,  Harvey  was  anticipated  also  in  modern  times 
by  Csesalpinus,  who  observes1  that  "  it  happens  that  when  the  heart  is 
contracting,  the  arteries  are  dilated,  and  it  dilating,  are  contracted." 

For,  on  account  of  the  vessels  ending  in  the  heart,  some  pour  their 
contents  into  this  substance,  as  the  vena  cava  into  the  right  ventricle 
and  venous  artery  (pulmonary  vein)  into  the  left ;  some  draw  out,  as 
the  arterial  aorta,  from  the  left  ventricle,  and  the  arterial  vein  (pulmo- 
nary artery),  nourishing2  the  lungs  from  the  right,  but  in  all  are  valves 
placed  and  adapted  to  that  use  that  their  mouths,  allowing  to  enter,  do 
not  lead  out  again,  and  those  leading  out  to  do  not  allow  to  enter  again; 
it  so  happens  that,  the  heart  contracting,  the  arteries  are  dilated,  and 
dilating,  contracted,  not  at  once,  as  appears. 

I  might  dwell  further  upon  the  numerous  observations,  demonstra- 
tions, and  arguments  based  upon  vivisections,  comparative  anatomy, 
pathology,  etc.,  to  be  found  in  Harvey's  work.  The  above  brief  de- 
scriptions will  suffice,  however,  in  giving  an  idea  of  the  general  methods 
of  investigation  and  the  results  accomplished.  The  proofs  advanced  by 
Harvey  were  so  numerous  and  convincing  as  to  render  the  conclusion 
that  the  blood  circulates  inevitable.  It  was  the  only  theory  that  would 
explain  all  the  facts,  the  only  view  that  enabled  one  to  sift  the  truth 
from  the  error  in  the  theories  that  had  been  advanced  before  Harvey '3 
time.  There  is  no  doubt  that  Harvey  was  the  first  to  teach  that  the 
blood  flows  from  the  right  side  of  the  heart  through  the  lungs  back  to 
the  left  side  of  the  heart,  thence  into  the  aorta  and  arteries  throughout 
the  body,  from  the  arteries  into  the  veins,  returning  by  the  veins  to  the 
heart  again — in  a  word,  that  he  was  the  first  to  describe  thoroughly  the 
entire  circulation ;  but  it  must  be  admitted  that  he  did  not  demonstrate 
it,  for  there  is  no  reason  to  suppose  that  Harvey  ever  understood  exactly, 
still  less  demonstrated,  the  manner  in  which  the  blood  flows  from  the 
arteries  into  the  veins,  since  the  capillaries  were  not  discovered  till  after 
his  death. 

With  the  discovery  of  the  capillaries  by  Malpighi  and  Leeuwenhoek 
the  entire  circulation  was  for  the  first  time  demonstrated.  That  Harvey 
did  not  understand  the  manner  in  which  the  blood  flowed  from  the 
arteries  into  the  veins  is  evident  from  his  own  description.  His  words3 
are:  "Signum  est,  etc.,  sanguinum  ab  arteriis  in  venas  et  non  contra 
permeare  et  aut  anastomosis  vasorum  esse  aut  porositates  carnis  et  par- 
tium  solidarum  pervias  sanguini  esse" — that  it  "is  obvious  that  the 
blood  passes  from  the  arteries  into  the  veins,  etc.,  and  not  the  contrary; 
and  that  there  are  either  anastomoses  of  the  vessels  or  porosities  of  the 

1  Qusestionum  Peripatetic-arum,  1.593,  Lib.  Quint.  Qusest.  iv.  p.  122. 

2  It  will  be  observed,  from  Cicsalpinns  referring  to  the  pulmonary  artery  being  nutritive,  that,  as 
already  mentioned,  he  did  not  understand  the  pulmonary  circulation. 

3  Cap.  xi.  p.  48,  Secundum  suppositum  Couflrmatur. 


388     HISTORY    OF    THE     DISCOVERY    OF    THE    CIRCULATION. 

flesh  and  solid  parts  that  are  pervious  to  the  blood."  Had  Harvey  ever 
seen  the  capillaries,  or  even  had  an  idea  of  their  structure,  we  may  be 
assured  that  his  description  would  have  been  a  graphic  one.  There 
would  have  been  no  obscurity  in  reference  to  such  an  all  important 
matter.  That  Harvey  means  by  the  word  porositates,  porosities  or 
holes,  and  not  capillaries,  is  evident  from  the  way  in  which  he  uses  this 
word  in  the  introduction  to  the  Exereitatio,  where,  in  speaking  of  the 
theory  of  the  ancients  as  regards  the  transmission  of  the  blood  through 
the  septum  of  the  heart,  he  says  they  hold  "  that  there  are  numerous 
porositates  in  the  septum  of  the  heart,  adapted  for  the  transmission  of 
the  blood  ;  but,  by  Hercules,  there  are  no  porositates,  neither  can  they 
be  demonstrated."  If  by  porositates  Harvey  means  capillaries,  he  would 
deny,  then,  that  there  are  any  capillaries  in  the  septum  of  the  heart. 
Harvey  appears  to  me  to  use  the  word  porositates  just  in  the  same  sense 
(that  of  holes  or  porosities)  as  used,  as  we  have  seen,  by  De  Carpi,  Vesalius, 
etc.,  in  the  description  of  the  septum  of  the  heart.  As  regards  the  word 
anastomoses,  Servetus  and  Caesalpinus  speak  of  the  arteries  passing  into 
veins  by  anastomoses,  and  there  is  no  more  reason  for  supposing  that 
Harvey  understood  by  this  word  capillaries,  than  that  they  did. 

For  the  discovery  of  the  capillaries,  in  1661,  science  is  indebted  to 
Malpighi.1  In  examining  the  lung  of  a  living  frog,  by  means  of  the 
microscope,  this  distinguished  physiologist  actually  saw  the  blood  passing 
from  the  arteries  into  the  veins  by  means  of  extremely  delicate  tubes,  at 
once  the  terminal  branches  of  the  arteries  and  the  beginnings  of  the 
veins.  These  minute  intermediate  connecting  tubes,  the  capillaries, 
were  also  seen  by  Malpighi  in  the  mesentery  of  the  living  frog  as  well 
as  in  the  lung.  Some  time  after  Malpighi 's  discovery,  the  capillary 
circulation  was  observed  by  Leeuwenhoek2  (1688),  the  Dutch  naturalist, 
with  a  microscope,  in  the  lung  of  a  bat,  in  the  tadpole's  tail,  and  in  the 
fins  of  different  kinds  of  fish.  From  that  time  forward,  the  magnificent 
spectacle  of  the  capillary  circulation  became  with  microscopists  a  favorite 
subject  for  popular  demonstrations.  Between  1628,  the  epoch  of  the 
appearance  of  the  De  motu  cordis  of  Harvey,  and  1661,  the  year  of 
the  discovery  of  the  capillaries  by  Malpighi,  our  knowledge  of  the  cir- 
culation was  extended  by  the  discovery  of  the  lacteals,  etc.  Obviously, 
without  a  knowledge  of  the  lymphatic  system,  that  of  the  circulation  of 
the  blood  would  be  far  from  complete.  In  this  connection,  however,  it 
will  be  only  necessary  to  allude  to  the  names  of  Eustachius,  Aselli, 
Pecquet,  Rudbeck,  and  Bartholinus,  whose  contributions  to  the  dis- 
covery of  the  lymphatic  system  have  already  been  referred  to  in  the 
chapters  treating  of  absorption.  During  the  seventeenth  century 
our  knowledge  of  the  exact  manner  in  which  the  blood  flows  to 
all  parts  of  the  economy  was  greatly  extended  by  the  study  of  the 
vascular  system,  by  means  of  injections.  It  is  true  this  method 
of  investigation  had  been  occasionally  attempted  before  this  period, 
but  with  little  success.     It  was  not  until  Ruysch3  had  perfected  the 

i  MarcelH  Malpighi,  Opera  Omnia,  Lug.  Bat.,  1G87.  Tomus  secundus  De  Pulnionibus  Epistola  ii. 
p.  328 

a  Arcan.  Nat   Lugd.  Bat  ,  1722,  pp.  158,  1G3. 

3  For  an  account  of  lluyscb,  see  eloge,  by  Fontenelle,  in  Hist,  de  l'Acad.  Sciences,  1731,  and  Hyrtl, 
Lebrbucb  der  Anatoniie,  1881,  p.  61. 


DEMONSTRATION    OF    CIRCULATION    BY    INJECTIONS.      389 

methods  of  Swammerdam  and  Home,  and  had  demonstrated,  by  his 
very  perfect  injections,  the  manner  in  which  the  bloodvessels  are  dis- 
tributed through  the  tissues,  that  this  method  of  study  became  universal 
with  anatomists.  It  can  readily  be  understood  that  when  arteries,  capil- 
laries, and  veins  are  filled  with  a  colored  injection,  how  much  easier  the 
course  of  these  vessels  can  be  made  out,  with  either  scalpel  or  microscope, 
than  if  these  bloodvessels  were  simply  studied  in  the  state  in  which  they 
are  usually  found  in  the  body  after  death.  Indeed,  one  of  the  most 
striking  demonstrations  of  the  continuity  of  the  vascular  system  consists 
in  injecting  a  fluid  into  an  artery  until  the  fluid  escapes  by  an  opening 
made  in  the  vein.  Further,  during  the  seventeenth  century,  so  fertile 
in  discovery,  the  first  attempts  were  also  made  in  the  study  of  the  circu- 
lation of  the  invertebrata,  Willis,1  for  example,  describing  the  results  of 
his  researches  upon  the  circulation  of  the  oyster,  lobster,  etc.  It  is, 
however,  only  during  the  present  century  that  physiologists  have  under- 
stood the  circulation  of  the  blood  as  it  takes  place  in  the  mollusca, 
articulata,  etc.,  the  vascular  system  of  animals,  like  insects,  crabs, 
spiders,  oysters,  snails,  etc.,  differing  very  much  from  that  of  man  or 
the  mammalia ;  Milne  Edwards,  more  especially,  having  shown,  among 
other  peculiarities,  for  example,  that  the  interorganic  spaces  or  lacunae 
play  the  part  of  bloodvessels  in  the  invertebrata,  as  is  the  case  in  certain 
parts  of  the  body  of  vertebrates  also.  Within  the  past  twenty-five  years 
great  advances  have  been  made  in  extending  our  knowledge  of  the  cir- 
culation in  other  directions.  Thus,  by  the  introduction  of  the  graphic 
method  of  study,  we  have  seen,  by  means  of  kymographions,  sphygmo- 
graphs,  cardiographs,  etc.,  that  we  can  determine  blood  pressure,  the 
rapidity  with  which  the  blood  flows  in  the  system,  etc.,  while  the  dis- 
coveries of  Bernard,  Brown- Sequard,  Ludwig,  etc.,  have  shown  us  how 
local  variations  in  the  general  circulation  are  due  to  the  influence  of  the 
vasomotor  nerves. 

If  our  account  has  been  a  correct  one,  the  history  of  the  discovery 
of  the  circulation,  recapitulated,  divides  itself  naturally  into  a  series  of 
epoch-making  periods — 

1.  The  structure  and  functions  of  the  valves  of  the  heart.  Erasis- 
tratus,  B.  C.  304. 

2.  The  arteries  carry  blood  during  life,  not  air.      Galen,  A.  D.  165. 

3.  The  pulmonary  circulation.      Servetus,  1553. 

4.  The  systemic  circulation.     C?esalpinus,  1593. 

5.  The  pulmonic  and  systemic  circulations.     Harvey,  1628. 

6.  The  capillaries.     Malpighi,  1661. 

The  history  of  the  discovery  of  the  circulation,  like  all  other  great 
movements,  social,  political,  and  scientific,  illustrates  the  profound 
truth  that  intellectual  development  is  as  surely  a  growth  regulated  by 
law  as  the  life  of  a  plant  or  animal.  That  no  intellect,  however 
magnificent,  rises  so  above  the  conditions  of  its  environment  as  to  make 
it  doubtful,  for  a  moment,  that  the  discovery  would  have  been  made 
sooner  or  later,  even  had  the  name  with  which  it  is  usually  associated, 
never  existed.     Every  mind  is  the  product  of  its  age.     All  the  circum- 

i  Willis's  Works,  translated  bv  8.  Pordage,  London.  1684 :  Of  the  Soul  of  Brutes,  Chap.  iii.  pp.  10,  11, 
Tables  ii.  iii. 


390    HISTORY    OF    THE    DISCOVERY    OF    THE    CIRCULATION. 

stances  prove  that  intellectual  Europe  at  the  end  of  the  sixteenth 
century  was  ready  to  accept  the  circulation  of  the  blood.  Had  the 
discovery  been  made  some  centuries  sooner  it  would  have  fallen  still- 
born. All  Italy,  at  that  period,  was  alive  with  speculation,  hypothesis, 
theory,  as  to  the  manner  in  which  the  blood  flowed  through  the  body, 
and  above  all,  Padua.  Let  anyone  compare  the  works  of  the  great 
Italian  anatomists  and  physiologists  of  the  sixteenth  century,  in  their 
Latin  or  Italian  dress,  with  the  admirable  work  of  Harvey  on  the 
circulation,  in  the  original,  and  not  in  an  English  translation,  and  he 
will  be  impressed  with  the  fact  that  the  same  mode  of  thought  and 
expression  pervades  both.  In  his  methods  of  investigation,  observation, 
and  arguments,  Harvey  is  essentially  Italian.  By  birth  an  English- 
man, in  thought  Italian,  Harvey  lived  and  died  a  student  of  Padua. 

The  discovery  of  the  circulation  of  the  blood,  as  we  learn  from  this 
necessarily  brief  account,  belongs,  therefore,  to  no  one  age,  country,  or 
person.  Its  history,  extending  as  it  does  over  a  period  of  more  than 
2000  years,  naturally  suggests  that  the  subject  would  have  attracted 
the  attention  of  the  great  medical  minds  of  all  time ;  and  such  we 
have  seen  was  the  case.  Far  from  the  grandest  generalization  in 
the  whole  range  of  biology  being  discovered  in  its  entirety  by  one 
mind,  we  have  seen  how,  little  by  little,  it  was  gradually  established 
by  many  observers ;  that  long  intervals  would  elapse  without  any 
progress  being  made,  when  suddenly  some  ancient  error  would  be 
dissipated  and  fade  away  in  the  light  of  advancing  science.  Such  a 
history  ought  to  encourage  every  student,  for  however  trivial  and  unim- 
portant his  experiments  or  observations  may  appear  at  the  time,  every 
new  fact  once  well  established  will  sooner  or  later  assume  its  appro- 
priate place  as  a  part  of  some  future  generalization ;  the  chain  of  facts 
leading  to  a  great  discovery  being  united  together  like  living  things, 
each  linked  with  those  that  have  passed  away  with  those  still  to  come. 
Discoveries  great  in  themselves  have  often  borne  no  fruit  at  the  time, 
falling  on  barren  soil,  the  human  mind  not  being  sufficiently  developed 
to  appreciate  them.  With  the  progress  of  knowledge,  however,  the 
significance  of  discoveries  made  often  ages  ago  and  long  forgotten, 
become,  in  time,  apparent  to  all.  Truth,  like  the  rays  of  the  rising 
sun,  is  perceived  first  by  those  whose  minds  soar  above  the  intellectual 
horizon  of  their  day,  but  sooner  or  later  its  genial  influence  is  felt  by 
their  humble  followers,  by  all  alike,  all  in  good  time. 


CHAPTEK   XXY1. 

RESPIRATION. 

We  have  seen  that  all  vital  activity  is  accompanied  by  waste,  that 
mental,  muscular,  and  secretory  action,  and  the  production  of  animal  heat, 
involve  the  development  of  carbonic  acid,  urea,  etc.  Such  principles 
produced  through  the  decomposition  of  the  food  and  tissues,  if  retained 
in  the  system  soon  cause  death,  hence  the  necessity  of  their  being 
eliminated ;  excreted.  As  the  degree  of  vital  activity  is  conditioned 
by  that  of  the  cell,  of  fermentation,  oxidation,  etc.,  and  as  it  is  through 
respiration  that  oxygen  is  absorbed,  and  carbonic  acid  exhaled,  it  is 
evident  that  this  function  is  both  absorbing  and  excretory  in  character, 
and  must  constitute  a  most  important  part  of  nutrition.  As  might  be 
expected,  therefore,  the  absorbing  of  oxygen  and  elimination  of  carbonic 
acid  are  not  necessarily  limited  to  any  part  of  the  body,  but  may  go  on 
in  every  part  of  it.  Further,  while  the  carbonic  acid  excreted  is,  to  a 
considerable  extent,  due  to  the  combination  of  the  oxygen  absorbed 
with  the  carbon  of  the  body,  there  is  no  reason  to  suppose  that  the  car- 
bonic acid  excreted  at  any  one  moment  is  produced  through  the  combus- 
tion of  the  oxygen  supplied  by  the  air  inspired  at  that  moment.  On  the 
contrary,  the  oxygen  may  have  been  locked  up  in  the  tissues,  and  sup- 
plied, not  from  the  lungs,  but  from  a  different  part  of  the  economy 
altogether.  In  fact,  an  animal  will  exhale  carbonic  acid  in  an  atmos- 
phere of  hydrogen.  Under  such  circumstances,  the  oxygen  of  the  car- 
bonic acid  must  have  been  absoi'bed  at  some  previous  period. 

In  the  widest  sense  of  the  term  respiration  may  then  be  considered 
as  the  process  by  means  of  which  oxygen  is  absorbed  by  the  system,  and 
carbonic  acid  is  excreted,  whatever  may  be  the  source  of  the  latter.  It 
is  often  said  that,  while  animals  inhale,  plants  exhale  oxygen,  and  that 
animal  and  vegetable  life  stand,  therefore,  in  a  complementary  relation 
to  each  other.  In  one  sense  this  is  true,  since  green  plants  under  the 
influence  of  solar  light  decompose  carbonic  acid  and  water,  giving  up 
the  oxygen  and  appropriating  the  carbon,  elaborating  the  latter  into 
starch,  fat,  cellulose,  etc.  Animals,  on  the  other  hand,  through  the 
absorption  of  oxygen,  burn  the  carbon  of  their  food  produced  by 
plants,  and  exhale  carbonic  acid.  This  antithesis  between  plant  and 
animal  life  exists  only  so  long  as  the  plant  is  regarded  as  the  means  by 
which  inorganic  matter  is  combined  in  a  form  suitable  as  nutriment  for 
the  animal.  When,  however,  the  remaining  phenomena  of  plant  life 
are  considered,  such  as  the  germination  of  the  seed,  the  expansion  of 
the  leaf,  the  budding  and  flowering,  the  movement  of  the  sap,  it  will  be 
found  that  all  such  depend  upon  the  absorption  of  oxygen,  and  cease 
when  the  plant  is  deprived  of  it.  Respiration,  therefore,  is  as  impor- 
tant a  function  in  plant  as  in  animal  life. 


392 


RESPIRATION. 


The  phenomenon  of  respiration  or  breathing  in  animals  is  usually 
associated  with  the  presence  of  specialized  organs,  like  lungs,  gills,  etc. 
Such  structures  are,  however,  not  indispensable  for  the  performance  of- 
this  function,  since  the  muscle  of  a  frog,  when  separated  from  the 
animal  and  drained  of  its  blood,  will  absorb  oxygen  and  excrete  car- 
bonic acid  as  long  as  the  muscle  retains  its  irritability.  There  are, 
indeed,  two  kinds  of  respiration,  an  internal  one,  taking  place  in  all 
parts  of  the  body,  the  tissues  giving  up  to  the  blood  the  carbonic  acid 
generated  in  them,  and  absorbing  oxygen  from  it,  and  an  external  one, 
the  blood  giving  up  to  the  atmosphere  through  the  lungs  or  skin  its  car- 
bonic acid  and  receiving  oxygen.  It  is  the  latter  form,  or  external 
kind  of  respiration,  ordinarily  known  as  breathing,  that  we  propose 
considering  more  particularly  at  present. 

A  respiratory  organ  consists  essentially  of  a  membrane  separating 
tissue  or  blood,  containing  carbonic  acid,  on  the  one  hand,  from  the 
atmosphere,  or  some  other  medium  containing  oxygen,  on  the  other ; 
the  membrane  being  of  such  a  character  as  to  permit  of  osmosis. 

As  an  interesting  illustration  of  the  osmosis  of  the  carbonic  acid  of 
the  blood  and  oxygen  through  animal  membrane  may  be  mentioned  the 
experiment  performed  more  than  fifty  years  ago  by  our  late  colleague, 
Prof.  R.  E.  Rogers,  in  which  a  fresh  pig's  bladder  having  been  filled 
with  venous  blood,  and  enclosed  in  a  bell  glass  of  oxygen,  a  large  quan- 
tity of  carbonic  acid  left  the  blood  and  passed  through  the  membrane ; 
wdrile,  on  the  other  hand,  a  quantity  of  oxygen  disappeared,  having 
passed  through  the  membrane  in  the  reverse  direction  into  the  blood. 

Whether  the  animal  be  aquatic  or  terrestrial,  simple  or  complex, 
the  respiratory  organs  are  only  modifications  of  this  simple  membranous 

type  of  structure,  and  this  will  be  found  to 
be  true,  as  they  appear  in  the  form  of  skin, 
gills,  tracheae,  or  lungs.  Thus,  in  many 
of  the  lower  forms  of  life,  as  in  the  hydrozoa 
and  actinozoa,  of  which  the  jelly  fish  (Fig. 
209)  and  anemone  are  familiar  examples, 
are  simply  formed  animals,  in  which  the 
differentiation  of  the  functions,  or  the  di- 
vision of  labor  is  not  carried  to  any  great 
extent,  respiration  is  effected  by  the  gen- 
eral cutaneous  surface,  the  ectodum  or  skin 
readily  permitting  an  exchange  between 
the  oxvsren  dissolved  in  the  sea-waters  and 
the  carbonic  acid  developed  within  their 
bodies.  In  the  star  fish,  sea  urchin,  and 
echinodermata  generally,  respiration,  while 
still  chiefly  cutaneous,  is,  to  a  certain  ex- 
tent, localized,  the  ambulacral  suckers  or 
feet  acting  probably  also  as  respiratory 
organs.  In  the  holothuroidea,  also  echinodermata,  which,  from  their 
fancied  resemblance  to  cucumbers,  are  popularly  known  at  the  sea  shore 
by  that  name,  respiration  is  still  more  specialized,  being  effected  by  an 
arborescent-like  organ,  a  growth    or  diverticulum   from   the   terminal 


Fig.  209 


^fpr^'% 


Jelly  fish.     (Milne  Edwards.) 


RESPIRATION    IN    I  N  V  ER  TEB  R  AT  A  . 


393 


portion  of  the  alimentary  canal,  which  dividing  and  subdividing  tree- 
like, reaches  to  the  anterior  portion  of  the  body.  This  structure, 
floating  freely  in  the  visceral  cavity,  can,  at  the  will  of  the  animal,  be 


Fig.  "210. 


Doris  Job  nstoni,  showing  tlie  tuft  of  external  gills. 
(Carpenter.) 


filled  through  the  anus  with  sea-water,  which  osmosing  into  the  visceral 
cavity  passes  thence  into  the  water  vascular  system.  On  the  other 
hand,  the  respiratory  organs,  in  many  animals,  assume  the  form  of 
gills,  delicate  membranous-like  structures,  whose  thin  walls  readily  permit 
of  an  osmosis  between  the  oxygen  of  the  surrounding  water  and  the 
carbonic  acid  of  the  blood  circulating  within.  Such  a  type  of  respira- 
tion obtains  in  the  mollusca,  of  which  the  oyster,  scallop,  cuttle-fish, 
and  cloris  (Fig.  210)  are  examples ;  in  fishes,  the  perennibranchiate 
batrachia  (Fig.  211). 

Another  form  of  respiration  is  the  tracheal.  This  is  seen  in  insects, 
centipedes,  etc.,  and  consists  of  innumerable  delicate  membranous 
branching,  tubes,  ramifying  throughout  the  entire  body  of  the  animal, 
and  opening  externally  by  usually  lateral  apertures  the  spiracles  or 
stigmata,  between  the  layers  of  which  the  trachse  consists  is  inclosed  a 
spirally  convoluted  fibre,  to  which  is  due  their  strength  and  flexibility. 
The  air  enters  by  the  spiracles  or  openings,  and  is  conveyed  by  the 
tracheae,  or  breathing  tubes,  to  all  parts  of  the  system.  Finally,  in 
batrachia,  reptiles,  birds,  and  mammals,  including  man,  respiration  is 
effected  by  the  skin  and  lungs.  The  action  of  the  skin  as  a  respiratory 
surface  will  be  considered  with  the  other  functions  of  that  structure, 
and  in  describing  the  lungs  in  man,  let  us  begin  with  a  more  simple 
type  of  lung  than  that  of  the  frog,  for  example. 

The  lungs  of  the  frog  (Fig.  212)  consist  of  two  vascular  bladder-like 
sacs,  communicating  directly  by  short  bronchi,  or  rather  bronchial  open- 
ings, with  the  larynx.  On  opening  the  lung  the  inner  surface  (Fig.  213) 
will  be  seen  to  be  more  or  less  honeycombed,  and  the  alveoli  subdivided 
into  still  smaller  spaces,  or  cells.  These  cells  all  communicate  with 
the  central  pulmonary  cavity,  and  are  lined  with  a  capillary  network 
intermediate  between  the  arterioles  running  along  the  attached  borders 
of  the  septa  and  the  venules  along  the  free  borders.  It  is  evident  that 
a  far  greater  extent  of  vascular  surface  is  exposed  to  the  air,  by  this 
segmented  or  honeycombed  disposition  of  the  inner  surface,  than  if  the 
latter  was  smooth.     If  the  lungs  of  the  frog  be  now  compared  with 


394 


RESPIRATION. 


those  of  a  lizard  or  turtle,  the  only  noticeable  difference  is  that  this  seg- 
mentation of  the  lung  is  more  marked,  while  in  hirds  and  mammals  it 


Fig.  212. 


Fig.  213. 


Respiratory  organs  of  a  frog,  as  seen  on  their  anterior 
surface,  a.  Hyoidean  apparatus.  b.  Cartilaginous 
ring  at  the  root  of  the  lungs,  c.  Pulmonary  sacs,  cov- 
ered with  vascular  ramifications.     (Carpenter.) 


Lung  of  frog,  showing  its  internal  surface. 
(Dalton.) 

is  carried  to  such  an  extent 
that  each  lung  consists  essen- 
tially of  an  immense  number  of 
these  honey-combed  sacs,  sub- 
dividing into  cells,  the  extent  of 
the  vascular  surface  exposed  to 
the  air  being  enormously  increased.  When  we  come  to  study  develop- 
ment we  shall  see  that  the  lungs  in  mammals  begin  as  buds  or  sac- 
like  diverticula  of  the  oesophagus,  which  soon  segment.  In  this 
transitory  condition  the  lungs  of  the  mammalian  embryo  arc  comparable 
to  those  of  the  frog.  As  development  advances  this  segmentation  con- 
tinues until  the  bronchus,  instead  of  opening  into  one  pulmonary  sac, 
as  in  the  frog,  through  its  division  into  bronchial  tubes,  opens  into  an 
innumerable  number.  The  ultimate  sacs  are  then  known  as  pulmonary 
lobules,  and  the  little  honeycombed  spaces  as  air  cells.  A  lobule  of 
the  mammalian  lung  acts,  therefore,  like  the  whole  lung  of  the  frog,  the 
only  difference  being  that  it  is  smaller,  the  air  cells  in  one  being  seen 
only  by  aid  of  the  microscope,  in  the  other  being  perfectly  visible  to 
the  naked  eye. 

It  is  worthy  of  mention  that  the  frog  at  different  periods  of  its 
existence  breathes  by  skin,  gills,  and  lungs,  and  that  the  transitory 
stages  through  which  its  respiratory  organs  pass  are  permanently  re- 
tained in  the  lower  forms  of  life.  The  respiratory  organs  in  man,  in  the 
widest  sense  of  the  term,  include  the  nares,  mouth,  pharynx,  larynx, 
trachea,  lungs,  thorax,  and  appropriate  muscles.  That  the  nares,  not 
the  mouth,  constitute  the  natural  entrance  for  the  air  to  the  lungs  is 
shown  by  the  fact  that  in  certain  mammals  breathing  is  accomplished 
through  the  nares  alone.  Thus  in  the  cetacea,  of  which  the  whale, 
dolphin,  porpoise,  etc.,  are  examples,  the  soft  palate  is  very  much 
developed  and  so  disposed  to  embrace  the  glottis  and  maintain  the 
cavity  of  the  larynx  in  communication  with  the  posterior  nares,  a  free 
passage  way,  however,  being  left  on  either  side  for  the  food.  Such  a 
disposition  of  the  parts  makes   it  possible  for   the  elephant   to   use   its 


STRUCTURE    OF    LARYNX. 


395 


nose  or  trunk,  pharynx  and  larynx  as  a  siphon  to  suck  up  its  drinks 
and  transfer  the  same  to  the  mouth,  at  the  moment  that  the  latter  is 
open  the  posterior  nares  communicating  with  the  glottis  only.  In  the 
horse,  camel,  etc.,  the  soft  palate  is  also  well  developed,  and  surrounds 
the  large  epiglottis  to  such  an  extent  as  to  cut  off  completely  all  com- 
munication between  the  mouth  and  pharynx,  except  at  the  moment  of 
deglutition.  Indeed,  in  the  horse,  if  the  facial  nerves  which  supply 
the  muscles  of  the  external  nares  be  divided,  the  animal  dies  from 
asphyxia. 

In  describing  the  structure  of  the  hippopotamus,  the  author  called 
attention1  to  the  fact  that  when  the  animal  passes  under  the  water,  the 
larynx  is  so  elevated  within  the  pharynx  that  a  continuous  passage  is 
offered  to  the  air  from  the  external  nares  to  the  lungs,  enabling  the  animal 
to  breathe  when  almost  entirely  submerged.  A  similar  elevation  of  the 
larynx  is  seen  in  the  young  kangaroo,  and  to  a  certain  extent,  also,  in  the 
human  fetus  and  infant.  The  ill  effects  often  experienced  in  breath- 
ing through  the  mouth  in  a  cold,  dry  atmosphere  further  prove  that 
the  natural  entrance  to  the  respiratory  tract  is  the  nose,  since  the  air 
as  it  passes  over  the  partly  ciliated  moist  and  very  vascular  and  warm 
mucous  membrane  lining  the  nasal  cavities  absorbs  water,  and  is 
elevated  to  the  temperature  of  the  body  before  entering  the  lungs. 
The  action  of  the  nares  in  ordinary  breathing  is  not  very  apparent, 
but  when  the  breathing  becomes  labored,  then  it  is  very  evident. 
The  air  having  passed  the  nose  and  the  pharynx,  enters  the  larynx,  a 
triangular-like    structure  surmounting  the   trachea   and    consisting  of 


Fig.  214. 


Human  larynx,  viewed  from  above  in  its 
ordinary  post-mortem  condition.  5.  Vocal 
cords.  \.  Thyroid  cartilage.  4.  Arytenoid 
cartilages.  0.  Opening  of  the  glottis.  (Dal- 
ton.) 


The  same,  with  the  glottis  opened  by  separa- 
tion of  the  vocal  cords.  5.  Vocal  cords.  1. 
Thyroid  cartilage  4.  Arytenoid  cartilages. 
0.  Opening  of  the  glottis.     (Dalton.) 


sufficiently  rigid  cartilage  to  resist  atmospheric  pressure  united  by 
ligaments  and  movable  through  muscles.  The  detailed  structure  of 
the  larynx  we  will  defer  till  our  account  of  the  voice,  considering  at 


1  Proc.  Acad.  Nat.  Sciences,  p.  130.     Philadelphia,  1881. 


396 


RESPI  RATION. 


Fig.  216. 


present  only  such  of  its  parts  as  influence  respiration.  The  larynx  is 
lined  with  mucous  membrane,  continuous  with  that  of  the  pharynx;  the 
epithelium,  however,  except  that  covering  the  vocal  cords,  is  of  the 
ciliated,  columnar  variety,  the  movement  of  the  cilia  heing  from  helow, 
upward.  If  the  larynx  be  viewed  from  above  (Figs.  214,  215),  or  in 
section  (Fig.  216),  it  will  be  observed  that  it  is  divided  into  an  upper 
and  lower  compartment  by  the  rima  glottidis  (0),  or  the  aperture  of 
the  glottis,  a  triangular-like  orifice,  the  sides  and  base  of  which  are 
formed  by  the  true  vocal  cords  (Figs.  214,  216)  (5,  5)  and  arytenoid 
cartilages  (4).  The  vocal  cords,  or,  more  properly,  the  vocal  mem- 
branes, consist  of  elastic  tissue  covered  with  very  thin  mucous  mem- 
brane, and  extending  from  the  thyroid  cartilages  (Fig.  216,  1  and  2), 

anteriorly  to  the  cricoid  (3),  and  base  of 
the  arytenoid  cartilages  (4)  posteriorly.  The 
upper  edges  of  the  vocal  membrane  extend- 
ing from  the  reentering  angle  of  the  thyroid 
cartilage  to  the  base  of  the  arytenoid  are 
somewhat  thickened,  and  are  usually  and 
incorrectly  described  as  separate  organs,  the 
"vocal  cords."  The  upper  or  false  vocal 
cords,  so-called  because  they  have  no  influ- 
ence in  the  production  of  voice,  are  the 
thickened  upper  edges  of  the  ventricle  or 
sac-like  pouches  extending  outward  and  up- 
ward from  the  larynx  between  the  vocal 
cords,  and  lined  with  the  mucous  membrane 
of  the  same.  The  glottis  or  triangular 
orifice  between  the  vocal  membranes  and 
arytenoid  cartilages  is  the  passage  through 
which  the  air  from  the  nose  and  pharynx 
enters  the  trachea  and  lungs,  and  during  life 
is  alternately  dilated  and  contracted  syn- 
chronously with  the  movements  of  the  chest. 
During  inspiration  the  glottis  (Fig.  215) 
opens,  admitting  the  air  freely  to  the 
trachea,  while  in  expiration  as  the  air  is 
expelled  upward  from  below  the  vocal  mem- 
branes collapse.  These  movements  constitute  the  respiratory  move- 
ments of  the  glottis  and  are  increased  or  diminished  in  intensity  in 
proportion  to  those  of  the  chest.  We  shall  see  that  while  expiration  is 
usually  a  passive  process,  inspiration  is  an  active  one,  and  its  tendency 
is  to  draw  the  vocal  membranes  together.  This  is  provided  against, 
however,  through  the  action  of  the  posterior  crico-arytenoid  muscles, 
which  arise  from  the  posterior  surface  of  the  cricoid  cartilage  converge 
upward  and  outward,  and  are  inserted  into  the  base  of  the  arytenoid 
cartilages.  In  contracting,  these  muscles,  therefore,  dilate  at  the 
moment  of  inspiration  the  glottis.  During  expiration,  however,  these 
muscles  are  relaxed,  the  vocal  membranes  through  their  elasticity,  and 
through  the  contraction  of  the  lateral  crico-arytenoid  muscles  are 
approximated,  and  the  expired  air  separates  them  as  it  passes  upward 


View  of  the  vocal  membrane.  1. 
Left  half  of  the  thyroid  cartilage. 
2.  Right  half  turned  forward  and 
partly  cut  away.  3.  Cricoid  car- 
tilage. 4  Arytenoid  cartilages.  5. 
Right  half  of  the  vocal  membrane. 
6.  Upper  border  of  the  left  half  7. 
Arytenoid  muscle  The  upper  bor- 
ders of  the  vocal  membrane,  ex- 
tended between  the  arytenoid  car- 
tilages and  the  thyroid,  constitute 
the  so-called  "true  vocal  cords." 
(Leidy.) 


STRUCTURE    OF    TRACHEA. 


397 


from  the  trachea.     The  importance  of  the  epiglottis  covering  the  larynx 
during   deglutition,  and  thereby  preventing  foreign   bodies,   especially 


Fig.  217. 


Human  larynx,  trachea,  bronchi,  and  lungs;  showing  the  ramification  of  the  bronchi,  and  the 
division  of  the  lungs  into  lobules.     (Dalton.) 


of  a  liquid  nature,  from  passing  into  the  larynx 
having  been  already  noticed,  it  will  not  be 
necessary  to  dwell  further  upon  the  function  of 
this  structure  in  its  relation  to  deglutition  and 
respiration. 

The  inspired  air  having  passed  through  the 
larynx  enters  the  trachea  (Fig.  217,  T),  a  tube 
from  10  to  12  cm.  long  (4  to  4J  in.),  and  ^ 
cm.  (f  in.)  in  width,  beginning  at  the  lower 
border  of  the  cricoid  cartilage  above  and 
terminating  as  the  two  bronchi  below.  The 
trachea  consists  of  16  to  20  cartilaginous 
rings,  or,  more  correctly,  in  the  form  of  arcs 
the  posterior  third  of  each  ring  being  im- 
perfect, deficient  in  cartilage,  the  intervening 
space  being  filled  up  with  loose  fibrous  tissue. 
The  cartilaginous  rings  are  connected  by  a 
strong  fibro-elastic  membrane,  which  so  extends 
over  and  under  them  in  a  thinned  condition 
that  they  are,  as  it  were,  imbedded  within   it. 


Fig.  218. 


Single  lobule  of  human  lung 
a  Ultimate  bronchial  tube.  b. 
Cavity  of  lobule.  c,  c,  c.  Pul- 
nionory  cells,  or  vesicles.     (Dal. 

TON.) 

The  last  ring  of  the 


trachea  is  somewhat  modified  in  shape,  its  lower  border  being  brought 


;;:••> 


RESPIRATION. 


to  a  median  point  so  as  to  accommodate  itself  to  the  bronchi.     Within 

the  fibrous  tissue  filling  up  the  posterior  third  of  the  cartilaginous  rings 
are  found  unstriped  muscular  tissue,  the  fibres  of  which  are  disposed 
in  a  transverse,  and  to  a  certain  extent,  also  in  a  longitudinal  direc- 
tion. The  action  of  these  muscular  fibres  sometimes  called  the  tracheal 
muscles,  is  to  diminish  the  area  of  the  trachea  by  approximating  the 
cartilaginous  rings,  and  the  ends  of  each  ring.  The  trachea  is  lined 
with  mucous  membrane,  its  epithelium  being  of  the  columnar  ciliated 
character.  The  motion  of  the  cilia  being  from  below,  upward,  a  cur- 
rent is  produced  by  which  the  mucus  is  carried  upward  toward  the 
larynx. 

The  composition  of  the  nasal  and  bronchial  mucus  is  given  in  : 

Table  LVI.1 — Composition  of  Nasal  Mucus. 


Water  .......... 

993.00 

Mucosin        ......... 

53.30 

Sodium  lactate     ........ 

1.00 

Organic  crystalline  principles      ..... 

2.00 

Fatty  matters  and  cholesterin      ..... 

Sodium  and  potassium  chloride  ..... 

5.60 

Phosphates  ...         ...... 

Sodium  sulphate  and  carbonate  ..... 

3.50 
0.90 

5le  LVII.2 — Composition  of  Bronchial  and  Pulmonary  Mu< 

955  520 

Mucosin      .......... 

23.754 

Watery  extract  ......... 

S.OOG 

Alcoholic  extract        ........ 

1.810 

Fat 

2.887 

Sodium  chloride         ........ 

5.825 

"         sulphate         ........ 

"         carbonate       ........ 

0.400 
0.198 

"         phosphate      ........ 

Calcium  phosphate  with  traces  of  iron       .... 

0.080 
0.974 

carbonate     ........ 

0.291 

Silica  and  calcium  sulphate       ...... 

0.255 

1000.000 

Although  the  cilia  are  microscopic,  varying  in  length  from  the  i^-g-th 
to  the  nj-Q-th  of  a  mm.  (the  25100th  to  40100th  of  an  inch)  in  length  ; 
nevertheless,  through  their  vibratory  motion  a  greater  force  is  exerted 
than  might  be  expected.  The  mechanical  effect  produced  by  the  motion 
of  the  vibratile  cilia  can  be  shown  by  means  of  the  instrument  devised 
by  Wyman,3  or  by  that  of  Calliburces. 

The  latter,  as  made  for  the  author  by  Aubrey,  of  Paris,  consists  (Fig. 
219)  of  a  brass  stage  H,  11  cm.  long  and  7  cm.  wide  (4.5  and  3  inches), 
which  can  be  elevated  and  depressed  on  a  vertical  axis  (K)  by  means  of 
the  screw  M,  whose  movement  is  graduated.  The  brass  stage  supports  a 
cork  (I)  5  cm.  long  and  3  cm.  wide  (2  and  1.2  inches),  and  the  vertical 
axis  L,  an  aluminium  rod,  5  cm.  long  (2  inches)  and  with  a  diameter  of 
1.5  mm.  (1.25th  of  an   inch)  horizontally  disposed,  and  terminating  in 

1  Robin  :  Lemons  sur  les  humeurs,  p.  450.     Paris,  1867. 

2  Xasse :  Journal  ofprakt.  Chemie,  1813,  Baud  xxix.  S.  65. 

3  Experiments  with  vibrating  cilia,  American  Naturalist,  vol.  v.  p.  611,  1871. 


APPARATUS    OF    CALLIBURCES. 


399 


Fig.  219. 


an  index  (F)  and  partly  surrounded  by  glass.  The  vertical  index  (L)  is 
surmounted  by  a  brass  disk  N,  through  which  passes  a  safety  tube 
into  which  hot  water  can  be  poured, 
by  means  of  which  the  surrounding 
atmosphere  can  be  kept  moist,  and  at 
a  temperature  of  about  28°  Cent. 
(82°  Fahr.),  and  a  thermometer  (P)  for 
indicating  the  same.  The  brass  stage, 
axis,  and  disk,  etc.,  can  be  covered 
with  a  glass  cylinder.  Before  doing 
this,  the  mucous  membrane,  the  mo- 
tion of  whose  cilia  is  to  be  examined, 
that  of  the  oesophagus  of  the  frog. 
for  example,  is  placed  upon  the  cork, 
and  the  brass  stage  (H)  elevated  by 
the  screw  (M)  until  the  membrane  is 
almost  in  contact  with  the  aluminium 
rod.  When  properly  adjusted,  and 
the  membrane  kept  moist  and  warm 
by  the  means  just  indicated,  the 
aluminium  rod  will  rotate  on  its  axis, 
the  index  at  its  end  (F)  moving 
over  the  graduated  brass  circle. 
having  a  diameter  of  2.(3  cm.  (l.<»4 
inch).  Usually  the  index  will  move 
around  the  circle  once  in  three 
minutes,  and  the  motion,  under 
favorable  circumstances,  will  continue 
for  an  hour  and  upward.  As  the 
aluminium  rod,  with  the  glass  sur- 
rounding it,  and  the  index  weigh  about  0.073  gr.  (1.05  grain),  it  is 
evident  that  considerable  mechanical  effect  is  produced  relatively  to  the 
small  size  of  the  organs  exerting  the  force.  The  motion  of  the  cilia  of 
human  mucous  membrane  can  often  be  seen  upon  the  surface  of  recently 
extracted  nasal  polypi  when  the  latter  are  viewed  under  the  microscope. 
The  trachea  terminates  inferiorly  in  the  bronchi  (Fig.  217,  B);  the 
right  bronchus,  differs  from  the  left  in  beino-  the  shortest,  attaining, 
usually,  a  length  of  2..")  cm.  (1  inch),  while  the  left  is  almost  twice  as 
long.  The  general  structure  of  the  bronchi  corresponds  in  every  way  to 
that  of  the  trachea  ;  the  cartilaginous  rings  are,  however,  shorter  and 
narrower,  and  less  numerous,  the  right  bronchus  consisting,  usually,  of 
from  six  to  eight  rings,  the  left  of  from  nine  to  twelve.  Each  bronchus 
divides  and  subdivides  dichotomously  into  the  bronchial  tubes  (Fig.217). 
The  latter,  diverging  in  every  direction,  and  never  anastomosing,  gradu- 
ally become  smaller  and  smaller,  and  more  delicate  in  structure,  and 
when,  finally,  they  are  reduced  to  about  a  diameter  of  the  Ath  of  a  mm. 
(y^o^h  °f  an  inch)i  they  terminate  in  a  primary  lobule  (Fig.  218).  The 
bronchial  tubes  differ  in  several  respects  from  the  bronchi,  of  which 
they  are  the  diverging  branches.  Tims,  in  the  larger  ones,  the  carti- 
lages are  disposed  as  irregular-shaped  plates,  of  various  sizes,  all  over 


Apparatus  of  C'alliburces. 


400 


RESPIRATION, 


the  sides  of  the  tubes  instead  of  in  the  form  of  imperfect  rings ;  in  the 
medium-sized  tubes  the  cartilages  become  smaller  and  less  numerous, 
while,  finally,  in  tubes  having  a  diameter  of  less  than  -i-  of  a  mm. 
(_i_th  of  an  inch)  they  disappear  altogether.  The  terminal  bronchial 
tubes  then  consist  of  a  delicate  fibro-elastic  external  membrane,  containing 
circular  muscular  fibres  and  a  very  thin  lining  of  mucous  membrane,  the 
epithelium  of  which  is,  however,  still  ciliated.  As  just  stated,  each 
bronchial  tube  finally  terminates  in  a  primary  lobule.  The  primary 
lobule,  with  a  diameter  usually  of  2  mm.  (TVtQ  °f  an  inch),  consists  of 
a  sac,  which  is  essentially  an  expansion  of  the  terminal  bronchial  tube, 
hence  its  name  of  infundibulum.  The  cavity  of  the  primary  lobule 
(Fig.  218,  b)  is  subdivided  by  thin  partitions,  projecting  from  its  inner 
surface  into  secondary  compartments,  or  alveoli  c,  the  pulmonary  air 
cells  having  a  diameter  of  from  |-th  to  \d  of  a  mm.  (-j^j-th  to  -^th  of 
an  inch) ;  these,  while  separated  from  each  other  by  the  partitions,  com- 
municate with  the  central  cavity  or  intercellular  air  passages,  which,  in 
turn  opens  into  the  terminal  bronchial  tube,  through  which  the  inspired 
air  ultimately  passes  to  the  air  cells.  The  air  cells,  amounting  to  over 
seventeen  millions  in  number,  and  representing  an  area  of  nearly  two 
hundred  square  metres  (1800  feet),  are  polyhedral  sacs,  surrounded  by 
anastomosing  elastic  fibres,  and  consist  of  a  fibro-elastic  wall,  contain- 
ing, probably,  some  muscular  fibres,  and  lined  with  a  tessellated  epithe- 
lium. The  epithelium  is  more  homogeneous  and  easily  demonstrated 
in  the  foetus  than  in  the  adult.  If  the  primary  lobule  of  the  human 
lung  be  now  compared  with  the  lung  of  the  frog,  it  will  be  seen  that  it 
represents  the  entire  frog's  lung  in  miniature.  The  primary  lobules  of 
the  human  lung  unite  through  connective  tissue  into  larger  secondary 
lobules,  and  the  latter,  uniting,  constitute  a  lung.  The  polyhedral  mark- 
ings upon  the  surface  of  a  lung  indicate  the  margins  of  the  secondary 
lobules,  while  careful  examination  will  disclose  also  the  outlines  of  the 

primary  lobules  composing  the  secondary 
ones.  Finally,  the  integration  of  the  pri- 
mary lobules  into  the  secondary  ones,  and 
the  latter  into  lobes,  carried  still  further 
into  the  left  lung  than  in  the  right,  the 
former  consisting  of  two  lobes,  the  latter  of 
three.  While  the  lungs  are  nourished  by 
the  bronchi,  it  is  by  means  of  the  pul- 
monary arteries  that  the  venous  blood  is 
carried  to  them  from  the  right  side  of  the 
heart  and  aerated.  The  pulmonary  artery 
arising,  as  we  have  seen,  from  the  right 
ventricle  of  the  heart,  soon  divides  into  a 
right  and  left  branch  for  either  hms.  Fol- 
lowing  the  bronchus  and  bronchial  tubes, 
the  artery  divides  and  subdivides,  the 
branches  becoming  smaller  and  smaller  as 
they  approach  the  primary  lobules  (Fig.  220),  until  finally  they  termi- 
nate as  the  pulmonary  capillaries.  The  terminal  arterial  capillaries 
surround  each  alveolus  or  air  cell  as  a  vascular  circle,  which  anastomoses 


Fig.  2-20. 


Diagram  of  two  primary  lobules  of 
the  lungs,  magnified.  1.  Bronchial 
tube.  2.  A  pair  of  primary  lobules 
connected  with  fibro-elastic  tissue.  3. 
Intercellular  air  passages.  4.  Air  cells. 
5.  Branches  of  the  pulmonary  artery 
and  vein.     (Leidy.) 


STRUCTURE    OF    PLEURA.  401 

with  those  of  the  adjacent  alveoli.  From  these  vessels  arise  a  capillary 
network  (Fig.  220),  so  closely  set  that  the  meshes  are  even  smaller  than 
the  diameter  of  the  vessels  themselves,  the  latter  having  usually  a  diameter 
of  from  -g^th  to  T^-g-th  of  a  mm.  (-juVo^1  t0  5 0*0 0 tn  °f  an  incn)-  This 
network  supports  the  bottom  of  each  air  cell,  and  the  blood  that  it 
carries  is  separated  from  the  air  of  the  cells  only  by  its  "wall  and  the 
extremely  delicate  epithelial  lining  of  it.  The  carbonic  acid  of  the 
venous  blood  conveyed  to  the  lungs  by  the  pulmonary  artery  is  thus 
separated  from  the  oxygen  of  the  air  within  the  air  cells  brought  by  the 
trachea  by  nothing  but  the  Avail  of  the  capillary  and  epithelium  of  the 
air  cell.  The  rapidity  with  which  the  osmosis  of  these  gases  takes  place 
through  such  a  delicate. septum  will,  therefore,  be  readily  imagined;  the 
osmosis  being  still  further  insured  through  the  great  vascularity  of  the 
parts,  the  respiratory  surface  being  thereby  continually  kept  moist,  which 
greatly  promotes  the  exchange  of  the  gases. 

The  full  influence  of  the  air  upon  the  blood  is  further  secured  in  that 
the  capillary  plexus  is  so  disposed  between  the  walls  of  two  adjacent  air 
cells  that  one  of  its  surfaces  is  exposed  to  each.  It  has  been  estimated1 
that  a  thin  layer  of  blood  of  150  square  metres  (1350  feet)  is  exposed 
in  the  lungs  to  the  air  of  the  air  cells,  and  that  this  blood,  amounting  to 
perhaps  2  litres  (4  pints),  is  renewed  10,000  times  in  twenty-four  hours. 
This  estimate  is  based  upon  the  assumption  that  the  surface  of  the  capil- 
laries is  equal  to  about  three-fourths  the  surface  of  the  air  cells.  That 
this  is  not  an  exaggeration  may  be  inferred  from  the  fact  of  an  injected 
lung  appearing  to  consist  of  nothing  but  capillaries.  From  the  capillary 
network  surrounding  the  air  cells  the  pulmonary  veins  arise,  which, 
uniting  with  each  other,  gradually  form  four  larger  trunks,  which  finallv 
terminate  in  the  left  auricle  of  the  heart  and  convey  to  it  the  aerated 
oxygenated  blood  to  be  distributed,  as  we  have  seen,  by  the  arterial 
system  to  all  parts  of  the  body. 

Having  described  the  pulmonary  air  cells  and  bloodvessels,  the  passage 
by  osmosis  of  the  carbonic  acid  from  the  blood  into  the  air  cells  and  of 
the  oxygen  from  the  air  cells  into  the  blood,  let  us  now  consider  the 
means  by  which  the  external  air  is  drawn 
into  the  lungs  and  the  carbonic  acid  ex- 
pelled from  them. 

The  heart  and  lungs  are  suspended  by 
the  great  bloodvessels  in  the  thoracic 
cavity.  The  thorax  consists  of  the  ster- 
num anteriorly,  the  dosal  vertebra  pos- 
teriorly, and  the  ribs  laterally.  It  is 
covered  in  above  by  the  cervical  muscles 
and  fascia,  below  by  the  diaphragm,  and 
laterally,  etc.,  by  the  intercostal  muscles. 
The  thoracic  cavity  is  therefore  air-tight. 

If    the  lungS   be    examined  in  Situ    it  'will  Diagrammatic  view  of  pleural  sacs. 

be  found  that  the  surface  of  each  lung  is  covered  with  a  serous  membrane 
continuous  with  that  lining  the  inner  surface  of  the  thorax  or  the  pleura. 

1  Kuss :  Physiologie,  1873,  p.  338. 

26 


402 


RESPIRATION 


To  understand  the  relations  of  the  pleura  to  the  lungs  and  walls  of  the 
thorax,  let  us  first  conceive  the  pleura  as  consisting  of  two  bladders 
(Fig.  221),  and  so  placed  within  an  empty  thorax  that  the  outer  wall 
(c)  of  each  bladder  will  adhere  to  the  inner  wall  (b)  of  the  thorax,  the 
inner  walls  (d)  of  each  bladder  remaining  free. 

Suppose  now  that  the  heart  and  lungs  be  inserted  between  the  inner 
free  walls  of  the  two  bladders,  and  that  each  of  the  latter  be  made  to 
adhere  to  the  surface  of  the  lung  with  which  it  is  in  contact.  Such  a 
disposition  being  made  (Fig.  222),  the  bladders  will  then  represent  the 
two  pleura,  the  inner  walls  (»/  d)  the  visceral  layer,  the  outer  wall  (c  e) 
the  parietal  layers,  and  the  space  between  the  layers  the  pleural  cavi- 
ties, the  spaces  between  the  bladders  or  the  pleura  constituting  the 
mediastinal  spaces,  the  narrow  septum  formed  through  the  union  of  the 

Fig   1222. 


Diagrammatic  view  of  pleural  sacs  with  heart  and  lungs  interposed. 


two  pleura  the  mediastinum.  In  health  the  opposed  surfaces  of  the 
visceral  and  parietal  layers  of  the  pleura  are  always  in  contact,  there 
being  only  fluid  enough  between  them  to  insure  their  gliding  smoothly 
over  each  other.  Practically,  therefore,  in  normal  respiration  there 
is  no  pleural  cavity.  This  must  necessarily  be  so,  since  the  thorax 
being  an  air-tight  cage,  as  it  dilates  through  the  action  of  the  inspira- 
tory muscles  and  recedes  from  the  lungs,  the  air  within  the  latter 
will  expand  and  become  rarefied ;  the  external  air  being  then  denser 
than  the  inside  air,  will  rush  through  the  trachea  into  the  lungs,  and 
expanding  the  latter  in  proportion  as  the  thorax  is  dilated,  keep  the 
visceral  layer  of  the  pleura  in  contact  with  the  parietal  one.  It  will  be 
observed  that  while  it  is  the  force  of  the  inspiratory  muscles  that  dilates 
the  chest,  it  is  the  pressure  of  the  air  that  expands  the  lungs,  and, 
further,  that  inasmuch  as  the  lungs  are  elastic  and  therefore  offer  a 
resistance  to  their  expansion,  the  air  must  overcome  this  resistance,  and 
hence  the  pressure  exerted  by  the  air  within  the  lungs  during  inspira- 
tion must  be  less  than  that  of  the  external  atmosphere.  The  significance 
of  this  fact  we  shall  see  shortly.  On  the  other  hand,  as  the  thorax  con- 
tracts as  its  capacity  diminishes,  the  air  within  the  lungs  exerting  now 


INSPIRATION    AND    EXPIRATION.  403 

a  greater  pressure  than  the  air  without,  will  pass  out  of  the  lungs, 
through  the  trachea  by  which  it  had  just  entered  the  lungs,  of  course 
collapsing,  their  elasticity  now  aiding  the  expulsion  of  the  air  to  the 
same  extent  as  it  formerly  opposed  its  entrance.  The  dilatation  of  the 
thoracic  cavity  and  the  taking  in  of  the  air  is  known  as  inspiration,  the 
contraction  of  the  thoracic  cavity  and  the  giving  out  of  the  air  expira- 
tion, the  two  acts  constituting  respiration. 

Let  us  consider  now  a  little  more  in  detail  the  means  by  which  this 
alternate  dilatation  and  contraction  of  the  thoracic  cavity  causing  respi- 
ration is  effected. 


CHAPTER    XXV11. 

MUSCLES  OF  RESPIRATION. 

Reflection  upon  the  origin  and  insertion  of  the  various  muscles 
acting  upon  the  thorax  makes  it  evident  that  some  of  these  muscles  in 
contracting  will  expand  the  chest,  causing  inspiration,  while  the  relax- 
ation of  these  muscles  together  with  the  elasticity  of  the  lungs  and  the 
action  of  certain  other  muscles,  will  contract  it,  causing  expiration. 
The  muscles  involved  in  the  production  of  respiration  will  then  natu- 
rally divide  themselves  into  two  groups,  those  of  inspiration  and  those 
of  expiration  (Table  LVIII.,  page  410).  To  the  study  of  these  let  us 
now  turn. 

Inspiration. 

Of  all  the  inspiratory  muscles  the  diaphragm  is  the  most  important, 
since  the  capacity  of  the  chest  is  enlarged  to  a  greater  extent  through 
its  contraction  than  by  that  of  any  other  muscle.  Indeed,  in  the 
male   sex   at  least,   as  we  shall  see,  gentle  breathing  is  accomplished 

Fig.  223. 


Interior  view  of  the  diaphragm.  1,  2,  3,  the  three  lobes  of  the  central  tendon,  surrounded  by  the 
fleshy  fasciculi  derived  from  the  inferior  margin  of  the  thorax,  the  crura,  4,  5,  and  the  arcuate  ligaments, 
6,  7  ;  8,  aortic  orifice  ;  9,  oesophageal  orifice  ;  10,  quadrate  foramen  ;  11,  psoas  muscle ;  12,  quadrate 
lumbar  muscle. 

almost  entirely  by  the  action  of  the  diaphragm.  The  diaphragm 
(Fig.  223),  arising  from  the  ensiform  cartilage  of  the  sternum,  the 
cartilages   of  the  six  or  seven  lower  ribs,  and  often,  also,  from   their 


THE     DIAPHRAGM. 


405 


osseous  portions  from  the  arcuate  ligaments  and  the  bodies  of  the  first, 
second  and  third  lumbar  vertebrae,  and  the  intervertebral  cartilages  of 
the  right  side,  and  from  the  bodies  of  the  first  and  second  lumbar 
vertebrae,  etc.,  of  the  left,  or  the  crurse,  covers  in  therefore  the  lower 
circumference  of  the  thorax.  From  this  origin  the  diaphragm  passes 
upward  into  the  cavity  of  the  thorax  as  a.  vaulted  arch  or  dome  (Fig. 
224,  B),  its  convexity  being  toward  the  lungs.     With  the  exception  of 

Fig.  224. 


Diagrammatic  sections  of  the  body  in  inspiration  and  expiration.  A.  Inspiration.  B.  Expiration. 
Tr.  Trachea.  St.  Sternum.  D.  Diaphragm.  Ab.  Abdominal  walls.  The  shading  roughly  indicates  the 
stationary  air. 

the  central  tendinous  portion,  the  diaphragm  consists  of  muscular 
fibres  of  the  voluntary  character.  It  presents  several  openings  through 
which  pass  the  oesophagus,  aorta,  vena  cava,  etc.,  and  it  is  supplied  by 
the  phrenic  nerve.  During  the  state  of  repose,  as  we  have  just  seen, 
the  diaphragm  presents  the  form  of  a  dome  or  of  a  vaulted,  arched  or 
curved  surface.  If  the  diaphragm,  however,  be  observed  during 
contraction,  as  can  be  readily  done  by  opening  largely  the  abdominal 
cavity  of  a  completely  insensible  living  mammal,  a  cat,  dog,  or  rabbit, 
for  example,  it  will  then  be  seen  that  through  the  contraction  of  its 
muscular  fibres  the  curved  surface  of  the  diaphragm  assumes  more  the 
form  of  a  plane  (Fig.  224,  A),  and  that  the  floor  of  the  thorax 
descends.  The  effect  of  the  descent  of  the  diaphragm,  therefore,  is  to 
enlarge  in  a  vertical  direction  the  capacity  of  the  thorax,  and  to  rarefy 
the  air  within  it.  The  external  air  being  then  denser  than  that  within 
the  thorax  rushes  into  the  latter  and  proportionally  distends  the  lungs 
in  consequence.  The  diaphragm  through  its  contraction  acts  then  as 
an   inspiratory  muscle ;  it  need  hardly   be  added,  however,  that   it  is 


40  f) 


MUSCLES    OF    RESPIRATION. 


not  the  diaphragm,  but  the  air,  that  actually  distends  the  lungs.  We 
are  in  the  habit  of  illustrating  the  action  of  the  diaphragm  in  respira- 
tion  by  the  simple  apparatus  represented  in    Fig.  225.      This  consists 


Fig.  225. 


Diagrammatic  view  of  apparatus  to  show  the  action  of  the  diaphragm. 


of  a  bell  jar  (a),  the  walls  of  which  correspond  to  the  thorax,  and  in 
which  are  suspended  the  lungs  (LL),  the  trachea  passing  through  the  air- 
tight fittincr  cork.  The  bottom  of  the  jar  is  closed  in  air-tight,  with 
India  rubber  corresponding  to  the  diaphragm.  It  is  needless  to  say 
that  there  is  no  such  amount  of  space  as  (d)  corresponding  to  the 
pleural  cavity  in  the  human  being  in  a  state  of  health.  Such  being 
the  disposition  of  the  parts,  by  pulling  down  the  India  rubber  (5)  the 
air  within  the  jar,  and  therefore  within  the  lungs,  becomes  rarefied 
as  indicated  by  the  rise  of  the  mercury  within  the  limb  (3)  of  the 
manometer.  The  external  air  will  therefore  rush  through  the  trachea 
into  the  lungs,  and  consequently  distend  them.  With  the  elevation  of 
the  India  rubber  the  condition  of  the  pressure  of  the  air  within  and 
without  the  jar  being  reversed,  the  air  will  pass  out  of  the  lungs,  the 
latter  collapsing.  It  will  be  observed  that  the  flattening  of  the 
diaphragm  just  referred  to  is  most  marked  at  its  lateral  portions,  or 
the  parts  under  the  lungs,  as  might  be  expected,  that  part  of  it 
immediately  under  the  heart  undergoing  but  little  change  in  form.  As 
the  diaphragm  descends  it  pushes  downward  and  forward  the  abdominal 
viscera,  and  as  the  anterior  and  lateral  walls  of  the  abdomen  are 
extensible,  they  give  way  to  the  pressure  so  exerted  and  are  protruded. 
With  each  inspiration,  therefore,  the  descent  of  the  diaphragm  in  man 
becomes  perfectly  evident  through  the  movement  of  the  abdomen. 
The  action  of  the  diaphragm  in  producing  inspiration  may  be  readily 
imitated  in  man  and  mammal  just  dead,  by  opening  the  abdomen  and 
pulling  the  central  tendon  downward.  The  external  air  will  rush  into 
the  lungs,  and  often  with  a  distinctly  audible  sound.  By  passing  a 
long  and  slender  needle  through  the  ensiform  cartilage  of  the  sternum 
of  a  completely  chloralized  animal,  a  rabbit,  for  example,  and  connect- 
ing the  eye  of  the  needle  by  a  silk  thread  (Fig.  226,  A),  with  a  little 
boxwood  pulley  (P),  whose  movements  are  inscribed  by  the  horizontal 
lever  (R)  on  the  recording  surface,  we  can  obtain  a  graphic  representa- 


STRUCTURE    OF    THORAX. 


-107 


Fig.  226. 


tion  of  the  descent  and  ascent  of  the  diaphragm  during  respiration. 
Too  much  importance  must  not,  however,  be  attached  to  this  method 
of  studying  the  movements  of  the  dia- 
phragm. While  the  vertical  diameter 
of  the  chest  is  enlarged  through  the 
descent  of  the  diaphragm,  nevertheless, 
through  its  attachment  to  the  sternum 
and  false  ribs  during  its  contraction 
through  the  pulling  of  the  sternum  and 
the  upper  false  ribs  downward  and  in- 
ward, and  the  lower  ribs  upward  and 
inward  toward  the  vertebral  column,  there 
would  be  a  tendency  to  diminish,  to  some 
extent,  the  capacity  of  the  thorax.  This 
effect  is,  however,  counteracted  by  the 
ribs  being  elevated  at  the  same  time  as 
the  diaphragm  descends,  and  through  the  action  of  certain  muscles, 
to  be  described  later.  The  elevation  of  the  ribs  is  such  a  constant 
accompaniment  of  the  descent  of  the  diaphragm  that  in  general  terms 
it  may  be  stated  that  inspiration  is  effected  by  the  descent  of  the  one, 
and  the  ascent  of  the  other,  and  this  is  true,  even  though  the  breathing 
appear  entirely  diaphragmatic. 

The  ribs  (Fig.  227)  pass  from  their  articulations  with  the  dorsal  ver- 
tebra? downward  and  forward ;  they  are  somewhat  twisted  in  shape  and 


Boxwood  pulley  for  recording  the 
movements  of  a  needle  inserted  in  the 
diaphragm.  A  light  lever  is  attached 
to  the  horizontal  arm.     (Sandeeson.) 


Fig.  221 


Front  view  of  the  thorax.  1,  2,  3.  The  three  pieces  of  the  sternum.  4,  5.  The  dorsal  vertebrae. 
6.  The  first  true  rib.  7.  Its  head.  8.  Neck.  0  Tubercle.  10.  The  seventh  true  rib.  11.  Costal  carti- 
lages.    12.  The  floating  ribs.     13.  Groove  for  the  iuteicostal  bloodvessels.     (Leidt.) 


are  twelve  in  number.  The  upper  seven  or  true  ribs  are  articulated 
with  the  sternum,  of  the  remaining  five  or  false  ribs,  the  eighth,  ninth, 
and  tenth  are  joined  to  the  seventh  rib,  the  last  two  ribs,  viz.,  the 


408  MUSCLES    OF    RESPIRATION. 

eleventh  and  twelfth,  arc  unattached  anteriorly  and  are  hence  known 
as  floating  ribs.  As  the  ribs  are  elevated  they  recede  from  each  other, 
the  distance  between  them  being  increased;  they  are  at  the  same  time 
rotated  outward,  assuming  a  more  horizontal  position,  and  in  tending 
to  straighten  themselves  become  less  curved.  Through  their  attach- 
ment to  the  sternum  the  lower  portion  of*  the  latter  is  thrown  forward, 
the  flexibility  of  this  part  of  the  thorax  being  mainly  due  to  the  sternal 
attachment  of  the  ribs  being  cartilaginous  and  not  osseous.  The  effect 
of  this  change  in  the  form,  position,  and  direction  of  the  ribs  and  ster- 
num is  to  enlarge  the  capacity  of  the  chest  in  every  direction  vertically 
through  the  separation  of  the  ribs,  laterally  through  their  rotation 
outward  and  straightening,  antero-posteriorly,  through  the  movement 
forward  of  the  sternum.  As  the  air  rushes  in,  distending;  the  lungs  of 
the  expanding  chest,  it  is  evident,  therefore,  that  inspiration  is  produced 
through  the  elevation  of  the  ribs  as  well  as  through  the  descent  of  the 
diaphragm.  The  extent  of  the  increase  of  the  capacity  of  the  chest 
through  the  elevation  of  the  ribs  is  greatly  influenced  by  the  length, 
degree  of  curvature,  character  of  the  angles  of  the  ribs,  etc.  Thus  from 
the  ribs  being  directed  obliquely  downward  and  forward  when  elevated, 
and  assuming  a  more  horizontal  position  their  external  ends  recede  from 
the  posterior  wall  of  the  thorax  and  increase  proportionally  its  antero- 
posterior diameter.  As  the  ribs  are  elevated  they  remain  nearly  parallel 
to  each  other,  it  follows,  therefore,  that  the  inspiratory  effect  produced 
by  this  movement  of  the  ribs  will  be  proportional  to  the  length,  or, 
more  accurately  speaking,  to  the  length  of  the  chord  of  the  arc  repre- 
sented by  the  curve  of  the  rib.  The  length,  however,  varies  consider- 
ably, increasing  rapidly  from  the  first  to  the  fifth  rib,  attaining  its 
maximum  at  the  eighth  rib,  diminishing  then  progressively  from  the 
ninth  to  the  twelfth.  Other  things  being  equal,  it  follows,  then,  that 
the  increase  in  the  antero-posterior  diameter  of  the  chest  is  greater  at 
the  level  of  the  seventh  to  the  ninth  ribs  than  at  the  upper  or  lower 
part  of  the  thorax.  It  is  for  this  reason  that  during  inspiration  the 
inferior  portion  of  the  sternum  moves  so  much  more  forward  than  the 
upper  portion.  The  transverse  diameter  of  the  chest,  on  the  other  hand, 
is  greatly  influenced  by  the  amount  of  the  curvature  of  the  ribs,  and 
this  varies  considerably.  Thus  the  curvature  increases  from  the  first 
to  the  third  ribs,  the  maximum  amount  being  about  that  of  the  sixth  ; 
there  is  but  little  difference,  however,  as  regards  the  curvature  of  the 
ribs  included  between  the  sixth  and  ninth.  The  amount  of  the  curvature 
can  be  measured  by  the  versed  sine  of  the  arc  of  the  circle  represented 
by  the  rib,  or,  what  is  the  same  thing,  the  distance  from  the  middle  line 
of  the  thorax  to  the  most  prominent  part  of  it  laterally.  The  angle 
made  by  the  osseous  part  of  the  ribs  with  their  sternal  or  costal  ones, 
and  the  length  of  their  cartilaginous  portions  increase  from  the  fourth 
to  the  seventh.  Consequently  it  is  in  this  part  of  the  thorax  that  the 
increase  of  capacity  due  to  the  elasticity  and  flexibility  of  the  cartilage 
is  greatest.  The  different  extent  to  which  the  capacity  of  the  thorax  is 
enlarged  in  its  various  diameters  during  inspiration,  the  influence  due 
to  the  variation  in  the  length,  curvature  of  the  ribs,  etc.,  are  shown  by 
the  diagrams  (Figs.  228,  229,  230,  and  231)  illustrating  the  admirable 


ACTION     OF    THE    RIBS. 


409 


and  exhaustive  work  of  Sibson.1  Let  us  consider  now  the  muscles  which 
elevate  the  ribs,  and  so,  together  with  the  action  of  the  diaphragm, 
cause  inspiration. 


Fig.  229. 


Dorsal  region. 
Expiration.  Inspiration. 


Anterior  region  of  the  thorax. 
Inspiration.  Expiration. 


Fig.  230. 


Fig.  231. 


Expiration. 


Inspiration. 


i   Phil.  Trans.,  1846. 


410 


MUSCLES    OF    RESPIRATION. 


Table  LVIIL- 

I  aspiration. 


-Muscles  of  Respiration. 

Expiration, 


Ordinary. 


Diaphragm 


I  ntcnial  intercostals, 
osseous  portion. 

Triangularis  sterni. 
Intra  costales. 


<  )1>I i(jue. 
Transversalis. 
Sacro  Lumbalis. 


External  intercostals. 

Internal  intercostals,  sternal  portion    . 

Scaleni  ...... 

Levatores  costaruru. 

Auxiliary. 

Serratus  posticus  superior    . 
Accessor i  us  ..... 
Sterno-cleido-mastoid  . 

Levator  anguli  scapula?. 
Trapezius,  superior  portion. 
Serratus  magnus. 
Pectorales  major,  inferior  portion. 
Pectorales  minor. 


These  muscles  are  usually  described  as  consisting  of  two  sets,  ordi- 
nary or  extraordinary,  or  auxiliary  (Table  LVIIL),  according  as  the 
breathing  due  to  their  action  is  easy  or  forced.  There  is,  however,  no 
such  sharp  line  of  demarcation  observable,  it  being  impossible  to  say 
just  where  ordinary  easy  breathing  ends,  and  forced  breathing  begins, 
great  difference  being  observed  in  this  respect  within  the  limits  of  health, 
according  to  individual  peculiarities.  There  are  certain  muscles,  how- 
ever, such  as  the  external  intercostals,  scaleni,  etc.,  which  intervene  in 

Fig.  232. 


View  of  several  of  the  middle  dorsal  vertebra?  and  ribs,  to  show  the  intercostal  muscles  (A.  B.).  yz. 
A.  From  the  side.  B.  From  behind.  1,  1.  The  levatores  costarum  muscles,  short  and  long.  2.  The 
external  intercostal  muscles.  3  The  internal  intercostal  layer  shown,  in  the  lower  of  the  two  spaces 
represented,  by  the  removal  of  the  external  layer,  as  seen  in  A  in  the  upper  space,  in  front  of  the  ex- 
ternal layer.  The  deficiency  of  the  internal  layer  toward  the  vertebral  column  is  shown  in  B.  (After 
Cloquet.) 

easy  inspiration ;  these  we  will  consider  first,  and  afterward  those 
coming  into  play  when  the  breathing  is  exaggerated.  That  the  external 
intercostal  muscles  (Fig.  232)  are  inspiratory  in  function  one  would 


ACTION    OF    THE    SCALENI.  411 

infer  from  their  attachments,  and  the  direction  of  their  fibres.  Passing 
from  rib  to  rib  from  above  downward,  and  from  behind  forward,  in  con- 
tracting these  muscles,  will  approximate  and  elevate  the  ribs.  Experi- 
ment justifies  this  view  of  the  inspiratory  function  of  the  external  inter- 
costal muscles,  since,  if  they  be  exposed  in  a  living  animal  with  each  inspi- 
ration, they  will  be  seen  in  contracting  to  elevate  the  ribs.  Inasmuch, 
however,  as  the  general  direction  of  the  sternal  portion  of  the  internal 
intercostals  is  also  from  above  downward,  and  rather  forward  than  back- 
ward, through  the  change  in  the  curve  of  the  rib,  analogy  would  lead  us 
to  suppose  that  their  action  is  the  same  as  that  of  the  external  inter- 
costals, and  that  they  must,  therefore,  be  also  regarded  as  inspiratory  in 
function.  This  view  is  confirmed  by  the  observations  of  Bernard,1  made 
upon  a  man  in  whom  the  pectoral  muscle  was  so  atrophied  as  to  permit 
of  an  experimental  investigation  of  the  function  of  the  partly  exposed 
sternal  portion  of  the  internal  intercostal  muscle.  When  the  sternal  part 
of  the  muscle  was  stimulated,  the  cartilage  of  the  second  rib  was  elevated, 
and  with  it  the  anterior  extremity  of  the  corresponding  osseous  rib. 

The  scaleni  passing  obliquely  downward  from  their  origin,  the  trans- 
verse processes  of  the  lower  six  cervical  vertebrae,  to  their  insertion,  the 
first  and  second  ribs,  in  acting  from  their  origin  during  contraction  will 
elevate  these  ribs,  and  indirectly  the  whole  thorax.  To  prove  that  the 
scaleni  do  act  in  this  way  it  is  only  necessary  to  squeeze  between  the 
fingers  the  part  of  the  neck  including  these  muscles  to  feel  them  contract 
with  each  inspiration.  The  movement  then  experienced,  the  so-called 
respiratory  pulse  of  Magendie,2  becomes  very  evident  when  the  superior 
part  of  the  chest  is  much  dilated.  The  action  of  the  scaleni  is  not  only  to 
elevate  the  ribs,  but  to  fix  the  first  rib  as  an  origin  from  which  the  inter- 
costal  muscles  that  elevate  the  ribs  can  act.  Ordinary  inspiration  is 
also  effected  by  the  levatores  costarum  (Fig.  232),  as  these  muscles, 
arising  from  the  transverse  processes  of  the  twelve  dorsal  vertebra?,  and 
inserted  fan-like  into  the  upper  edges  of  the  ribs  between  the  tubercles 
and  the  angles  in  contracting,  elevate  the  ribs.  The  action  of  the  mus- 
cles, which  we  have  just  considered,  usually  suffices  to  produce  easy 
inspiration.  When  breathing,  however,  becomes  difficult,  labored,  or 
very  difficult,  then  inspiration  is  aided  through  the  contraction  of  several 
muscles,  the  serratus  posticus  superior,  accessorius,  sterno-cleido-mas- 
toid,  levator  anguli  scapulas,  superior  portion  of  the  trapezius,  serratus 
magnus,  and  the  pectoral  muscles.  It  is  not  necessary  to  dwell  upon 
the  anatomical  disposition  of  these  muscles  to  prove  their  importance  in 
labored  inspiration.  It  is  evident  that  the  serratus  posticus  superior 
passing  from  the  vertebral  column  to  be  inserted  into  the  second,  third, 
fourth,  and  fifth  ribs,  will,  in  contracting,  elevate  the  ribs,  that  the 
accessorius,  extending  from  the  last  cervical  vertebrae  to  the  angle  of  the 
ribs,  will  produce  the  same  effect.  The  sterno-cleido-mastoid  acts  upon 
the  clavicle  and  sternum,  and  the  levator  anguli  scapulae,  trapezius,  and 
serratus  magnus,  through  the  scapula.  Finally,  the  upper  extremities 
being  fixed,  the  pectoral  muscles  reversing  their  action,  will  elevate  the 

1  Physiolosie.  tome  iii.  p.  2fi0. 

-  Precis  c'lemeutaire  de  physiologie,  2d  ed.,  tome  ii.  p.  323. 


412 


MUSCLES    OF    RESPIRATION. 


ribs;  their  force,  under  such   circumstances,   acting  upon   the  thorax. 
instead  of  from  it. 

Expiration. 


Expiration  is  essentially  a  passive  process,  consisting  in  the  return 
of  the  thorax  to  the  condition  in  which  it  was  before  inspiration.  The 
ascent  of  the  diaphragm,  and  the  descent  of  the  ribs  in  diminishing  the 
capacity  of  the  thorax,  cause  the  expulsion  of  the  air,  or  expiration. 
The  relaxation  of  the  inspiratory  muscles  is,  however,  accompanied  by 
the  contraction  of  certain  muscles  which  together  with  the  elasticity  of 
the  lungs  aids  in  expelling  the  air  from  the  chest.  Inasmuch  as  the 
fibres  of  the  osseous  portion  of  the  internal  intercostal  muscles 
(Fig.  232)  pass  from  rib  to  rib  in  exactly  the  opposite  direction  as 
those  of  the  internal  intercostal — that  is,  from  above  downward,  but 
backward — we  would  natually  conclude  that  in  contracting  they  would 
depress  the  ribs  instead  of  elevating  them,  that  their  function  is 
expiratory  instead  of  inspiratory.  Experiment  proves  that  this  view 
is  correct,  since,  if  the  osseous  portion  of  the  internal  intercostal 
muscles  be  exposed  in  a  living  animal  by  dissecting  off  the  external 
ones,  they  will  be  found  to  contract  during  expiration.  We  generally 
illustrate  this  antagonism  in  the  action  of  the  internal  and  external 
intercostal  muscles  by  a  simple  mechanical  arrangement  known  as 
Hamberger's  apparatus,  though  it  was  really  invented  by  Bernouilli. 
This  consists  (Fig.  233,  A)  of  two   bars  (a  and  b),  which  are  attached 

Fig.  233. 


1      b 

Diagram  of  models  illustrating  the  action  of  the  external  and  internal  intercostal  muscles. 
B,  inspiratory  elevation ;  C,  expiratory  depression.    (Huxley.) 

on  the  one  hand  to  a  long  vertical  rod  (c)  firmly  supported,  and,  on  the 
other  hand,  to  a  short  one  (d).  The  two  bars,  the  long  and  the  short 
vertical  rods,  represent  respectively  the  spinal  column,  two  ribs,  and  a 
portion  of  the  sternum.  The  two  bars  (a  and  b)  are  maintained  in  the 
horizontal  position  by  two  elastic  bands  (zvz  and  xy),  which  are  so 
attached  that  as  they  pass  from  bar  to  bar  they  cross  each  other  at 
right  angles.  The  elastic  band  (x y)  passing  from  above,  downward  and 
forward,  represents  the  external  intercostal  muscle,  the  band  (w  z) 
passing  from  above  downward,  but  backward,  the  osseous  portion  of 
the  internal  intercostal  muscle.     If  the  band  (w  z)  be  removed  (Fig. 


ACTION    OF    INTERCOSTAL    MUSCLES.  413 

233,  B),  there  being  nothing  to  oppose  the  elasticity  of  the  band  xy, 
or  the  external  intercostal  muscle,  the  bars  or  ribs  will  be  elevated. 
If  the  band  w  z  be  now  replaced,  and  the  band  xy  removed  (Fig. 
233,  6'),  then  the  bars  or  the  ribs  will  be  depressed,  there  being  nothing 
to  oppose  the  elasticity  of  the  band  w  z.  While  the  action  of  the 
external  and  internal  intercostal  muscles  in  respiration,  as  we  have 
described  them,  appears  to  be  capable  of  demonstration  in  the  living 
animal  and  imitated  by  mechanical  contrivances,  nevertheless,  it  must 
be  admitted  that  the  action  of  these  muscles  has  given  rise  to  more 
discussion  than  that  of  all  the  other  muscles  in  the  body,  and  that 
the  most  diverse  opinions  have  been  offered,  and  are  still  held  as  to 
their  function.  Thus,  while  according  to  Borelli,  Haller,  and  Cuvier, 
both  the  external  and  internal  intercostal  muscles  are  inspiratory,  just 
the  opposite  opinion,  that  they  are  both  expiratory,  was  held  by 
Vesalius,  Beau  and  Maissiat  and  Galen.  Bartholinus  considered  the  ex- 
ternal intercostals  to  be  expiratory,  the  internal  inspiratory,  while 
Spigelius  and  Vesling  held  the  external  intercostals  to  be  inspiratory, 
the  internal  expiratory.  The  external  and  internal  intercostals  were 
regarded  at  once  inspiratory  and  expiratory  by  Mayow  and  Magendie, 
while  according  to  Arantius  and  Cruveilhier,  both  the  internal  and 
external  intercostals  are  passive  in  inspiration  and  expiration,  perform- 
ing simply  the  office  of  a  resisting  wall  in  respiration. 

Whatever  view  may  be  held  as  to  the  function  of  the  internal  inter- 
costal muscles  in  respiration,  there  can  be  no  doubt  that  the  triangularis 
sterni  and  infracostalis,  and  usually  the  serratus  posticus  inferior  are 
expiratory  muscles.  The  triangularis  sterni  acting  from  its  origin,  the 
ensiform  cartilage,  the  lower  border  of  the  sternum,  and  the  lower  costal 
cartilages,  in  drawing  down  the  cartilages  of  the  second,  third,  fourth, 
and  fifth  ribs  must  diminish  the  capacity  of  the  chest.  The  infracostales 
produce  the  same  effect,  their  fibres  passing  from  the  inner  surface  of 
one  rib  to  the  inner  surface  of  the  first,  second,  and  third  below,  their 
action  being  from  below  upward.  The  muscles  that  we  have  just 
described  usually  suffice  in  tranquil  expiration ;  in  difficult  or  labored 
expiration,  in  the  acts  of  blowing,  phonation,  etc.,  the  muscles  entering 
into  the  formation  of  the  abdominal  walls  also  come  into  play.  The 
general  effect  of  these  muscles,  viz.,  the  external  and  internal,  oblique 
transversalis,  sacro-lumbalis,  etc.,  is  in  contracting  to  push  up  the  ab- 
dominal viscera  and  diaphragm  into  the  thorax,  diminishing  its  capacity 
in  the  vertical  diameter;  these  muscles,  however,  in  being  attached  to 
the  ribs  or  costal  cartilages  depress  at  the  same  time  the  ribs  and  con- 
sequently diminish  the  thorax  in  its  antero-posterior  and  transverse 
diameters  also.  The  effect  of  the  action  of  these  muscles  is,  therefore, 
to  aid  powerfully  in  the  expulsion  of  the  air  from  the  chest  in  forced 
expiration.  As  their  action  and  that  of  the  diaphragm  is  more  or  less 
voluntary,  and  being  at  the  same  time  opposed  to  each  other,  the  in- 
tensity and  duration  of  expiration  can,  to  a  great  extent,  be  regulated 
arbitrarily  ;  the  importance  of  this  relation  is  well  seen  in  singing,  in 
performing  upon  wind  instruments,  etc.,  the  skill  exhibited  depending 
largely  upon  the  nicety  with  which  the  contractions  of  these  muscles 
can  be  adjusted  to  each  other. 


414  MUSCLES    OF    RESPIRATION. 

We  have  already  seen  that  the  lungs  arc  elastic,  and  were  it  not  for 
the  pressure  exerted  upon  the  inner  surface  of  the  lungs  by  the  inspired 
air  the  lungs  would  collapse  in  virtue  of  this  elasticity,  and  a  considerable 
space  in  consequence  would  be  left  between  the  lungs  and  the  chest-wall. 
The  natural  tendency  of  the  lungs  to  contract  through  their  elasticity  is 
well  seen  when  air  is  allowed  to  enter  the  pleural  cavities.  Under  such 
circumstances  the  atmospheric  pressure  being  exerted  equally  on  both 
the  inner  and  outer  surfaces  of  the  lungs,  there  is  nothing  to  oppose 
their  elasticity  and  the  lungs  therefore  collapse.  If  one  end  of  a  tube 
be  passed  into  the  trachea  of  an  animal  just  dead,  and  ligated,  and  the 
other  end  be  inserted  into  a  water  or  mercurial  manometer,  with  the 
entry  of  air  through  an  opening  made  into  the  pleural  cavity  the  lungs 
will  collapse  in  virtue  of  their  elasticity,  the  level  of  the  liquid  in  the 
proximal  end  of  the  manometer  will  be  observed  to  fall,  that  of  the  distal 
end  to  rise,  the  difference  in  the  level  of  the  two  indicating  and  meas- 
uring the  amount  of  elastic  force  exerted.  It  was  in  this  way  that  Carson1 
first  showed  that  the  elasticity  of  the  lungs  in  the  calf,  sheep,  or  dog 
would  support  a  column  of  water  twelve  to  eighteen  inches  in  height,  and 
in  the  rabbit  six  to  ten  inches.  The  elastic  force  of  the  lungs  amounting 
to  half  a  pound  on  the  square  inch  in  man,  not  only  aids  the  expiratory 
muscles,  therefore,  in  expelling  the  air  from  the  chest,  but  through  the 
suction  force  exerted  also  elevates  the  diaphragm,  restoring  it  to  the  dome- 
like form  it  presents  before  inspiration.  Finally,  the  contractility  of  the 
bronchi  and  elasticity  of  the  thoracic  walls  themselves  contribute  in  ex- 
pelling the  air  from  the  chest.  It  is  usually  considered  that  in  inspira- 
tion the  upper  ribs  are  elevated  before  the  lower,  and  in  expiration  the 
lower  ribs  are  depressed  before  the  upper,  the  motion  being  wave-like 
from  above  downward  and  from  below  upward.  According  to  the  recent 
observations  of  Rausome2  it  would  appear,  however,  that  the  reverse  ob- 
tains, the  lower  ribs  in  inspiration  being  elevated  first  and  the  upper  ones 
last,  and  that  in  expiration  it  is  the  upper  ribs  that  are  depressed  first  and 
the  lower  ones  last.  Even  if  such  is  the  case,  it  is  not  inconsistent  with 
the  view  that  the  upper  part  of  the  chest  is  moved  first  in  inspiration, 
the  lowest  last,  since  if  the  scaleni  act  before  the  intercostal  muscles  the 
upper  ribs  would  be  elevated  before  the  lower  by  the  action  of  the  scaleni, 
even  if  the  lower  intercostal  muscles  contracted  before  the  upper.  It  is 
possible  that  the  difference  of  opinion  in  reference  to  the  order  in  which 
the  ribs  are  elevated  and  depressed  is  due  to  the  action  of  the  intercostal 
muscles,  being  considered  without  reference  to  the  simultaneous  action 
of  the  other  respiratory  muscles. 

While,  in  a  general  wTay,  it  can  be  said  that  inspiration  is  due  to  the 
descent  of  the  diaphragm  and  the  ascent  of  the  ribs,  and  expiration  to 
the  ascent  of  the  diaphragm  and  descent  of  the  ribs,  nevertheless  there 
is  a  noticeable  difference,  more  particularly  studied  by  Bean  and  Maissiat,3 
as  to  the  relative  importance  of  the  parts  played  by  the  diaphragm  and 
the  ribs,  as  observed  in  the  breathing  of  the  two  sexes.  Thus  while  in 
the  male  sex  breathing  is  accomplished   by  the  diaphragm  and  the  in- 

i  Phil.  Trans  ,  1820.  "  Stetliometer,  1876,  p.  37. 

3  Archives  generates  de  medecine,  1843,  3d  ser.  t.  xv.  p.  307  ;  4th  ser.  1843,  t.  i.  p.  2U5  ;  t.  ii.  p.  257  ; 
t.  iii.  p.  249. 


DIFFERENCE     OF     RESPIRATION    IN    SEXES. 


415 


ferior  part  of  the  thorax,  or  the  portion  below  the  sixth  rib,  in  the  female 
sex  it  is  the  superior  part  of  the  chest,  or  that  above  the  seventh  rib 
(Figs.  234,  235),  which  takes  an  active  part  in  respiration.     It  might  be 


Fig.  234. 


Fig.  235. 


The  changes  of  the  thoracic  and  abdominal 
walla  of  the  male  during  respiration. 


The  same  in  the  female.     (Hutchinson.) 


supposed  that  the  superior  costal  type  of  breathing  characteristic  of  the 
female  is  due  to  peculiarities  of  dress,  such  as  the  wearing  of  corsets,  the 
squeezing  of  the  waist,  etc.,  which  would  interfere  with  or  prevent  even 
the  lower  part  of  the  chest  expanding.  That  this  is  not  the  only  cause, 
however,  is  proved  by  the  fact  that  the  superior  costal  type  of  breathing 
prevails  even  in  females  that  have  never  at  any  time  worn  any  kind  of 
clothing  whatever.  That  the  superior  costal  type  of  breathing  is  of 
advantage  to  the  female  is  obvious  when  one  considers  the  extent  to 
which  the  abdominal  viscera  and  diaphragm  are  pushed  up,  as  is  the 
case  during  pregnancy,  through  the  enlargement  of  the  uterus.  Under 
such  circumstances,  if  the  breathing  of  the  female  was  of  the  inferior 
costal  type  and  diaphragmatic,  like  that  of  the  male,  inspiration  would 
be  difficult  and  labored.  It  is  also  on  account  of  this  peculiarity  in 
breathing  that  women  can  tolerate  with  so  little  inconvenience  large 
accumulations  of  fluid  in  the  abdominal  cavity.  While  in  the  adult  the 
diaphragmatic  inferior  costal  type  of  respiration  of  the  male  as  contrasted 
with  the  superior  costal  type  of  the  female  is  perfectly  evident,  the  dis- 
tinction in  young  children  is  not  noticeable.  Indeed,  children  under 
about  ten  years  of  age  breathe  almost  entirely  by  the  diaphragm.  It 
is  not,  as  a  general  rule,  until  near  puberty  that  the  distinction  in 
breathing  characteristic  of  the  adult  sexes  becomes  apparent.  Haller,1 
however,  states  that  the  difference  in  the  types  of  breathing  in  the  sexes 
in  some  cases  manifested  itself  as  early  as  the  first  year. 


1  Pralectiones  Academne,  tomus  v.  p.  144. 


CHAPTER    XX  VI  I  I  . 

INSPIRATORY  MOVEMENTS  AS  STUDIED  BY  THE 
GRAPHIC  METHOD. 

Notwithstanding  that  the  respiratory  movements  are  evident  to 
the  eye,  and  that  the  respiratory  organs  can  be  connected  without  injury 
with  apparatus  for  recording  their  movements,  it  must  be  admitted  that 
the  application  of  the  graphic  method  to  the  study  of  respiration  does 
not  give  as  satisfactory  results  as  is  the  case  in  the  study  of  the  circula- 
tion. Of  the  instruments  devised  for  the  recording  of  the  respiratory 
movements  graphically,  we  have  found  the  pneumograph  and  steth- 
ometer  to  be  among  the  most  useful.  The  pneumograph,  invented  by 
Marey,1  in  its  present  form,  modified  by  Verdin  (Fig.  236),  consists  of 
an  elastic  plate  A,  having  an  area  of  26  cm.  (4  square  inches),  which 

Fig.  236. 


Pneumograph. 


is  applied  to  that  part  of  the  chest  whose  movements  it  is  desired  to 
study,  and  firmly  secured  there  by  tapes  passing  around  the  neck  from 
the  edge  of  the  plate  and  around  the  chest  from  the  pillars  B  and  C,  pro- 
jecting from  the  plate.  To  the  lower  end  of  the  pillar  B  is  attached  a  spring 
(D),  the  free  end  of  which  is  so  attached  that  it  presses  against  the  elastic 
membrane  covering  in  the  lower  surface  of  an  air-drum  (E),  the  latter 
communicating  through  a  caoutchouc  tube  (F),  with  a  recording  tambour. 
With  the  bending  of  the  elastic  plate  A  through  the  expansion  of  the 
chest,  the  pillars  B  and  C  recede  from  each  other,  the  spring  D 
ceasing  at  the  same  time  to  press  on  the  membrane  of  the  air-drum  E. 
The  air  within  the  drum  being  therefore  rarefied,  the  air  from  the  re- 
cording tambour  is  drawn  into  it,  and  the  lever  attached  to  the  tambour 
is  depressed.  With  the  contraction  of  the  chest  the  elastic  plate 
straightens,  the  pillars  approach  each  other,  the  spring  presses  again 
the  elastic  membrane,  the  air  is  driven  out  of  the  drum  into  the  tam- 
bour, and  the  lever  is  elevated.  The  depression  of  lever  corresponds, 
therefore,  to  inspiration,  the  elevation  to  expiration.  By  placing  the 
lever  of  the  recording  tambour  in  contact  with  the  blackened  surface  of 


La  methode  Graph ique,  p.  542 


METRONOME, 


417 


the  cylinder  moving  by  clockwork,  we  obtain  a  trace  like  that  of 
Fig.  237,  representing  the  breathing  of  a  man  set.  thirty  years.  In 
this  trace  the  distance  from  a  to  c  represents  one  inspiration  ;  the  part 
of  the  trace  from  a  to  5,  due  to  the  descent  of  the  lever,  being  inspira- 


Fig.  237. 


Upper  line,  trace  of  chronograph.  Lower  line,  trace  of  respiratory  movements  Taken  with  pneumograph . 

tory  in  orgin,  that  of  b  to  c  due  to  the  ascent  of  the  lever  expiratory. 
It  will  be  observed  that  the  inspiratory  movement,  as  recorded  in  its 
trace,  a  to  b,  is  extremely  abrupt,  becoming  more  gradual  at  its  close, 
and  that  the  expiratory  movement  (b  to  c)  is  equally  abrupt  at  the 

Fig.  238. 


beginning,  but  that  the  gradual  movement  at  the  termination  is  more 
marked  even  than  in  the  case  of  the  inspiratory  movement.  In  order 
to  determine  accurately  the  number  of  respirations  in  a  given  time,  the 
length  of  time  of  one  respiration,  the  relative  duration  of  one  expira- 

27 


418  RESPIRATORY    MOVEMENTS. 

tion  and  inspiration  ;  the  existence  of  pauses,  if  any,  after  inspiration 
and  expiration,  it  is  necessary  to  make  use  of  some  chronographic  appa- 
ratus, by  means  of  which  we  can  record  graphically  the  time  elapsing 
during  which  the  respiratory  movements  are  being  studied.  For  this 
purpose  we  make  use  of  the  metronome  in  connection  with  an  electro- 
magnet. The  metronome  (Fig  238)  is  the  same  as  that  used  by  musi- 
cians, except  that  it  is  so  constructed  that,  in  a  definite  ratio  of  each 
beat  of  the  pendulum  a  spring  is  elevated  and  depressed,  to  which  are 
attached  two  needles,  dipping  into  mercury  cups.  This  is  accomplished 
by  drawing  out  or  pushing  in  a  rod  to  which  the  spring  carrying  the 
needles  is  attached,  and  which,  by  so  doing,  brings  the  spring  in  contact 
with  the  periphery  of  either  one  or  four  wheels  having  a  different 
number  of  cogs.  The  number  of  movements  of  the  spring  will  depend, 
therefore,  upon  the  particular  wheel  with  whose  cogs  it  is  in  contact. 
The  four  wheels  are  rotated  by  the  axis  common  to  them,  a  fifth  one, 
whose  motion  is  due  to  the  axis,  being  moved  by  clockwork,  which 
is  regulated  by  a  pendulum.  With  the  elevation  of  the  spring  the 
needles  are  raised  out  of  the  mercury  in  the  cups,  and  with  its  de- 
pression they  sink  into  it  again.  As  the  needles  are  elevated  and 
depressed  the  current,  passing  from  the  battery  through  the  needles  and 
mercury  to  the  electro-magnet,  is  made  or  broken,  and  the  marker  con- 
nected with  the  latter  synchronously  depressed  and  elevated  in  the 
manner  already  described.  In  the  trace  obtained  by  applying  the 
marker  of  the  electro-magnet  to  the  blackened  surface  of  the  revolving 
cylinder,  the  difference  between,  in  this  instance,  each  of  the  two  verti- 
cal lines  is  equal  to  one  second,  the  pendulum  beating  at  the  rate  of 
sixty  seconds  to  the  minute,  and  the  spring  coming  in  contact  with  the 
cogs  of  the  second  wheel.  The  experiment  lasting  one  minute,  the 
number  of  respirations  was  determined  to  be  twenty,  a  little  over  what  we 
shall  see  is  the  usual  average.  It  will  be  observed  from  a  comparison 
of  the  traces  (Fig.  237)  that  the  duration  of  one  respiration  was  three 
seconds,  the  inspiratory  part  lasting  one  second,  the  expiratory  two 
seconds,  and  that  the  expiratory  lasted,  therefore,  twice  as  long  as  the 
inspiratory  effort ;  further,  that  there  was  no  appreciable  pause,  either 
after  inspiration  or  expiration,  a  gradual  slowing  up  of  the  movement 
only  being  noticeable  after  either.  Finally,  the  little  undulations  of 
the  trace  noticeable  at  the  termination  of  expiration  are  cardiac  in 
origin. 

The  object  of  the  stethometer  is  not  only  to  record  the  respiratory 
movements  graphically,  but  to  determine  also  their  extent.  The  instru- 
ment, as  devised  by  Sanderson,  and  constructed  for  the  author  by 
Hawksley,  consists  (Fig.  239)  of  two  parallel  bars,  30  cm.  (12  inches) 
in  length,  the  lower  ends  of  which  are  firmly  screwed  at  right  angles 
into  a  crossbar  so  as  to  form  a  rigid  frame.  Through  one  of  the  bars 
passes  a  slender  rod  (B'),  terminating  in  a  convex  ivory  knob  (B).  By 
means  of  a  screw  the  extent  to  which  the  rod  and  knob  are  pushed  within 
the  frame  can  be  varied  as  needed  and  firmly  fixed.  The  opposite  bar 
carries  a  spring  (I),  the  upper  part  of  which  carries  a  horizontal  pin, 
terminating  at  one  end  in  an  ivory  knob,  and  at  the  other  in  a  brass 
disk,  the  latter  being  in  contact  with  the  tambour  (A)  attached  to  the 


ST  ETHO  METER. 


419 


upper  part  of  the  bar.  The  two  ivory  knobs  not  only  face  each  other, 
but  lie  in  the  same  avis.  The  receiving  tambour  communicates  by 
means  of  the  tube  J  with  the  recording  portion  of  the  apparatus,  and 
also  through  the  T  tube  with  an  India-rubber  ball,  the  latter  being  used 
to  fill  both  tambours  and  communicating  tube  (D). 

Fig.  239, 


Recording  stethometer.  A.  Tympanum.  B.  Ivory  knob.  B'.  Rod  which  carries  the  kuob  opposed  to 
B.  C,  T-tube,  by  which  A  communicates,  on  the  one  hand,  with  the  recording  tympanum,  on  the  other 
wiih  an  elastic  bag  (D).  Thi  purpose  of  the  bag  is  to  enable  the  observer  to  vary  the  quantity  of  air  in 
the  cavity  of  the  tympana  at  will.  The  tube  leading  to  it  is  closed  by  a  clip  when  the  instrument  is  in 
use.     (Sanderson.) 

The  manner  of  adapting  the  stethometer  to  the  chest  will  depend 
upon  the  part  whose  movement  it  is  desired  to  examine.  If,  for  ex- 
ample, we  wish  to  obtain  a  graphic  representation  of  the  movements  of 
the  chest  in  a  transverse  direction,  let  the  instrument  be  so  applied  that 
the  ivory  knobs  will  press  upon  the  eighth  rib.  The  knob  being  firmly 
fixed  with  the  expansion  of  the  chest,  the  rib  will  press  outwardly  the 
knob  of  the  receiving  tambour,  the  air  will  be  driven  out  of  it  into  the 
recording  one,  and  the  lever  will  be  elevated  ;  with  the  contraction  of 
the  chest  the  air  will  return  from  the  recording  to  the  receiving  tam- 
bour lever,  and  the  lever  will  be  depressed.  With  the  stethometer, 
therefore,  inspiration  corresponds  to  the  elevation  of,  and  expiration  to, 
the  pressure  of  the  recording  lever,  just  the  opposite  to  what  happens, 
as  we  have  seen,  when  the  pneumograph  is  used.  To  obtain  a  trace 
representing  the  enlargement  of  the  chest  in  an  antero-posterior  direc- 
tion, the  stethometer  can  be  applied  so  that  the  ivory  knobs  are  in  con- 
tact with  the  manubrium  sterni  and  the  third  dorsal  spine,  or  the  ensi- 
form  cartilage  and  the  tenth  dorsal  spine  respectively.  Fig.  240  is  that 
of  the  trace  obtained  by  the  stethometer  as  applied  to  the  seventh  ribs 


420 


RESPIRATORY    MOVEMENTS. 


iii  the  case  of  a  healthy  man,  jet  thirty  years,  and  is  a  graphic  repre- 
sentation, therefore,  of  the  respiratory  movements,  in  so  far  as  they 
depend  upon  the  enlargement  of  the  chest  in  a  transverse  direction  in 


Fig.  240. 


that  particular  part  of  the  chest.  It  is  not  necessary  to  dwell  upon  the 
peculiarities  of  the  trace  recorded  by  the  stethometer.  It  will  be  ob- 
served that  the  part  of  the  trace  from  a  to  b  corresponds  to  the  inspira- 
tion, that  from  b  to  c  to  expiration,  and  that  the  relative  duration  of 
inspiration  to  expiration  is  somewhat  different  from  that  observed  in 
the  trace  obtained  by  the  pneumograph,  the  number  of  respirations 
being  in  this  case  eighteen  to  the  minute.  Here  and  there,  it  will  be 
noticed  that  the  breathing  became  more  marked.  In  order  to  deter- 
mine the  extent  of  the  enlargement  of  the  chest  by  the  stethometer, 
the  instrument  must  be  graduated.  This  can  be  done  either  by  placing 
successively  between  the  ivory  buttons  rods  differing  by  a  known  length, 
and  observing  the  different  levels  to  which  the  lever  is  elevated,  accord- 
ing to  the  rod  used,  the  vertical  distances  between  the  horizontal  lines 
made  by  the  lever  corresponding  to  a  definite  increase  in  the  distance 
between  the  ivory  knobs  of  the  particular  diameter  of  the  chest  ex- 
amined, or  by  placing  directly  underneath  the  ivory  knobs  a  graduated 
rod,  carrying  a  vertical  slide,  which  can  be  pushed  against  the  movable 
knob,  and  noticing  the  different  heights  to  which  the  recording  lever  is 
elevated  In  the  trace  represented  in  Fig.  240,  the  elevation  of  the 
lever  through  the  space  a  to  b  corresponds  to  an  increase  of  about  2 
mm.  (y^th  of  an  inch)  in  the  lateral  diameter  of  the  chest. 

While  in  tranquil  breathing  the  increase  in  the  antero-  posterior 
diameter  of  the  thorax  may  be  only  one  mm.  (23-th  of  an  inch)  inforced 
breathing,  according  to  Rausome,1  it  may  amount  to  as  much  as  12  to 
30  mm.  (i  to  1.2  in.). 

In  describing;  the  circulation  it  will  be  remembered  that  attention  was 
called  to  the  large  undulations  present  in  the  curve  of  blood  pressure, 

1  Sanderson  :  Handbook  Phys.  Lab.,  p.  302. 


TRACES    OF    BLOOD    PRESSURE.  421 

and  which  at  that  time  were  simply  stated  as  being,  to  a  certain 
extent  at  least,  respiratory  in  origin.  In  order  to  study  the  influence 
of  the  respiration  upon  the  circulation,  it  is  essential  that  a  compari- 
son should  be  made  between  the  curves  of  blood  pressure  and  respira- 
tion taken  simultaneously.  In  the  case  of  man  this  can  be  done  by 
applying  at  the  same  time  the  cardiograph  and  pneumograph  and 
comparing  the  traces  so  obtained,  or  in  an  animal  by  connecting  a 
recording  tambour  with  its  trachea,  and  comparing  the  respiratory  trace 
so  obtained  with  that  of  the  pressure  of  the  blood  in  its  carotid  artery, 
taken  in  the  manner  already  described.  A  comparison  of  the  traces 
of  the  respiratory  movements  and  the  blood  pressure  in  a  rabbit 
(Fig.  241),  taken  by  the  latter  method,  shows  that  in  this  case  at  least 
the  insniration  is  almost,  if  not  absolutely,  synchronous  with  the  rise  of 

\AAI\AAAAAfO\J\AJ\NXAAJ 


Traces  of  blood  pressure  and  respiratory  movements  of  rabbit  taken  simultaneously.    Upper  trace  blood 
pressure.     Lower  trace  respiratory  movements. 

blood  pressure  and  expiration  with  the  fall,  the  relation  between  the  two 
naturally  suggesting  that  inspiration  is  the  cause  of  the  one,  expiration 
of  the  other.  Nevertheless,  reflection  makes  it  clear  that  respiration  on 
the  whole  favors  the  circulation  of  the  blood  even  though  inspiration 
promotes  it  to  a  greater  extent  than  expiration.  Let  us  consider  in 
detail  a  little  why  this  must  be  the  case.  During  inspiration,  as  the 
chest  expands,  the  air  within  the  lungs  becomes  rarefied  and  the  external 
air  passes  through  the  trachea  from  without  inward.  In  doing  this, 
however,  the  external  air  has  overcome  the  elasticity  of  the  lungs,  the 
pressure  exerted  by  the  air  within  the  lungs  upon  the  intrathoracic 
vessels  will  therefore  be  that  of  the  ordinary  atmospheric  pressure,  less 
the  pressure  due  to  the  elasticity  of  the  lungs.  Suppose,  for  example, 
that  the  pressure  exerted  by  the  elasticity  be  half  a  pound  to  the  square 
inch,  then  the  pressure  exerted  by  the  air  within  the  lungs  upon  the 
great  bloodvessels  will  be  only  fourteen  and  a  half  pounds,  that  of  the 
atmosphere  being  fifteen  pounds.  The  effect  of  this  difference  of  the 
atmospheric  pressure  within  and  without  the  chest  during  inspiration  is 
that  a  greater  quantity  of  venous  blood  being  forced  through  the  great 
veins  toward  the  right  auricle  of  the  heart  and  thence  through  the 
lungs,  a  proportionately  greater  quantity  of  arterial  blood  passes,  there- 
fore, through  the  left  ventricle  into  the  aorta,  the  result  of  which  will 
be  to  increase  the  blood  pressure.  The  flow  of  the  venous  blood  from 
the  periphery  to  the  heart  being  promoted  by  inspiration,  it  might  be 
supposed  that  the  flow  of  the  arterial  blood  in  the  reverse  direction 
would  be  proportionally  retarded.  It  must  be  remembered,  however, 
that  the  pressure  exerted  by  the  extrathoracic  air  upon  the  thin,  flaccid 


422 


RESPIRATORY    MOVEMENTS. 


Avails  of  the  veins  will  produce  a  greater  effect  than  upon  the  thick, 
resisting  coats  of  the  arteries,  and  that  the  pressure  of  the  external  air 
so  exerted  is  not  much  in  excess  of  the  resistance  that  the  heart  has  to 
overcome  in  driving  the  blood  from  the  ventricle  into  the  arterial  system 
during  its  systole.  Further,  during  expiration  the  conditions  are  the 
reverse  of  those  obtaining  in  inspiration,  the  intra  thoracic  pressure 
being  now  greater  than  the  extrathoracic.  The  pressure  so  exerted 
now  adds  itself  to  the  elasticity  of  the  arteries  and  promotes  the  flow  of 
the  blood  from  the  heart  to  the  periphery,  while  the  valves  prevent  to 
any  extent  regurgitation  of  the  venous  blood.'  Respiration,  on  the 
whole,  therefore,  favors  the  circulation,  since  inspiration  aids  the  flow 
of  the  venous  blood  without  offering  any  great  obstacle  to  the  arterial 
flow,  while  expiration  favors  the  flow  of  the  arterial  blood  without 
retarding  to  any  extent  the  venous  flow,  and  while  it  is  true  that  in  the 
influence  of  respiration  upon  the  circulation,  inspiration  is  more  impor- 
tant than  expiration,  nevertheless  the  difference  in  the  effect  of  the  two 
is  too  small  to  warrant  the  conclusion  that  the  large  rise  and  fall  in  the 
blood  pressure  are  entirely  caused  by  inspiration,  on  the  one  hand,  and 
expiration  on  the  other.  Further,  in  the  dog  and  in  the  rabbit  also,  at 
times,  there  is  no  absolute  synchronism  between  the  vascular  and  respi- 
ratory rhythms ;  in  the  dog,  for  example  (Fig.  242),  the  rise  in  the  blood 
pressure  lasting  not  only  to  the  end  of  the  inspiration,  but  during  a  part 

Fig.  242. 


Comparison  of  blood  pressure  curve  with  curve  of  intrathoracic  pressure.  To  be  read  from  left  to  right. 
a  is  the  Hood-pressure  curve,  with  its  respiratory  undulations,  the  slower  heats  on  the  descent  being 
very  marked,  b  is  the  curve  of  intrathoracic  pressure  obtained  by  connecting  one  limb  of  a  manometer 
with  the  pleural  cavity.  Inspiration  begins  at  i,  expiration  at  e.  The  intrathoracic  pressure  rises  very 
rapidly  after  tin/  cessation  of  the  inspiratory  effort,  and  then  slowly  falls  as  the  air  issues  from  the  chest ; 
at  the  beginning  of  the  inspiratory  effort  the  tall  becomes  more  rapid.     (Foster.) 

of  expiration,  and  the  fall  in  blood  pressure  lasting  not  only  till  the  end 
of  expiration,  but  during  a  part  of  inspiration.  This  want  of  syn- 
chronism between  the  rhythms,  together  with  the  fact  that  the  large 
undulations  characteristic  of  blood  pressure  persist  even  after  all  respi- 
ratory movements  have  ceased,  proves  that  there  must  be  some  influence 
other  than  respiration  concerned  in  their  production.  Thus  if  an  animal, 
a  rabbit,  for  example,  be  curarized,  in  which  condition  the  respiratory 
nerves  cease  to  act  altogether,  the  heart  continues  to  beat,  artificial 
respiration  be  maintained  and  a  trace  of  the  blood  pressure  be  taken,  a 
carve  like  that  of  Fig.  242  will  be  obtained.     If  now  the  artificial  respi- 


MAINTENANCE    OF    ARTIFICIAL    RESPIRATION, 


•±23 


ration  be  discontinued  the  blood  pressure  rises,  while  the  character  of 
the  curve  changes;  nevertheless,  a  rhythmical  rise  and  fall  still  occur, 
like  that  of  Fig.  242,  b.  The  curve  so  obtained  is  known  as  that  of 
Traube,  from  having  been  first  described  by  that  observer.  Inasmuch 
as  respiration  has  entirely  ceased  and  both  vagi  even  being  divided,  it 


\  A  I 


Fig.  243. 


A^ 


IM 


!    !\   It  f\    i\      \   MM 

\W\\    \     \l\i\!\i 

Mil!  1/     MI  «  " 


^    It   V 

\  •'  I  ! 
if   i! 


iJ    k'    V 


i/' 


i    J!   ! 
«  •'  I  ! 

U  H 

II    i' 

1/ 


i  A  / 

l.   /  i  i 

'  !  \! 
I  i  V 

\i 

U 


A    ". 

I  ft 

Si  vii 


Tranbe's  curves.     (Foster) 


is  evident  that  the  large  undulations  cannot  be  due  to  respiration.  The 
only  way  of  accounting  for  them  is  by  supposing  that  they  are  of  vaso- 
motorial  origin,  the  rhythmic  rise  and  fall  in  the  blood  pressure, 
through  the  rhythmic  constriction  of  the  arteries,  being  due  to  a  rhyth- 
mic stimulus  emanating  from  the  vasomotor  centre  of  the  medulla.  This 
view  is  confirmed  by  the  following  facts :  that  the  phenomena  in  question 
are  much  less  marked  if  the  spinal  cord  be  divided  below  the  medulla, 
and  that  the  undulations  persist  even  after  the  heart  itself  be  removed, 
and  the  circulation  be  maintained  artificially.  It  is  difficult  to  under- 
stand why  the  vascular  rhythm,  due  to  the  vasomotor  centre,  should 
simulate  and  be  superimposed  upon  the  respiratory  rhythm  due  to  the 
medullary  respiratory  centre,  unless  through  conditions  in  the  evolution 
of  the  animal  and  which  we  are  not  familiar  with,  the  two  centres  in  the 
medulla  have  been  gradually  brought  to  act  synchronously.  It  will  be 
seen,  therefore,  that  while  the  rise  and  fall  in  the  blood  pressure  are 
influenced  by  inspiration  and  expiration,  the  phenomenon  is  independent 
of  respiration,  or  probably  that  both  are  influenced  by  a  common  cause, 
the  condition  of  the  blood  in  the  medulla  acting  as  a  stimulant  to  the 
vascular  and  respiratory  centres. 

In  the  study  of  the  circulation  and  respiration,  as  in  the  present  case,  it 
is  often  necessary  to  maintain  artificial  respiration.  We  take  the  oppor- 
tunity, therefore,  of  describing  the  apparatus  made  for  us  by  Hawksley, 


424 


RESPIRATORY    MOVEMENTS. 


of  London,  and  which  we  have  found  useful  in  effecting  this  object.  The 
apparatus  is  essentially  a  mercurial  pump,  and  consists  (Fig.  244)  of 
two  chambers,  cast-iron  cylinders  (A  and  13,  B  not  seen  in  Fig.  244), 
concentrically  disposed  and   firmly  fixed  in  a  solid  frame   (C).      The 


Fig.  244. 


Mercurial  pump  fur  artificial  respiration. 

upper  space  D  between  the  cylinders  contains  mercury,  through  which 
the   bell-jar    E  covering   the  internal  cylinder  B    is  elevated    or   de- 
pressed by  the  vertical  motion  of  the  rod  F  connecting  it  with  the 
wheel  G,  to  the  rotation  of  which  the  motion  of 
Fig.  245.  ^e  ro(j  ja  due.     The  internal  cylinder  B  opens 

externally  through  the  two  brass  nozzles  H  and  I. 
Each  of  these  nozzles  is  provided  with  a  valve, 
which,  however,  open  in  opposite  directions — that 
of  H  from  without  inward,  that  of  I  from  within 
outward.  As  the  bell-jar  is  elevated  the  air 
passes  through  H  into  the  internal  cylinder,  and 
canuia.  as  it  descends  the  air  passes  out  of  it  through  I, 

and  thence  by  means  of  a  tube  terminating  in  a 
canuia  to  the  trachea  of  the  animal  whose  respiration  is  to  be  maintained 
artificially.  The  canuia  that  we  use  for  insertion  into  the  trachea  is 
that  of  Ludwig,  and  consists  of  a  tube  of  glass  (Fig.  245)  of  which 
the  end  a,  when  in  situ,  faces  the  lungs  and  through  which  the  air 
to  be  inspired  passes,  the  expired  air  escaping  by  a    small  opening 


RESPIRATORY    MURMUR.  425 

The  rotation  of  the  wheel  G,  to  which  the  action  of  the  respiratory 
pump  is  due,  is  effected  by  a  Backus  water  motor  (K)  to  which  the 
wheel  is  connected  by  the  band  I.  The  water  supplying  the  motor  is 
conveyed  to  it  from  the  hydrant  in  the  laboratory  by  the  tube  M  and 
away  from  it  to  the  waste-pipe  by  the  tube  N. 

In  ordinary  tranquil  respiration  no  sound  is  heard  unless  the  ear  be 
applied  directly  to  the  chest,  excepting  Avhen  the  mouth  is  closed  and 
the  breathing  exclusively  nasal,  then  a  soft  murmur  accompanies  both 
inspiration  and  expiration.  If  the  ear,  or,  better,  the  stethoscope,  be 
successively  applied  over  the  trachea  and  the  chest,  a  very  noticeable 
difference  will  be  observed  in  the  character  of  the  sound  heard,  as  the 
air  passes  through  these  parts  both  in  inspiration  and  expiration.  As 
might  be  expected,  as  the  air  passes  in  and  out  of  the  trachea,  the 
character  of  the  sound  is  tubular.  In  inspiration,  the  sound,  attaining 
its  maximum  intensity  immediately,  maintains  it  to  the  close  of  the  act, 
when  it  rather  suddenly  ceases.  Immediately,  or  after  a  very  brief 
interval,  the  expiratory  sound  follows,  attaining  soon  its  maximum 
intensity,  but,  unlike  the  inspiratory  sound,  rather  dying  away  than  ceas- 
ing abruptly.  As  the  air  passes  into  the  small  bronchial  tubes  and  expands 
the  pulmonary  air  cells  it  gives  rise  to  a  sound  difficult  of  description, 
and  which  can  only  be  appreciated  by  being  heard.  It  is  usually  de- 
scribed as  being  of  a  breezy  or  vesicular  character,  and  is  less  intense 
than  the  tracheal  murmur.  The  sound  gradually  increases  in  intensity 
fi*om  the  beginning  to  the  end  of  inspiration,  and  ceases  rather 
abruptly.  The  inspiratory  murmur  is  followed  without  any  interval  by 
the  expiratory  one,  lower  in  pitch,  less  intense,  and  lasting  a  shorter 
time.  It  must  be  mentioned,  however,  that  the  expiratory  murmur  is 
frequently  absent.  Certain  modifications  of  the  respiratory  sounds  and 
movements,  such  as  snoring,  coughing,  sneezing,  sighing,  yawning, 
laughing,  sobbing,  and  hiccoughing  need  only  a  passing  notice,  since 
they  are  simply  exaggerations  of  either  the  inspiratory  or  expiratory 
movements,  or  of  both.  Snoring,  a  sound  too  familiar  to  need  de- 
scription, occurs  when  the  mouth  is  open,  and  is  due  to  a  vibration  or 
flapping  of  the  velum  palati  between  the  two  currents  of  air  from  the 
mouth  and  nose  together  with  a  vibration  of  the  air  itself.  Coughing 
and  sneezing,  usually  involuntary  acts,  consist  in  a  deep  inspiration, 
followed  by  a  convulsive  expiration,  differing  only  in  degree,  the  air  in 
the  first  instance  being  expelled  by  the  mouth,  in  the  second  by  both 
mouth  and  nares.  Sighing  and  yawning  are  due  to  the  same  cause — 
want  of  oxygen  in  the  blood — and  differ  from  each  other  only  in  the 
former  being  voluntary,  the  latter  involuntary.  In  both  these  acts  a 
prolonged  and  deep  inspiration  is  followed  by  a  quick  and  usually  audi- 
ble expiration.  Laughing  and  sobbing,  though  expressing  very  differ- 
ent emotions,  are  pi'oduced  very  much  in  the  same  way,  and  are  the 
result  of  short,  quick,  convulsive  movements  of  the  diaphragm,  which 
are  accompanied  by  the  action  of  the  facial  muscles  producing  those 
changes  in  the  features  so  characteristic  of  joy  or  sorrow.  Laughing 
and  sobbing,  like  yawning,  are,  so  to  speak,  catching,  or  contagious. 
Hiccough  is  a  purely  inspiratory  act,  and  consists  in  sudden  convulsive 
involuntary  contractions  of  the  diaphragm,  the  glottis  constricting 
spasmodically  at  the  same  time  ;  the  well-known  sound  is  due  to  the 


426  RESPIRATORY    MOVEMENTS. 

air  striking  against  the  closed  glottis.  Hiccough  is  frequently  caused 
by  partaking  too  rapidly  of  dry  food  or  effervescing  and  alcoholic  drinks, 
and  is  not  an  infrequent  symptom  of  disease. 

It  is  obviously  of  importance  that  the  number  of  respirations  in  a 
given  time  be  determined  as  accurately  as  possible.  A  great  difference 
of  opinion,  however,  ha,s  prevailed,  in  this  respect,  among  physiologists, 
Haller,1  for  example,  giving  twenty  respirations  a  minute  as  the  normal 
number;  Magendie,2  fifteen  ;  Milne  Edwards,3  sixteen  to  twenty-two. 
This  disagreement  in  the  result  of  ;i  mere  matter  of  observation  is  due, 
in  some  instances,  to  the  number  of  cases  examined  having  been  too 
limited  to  warrant  a  general  conclusion,  and,  in  others,  to  influences 
modifying  the  number  of  respirations  within  the  limit  of  health  not 
having  been  taken  into  consideration.  The  importance  of  examining  a 
great  number  of  cases  before  drawing  any  conclusion  as  to  the  average 
number  of  respirations  per  minute  is  well  shown  by  the  observations  of 
Hutchinson.4  Of  1887  cases  examined  (Table  L1X.),  in  561  the 
number  of  respirations  was  found  to  be  twenty  per  minute ;  in  239 
cases,  sixteen  per  minute;  in  79  cases,  nine  to  sixteen  per  minute. 
Such  a  difference  in  the  number  of  respirations,  as  observed  in  these 
three  sets  of  cases,  and  also  of  the  remaining  ones  of  the  table,  prove 
that  there  must  be  numerous  conditions  influencing  the  rapidity  of  the 
respiratory  movements  as  we  have  seen  is  the  case  with  the  pulse. 

Table  LIX.5 — Respirations. 


Per  minute. 

No.  of  cases. 

Per  minute. 

No.  of  cases 

9  to  16 

.       79 

21  . 

.     129 

16  . 

.     239 

22  . 

.     143 

17  . 

.     105 

23  . 

.       42 

IS. 

.     195 

24. 

.     243 

19  . 

.       74 

24  to  40 

.       78 

20  . 

.     561 

In  a  total  of  these  1887  cases  the  majority  breathed  16  to  24; 
one- third  20  respirations  per  in  mute. 

Among  these  the  influence  of  age  is  very  important,  thus,  as  shown 
by  Quetelet6  (Table  LX.),  the  number  of  respirations  at  birth  are  more 
than  double  the  number  at  twenty  years  of  age,  and  from  this  age 
upward  the  number  of  respirations  diminishes.  It  is  evident,  therefore, 
that  the  number  of  respirations  per  minute,  as  deduced  from  the 
examination  of  a  number  of  individuals,  will  depend,  eceteris  paribus, 
upon  their  age;  and  we  should  expect  to  find  young  persons  breathing 
more  rapidly  than  old  ones.  It  will  be  readily  understood,  therefore, 
Avhy  560  persons,  on   an  average,  should  be  found  to  breathe  twenty 

Table  LX. — Respirations  at  Different  Ages. 

Per  mil. ill'-.  Age. 

44 At  birth. 

26  .........       5  years. 

20 15  to  20  years. 

19 20  to  25 

16 30 

18 30  to  50       " 

1  Elemeiita  Physiologic,  t.  iii.  p.  289.  2  Precis  elementaire  de  Physiologie,  t.  iii.  p.  337. 

3  Physiologic,  tome  ii.  p,  480.  4  Cyclopaedia  of  Aunt   ami  I'hys.,  vol.  iv   part  2,  p.  1085. 

6  Hutchinson,  op.  cit.  6  Quetelet :  Sur  Tliomme,  etc.,  1835,  t.  ii.  p   84, 


NUMBER    OF    RESPIRATIONS.  427 

times   per   minute,  and   239   persons  only  sixteen,  if  the  first  set  ex- 
amined are.  on  an  average,  younger  than  the  second  set. 

In  speaking  of  the  various  conditions  that  modify  the  number  of 
cardiac  beats  in  a  given  time,  the  influence  of  size  was  noticed,  it 
being  mentioned  that  the  number  of  cardiac  beats  in  a  given  time  was 
more  numerous  in  the  young  and  small  child,  and  young  and  small 
animal,  than  in  the  adult  man  or  large  animal.  Now,  the  same  relation 
that  we  have  just  pointed  out  as  existing  between  youth  and  the  num- 
ber of  respirations  in  man,  will  also  be  found  to  prevail  if  large  animals 
are  compared  with  small  ones,  or  if  the  same  animal  be  compared  at 
different  ages.  Thus,  as  observed  by  Milne  Edwards,1  and  by  the 
author,  while  the  number  of  inspirations  in  the  whale  is  only  about  four 
or  five  in  the  minute,  and  in  the  rhinoceros,  hippopotamus,  giraffe,  and 
horse  ten  to  the  minute,  the  number  of  respirations  are  thirty-five  or 
more  in  the  same  period  of  time  in  the  rabbit  and  guinea-pig,  while, 
according  to  Colin,2  the  number  of  respirations  being  thirteen  to  six- 
teen in  the  sheep,  will  be  sixteen  to  seventeen  in  the  lamb;  in  the  cow- 
fifteen  to  eighteen  ;  in  the  calf,  eighteen  to  twenty  ;  in  an  adult  dog, 
fifteen  to  eighteen  ;  in  the  young  dog,  eighteen  to  twenty.  The  cause  of 
this  difference  in  the  number  of  respirations,  according  to  the  age  and 
size  of  the  animal  is,  no  doubt,  due,  as  in  the  case  of  the  number  of 
cardiac  beats,  to  the  same  cause,  that  of  the  vital  processes  generally 
being  more  active  in  small  animals  than  in  large  ones. 

Sex  stems  to  influence  but  little  the  number  of  respirations,  no 
appreciable  difference  being  observed  in  boys  or  girls  ;  young  men, 
however,  breathe  a  little  more  rapidly  than  young  women  of  the  same 
ag< .  Everyday  experience  teaches  us  to  what  an  extent  respiration 
may  be  accelerated  by  nervous  excitement  and  exercise.  The  influ- 
ence of  muscular  exertion  is  not  limited  simply  to  active  exercise,  the 
mere  change  from  the  recumbent  to  the  sitting  position,  or  of  standing 
up.  will  inciease  the  respiratory  movements.  Thus,  Dr.  Guy  states 
that  lying  down  the  number  of  his  respirations  was  13  per  minute, 
while  sitting  19,  and  when  standing  up  22.  As  might  be  expected, 
during  sleep  the  number  of  respirations  is  diminished,  according  to 
Quetelet,3  the  diminution  being  about  1  in  4.  or  2o  per  cent.  It  will 
be  seen,  from  what  has  just  been  said,  that  the  number  of  respirations 
must  vary  very  much  within  the  limits  of  health;  and  that,  therefore, 
only  an  approximately  average  number  can  be  ascertained.  Of  1887 
cases  examined  by  Hutchinson,4  llol  breathed  from  16  to  24  times, 
and  nearly  one-third  of  them  20  times  a  minute.  The  average  number 
of  respirations  we  have  found  to  be  from  18  to  20  times  a  minute,  and 
we  may  add  here,  incidentally,  that  during  each  respiration  there  are 
about  four  heart  beats. 

Mechanical  Work  Performed  during  Respiration. 

It  will  be  remembered  that,  in  describing  the  circulation,  it  was  esti- 
mated that  the  mechanical  work  performed  by  the  heart  amounted,  in 

1  Physiologie,  tome  ii.  p.  7  Physiologic  Compares,  t.  i:.  p.  152. 

■';  Op.  fit.,  p.  88  *  Op.  i  it,  p.  1085. 


428  RESPIRATORY    MOVEMENTS. 

twenty-four  hours,  to  128  tons.  We  shall  see,  hereafter,  in  the  inves- 
tigation of  the  sources  of  the  forces  of  the  body,  that  it  is  equally 
important  to  determine,  as  far  as  possible,  the  mechanical  work  per- 
formed by  the  respiratory  muscles  in  the  same  period  of  time.  This 
may  be  estimated,  at  least  approximately,  in  the  same  way  as  in  the 
case  of  the  heart,  by  multiplying  the  weight  by  the  height  raised.  It 
has  already  been  mentioned  that  the  intrathoracic  is  less  than  the  extra- 
thoracic  pressure,  owing  to  the  elasticity  of  the  lungs  offering  a  resist- 
ance to  the  inspired  air  distending  them.  It  is  evident,  therefore,  that, 
at  each  inspiration,  the  chest  lifts  so  much  of  the  external  atmosphere 
pressing  down  upon  it  as  is  not  opposed  by  the  corresponding  part  of  the 
internal  atmosphere,  or  that  part  opposed  by  the  elasticity  of  the  lungs. 
Now  the  difference  between  the  intra-  and  extrathoracic  pressure,  or  the 
excess  in  weight  of  the  external  over  the  internal  air,  can  be  pretty  accu- 
rately determined  by  inspiring  air  out  of  a  mercurial  manometer  through 
one  nostril,  the  mouth  and  other  nostril  being  closed.  Let  us  admit 
that  about  40  cubic  inches  of  air  be  inspired  in  this  manner,  and, 
with  Donders/'that  57  mm.  of  mercury  (2.2  inches)  be  sucked  up  in 
the  proximal  limb  of  the  manometer,  and  that  this  represents  the  excess 
in  the  pressure  of  the  external  over  the  internal  air ;  and  further,  that  we 
add  15  mm.  to  this  on  account  of  the  resistance  of  the  lungs,  then  by 
multiplying  72  mm.  (2.8  inches)  by  20  sq.  decim.  (133  inches),  or 
the  area  of  the  thoracic  walls,  the  quotient,  1440  sq.  decim.,  or  194.4 
kilom.,  or  about  427.68  pounds,  will  be  the  weight  in  mercury  raised 
by  the  inspiratory  muscles  of  the  thoracic  walls.  Let  us  also  suppose, 
with  Fick,2  that  in  raising  this  weight  the  thoracic  walls  traverse  a 
distance  of  0.001  meter  (about  -gVth  of  an  inch),  then  the  quotient  of 
194.4  kilom.  by  0.001,  or  0.1944  meter  kilogrammes  (1.4  foot-pounds) 
will  be  the  work  done — that  is,  the  inspiratory  muscles  of  the  thorax  do 
an  amount  of  work  equal  to  raising  1.4  pounds  through  one  foot.  In 
the  same  way,  by  multiplying  the  area  of  the  diaphragm  3.5  sq.  decim. 
(about  57  sq.  in.)  by  82  mm.  of  mercury,  10  mm.  being  added  to  the 
72  on  account  of  the  abdominal  pressure,  the  quotient,  287  sq.  decim., 
or  38.7  kilom.  (about  85.14  pounds),  will  be  the  weight  raised  by  the 
diaphragm.  Multiplying  the  latter,  or  38.7  kilom.,  by  0.114  meter 
(about  y3g-th  of  an  inch),  the  distance  traversed  by  the  diaphragm,  the 
quotient,  or  0.44  meter  kil.  (3  pounds),  will  be  the  work  done  by 
the  diaphragm  ;  and  the  total  work  0.1944  +  0.44  =  0.63  meter  kil. 
(4  -j-  3  =  4.4  foot-pounds) — that  is,  the  work  done  by  the  inspiratory 
muscle,  at  each  inspiration  is  equal  to  the  work  of  raising  4.4  pounds 
through  one  foot. 

It  will  be  observed  that,  during  expiration,  the  mercury  rises  higher 
in  the  manometer  than  in  inspiration ;  for  example,  in  an  experiment 
where  2  inches  of  mercury  were  elevated  in  inspiration,  2J  inches  were 
elevated  in  expiration  ;  and  further,  that  the  difference  in  the  level  of 
the  mercury  during  inspiration  and  expiration  depends  upon  the  depth 
of  the  inspiration.     It  might  naturally  be  concluded,  from  these  experi- 

1  Physiologie  des  Menschen,  Erster  Band,  S.  419.     Leipzig,  1859. 

2  Die  Hedicinische  Physik,  S.  209.     Braunschweig,  1866. 


WORK    PERFORMED    DURING    RESPIRATION.  429 

ments,  that  the  expiratory  force  was  greater  than  the  inspiratory.  It 
will  be  remembered,  however,  that  expiration  is  due,  not  only  to  the 
passive  relaxation  of  the  inspiratory  muscles,  but  to  the  active  contrac- 
tion of  the  thoracic  walls,  due  to  their  elasticity,  which  the  inspiratory 
muscles,  in  dilating  the  thorax,  must  overcome,  just  as  the  air  in  enter- 
ing the  lungs  must  overcome  their  elasticity.  The  force  of  the  inspira- 
tory muscles  is  expended,  therefore,  not  only  in  elevating  the  mercury 
in  the  manometer,  but  in  overcoming  the  thoracic  elasticity,  which 
amounts  to  about  half  a  pound  (7.8  ounces)  on  the  square  inch.  It  is 
to  this  latter  force  which  is  due,  during  expiration,  the  excess  just  noticed 
in  the  elevation  of  the  mercury  in  the  manometer,  and  which  may  be 
taken  as  a  measure  of  it.  But  since  this  force  is  overcome  by  the  inspi- 
ratory muscles  in  dilating  the  thorax,  it  should  be  estimated  as  inspira- 
tory rather  than  as  expiratory  power.  As  in  the  experiment  just  per- 
formed, the  excess  of  half  an  inch  or  more  of  mercury  elevated  during 
expiration  is  one-fourth  that  of  the  two  inches  elevated  during  inspira- 
tion, one-fourth  of  the  mechanical  work  performed  during  inspiration  as 
indicated  by  the  manometer,  should  be  added  to  the  latter,  which  will 
make  the  amount  of  mechanical  work  done  during  each  inspiration  equal 
to  5.5  foot-tons,  not  including,  however,  the  weight  of  the  ribs  lifted. 

It  should  be  mentioned  that  it  is  only  in  deep  inspirations  that  the 
opposing  force  offered  by  the  thoracic  walls,  and  to  be  overcome  by 
the  inspiratory  muscles,  becomes  very  apparent  in  the  mercurial  man- 
ometer. This  is  as  might  be  expected,  since  the  elastic  force  put  forth 
by  the  thoracic  walls  in  their  reaction  will  be  proportional  to  the  extent 
to  which  they  have  been  stretched  by  the  inspiratory  force  distending 
them.  It  is  for  this  reason  that  the  mercury  rises  so  little  higher  in 
expiration  than  in  inspiration  in  the  manometer  during  tranquil  breath- 
ing. The  mechanical  work  performed  will  be,  therefore,  less  in  tranquil 
than  in  deep  inspiration. 

It  is  needless  to  mention  that  whatever  estimate  is  accepted,  it  must 
vary  with  the  capacity  of  the  chest,  number  of  respirations,  etc.,  and 
can  only  be  considered  as  approximately  true.  Admitting,  however, 
that  a  mechanical  work  equal  to  raising  5.5  pounds  through  1  foot  is 
performed  by  the  inspiratory  muscles  during  each  inspiration,  and 
supposing  further,  that  the  individual  inspires  18  times  a  minute,  then 
99  pounds  are  raised  1  foot  during  a  minute,  5940  pounds  during  an 
hour,  142,560,  or  over  63  tons  during  the  day.  If,  however,  the 
chest  be  less  expanded  than  we  have  supposed  it  to  be,  and  proportion- 
ately less  mercury  sucked  up  out  of  the  manometer  during  inspiration, 
and  less  expelled  during  expiration,  for  example,  one-third  less,  and 
the  number  of  inspirations  be  fewer,  it  is  evident  that  the  above 
estimate  will  be  reduced  to  about  21-foot  tons.  Inasmuch  as  we  have 
seen  that  expiration  is  rather  a  passive  than  an  active  process,  a 
return  to  a  condition  of  equilibrium,  the  work  done  by  the  expiratory 
muscles  was  not  taken  into  consideration  in  the  above  estimate,  and 
can,  for  the  reason  just  given,  be  neglected.  If,  however,  the  expi- 
ration becomes  active  and  deep,  then  the  work  performed  may  amount, 
as  shown  by  essentially  similar  calculation,  to  nearly  as  much  as  that 
performed  during  inspiration. 


430 


I ;  E  srlKATOEY    MO  V  K  M  E  X  T  S . 


Breathing  Capacity. 

On  account  of  the  importance  of  ventilation,  of  estimating  the 
amount  of  oxygen  absorbed,  and  carbonic  acid  exhaled,  of  determin- 
ing the  amount  of  heat  produced  in  the  body,  etc.,  it  is  necessary  thai 
the  amount  of  air  inspired  and  expired  during  respiration  should  be 
accurately  measured.  For  this  purpose  we  make  use  of  the  spirometer. 
The  instrument  described  by  Hutchinson1,  and  somewhat  modified  by 
Rawksley  for  the  author,  consists  (Fig.  246)  essentially  of  a  cylindrical 

vessel  (A),  with  a  capacity  of  about 
Fig.  246.  7.5     litres    (2    gal.),    containing 

water,  out  of  which  a  receiver  (B) 
can  be  elevated  and  depressed  by 
breathing  into  it  through  a  tube 
(C),  and  then  the  height  to  which 
the  receiver  is  elevated  and  de- 
pressed, as  shown  by  the  scale  D 
indicating  the  volume  of  the  air 
expired  and  inspired.  In  using  the 
spirometer,  it  should  be  placed 
upon  a  firm,  level  table,  about 
three  feet  from  the  ground.  The 
water  tap  then  having  been 
turned  off,  and  the  air  tap 
opened,  clear,  cold  water  is 
poured  through  the  spout  of  the 
cylindrical  vessel  A,  until  it  is 
full,  any  excess  of  water  run- 
ning off  by  the  tap  in  commu- 
nication with  the  air  tube. 
Enough  colored  spirit  is  poured 
into  the  U-shaped  tube,  until 
it  stands  at  a  level  of  about 
3.5  inches.  The  counterpoising 
weights  being  then  suspended 
within  the  framework  M,  and 
over  the  pulleys,  and  the  air  tap 
closed,  the  instrument  is  ready  for  an  observation  The  person  whose 
breathing  capacity  is  to  be  determined  standing  erect  with  head  thrown 
backward,  and  loosely  attired,  applies  by  the  mouth-piece  the  flexible 
tube  C  to  his  mouth  and  expires  into  the  spirometer.  The  air  from 
his  lungs  passes  thence  into  the  tube  E,  elevating  the  receiver  B,  the 
volume  of  air  expired,  expressed  in  cubic  inches,  being  shown  by  the 
number  of  the  scale  to  which  the  index  connected  with  the  receiver 
has  been  elevated.  At  the  termination  of  the  expiratory  effort,  the 
air-tap  must  be  closed. 

Each  division   of  the  scale  corresponds  to  two  cubic   inches.     The 
descent  of  the  lever  through  an  inspiratory  effort,  as  indicated  by  the 


Hutchinson's  spirometer. 


i  Op,  cit.,  p.  1069. 


TIDAI/    AIR-  431 

scale  read  in  the  reverse  direction,  will  give  the  amount  of  air  inspired. 
The  volume  of  air  must,  however,  be  corrected  for  temperature,  for  the 
temperature  of  the  air  will  be  at  once  reduced  to  the  temperature  of  the 
water  in  the  spirometer,  to  which  it  has  passed,  and  which  is  warm  or 
cold  according  to  the  season.  Practically  the  change  in  the  bulk  of  the 
air  will  amount  to  about  5-^  for  every  degree  Fahr.,  and  the  difference 
should  be  added  or  subtracted  as  the  temperature  of  the  room  in  which 
is  the  spirometer  is  below  or  above  60°.  Suppose,  for  example,  295 
cub.  in.  be  breathed  into  the  spirometer,  the  temperature  of  the  room 
being  55°,  then  2.9  cub.  in.  should  be  added  to  the  295  cub.  in.,  since 
--g-g-  equals  y^-jj-  of  295,  equals  2.95  cub.  in.  ;  on  the  other  hand,  if  the 
air  be  at  a  temperature  of  70°,  then  5.9  cub.  in.  should  be  subtracted 
from  the  295,  since  -^T  equals  -^  of  295,  equals  5.9  cub.  in.  The 
U-shaped  tube  acts  as  a  gauge,  since,  as  long1  as  the  colored  fluid 
remains  at  the  same  level  in  its  two  limbs,  the  densit}-  of  the  air  within 
and  without  the  receiver  is  the  same,  which  is  necessarily  an  indispen- 
sable condition  in  the  working  of  the  instrument.  In  order  to  expel 
the  air  from  the  receiver,  and  return  it  to  its  original  position,  the  plug 
is  removed  with  one  hand,  while  the  receiver  is  depressed  with  the 
other.  The  experiments  having  been  concluded,  and  it  is  desired  to 
empty  the  water  out  of  the  spirometer,  it  is  only  necessary  to  open  the 
water-tap.  If  a  healthy  adult  breathe  easily  into  the  spirometer  in  the 
manner  indicated,  it  will  be  found  that  usually  about  20  cub.  in.  pass 
into  the  instrument  with  each  expiration.  If  now  the  air  be  expelled, 
and  the  receiver  returned  to  its  original  position,  and  the  air-tap  be 
opened,  fresh  air  will  pass  freely  into  the  receiver,  and,  the  pressure  of 
the  air  within  and  without  being  the  same,  the  receiver  will  be  elevated 
by  the  counterpoising  weights.  Suppose  a  hundred  cubic  inches  of  air 
have  been  passed  in  this  way  into  the  receiver,  and  now  a  gentle  inspira- 
tory effort  is  made,  the  receiver  will  descend,  and  it  will  be  found  that 
its  index  has  fallen  to  the  number  80  on  the  scale,  showing  that  1^0  cub. 
in.  of  air  have  been  inspired.  By  experimenting  in  this  way  upon  a 
number  of  persons,  it  will  be  found  that,  eceteris paribus,  on  the  average, 
that  in  easy,  tranquil  breathing  about  20  cub.  in.  of  air  are  taken  into 
the  lungs  Avith  each  inspiration,  and  about  20  cub.  in.  are  given  out  with 
each  expiration.  In  reality  the  expired  air  is  about  5V'1  ro"71ut'1  ^ess  m 
volume  than  the  inspired  air.  This  is  due,  as  we  shall  see,  to  the  fact 
of  the  carbonic  acid  excreted  being  a  little  less  in  amount  than  the 
oxygen  absorbed.  The  20  cub.  in,  of  air  inspired  and  expired  during 
each  respiration  are  usually  known  as  the  tidal  or  ordinary  breathing  air. 
If  now  a  forcible  expiration  be  made,  not  only  will  20  cub.  in.  of  air  pass 
into  the  spirometer,  as  in  easy  breathing,  but  as  much  as  100  additional 
cub.  in.  This  extra  quantity,  so  to  speak,  of  expired  air  is  not  usually 
changed  in  respiration,  but  only  when  the  necessity  is  felt  of  more  com- 
pletely renovating  the  air  in  the  lungs,  and  is  called,  therefore,  the 
reserve  or  supplemental  air,  and  amounts  to  about  100  cub.  in.  In  pro- 
longed expiratory  efforts,  such  as  sneezing  and  blowing,  this  reserve  air 
is  more  or  less  expelled.  As  the  reserve  air  is  vitiated  through  contin- 
ually receiving  water  and  carbonic  acid  from  the  blood  of  the  lungs, 
pearl-divers  and  others  who  are  in  the  habit  of  temporarily  arresting 


432  RESPIRATORY-    MOVEMENTS. 

their  respiration,  instinctively  first  get  rid  of  their  reserve  air  by  forcibly 
expiring  several  times,  and  then  fill  their  lungs  with  fresh  air.  If  the 
chest  be  now  enlarged  by  a  forcible  inspiration  instead  of  an  expiration, 
the  spirometer  having  been  suitably  arranged,  as  much  as  110  cub.  in. 
can  be  withdrawn  from  the  instrument  over  and  above  the  20  cub.  in. 
due  to  an  ordinary  inspiration.  This  constitutes  what  is  known  as  the 
complemental  air,  and  usually  amounts  to  110  cub.  in.  It  is  drawn 
upon  whenever  an  effort  is  made  that  demands  a  temporary  arrest  of 
respiration,  in  blowing,  yawning,  sneezing,  etc.,  to  a  certain  extent  in 
sleep,  when  the  breathing  is  deep,  at  the  moment  immediately  preceding 
some  muscular  effort,  etc.  The  complemental  air  can  also  be  indirectly 
estimated  by  deducting  the  sum  of  the  tidal  and  reserve  airs  (20  cub.  in. 
plus  100  cub.  in.)  from  the  volume  of  the  external  breathing  air,  or 
that  which  can  be  expelled  from  the  lungs  by  the  most  forcible  expira- 
tion after  the  most  profound  inspiration,  and  which,  we  shall  see  in  a 
moment,  amounts  to  230  cub.  in.  ;  thus  230  cub.  in.  less  120  cub.  in. 
equals  110  cub.  in.  The  capacity  of  the  lungs,  and  the  fact  that  after 
death  they  always  contain  air,  make  it  evident  that  the  air  is  never 
entirely  expelled,  even  by  the  most  powerful  expiration.  A  certain 
quantity  of  air,  therefore,  always  remains  in  the  lungs.  It  is  known  as 
the  residual  air,  and  may  be  approximately  considered  as  amounting  to 
100  cub.  in.  The  amount  of  the  residual  air  cannot  be  determined 
directly,  either  in  the  living  or  dead  body,  since  the  volume  of  air  Avithin 
the  lungs  after  an  ordinary  expiration  consists  of  the  sum  of  the  reserve 
and  residual  airs.  If  this,  however,  can  be  determined,  the  deduction 
from  it  of  the  reserve  air  will  give  the  residual  air.  Now  it  is  well 
known  that  hydrogen  gas  when  inspired  is  not  absorbed  by  the  blood, 
and  that  gases  will  diffuse  into  each  other  until  the  mixture  becomes 
uniform  :  availing  himself  of  these  facts,  Grehaut1  made  the  subject  of 
his  experiments  inspire  a  definite  quantity  of  hydrogen  gas  until  the 
mixture  of  hydrogen  and  air  became  uniform,  and  then  estimated  by 
analysis  of  the  expired  air  the  quantity  of  air  remaining  in  the  lungs, 
and  necessarily  represented  by  the  volume  of  the  hydrogen  lost.  The 
amount  of  air — that  is,  the  sum  of  the  reserve  and  residual  air — in  the 
lungs  at  the  beginning  of  the  experiment  can  be  then  easily  calculated, 
and  was  shown  by  Grehaut  to  amount  to  nearly  200  cub.  in.  Deducting 
from  this  the  reserve  air,  or  100  cub.  in.,  the  remainder,  100  cub.  in., 
is  the  residual  air.  Assuming  the  mean  capacity  of  the  chest  to  amount 
to  312  cub.  in.,  and  allowing  100  cub.  in.  for  the  heart  and  great  blood- 
vessels, and  100  cub.  in.  for  the  parenchymatic  structure  of  the  lungs, 
there  would  remain  little  more  than  100  cub.  in.  for  the  residual  air, 
which  is  the  estimate  given  by  Hutchinson.2 

While  the  method  just  described  gives  a  sufficiently  accurate  determi- 
nation of  the  respiratory  capacity,  more  exact  results  are  obtained  when 
the  tube  of  the  spirometer  communicates  with  a  mask  closely  fitting  to 
the  face  of  the  person  experimented  upon.  The  mask  is  provided  with 
two  openings  furnished  with  valves  working  in  opposite  directions. 
Through  one  of  the  openings  the  expired  air  is  expelled,  while  through 

1  Journal  de  l'Anatomie,  1864,  p.  523.  2  Op.  cit.,  p.  1067. 


RESPIRATION    APPARATUS. 


433 


the  other  the  air  to  be  inspired  passes  from  the  spirometer.  A  more 
simple  and  equally  effective  apparatus  consists  of  two  ivory  tubes  which 
are  inserted  tightly  into  the  nostrils  and  which  connect  with  a  common 
tube,  dividing  into  two  branches;  one  of  these  communicates  with  the 
spirometer  and  transmits  the  air  to  be  breathed,  the  other  allows  the 
expired  air  to  escape.  Each  of  the  branches  is  provided  with  a  valve 
which  opens  in  opposite  directions.  According,  therefore,  to  which  of 
the  ivory  tubes  is  inserted  into  the  nose  the  air  can  be  either  inspired 
from  or  expired  into  the  spirometer.  In  determining  the  amount  of  air 
inspired  or  expired  by  an  animal  in  a  given  time,  we  make  use  of  a  con- 
venient apparatus  constructed  for  this  purpose  by  Dr.  A.  P.  Brubaker, 
and  which,  in  principle,  is  essentially  the  same  as  that  commonly  known 
as  Rosenthal's  apparatus.      It  consists  of  a  small  spirometer  (Fig.  247), 


Fig.  247. 


Brubaker' s  respiration  apparatus. 

the  internal  cylinder  or  gasometer  (D)  having  a  capacity  of  700  c.  cm. 
(43  in.)  and  equipoised  by  a  bag  of  shot*  Through  the  under  part  of 
the  outer  cylinder  (E),  which  is  firmly  cemented  to  the  stand,  passes  a 
T-shaped  tube  (D)  connected  with  the  tubes  and  valves  which  transmit 
the  air  to  and  from  the  gasometer.  To  one  end  of  the  tube  (K)  passing 
from  the  mask  closely  fitting  to  the  face  of  the  animal  is  adapted  a  tube 

28 


434  RESPIRATORY    MOVEMENTS. 

(I)  for  transmitting  the  air  to  be  inspired,  and  to  the  other  end  the  tube 
and  valve  (M  N  0)  for  carrying  off  the  expired  air.  The  valves  (F  N), 
just  referred  to,  are  the  same  as  those  used  by  Voit  in  his  respiratory 
apparatus  shortly  to  be  described,  and  consist  of  oval  glass  bulbs  con- 
taining mercury.  It  is  evident  that  as  Ions;  as  these  valves  are  in  the 
position  shown  in  Fig.  247  the  air  will  only  pass  in  the  direction  indi- 
cated by  the  arrows.  By  reversing  the  valves  (F  N)  the  expired  air 
will  return  back  to  the  spirometer,  and  so  can  be  measured.  In  using 
the  apparatus  the  gasometer  must  be  first  raised  by  the  hand  through 
the  whole  extent  or  to  a  given  height,  the  volume  of  air  entering  being 
determined  by  the  scale.  As  soon  as  the  gasometer  has  descended  by 
the  exhaustion  of  the  air  through  the  inspiration  of  the  animal  it  must 
be  raised  again — that  is,  if  the  observation  is  to  last  any  length  of  time. 
By  connecting  the  tube  Gr  with  a  suitable  reservoir  the  animal  can  be 
made  to  breathe  any  gas  that  is  desired,  and  the  amount  inspired  in  a 
given  time  approximately  determined,  the  Huid  used  in  the  spirometer 
will  then  depend  upon  the  kind  of  gas.  The  manner  in  which  the  ex- 
pired gas  is  analyzed  will  be  explained  shortly.  The  great  advantage 
of  the  apparatus  just  described,  as  compared  with  that  of  Rosenthal,  is 
due  to  the  fact  of  so  little  resistance  being  offered  by  either  the  valves 
or  the  gasometer,  the  air  in  fact  being  inspired  by  the  animal  with  little 
or  no  exertion,  whereas  in  Rosenthal's  apparatus  the  valves  used  being 
Midler's,  and  the  gasometer  being  immersed  in  mercury,  the  latter  can 
be  only  raised  with  difficulty  by  a  large  animal  and  not  at  all  by  a  small 
one. 

We  have  incidentally  alluded,  a  moment  since,  to  the  extreme  breath- 
ing capacity ;  by  this  is  meant  the  volume  of  air  which  can  be  expelled 
from  the  lungs  by  the  most  forcible  expiration,  after  the  most  profound 
inspiration,  or  the  volume  that  can  be  inspired  by  the  most  forcible  in- 
spiration after  the  most  profound  expiration.  It  was  called  by  Hutchin- 
son1 the  vital  capacity,  as  signifying  the  capacity  or  volume  of  air 
which  can  only  be  displaced  by  living  movements,  and  was  determined 
by  this  observer  to  amount  in  a  man  of  medium  height  (5  feet  8  inches) 
to  230  cubic  inches,  being  equal  to  the  sum  of  the  tidal  reserve  and 
complemental  airs. 

The  experiments  upon  which  this  conclusion  was  based  were  made 
by  means  of  the  spirometer,  upon  nearly  5000  persons.  Hutchinson 
also  showed  that  the  vital  capacity  is  influenced  by  various  conditions. 
Thus,  it  was  ascertained  that,  for  every  inch  of  height  between  five  and 
six  feet,  the  extreme  breathing  capacity  is  increased  eight  cubic  inches. 
The  position  of  the  body  affects  the  vital  capacity.  Thus,  in  one  indi- 
vidual while  standing  erect,  it  was  260  cubic  inches,  and  when  recumbent 
it  was  230,  a  difference  of  30  cubic  inches.  The  vital  capacity  is  influenced, 
without  doubt,  by  weight,  but,  as  the  weight  usually  increases  with  the 
height,  it  is  difficult  to  separate  the  effect  of  one  from  that  of  the  other. 
Age  has  also  an  influence,  the  vital  capacity  increasing  up  to  the  thirtieth 
year  of  life,  and  then  diminishing  to  the  sixtieth.  The  vital  capacity 
is  also  affected  by  the  sex,  being  greater,  as  shown  by  Herbst,2  in  the 

i  Op.  cit.,  p.  1065.  -'  Meckel's  Archiv  f.  Anat.  u.  Phy?.,  p.  3,  S.  103,  1828. 


Graham's  law.  435 

male  than  in  the  female.     As  might  be  anticipated,  any  diseased  con- 
dition  affecting  the  mobility  of   the  thorax   or   the  dilatability  of  the 
lungs,   -will   modify,   more  or  less  profoundly,   the  extreme  breathing 
capacity,  hence  the  importance  of   the  latter  as   a  test  of  health  or 
disease.     Thus,  should  a  person's  vital  capacity  be  found  to  be  190  cubic 
inches  instead  of  230  inches,  a  deficiency  of  17   per   cent.,  unless  ex- 
cessively fat,  it  would  be  reasonable  to  suspect  in  such  a   person  the 
presence  of  pulmonary  disease ;  and,  yet,  in  phthisis,  the  vital  capacity 
may   be  only  23  inches,  the  deficiency  amounting  to  201  inches,  or 
90  per  cent.,  and  yet  life  be  maintained.1     Inasmuch  as  the  extreme 
breathing  air  is  made  up  of  the  tidal  reserve  and  complemental  airs,  the 
latter    will    be  affected    by    the   same  conditions  as  the  former.     As 
the   effects,   however,   are  less  marked   than  where  the  whole  volume 
of  air  is   considered,  it  will  be  necessary  to  call  further  attention  to 
them.      When    it    is    remembered  that,    with    each  inspiration,     only 
about  twenty  cubic   inches  of  air  are  introduced,  sufficient  to  fill    the 
trachea  and  large  bronchial  tubes,  it  is  evident  that  there  must  be  some 
subsidiary   force  acting  in   addition   to  the  ordinary  respiratory  move- 
ments of  the  chest  by  which  the  fresh  air  is  brought  to  the  air  cells  and 
the  vitiated  air  expelled.     The  interchange  between  the  fresh  air  in  the 
upper  part  of  the  lungs  and  the  vitiated  air  in  the  lower  part,  is  un- 
doubtedly due  to  the  diffusion  of  the  air  containing  oxygen  and  carbonic 
acid,  and  which  goes  on,  according  to  the  lawT  established  by  Graham,2 
that  the  diff'usibility  of  gases  is  inversely  proportional  to  the   square 
root  of  their  densities — that  is,  that  the  diffusion  of  oxygen   is  to  the 
diffusion   of   carbonic   acid  as  the  square  root  of  the  density  of  car- 
bonic acid,  or  j/1.529  =  1.237,  is  to  the  square  root  of  the  density  of 
oxygen,  or  t/1.1056  =  1.0514,  or  1.237  :  1.0514  :  :  95  :  81.  Accord- 
ing to  this  law,  then,  the  lighter  gas,  the  air,  with  its  oxygen,  will 
descend  more  rapidly   than  the  carbonic  acid,   the  heavier   gas,   will 
ascend,  91  parts  of  oxygen  replacing  81   parts   of  carbonic  acid.     As 
this  diffusion  is  continually  going  on  between  these  gases,  the  air  in  the 
pulmonary  air  cells,  where  the  exchange  between  the  oxygen  and  car- 
bonic acid  takes  place,   has  a  tolerably  uniform  composition,  and  the 
aeration  of  the  blood  is  far  less  intermittent  in  its  character  than  the 
respiratory  movements  of  the  thorax.    The  passage  of  the  oxygen  from 
the   air  of  the  pulmonary  air  cells   into  the  blood  of  the  pulmonary 
capillaries,  and  of  carbonic  acid  in  the  reverse  direction  from  the  blood 
into  the  air,  is  due  to  the  fact  of  the  tension  of  the  oxygen  of  the  air 
being  higher  than  that  of  the  blood,  and  of  the  tension  of  the  carbonic 
acid  of  the    blood  being  higher  than  that  of  the   air.     Necessarily, 
therefore,  the  oxygen  of  the  air  within  the  lungs  will  pass  through  the 
wall  of  the  air  cell  and  capillary  into  the  blood,  thence  into  the  red 
corpuscles,  combining,  as  we  have  seen,  with  the  haemoglobin  of  these 
bodies,  while  the  carbonic  acid  will  pass  in  the  reverse  direction  from 
the  blood  through  the  wall  of  the  capillary  and  wall  of  the  air  cell  into 
the  lungs,  and  thence  out  of  the  body.     It  is  possible  that  the  pulmo- 
nary epithelium  in  acting  as  a  secretory  surface  may  also  exercise  some 

1  Hutchinson,  op.  cit.,  p.  1079.  -  Trans,  of  Royal  Soc.  Kdinb.,  vol.  xii.  p.  573,  1834. 


436 


RESPIRATORY    MOVEMENTS. 


Fig.  248. 


influence  in  promoting  the  absorption  of  oxygen  and  elimination  of 
carbonic  acid.  On  the  other  band,  the  oxygen  of  the  arterial  blood 
will  readily  diffuse  through  the  wall  of  the  capillary  into  the  tissues, 
the  tension  of  the  oxygen  in  the  latter  being  so  low  as  to  amount,  prac- 
tically, to  nothing,  the  oxygen  combining  in  some  stable  form  as  rapidly 
as  absorbed.  While,  owing  to  the  continual  production  of  carbonic  acid 
in  some  unknown  way  in  the  tissues  out  of  the  oxygen  absorbed,  the 
tension  of  the  carbonic  acid   of  the  tissues  being  always   higher  than 

that  of  the  blood  circulating  in  their 
midst,  the  carbonic  acid  will,  conse- 
quently, diffuse  iti  the  opposite  direction 
to  that  of  the  oxygen,  viz.,  from  the 
tissues  through  the  wall  of  the  capillary 
into  the  blood  now  become  venous 
through  deoxidation  of  most  of  its 
haemoglobin.  The  tension  of  the  gases 
in  the  blood  is  determined  by  means  of 
the  ierotonometer.  This  (Fig.  2-48)  con- 
sists of  a  long  glass  tube  A,  communi- 
cating above  by  means  of  the  stopcocks 
B  C  with  a  tube  (D),  bringing  the 
blood,  the  tension  of  whose  gases  is  to 
be  determined,  and  with  one(i?)  leading 
to  the  eudiometer  for  the  determination 
of  the  gases,  and  below  with  a  bell-jar 
((7),  standing  over  mercury,  and  with 
the  reservoir  of  mercury  H.  The  glass 
tube  is  first  entirely  filled  with  mercury 
so  as  to  exclude  the  air,  by  elevating  the 
reservoir  H,  and  is  then  surrounded  by 
hot  water  so  as  to  maintain  the  tem- 
perature of  the  blood  examined  at  that 
of  the  animal  from  which  it  was  drawn. 
The  glass  tube  A  is  then  filled  through 
the  depression  of  the  mercurial  reser- 
voir with  a  mixture  consisting  of  known 
quantities  of  nitrogen,  oxygen,  and 
carbonic  acid.  The  blood  being  allowed 
to  flow  from  the  artery  or  vein  of  the 
animal  for  a  moment  out  of  the  tube  D, 
so  as  to  exclude  the  air,  is  then  diverted 
into  the  gas  mixture  in  A.  As  the  blood  flows  down  through  the  tube 
into  the  mercury  the  mercury  is  driven  up  into  the  bell-jar  (6r),  while 
the  tension  of  its  oxygen  and  carbonic  acid  are  increased  or  diminished 
according  to  the  corresponding  tension  of  the  oxygen  and  carbonic  acid 
of  the  gas  mixture,  as  finally  determined  by  the  analysis  of  the  gases  in 
the  eudiometer  E,  into  which  the  gases  are  driven  by  the  elevation  of 
the  mercurial  reservoir.  The  general  results  as  to  the  tension  of  the 
oxygen  and  carbonic  acid  in   the  blood,  as  obtained   with  the  aeroto- 


iErutcmometer.     (IIoppe  Seylee.) 


TENSION  OF  GASES  IN  BLOOD.  437 

nometer  by  Pfliiger1  and  his  pupils,  Wolf  berg,2  Strassburg,8  Nussbaum,4 
are  as  follows : 

The  tension  of  oxygen  in  arterial  blood  (one  atmosphere  being  equal 
to  760  mm.  of  mercury)  is  equal  to  29.6  mm.  of  mercury,  corresponding 
in  amount  to  3.9  per  cent,  of  atmosphere,  that  of  carbonic  acid  being 
equal  to  21.2  mm.,  corresponding  in  amount  to  2.8  per  cent.  The  ten- 
sion of  oxygen  in  venous  blood  is  22.04  mm.  of  mercury,  corresponding 
in  amount  to  2.9  per  cent.,  that  of  carbonic  acid  being  equal  to  41  mm. 
of  mercury,  corresponding  in  amount  to  5.4  per  cent.  It  is  obvious, 
then,  such  being  the  tension  of  the  gases  of  the  blood,  that  since  the 
tissues  offer  no  resistance  to  the  passage  of  oxygen  from  the  arterial 
blood  (tension  29.6)  into  them  the  tension  of  their  oxygen  being  practi- 
cally nothing,  and  from  the  fact  of  carbonic  acid  being  continually  pro- 
duced in  the  tissues,  while  the  tension  of  the  carbonic  acid  in  the  arterial 
blood  is  low  (tension  21.2),  that  the  oxygen  of  the  arterial  blood  will  pass 
to  the  tissues,  and  the  carbonic  acid  away  from  them.  On  the  other 
hand,  the  tension  of  the  carbonic  acid  of  the  air  being  equal  to  only  0.38 
mm.  of  mercury,  it  existing  in  the  atmosphere  in  the  small  amount  of 
0.05  per  cent.,  while  the  tension  of  the  oxygen  of  the  air  amounts  to 
138  mm.  of  mercury,  corresponding  in  amount  to  20.8  vol.  per  cent., 
the  carbonic  acid  of  the  venous  blood  (tension  41)  will  diffuse  into  the 
air  (tension  0.38),  and  the  oxygen  of  the  air  (tension  138)  will  diffuse 
into  the  blood  (tension  22.04).  The  amount  of  the  gases,  and  the  con- 
dition in  which  they  exist  in  the  blood  have  already  been  considered. 

i  Pfl tiger's  Archiv,  Bd.  vi.  S.  43.  2  Ibid.,  Band  iv.  S.  465. 

3  Ibid.,  Band  vi.  S.  65.  *  Ibid.,  Band  vii.  S.  296. 


CHAPTER    XXIX. 

ABSORPTION  OF  OXYGEN— EXHALATION   OF   CARBONIC  ACID. 

Having  seen  that  the  essence  of  respiration  consists  in  the  absorp- 
tion of  oxygen,  and  the  giving  up  of  carbonic  acid,  etc.,  and  the  manner 
in  which  the  air  containing  these  gases  is  respired,  it  remains  for  us 
now  to  determine,  as  far  as  possible,  the  amount  of  oxygen  absorbed 
and  carbonic  acid  eliminated  by  the  system  in  a  given  time.  This  is 
one  of  the  most  difficult  problems  in  experimental  physiology,  and,  at 
the  same  time,  one  of  the  most  important,  since,  as  we  shall  see,  all  calcu- 
lations as  to  the  amount  of  animal  heat  produced  in  the  body  through 
oxidation  and  the  development  of  muscular  force,  etc.,  are  based  upon  the 
amount  of  oxygen  absorbed,  the  carbonic  acid  and  water  being  exhaled, 
in  a  measure  of  the  heat,  etc.,  so  produced.  Let  us  endeavor  to  deter- 
mine, first,  the  amount  of  oxygen  absorbed,  and  then  that  of  carbonic 
acid,  etc.,  exhaled  in  a  given  time.     This  can  be  done  in  several  ways, 


Fig.  249. 


Valentin  and  Bruuner's  respiration  apparatus. 


the  simplest  of  which  consists  in  comparing  the  composition  of  the  ordi- 
nary atmospheric  air  with  that  which  has  been  breathed,  with  the  object 
of  determining  the  amount  of  oxygen  absorbed  during  one  inspiration, 


VALENTIN    AND    BRUNNER'S    APPARATUS.  439 

and  multiplying  this  by  the  minutes,  hours,  etc.,  in  order  to  obtain, 
approximately  at  least,  the  amount  of  oxygen  absorbed  in  the  twenty- 
four  hours.  The  apparatus  of  Valentin  and  Brunner,  as  used  by  the 
author  for  this  object,  consists  (Fig.  249)  of  a  Woulflf  's  bottle  A  having  a 
capacity  of  about  a  litre  (61  cub.  in.).  One  of  the  openings  communi- 
cates with  the  mouth-piece  B,  into  which  the  person  expires,  the  air  first 
passing  through  pumice-stone  and  sulphuric  acid  C  so  as  to  dry  it.  The 
middle  opening  communicates  with  the  set  of  tubes  G  H I  K.  H  and  I 
contain  phosphorus  and  baryta  for  the  absorption  of  the  oxygen  and 
carbonic  acid  of  the  expired  air,  G  and  K  pumice-stone,  etc.,  that  of 
G  for  the  absorption  of  the  watery  vapors  that  may  have  escaped,  the 
pumice-stone,  etc.  in  C  K  for  retaining  that  taken  up  by  the  dry 
air  passing  through  the  baryta  solution,  and  which,  if  lost,  would  cause 
an  error  in  the  estimate  of  the  carbonic  acid  exhaled,  the  tubes  being: 
weighed  before  and  after  the  experiment.  Through  the  middle  opening 
of  the  Woulff's  bottle  a  funnel  (D)  provided  with  a  stopcock  is  introduced, 
the  opening  being  then  hermetically  closed.  The  funnel  is  filled  with 
a  known  quantity  of  mercury.  The  manner  of  using  the  apparatus  is 
as  follows  :  having  breathed  for  say  fifteen  minutes  through  the  mouth- 
piece until  the  air  of  the  Woulff's  bottle  has  been  entirely  displaced  by 
the  expired  air,  the  mouth-piece  is  entirely  closed,  any  external  air 
being  further  prevented  from  passing  into  the  Woulff's  bottle  by  the 
mercury  in  E  acting  as  a  valve,  the  air-tightness  of  the  apparatus  being 
assured  by  the  rise  of  the  mercury  in  the  tube  F,  through  the  contrac- 
tion of  the  expired  air  in  A,  consequent  upon  its  cooling  and  the  closure 
of  the  tube  funnel.  The  stopcock  of  the  funnel  being  then  turned,  the 
mercury  passes  into  the  Woulff's  bottle,  displacing  a  known  quantity 
of  expired  air,  the  latter  passing  into  the  set  of  tubes  G  H  I  K,  pre- 
viously adjusted  to  the  middle  opening.  The  weight  of  the  tubes  H  and 
I  having  been  previously  determined,  their  increase  in  weight  will  give, 
respectively,  the  amount  of  carbonic  acid  and  oxygen  absorbed.  De- 
ducting now  the  amount  of  oxygen  so  obtained  from  the  expired  air 
from  that  contained  in  an  equal  quantity  of  ordinary  inspired  air,  the 
remainder  will  be  the  amount  of  oxygen  retained  in  the  inspiration  of 
such  a  quantity  of  air;  on  the  other  hand,  deducting  the  trace  of  car- 
bonic acid  usually  present  in  the  atmosphere  from  that  obtained  from 
the  expired  air,  and  the  remainder  will  be  the  amount  of  carbonic  acid 
exhaled  into  such  a  quantity  of  expired  air. 

The  ordinary  atmospheric  air  consists  of  a  mechanical  mixture 
rather  than  a  chemical  combination  of  nitrogen,  oxvgen,  with  small 
amounts  of  carbonic  acid  and  traces  of  ammonia.  100  parts,  by  measure, 
containing  nitrogen  79.19,  oxygen  20.81,  ammonia  0.04,  in  round 
numbers,  there  being,  on  an  average,  20  of  oxvgen  to  80  of  nitrogen.  If 
the  expired  air,  however,  be  analyzed  in  the  manner  just  described,  it 
will  be  found  that,  as  compared  with  the  ordinary  air,  it  has  lost  oxvgen 
and  gained  carbonic  acid,  water,  etc.  Thus,  if  an  ordinary  inspiration 
be  made — that  is,  320  c.  cm.  (20  in.)  of  air  inspired  containing  62  cm. 
(4  in.)  of  O,  and  249  cm.  (15  in)  of  N,  analysis  of  the  expired  air,  by 
means  of  phosphorus  or  pyrogallic  acid,  etc.,  will  show  that  46.8  cm. 
(3  in.)  of  O  are  returned  to  the  atmosphere,  15.6  cm.  (1  in.)  of  oxygen 


-140  ABSORPTION    OF    OXYGEN,    ETC. 

having  been  absorbed  by  the  system — that  is,  -^th  of  the  air  breathed 
represents  the  amount  of  oxygen  absorbed.  On  this  supposition,  about 
425  litres  (15  cub.  feet)  of  oxygen  would  be  absorbed  in  twenty -four 
hours  by  an  adult,  as  may  be  seen  from  the  following  calculation  : 

Table  LXI. 

20  cubic  inches  of  air  changed  at  each  inspiration. 
18  respirations  per  minute. 

360 
60  minutes. 


21600 

24  hours. 


518400  cubic  inches  of  air  changed  in  24  hours. 

1728)    518400 

300  cubic  feet  of  air  changed  in  24  hours. 

20)  300 

15  cubic  feet  of  oxygen  absorbed  daily. 

Inasmuch,  however,  as  breathing  is  increased  both  in  rapidity  and 
volume  by  exercise,  it  might  be  naturally  inferred  that  the  estimate  of 
the  air  inspired,  and  of  oxygen  absorbed  in  twenty-four  hours,  just 
given,  is  too  low.  Such,  indeed,  is  the  case,  it  having  been  shown  by 
experiment  that  at  least  10,000  litres  of  air,  or  about  350  cubic  feet,  are 
inspired  daily,  and  500  litres  of  oxygen,  or  17.5  cubic  feet,  absorbed — 
that  is,  about  20  litres,  or  1220  inches,  of  oxygen,  per  hour.  This  last 
estimate  agrees  very  well  with  the  mean  results  of  Valentin  and 
Brunner,1  obtained  by  the  above  method.  These  observers  determined 
the  amount  of  oxygen  absorbed,  by  analysis  of  the  expired  air  in  a 
number  of  cases,  the  amount  of  oxygen  present  in  an  equal  quantity 
of  inspired  air  having  been  previously  determined.  In  the  first  of 
these  experiments  the  amount  of  oxygen  absorbed  was  about  27.12 
grammes,  19  litres,  and  in  the  second,  33.32  grammes,  about  23  litres, 
per  hour.  The  difference  between  these  two  results,  as  compared  with 
each  other,  and  that  we  have  just  given,  was  probably  due  to  the 
difference  in  the  number  of  the  respirations,  capacity  of  chest,  amount 
of  air  breathed,  etc.  The  amount  of  oxygen  absorbed  can  also  be 
indirectly  determined  by  calculation  from  the  amount  of  carbonic  acid 
excreted.  This  method  will  be  explained  presently,  when  we  describe 
the  respiration  apparatus  of  Pettenkofer  and  Voit,  for  the  determina- 
tion of  the  carbonic  acid,  etc.,  excreted.  According  to  Pettenkofer, 
the  amount  of  oxygen  absorbed  per  hour  was  about  23  litres,  the  same 
as  that  determined  in  the  case  of  Brunner.  Whatever  the  amount 
may  be  of  oxygen  absorbed,  whether  it  be  accepted  or  not,  as  amounting 
exactly  to  425  litres  (15  cubic  feet),  more  or  less,  in  twenty-four  hours, 
it  is  very  evident,  and  this  is  the  important  point,  practically,  as  regards 
the  subject  of  ventilation,  and  it  cannot  be  too  much  insisted  upon,  that 
every  human  being  requires  an  enormous  amount  of  fresh  air  in  twenty  - 

1  Valentin :  Lehrbuch  der  Pliysiologie  des  Menschen,  1847,  Baud  i    S.  5G5,  S.  586. 


AMOUNT    OF    OXYGEN    ABSORBED.  441 

four  hours.  This  is  due,  not  only  to  the  fact  that  of  the  air  breathed, 
only  one-twentieth  represents  oxygen  absorbed,  but  also,  as  we  shall  see, 
to  the  continual  vitiation  of  the  air  through  the  carbonic  acid  and  organic 
matters  expired  into  it,  and  to  the  air  being  then  less  fit  to  give  up 
oxygen  to  the  blood  and  take  up  carbonic  acid  from  it.  While  it  is 
quite  true  that  human  beings  can,  apparently,  accustom  themselves  to 
live  in  an  atmosphere  absolutely  foul,  to  breathe  over  and  over  again, 
the  same  poisonous  air,  it  is  only  at  the  expense  of  their  health  that 
this  is  possible,  death  resulting  sooner  or  later,  from  oxygen  starvation 
as  surely,  though  it  may  be  as  slowly,  as  that  from  ordinary  inanition. 
We  have  seen  that  in  ordinary  healthy  breathing  about  10,000  litres 
(350  cubic  feet)  of  air  are  inspired  in  twenty-four  hours.  The  air  in  a 
room  7  feet  long,  wide,  and  high,  and  therefore  amounting  to  about 
9466  litres  (343  cubic  feet),  would  about  suffice  for  furnishing  the 
oxygen  required  by  a  human  being  confined  in  it  for  twenty-four  hours ; 
and  that  on  the  supposition  that  the  air  was  perfectly  pure  and  fresh. 
As  we  shall  see,  however,  double  that  quantity  (20  cub.  met.,  about  650 
feet)  must  be  supplied,  even  per  hour,  if  the  air  of  the  room  is  to  be 
kept  in  a  wholesome  condition,  free  from  vitiation  by  carbonic  acid. 
While,  on  the  average,  the  oxygen  absorbed  in  twenty-four  hours  is 
about  what  we  have  estimated,  the  amount  in  any  given  time  will  vary, 
being  greater  or  less  according  to  the  condition  of  the  digestive  system, 
the  external  temperature,  muscular  activity,  etc.  Thus,  during  diges- 
tion, or  if  muscular  exercise  be  taken,  or  the  external  temperature  be 
lowered,  we  should  expect  to  find  the  amount  of  oxygen  absorbed  in- 
creased, and  such  is  the  case,  as  was  shown  experimentally  by  Lavoisier 
and  Seguin1,  the  results  of  whose  observations  may  be  summed  up  as 
follows  : 

1.  A  man  during  repose  and  fasting,  the  external  temperature  being 
32.5°  (90°  F.),  consumes  hourly  24.002  lit.  (1465  cub.  in.)  of  oxygen. 

2.  During  repose  and  fasting,  but  with  the  external  temperature  at 
15°  (59°  F.),  he  consumes  hourly  26.660  lit.  (1627  cubic  inches)  of 
oxygen. 

3.  During  digestion  a  man  consumes  hourly  37.689  lit.  (2300  cubic 
inches)  of  oxygen. 

4.  While  fasting  and  raisins;  in  fifteen  minutes  a  weight  of  7  kil. 
(about  16  pounds)  343  to  a  height  of  199  in  776  (656  feet)  the  man 
consumes  hourly  63.477  lit.  (3874  cubic  inches)  of  oxygen. 

5.  During  digestion  and  raising  a  weight  of  7  kil.  343  to  a  height 
of  211  inches  146  (700  feet)  the  man  consumes  hourly  91  lit.  248 
(5568  cubic  inches)  of  oxygen. 

It  must  always  be  a  source  of  regret  that  Lavoisier  did  not  describe 
the  apparatus  in  which  he  placed  Seguin,  and  by  means  of  which  he 
obtained  the  results  just  given.  There  is  not  the  slighest  reason,  how- 
ever, to  doubt  their  accuracy,  the  genius  of  Lavoisier  being  as  con- 
spicuously manifested  in  the  disposition  of  experimental  detail,  as  in 
the  establishment  of  grand  generalizations.  In  all  probability  the 
apparatus  used  was  essentially  the   same  as   in  the  case  of  the  experi- 

1  Mem.  de  l'Acad.  des  Sciences,  1789,  p.  575 


442  ABSORPTION    OF    OXYGEN,    ETC. 

ments  performed  upon  the  guinea-pig  with  the  same  object,  that  of 
determining  the  amount  of  oxygen  absorbed  and  carbonic  acid  exhaled 
in  a  given  time,  consisting  in  that  instance1  of  a  bell-jar  standing 
over  a  pneumatic  trough,  within  which  the  animal  was  introduced  and 
supported,  after  being  passed  up  through  the  water  of  the  trough, 
oxygen  being  introduced  as  needed,  in  known  quantities,  and  the 
carbonic  acid  exhaled  absorbed  by  alkali.  It  might  be  supposed  that 
the  results  of  Lavoisier,  just  given,  would  have  been  shown  by  more 
modern  methods  of  investigation,  not  to  be  absolutely  correct.  Even 
if  such  should  hereafter  be  shown  to  be  the  case,  it  would  not  affect  the 
value  of  the  relative  results,  and  that  is  what  is  essentially  needed  for 
such  a  comparison  as  the  above.  During  sleep,  as  might  be  expected, 
the  amount  of  oxygen  consumed  is  considerably  diminished,2  while  in 
hibernating  animals,  as  in  the  marmot,  for  example,  it  is  so  small  that 
little  or  no  difference  can  be  detected  in  the  composition  of  the  air  in 
which  the  animal  has  remained  for  three  hours  when  in  this  torpid  state.3 
Indeed,  according  to  Regnault  and  Reiset,4  only  one-thirtieth  of  the 
usual  amount  of  oxygen  is  absorbed  by  the  animal  when  in  this  con- 
dition. It  may  be  mentioned  in  this  connection,  also,  that  very  little 
oxygen  is  absorbed  by  the  young  of  all  animals.5  It  has  been 
recently  shown  by  Paul  Bert6  that  any  increase  or  diminution  in 
barometric  pressure  acts  upon  living  beings  in  increasing  or  diminishing 
the  tension  of  the  oxygen  in  the  air  they  breathe,  and  the  blood  that 
circulates  through  their  tissues,  and  that  any  increase  or  diminution 
in  atmospheric  pressure  is  unfavorable  to  living  beings  accommodated 
as  they  now  are,  to  the  present  tension  of  atmospheric  oxygen. 
Indeed,  according  to  this  observer,  all  life  perishes  in  air  sufficiently 
compressed.  With  a  pressure  simply  of  several  atmospheres  symptoms 
of  narcotic  poisoning  set  in  similar  to  those  experienced  in  breathing 
an  atmosphere  containing  an  excess  of  carbonic  acid,  and  due  probably 
to  the  same  cause,  namely,  an  excess  of  carbonic  acid  in  the  blood. 
With  still  higher  pressure,  4  of  oxygen — that  is,  20  atmospheres,  and 
upward — death  takes  place  from  asphyxia,  accompanied  with  convul- 
sions, as  when  caused  by  a  deficiency  of  oxygen.  Precisely  the  same 
effect  is  caused  by  the  gradual  diminution  of  atmospheric  pressure.  A 
sudden  diminution,  however,  causes  death  probably  through  the  libera- 
tion of  gases  in  the  blood,  which  interfere  mechanically  with  its  circu- 
lation. 

As  might  be  expected  from  the  nature  of  the  case,  the  determination 
of  the  amount  of  oxygen  absorbed  by  a  human  being  in  a  given 
time  must  be  of  an  approximate  character.  With  animals,  however, 
it  is  different,  and  especially  in  the  case  of  small  ones,  in  which 
the  conditions  are  very  favorable,  the  determination  of  the  oxygen 
absorbed,  as  well  as  the  carbonic  acid  expired,  can  be  most  accurately 
made.     The  most  perfect  apparatus  for  this  purpose  is  that  first  used 

1  Op.  cit.,  p.  572. 

i  Milne  Eil  wards :  Physiologie,  tome  ii.  p.  528. 

3  Spallanzani :  Mem.  snr  In  Respiration,  p.  334.     Geneva,  1803. 

4  Recherches  fiheniiqnea  snr  la  respiration  Ann.  <le  Chimie,  3d  ser.  1840,  tome  2fi,  p.  441. 

5  Legallois  (Envres,  tome  i.  p.  57.     W.  F   Milne  Edwards  :  De  1' Influence  des  ageus  Physiques  snr  la 
vie,  p    178      Pari--,  1824. 

6  La  Pressiou  Barometrique,  p.  1153.     Paris,  1878. 


REGNAULT'S    RESPIRATION     APPARATUS. 


443 


by  Regnault  and  Reiset,1  in  their  classical  researches  upon  respiration 
just  referred  to.  It  consists  essentially  of  a  receiver  filled  with  air 
enclosing  the  animal  to  be  experimented  upon,  and  which  communicates 
on  the  one  hand  with  a  reservoir  supplying  oxygen  as  fast  as  it  is  con- 
sumed during  respiration,  and  on  the  other  with  an  apparatus  for  the 
absorption  of  the  carbonic  acid  exhaled.  The  detailed  disposition  of  the 
apparatus,  as  made  for  the  author  by  Golaz,  of  Paris,  will  be  understood 

Fig.  250. 


Reguault  and  Reiset  respiration  apparatus. 

from  Fig.  250.  Within  the  tubulated  bell-jar  A,  immersed  in  the  cylin- 
der of  water  B,  is  placed  a  little  animal,  a  dog,  for  example,  the  sub- 
ject of  the  experiment.  The  animal  having  been  introduced  from 
below,  and  the  opening  hermetically  closed,  the  large  pipettes  G  G, 
filled  with  a  solution  of  potash  or  soda  of  known  strength  and  quantity, 
and  communicating  with  each  other  by  a  caoutchouc  tube,  absorb  and 
measure  the  C02  exhaled  into  the  air  of  the  jar  A,  the  air  being  drawn 
alternately  into  the  pipettes  G  G  through  their  elevation  and  depression 
by  hand  or  some  simple  mechanical  arrangement.  According  as 
oxygen  is  absorbed  by  the  animal,  the  gas  pressure  falls  in  A,  and  con- 
sequently the  oxygen  of  the  balloon  N,  under  the  pressure  of  the  calcium 
chloride  solution  in  P,  flows  through  M,  replacing  that  lost  in  A.     The 


1  Op.  cit.,  p.  299. 


444  ABSORPTION    OF    OXYGEN,    ETC. 

object  of  the  gas  pipette  a  is  to  enable  the  observer  to  draw  a  small 
sample  of  gas  out  of  A  for  analysis.  The  temperature  being  recorded 
by  the  thermometer,  and  the  tension  by  the  mercurial  manometer,  the 
amount  of  oxygen  absorbed,  and  carbonic  acid  exhaled,  can  be  determined 
by  the  following  formulae. 

1.  For  the  determination  of  the  weight  of  oxygen  delivered  from  one 
of  the  balloons  to  the  jar  containing  the  animal. 

x  =  F0.0014298  gr. \ v  H~  F  \n  which 

b     1  +  0.003670  '       760    ' 

x  =  the  weight  of  oxygen  delivered. 

V=  the  volume  in  centimetres  of  a  balloon  between  two  marks. 

0.0014298  gr.  =  weight  of  1  centimetre  of  oxygen. 

0.00367  gr.  =  coefficient  of  expansion. 

6  and  H  =  temperature  and  pressure  under  which  balloon   is  filled  with 

oxygen. 
F=  tension  of  aqueous  vapor  carried  over  to  oxygen  from  calcium  chloride 

solution,  and  about  equal  to  0.47  of  elastic  tension  of  vapor  of  water 

at  same  temperature. 

2.  For  the  determination  of  the  weight  of  oxygen  in  the  bell-jar  A 
at  the  beginning  of  the  experiment. 

x"  =  0.2095  X  1.4298  gr.  V  - X  H~  F,  in  which 

&  1+0.00367^  A       760    ' 

x"  =  weight  of  oxygen. 

0.2095  =  per  cent,  of  oxygen  in  the  atmosphere. 

1.4298  gr.  =  weight  of  1  litre  of  oxygen. 

V—  volume  of  air,  in  litres,  of  the  bell-jar  less  the  volume  of  the  animal. 

t     =  temperature. 

F  =  tension  of  aqueous  vapor  at  temperature  t. 

3.  For  the  determination  of  the  weight  of  the  oxygen  in  the  bell-jar 
at  the  end  of  experiment. 

x"'  \o  1.4298  gr.   V  - X  H~  F,  in  which 

&  1  +  1.00367*  760 

lo  ==  volume  of  oxygen  in  sample  of  air  drawn  out  of  bell-jar  through  tube 
at  end  of  experiment,  the  remaining  expressions  in  the  formula  being 
the  same  as  in  formula  2. 

4.  For  the  determination  of  the  excess  in  weight  of  oxygen  in  the 
bell-jar,  at  the  end  of  experiment,  over  that  at  the  beginning,  uncon- 
sumed  by  the  animal. 


5.  For  the  determination  of  the  weight  of  oxygen  (x)  consumed  by  the 
animal. 

x///  —  x"  -\-  b,  in  which 

x'"  —  x"  is  as  before,  b  the  weight  of  oxygen  of  the  balloons  unconsumed 
at  the  end  of  the  experiment,  x  being  then,  as  read  off  on  the  balloon, 
the  difference  in  weight  between  the  oxygen  at  the  beginning  and  end 
of  the  experiment. 


ludwig's  respiration  apparatus.  445 

6.  For  the  determination  of  the  carbonic  acid  exhaled  by  the  animal. 

1  // /•• 

if  =  le  1.9774  gr.  V v  —  p.  in  which 

°         1  +  0.00367*  ^       700 

>/  =  the  amount  of  carbonic  acid  in  the  bell-jar  at  end  of  experiment. 
lc  =  the  volume  of  carbonic  acid  in  sample  of  air  drawn. 
1.9774  =  weight  of  1  litre  of  carbonic  acid,  and  c  the  weight  of  carbonic  acid 
absorbed  by  pipettes,  Vt,  etc.,  the  same  as  before. 

7.  For  the  determination  of  the  weight  of  the  nitroo-en  in  the  bell- 
jar  at  beginning  of  experiment. 

Z  =  0.7905  X  1-2562  gr.  V X  ^—Ht  in  which 

h         1  +  0.00367*  760    ' 

Z  =  nitrogen,  0.7905  =  per  cent,  of  nitrogen  in  air. 
1.2562  =  weight  of  1   litre  of  nitrogen. 

8.  For  the  determination  of  the  weight  of  the  nitrogen  in  the  bell- 
jar  at  end  of  experiment. 

Z'  =  In  1.2562  gr.    V X  H~F.  in  which 

1  +  0.00367*  ^      760 

Z'  =  nitrogen,  In  volume  of  JVin  sample  of  air  drawn,  Vt,  etc.,  as  before. 

9.  For  the  determination  of  the  weight  of  nitrogen  absorbed  or  ex- 
haled. 

Z'  —  Z. 

The  advantage  of  this  apparatus  is  that  the  animal  suffers  no  incon- 
venience from  even  a  prolonged  confinement  within  the  chamber  A, 
that  the  oxygen  is  furnished  as  needed,  and  the  carbonic  acid  removed 
as  rapidly  as  produced,  and  that,  at  the  conclusion  of  the  experiment, 
the  composition  and  tension  of  the  air  within  the  jar  being  determined, 
the  amount  of  oxygen  absorbed  and  carbonic  acid  exhaled  can  be  accu- 
rately estimated.  A  more  modern  apparatus  used  by  Ludwig  and  his 
pupils,1  differs  from  that  of  Regnault  and  Reiset  just  described,  not  so 
much  in  principle  as  in  certain  mechanical  details.  The  most  notice- 
able of  these  is  the  ingenious  contrivance  by  means  of  which  the  oxygen 
expired  passes  from  g  (Fig.  251)  into  the  respiratory  tube  d,  communi- 
cating through  an  air-tight  covering  with  the  nostrils  of  the  animal  ate, 
alternately  with  the  passage  of  the  carbonic  acid  expired  into  the  bulbs 
f,  and  which  is  accomplished  through  the  alternate  expansion  and  con- 
traction of  the  valve  c.  For  with  the  rarefaction  of  the  air  through 
inspiration  the  valve  c  is  drawn  away  from  the  end  of  the  tube  b,  the 
effect  of  which  is  that  the  air  entering  the  tube  b  drives  the  water  out 
of  a,  which  in  turn  drives  the  oxygen  out  of  g  into  the  tube  d.  On  the 
other  hand,  with  the  condensation  of  the  air  through  expiration,  the 
valve  c  is  forced  back  close  to  the  end  of  the  tube  b,  the  flow  of  oxygen 
from  the  tubed  ceases,  the  carbonic  acid  exhaled  passing  into  the  bulbs  f. 
The  amount  of  oxygen  absorbed  in  a  given  time  by  an  animal  can  be 

1  Ludwicr's  Arbeiten. 


44(> 


ABSORPTION    OF     OXYGEN,    ETC. 


also  indirectly  deduced  sufficiently  accurately  for  ordinary  purposes  from 
the  amount  of  air  inspired,  the  per  cent,  of  oxygen  absorbed  having 
been  determined,  by  Brubaker's  apparatus,  already  described ;  or  directly 


Ludwig's  respiration  apparatus. 


by  connecting  the  spirometer  of  that  apparatus  with  a  reservoir  con- 
taining a  known  weight  of  oxygen,  and  filling  the  cylinder  of  the 
spirometer  with  a  solution  of  calcium  chloride  instead  of  water,  to  avoid 
absorption  the  oxygen  of  the  air  in  the  spirometer,  etc.,  absorbed  by 
the  animal  being  replaced  by  that  flowing  from  the  reservoir,  and  the 
amount  so  consumed  in  a  given  time  at  least  approximately  determined. 
The  amount  of  carbonic  acid  exhaled  can  also  be  estimated  by  this 
apparatus  by  connecting  the  expiratory  tube  with  a  Pettenkofer  tube 
containing  a  solution  of  baryta,  and  using  the  volumetric  method,  as  will 
be  explained  in  a  moment.  If  the  air  that  has  been  breathed  be  com- 
pared with  an  equal  quantity  of  atmospheric  air,  it  will  be  found  to 
differ,  not  only  in  having  lost  oxygen  and  gained  carbonic  acid,  but  in 
being  laden  with  aqueous  vapor,  in  being  warmer,  and  containing  small 
quantities  of  ammonia,  nitrogen,  and  organic  matters.     The  determi- 


CARBONIC     ACID    EXHALED. 


447 


nation  of  the  amount  of  carbonic  acid  exhaled  in  a  given  time  is  as 
important  as  that  of  the  oxygen  absorbed,  since  the  carbonic  acid, 
taken  together  with  the  water  exhaled,  contains  the  oxygen  absorbed 
by  the    system    during  some    previous    period,  and  affords  the  means 


of  indirectly  estimating  the  same.  We.  therefore,  usually  determine  at 
the  same  time  the  amount  of  carbonic  acid  and  water  exhaled  by  the 
system,  and  for  this  purpose  Ave  make  use  of  Voit's  respiration  apparatus. 
This  consists,  as  constructed  for  the  author  by  C.  Stollventner  and 
Sohn,  of  Munich  (Fig.  252),  of  a  chamber  (H)  in  which  the  subject  of 


448  ABSORPTION    OF    OXYGEN,    ETC. 

the  experiment,  a  large  dog,  for  example,  is  placed ;  of  a  large  drum,  and 
pumps  worked  by  a  waterwheel  for  the  production  of  a  constant  draught 
of  fresh  air  through  the  apparatus;  of  hottles  and  tubes  containing 
appropriate  materials  for  the  absorption  of  the  water  and  carbonic  acid 
of  the  air  surrounding  the  chamber,  as  well  as  that  from  within  it;  and 
of  meters  for  registering  the  total  amount  of  air  that  has  passed  through 
the  chamber,  of  the  fractional  part  of  the  same  analyzed,  and  of  the  air 
surrounding  the  chamber  analyzed  for  comparison.  Professor  Voit's 
apparatus  is  an  improved  form  of  the  celebrated  respiration  apparatus, 
used  by  Pettenkofer,  Voit,  and  Ranke  in  their  researches  upon 
nutrition,  conducted  in  the  Munich  Physiological  Laboratory,  and  to 
which  we  shall  have  occasion  to  refer  hereafter.  It  differs  in  several 
important  respects  from  the  original  apparatus,  the  principal  of  which 
consist  in  the  substitution  of  a  water-wheel  as  a  motor  for  clock-work 
and  steam  engine,  of  mercurial  ventiles  for  Mliller's  valves,  in  a  greater 
proportion  of  the  air  being  directly  analyzed,  improved  gas  meters,  etc. 
By  substituting  for  the  chamber  H,  containing  the  animal,  one  (M) 
sufficiently  large  to  hold  a  man,  as  shown  in  Fig.  252,  the  amount  of 
carbonic  acid  normally  exhaled  by  a  human  being,  and,  under  various 
conditions,  can  be  conveniently  determined.  The  water  exhaled  cannot, 
however,  be  accurately  determined,  so  much  of  it  being  precipitated 
in  the  chamber.  The  chamber  H  (Fig.  252),  in  which  the  animal  is 
placed,  has  a  capacity  of  about  380  litres  (14  cubic  feet),  and  con- 
sists of  a  zinc  framework  in  which  solid  glass  plates  are  imbedded,  a 
part  of  which  at  the  front  of  the  chamber  is  movable  and  acts  as  a 
door.  The  other  two  openings  present,  with  a  diameter  of  2.7  cm.  (1 
in.),  are  for  the  entrance  and  exit  of  the  air  ventilating  the  chamber. 
The  air  entering  by  the  opening  a,  seen  through  the. large  chamber  M, 
passes  by  the  pipe  to  the  bottom  of  the  chamber,  and  having  traversed 
the  latter,  leaves  it  at  its  upper  portion  by  the  pipe  b  and  passes 
thence  by  the  pipe  d  3.5  metres  (11  feet)  in  length  (disconnected  with 
b  in  Fig.  252),  and  holding  2.4  litres  (4.8  pints),  into  the  large  gas 
meter  B,  having  a  capacity  of  28.57  litres  (7.6  gallons),  whence, 
having  been  measured,  it  is  expelled.  The  constant  current  of  air 
so  passing  is  drawn  out  of  the  tubes  d  b  and  chamber  H  by  the  rota- 
tion of  the  drum  of  the  gas  meter  B,  whose  axis  is  in  connection 
with  that  of  the  overshot  water-wheel  G,  through  the  teeth  of  the 
cog-wheel  on  the  axis  of  the  gas  meter  interlocking  with  those  of  the 
cog-wheel  on  the  axis  of  the  water-wheel.  The  water-wheel  having  a 
diameter  of  60  cm.  (23.2  in.),  and  carrying  on  its  circumference  24 
buckets  with  a  capacity  of  330  c.  cm.  (-|  of  a  pint),  is  kept  uniformly 
rotating  through  the  fall  of  water  conducted  through  the  pipe  f  from  a 
reservoir  holding  1440  litres  (360  gallons),  not  represented  in  the  figure, 
situated  in  the  room  above  the  laboratory;  the  water,  as  it  is  emptied  by 
the  buckets  passes  into  a  trough  and  thence  is  carried  away  by  the  waste 
pipe  K.  The  flow  of  water  from  the  pipe  f  can  be  regulated  as  to  rotate 
the  water-wheel  as  often  as  five  times  per  minute.  Such  a  rate,  how- 
ever, is  not  needed,  since  with  the  wheel  rotating  only  once  in  a  minute, 
or  sixty  times  to  the  hour,  and  with  an  expenditure  of  33  litres  (8  gal- 
lons) of  water,  over  1700  litres  of  air  pass  per  hour  through  the  chamber 
H,  or  five  times  as  much  as  we  have  seen  (2857  litres  passing  through  the 


voit's  respiration  apparatus.  449 

meter  -with  each  rotation  of  the  water-wheel)  is  required  in  the  case  of 
man,  and  with  such  a  velocity  as  not  to  produce  a  draught  (0.36  cm.  a 
second).  The  velocity  of  the  air  through  the  chamber  H  during  a  given 
time  can  be  always  readily  determined,  when  it  is  remembered  that  it  is 
equal  to  the  ratio  of  the  amount  of  air  to  the  sectional  area  it  passes 
through,  or  by  the  animometer.  The  manner  in  which  the  air  that  passes 
through  the  meter  is  recorded  being  essentially  the  same  as  in  gas 
meters,  a  brief  description  will  suffice.  The  circumference  of  the  dial- 
plate  is  divided  into  100  equal  spaces,  and  on  the  face  of  the  plate  are 
four  circles  each  circle  being  divided  into  ten  equal  spaces.  As  the 
large  hand  moves  once  around  the  circumference  of  the  dial-plate,  indi- 
cating that  100  litres  (200  pints)  of  air  have  passed  through  the  meter, 
each  division  of  the  circumference  being  equal  to  one  litre,  the  hand  of 
the  first  small  circle  moves  from  0  to  1,  and  while  the  large  hand  moves 
ten  times  around  the  circumference  of  the  dial-plate,  indicating  that 
1000  litres  of  air  have  passed  through  the  meter,  the  hand  of  the  first 
small  circle  moves  around  from  0  to  10,  and  the  hand  of  the  second 
small  circle  moves  from  0  tol.  In  the  same  manner  as  the  hand  of  the 
second  small  circle  moves  once  around  from  0  to  10,  indicating  that 
10,000  litres  of  air  have  passed  through  the  meter,  the  hand  of  the 
third  small  circle  moves  from  0  to  1,  and  as  the  hand  of  the  third  small 
circle  moves  once  around  the  cii'cumference  from  0  to  1,  indicating 
that  100,000  litres  of  air  have  passed  through  the  meter,  the  hands 
of  the  fourth  small  circle  move  from  0  to  1 ;  finally,  the  movement  of 
the  hand  of  the  fourth  small  circle  once  completely  around,  records  the 
passage  of  1,000,000  litres  of  air  through  the  meter. 

The  animal  having  been  placed  in  the  chamber  and  the  water-wheel 
set  in  motion,  as  the  air  containing  carbonic  acid  and  water  streams 
through  the  chamber  it  takes  up  in  addition  the  carbonic  acid  and  water 
exhaled  by  the  animal.  Inasmuch,  however,  as  with  the  wheel  rotating 
only  once  a  minute  and  the  experiment  lasting  six  hours,  over  10,000 
litres  of  air  pass  through  the  chamber,  it  becomes  evident  that  the  de- 
termination of  the  carbonic  acid  and  water  in  such  a  large  quantity  of 
air  would  involve  an  enormous  expenditure  of  time  and  labor.  We 
avoid  this  by  analyzing  a  fractional  part  of  the  air  passing  through  the 
chamber,  determining  the  carbonic  acid  and  water  that  it  contains  and 
multiplying  the  result  by  the  total  amount  of  air  as  recorded  by  the 
meter,  having  first  deducted  the  carbonic  acid  and  water  contained  in 
an  equal  quantity  of  the  air  surrounding  the  chamber.  To  effect  this, 
part  of  the  air  from  the  chamber  is  diverted  by  the  mercurial  pumps 
from  the  tube  d  into  the  tube  J.  The  latter  terminates  in  two  branches 
(J'  J")  which  are  connected  writh  two  mercurial  valves  (v'  v"),  the 
latter  not  represented  in  Fig.  253 ;  these  communicate  with  the  two 
mercurial  pumps,  one  of  which  is  represented  in  Fig.  253,  which  are 
alternately  elevated  and  depressed  through  the  movement  of  the  crank 
m  connected  with  the  axis  of  the  water-wheel,  the  one  pump  rising  as 
the  other  is  falling,  and  vice  versa.  The  pumps  communicate  also  with 
two  other  mercurial  valves  (wf  w"),  the  latter  not  represented  in 
Fig.  253,  tilted  in  the  opposite  direction  to  those  just  mentioned.  The 
air  must  pass,  therefore,  always  in  the  same  direction,  viz.,  from  the 

•29 


450 


ABSORPTION    OF    OXYGEN,    ETC, 


tube  J'  through  the  valve  v'  into  the  pump,  returning  through  the 
valve  w'  into  the  short  bottles  e  e  containing  pumice-stone  and  sulphuric 
acid  for  the  absorption  of  the  water,  thence  through  the  large  bottles 
g  containing  water  and  pumice-stone  for  resaturation,  then  through 
the  tubes  1 1,  containing  a  solution  of  baryta,  for  the  absorption  of  the 
carbonic  acid,  finally  escaping  by  the  meters  1  and  2,  2  not  represented 


h 


in  Fig.  253,  where  the  amount  is  measured.  As  the  air  passes  into  the 
chamber  it  contains  water  and  carbonic  acid.  In  order  to  determine  the 
amount  of  such  exhaled  by  the  animal  it  is  necessary  to  analyze  the  air 
surrounding  the  chamber.  This  is  done  in  exactly  the  same  way  and 
simultaneously  as  the  analysis  of  the  air  within  the  chamber  which  we 


voit's  respiration  apparatus.  451 

have  just  described,  the  air  surrounding  the  chamber  being  drawn  into 
a  tube  by  two  pumps  and  through  bottles,  tubes,  and  meters  similar 
to  those  described.  Having  determined  the  carbonic  acid  and  water  in 
a  given  quantity  of  air  surrounding  the  chamber,  this  is  deducted  from 
the  water  and  carbonic  acid  of  an  equal  quantity  of  air  that  has  passed 
through  the  chamber,  in  order  to  obtain  the  water  and  carbonic  acid 
exhaled  by  the  animal.  The  small  gas  meters  have  a  capacity  of  2.5 
litres  (5  pints),  and  the  circumference  of  each  is  divided  into  100  equal 
parts,  each  being  equal  to  25  c.  cm.  As  the  large  hand  moves  once  around 
the  circumference,  indicating  that  2500  c.  cm.  (2.5  litres)  have  passed 
through  the  meter,  the  small  hand  moves  over  one  space.  It  will  be 
also  observed  that  supposing  the  water-wheel  to  be  rotating  once  in  a 
minute,  that  while  25  c.  cm.  pass  out  of  the  small  meter  28,570  c.  cm. 
pass  out  of  the  large  one — that  is,  1142  times  more  air  passes  out 
of  the  large  meter  than  the  small  one.  The  amount  of  carbonic  acid 
and  water  exhaled  by  the  animal  in  one  hour,  as  determined  by  the 
absorption  bottles  and  tubes,  must  therefore  be  multiplied  by  1142,  and 
to  this  must  be  added  the  carbonic  acid  and  water  remaining  in  the 
chamber  H,  tube  c?,  and  the  two  meters  /and  II,  in  order  to  get  the  total 
amount  exhaled  by  the  animal.  The  double  set  of  absorbing  bottles, 
tubes,  meters,  etc.,  enable  us  to  analyze  a  definite  quantity  of  two 
samples  of  both  the  air  within  and  without  the  chamber,  and  of  so 
obtaining  the  average  amount  of  water  and  carbonic  acid  in  a  given 
quantity  of  inside  and  outside  air.  The  result  of  the  general  investiga- 
tion will  then  be  more  reliable  than  if  the  analysis  had  been  confined  to 
a  single  sample  of  inside  and  outside  air.  Further,  to  insure  success, 
the  gas  meters  ought  to  be  tested  before  every  experiment.  This  can 
be  done,  as  suggested  by  Voit,  by  allowing  water  to  flow  into  a  glass 
vessel  of  known  capacity,  the  vessel  being  connected  with  the  meter  so 
that  as  the  air  is  driven  out  of  the  vessel  by  the  water  it  passes  through 
the  meter,  or,  as  is  ordinarily  done  in  testing  our  gas  meters,  by  con- 
necting the  upper  opening  of  the  meter  by  which  the  air  usually  escapes 
with  a  vessel  of  known  capacity  containing  water.  By  removing  the  con- 
necting tube  t'  and  allowing  the  air  to  enter  the  meter  by  the  posterior 
opening,  as  the  water  in  known  quantity  flows  out  of  the  vessel  it  is 
replaced  by  the  air  that  has  passed  through  the  meter.  In  testing  the 
meters  the  author  has  found  that  there  is  usually  an  error  of  jA-^-th 
between  the  absolute  amount  of  air  that  has  passed  through  the  meter 
and  that  recorded  by  it,  which  must  be  subtracted  from  or  added  to 
the  latter,  as  the  case  may  be.  It  might  be  supposed,  from  part  of 
the  chamber  opening  and  closing  as  a  door,  that  some  of  the  air  contain- 
ing carbonic  acid  and  water  exhaled  by  the  animal  might  escape  through 
the  chinks  of  the  door.  The  draught  of  air  through  the  chamber,  how- 
ever, is  so  great  that  when  a  strong-smelling  substance  is  placed  within 
it  it  is  perfectly  imperceptible  at  the  door.  If  any  doubt,  however, 
should  exist  as  to  the  chamber  being  air-tight,  it  can  be  readily  made 
so  by  filling  up  the  chinks  of  the  door  with  wax,  or  a  mixture  of  it.  It 
is  very  important,  also,  that  the  tubing  connecting  the  different  parts  of 
the  apparatus  should  be  examined  in  this  respect  before  each  experiment. 
It  remains  for  us  now  to  describe  a  little  more  in  detail  than  we 


452  ABSORPTION    OF    OXYGEN,    ETC. 

have  done  the  manner  in  which  the  water  and  carbonic  acid  arc  deter- 
mined hy  means  of  the  absorbing  apparatus.  The  determination  of  the 
amount  of  water  is  very  simple.  The  bottles  (#,  e,  Fig.  253)  through 
which  the  air  from  within  and  without  the  chamber  passes  contain,  as 
already  stated,  pumice  stone  and  sulphuric  acid,  which  has  a  great 
avidity  for  water.  These  being  weighed  in  scales,  the  beams  of  which 
oscillate  with  the  addition  or  subtraction  of  the  y^o-th  of  a  grain,  before 
and  after  the  experiment,  the  difference  will  give  the  amount  of  water 
in  the  air  from  within  and  without  the  chamber;  the  hitter  amount,  as 
we  have  already  mentioned,  must  be  then  deducted  from  the  former,  in 
order  to  get  the  amount  of  water  exhaled  by  the  animal  into  the  frac- 
tional part  of  the  air  examined.  Suppose,  for  example  (see  Table  of 
Tabulated  Results),  of  two  samples  of  inside  air  of  1000  litres  each,  the 
mean,  or  1000  litres,  contained  1.2457  grammes  of  water,  and  of  equal 
quantities  of  outside  air,  the  mean  contained  1.1445  grammes  of  water, 
the  difference,  or  0.1012  gramme,  would  then  be  the  amount  of  water 
exhaled  by  the  animal  into  1000  litres  of  air  in  the  given  time.  The 
water  having  been  absorbed  as  the  air  passes  through  the  bottles  the 
dried  air  is  resaturated  as  it  passes  through  the  bottles  g,  the  saturated 
pumice  stone  within  them  giving  up  the  water  it  contains.  Were  not 
the  air  so  resaturated  it  would  take  up  water  from  the  solution  of  baryta 
through  which  the  air  next  passes,  and  this  must  be  avoided,  as  the 
solution  of  baryta  is  used  for  the  absorption  of  carbonic  acid.  Of  the 
eight  tubes  containing  the  baryta  solution,  four  are  large  and  four  are 
small.  The  large  tubes,  through  which  the  air  first  passes,  have  a  capacity 
of  460  c.  cm.  (28  cub.  in.),  the  small  ones  of  170  c.  cm.  (10  cub.  in.). 
The  tubes  are  placed  somewhat  obliquely,  in  order  that  the  air  shall 
pass  as  distinct  bubbles  through  the  solution,  the  greatest  amount  of 
air  surface  being,  therefore,  exposed  to  the  absorbing  action  of  the 
baryta.  The  solution  of  baryta  within  the  two  large  tubes  <,  only  one  of 
which  is  represented  in  Fig.  253,  receiving  the  air  from  the  inside  of  the 
chamber,  is  stronger  than  in  that  of  the  remaining  tubes,  both  in  the  two 
small  succeeding  ones  and  in  the  two  large  and  two  small  ones  through 
which  the  outside  air  passes.  The  strong  solution  of  baryta  is  made 
by  dissolving  21  grammes  of  baryta  in  8  litres  of  distilled  water,  the 
weak  one  by  dissolving  7  grammes  of  baryta  in  the  same  quantity  of 
•distilled  water.  It  will  be  found  experimentally,  as  will  be  seen  in  a 
moment,  that  about  90  c.  cm.  and  30  c.  cm.  of  a  solution  of  oxalic  acid 
but  recently  made  by  dissolving  2.8  grammes  of  chemically  pure  oxalic 
acid  in  1  litre  of  water  will  saturate  30  c.  cm.  of  the  strong  and  weak 
solutions  of  baryta,  respectively.  In  order  to  preserve  the  baryta  solution 
pure  it  is  essential  that  it  should  be  contained  in  a  bottle,  through  the 
stopper  of  which  pass  two  tubes;  through  one  the  solution  is  drawn  out 
by  suction  as  desired,  while  by  the  other  tube  the  air  enters,  having  been 
freed  from  its  carbonic  acid  by  its  passage  through  caustic  soda.  It  is 
best  to  determine  the  amount  of  carbonic  acid  absorbed  by  the  baryta  in 
the  case  of  a  small  animal.  We  usually  place  in  the  two  large  tubes  240 
c.  cm.  of  the  strong  solution,  and  in  the  remaining  six  tubes  50  c.  cm. 
of  the  weak  solution,  and  make  use  of  the  method  of  Pettenkofer,  as 
follows :    for  example,    of  the  strong  baryta,    the  water  having   been 


DETERMINATION  OF   CARBONIC  ACID  EXHALED.       453 

introduced  into  a  test  tube,  or  small  flask,  the  solution  of  oxalic  acid  is 
gradually  added  to  it  from  a  finely  graduated  burette.  With  each 
addition  of  oxalic  acid  the  test-tube  is  closed  with  the  thumb  and  shaken. 
As  an  indicator  of  the  point  of  neutralization  turmeric  paper  is  used. 
The  paper  is  dipped  into  the  liquid  from  moment  to  moment,  ceasing  to 
be  browned  when  the  liquid  is  nearly  neutralized  ;  at  this  instant,  a  drop 
of  the  liquid  is  placed  by  means  of  a  glass  rod  on  a  strip  of  the  paper, 
if  a  trace  of  alkaline  reaction  still  exists  a  brown  line  appears  at  the 
periphery  of  the  paper;  when  this  is  no  longer  the  case  the  point  of 
complete  neutralization  has  been  obtained.  Now  suppose,  before  an 
experiment  with  the  respiration  apparatus  it  was  ascertained  by  the 
means  just  described,  that  exactly  72.4  c.  cm.  of  oxalic  acid  neutralized 
25  c.  cm.  of  the  standard  strong  baryta  solution,  it  will  be  found  that  at 
the  end  of  the  experiment  it  requires  only  61.8  c.  cm.  of  oxalic  acid,  or 
10.6  c.  cm.  less,  to  neutralize  25  c.  cm.  of  the  strong  baryta  solution, 
drawn  out  of  the  tubes  by  means  of  a  pipette.  As  the  carbonic  air  passes 
through  the  latter  during  the  experiment  it  combines  with  part  of  the 
baryta,  and  there  is,  therefore,  less  baryta  to  combine  with  the  oxalic 
acid  after  the  experiment  than  there  was  before.  Now  as  for  each  milli- 
gramme of  carbonic  acid  that  combines  with  the  baryta  during  the  experi- 
ment there  will  be  1  c.  cm.  less  of  oxalic  acid  required  for  neutralization 
after  experiment,  it  follows  that  10.6  milligrammes  of  carbonic  acid 
must  have  been  absorbed  by  the  25  c.  cm.  of  the  baryta  solution,  since 
it  requires  10.6  c.  cm.  less  of  oxalic  acid  for  neutralization  after  the 
experiment  than  before.  In  other  words,  the  baryta  before  the  experi- 
ment combined  with  72.4  c.  cm.  of  oxalic  acid,  after  the  experiment 
with  61.8  c.  cm.,  because  during  the  experiment  it  combined  with  10.6 
milligrammes  of  carbonic  acid,  which  are  volumetrieally  equal  to  10.6 
c.  cm.  of  oxalic  acid.  As  Ave  placed  240  c.  cm.  of  the  strong  baryta 
solution  in  the  tube  t,  we  must  nowT  multiply  the  10.6  milligrammes  of 
carbonic  acid  obtained  from  the  2-3  c.  cm.  by  9.6,  in  order  to  obtain  the 
total.  The  manner  of  determining  the  carbonic  acid  absorbed  by  the 
weak  solution  of  baryta  being  essentially  the  same  as  that  just  described 
for  the  strong  one,  it  will  be  only  necessary  to  refer  for  details  to  the 
Table  of  Tabulated  Results,  giving  a  resume  synoptically  arranged  by 
Voit  of  the  result  of  an  experiment  upon  a  dog  obtained  by  the  respira- 
tion apparatus,  which  we  have  just  described  in  detail.  The  carbonic 
acid  exhaled  by  a  human  being  in  twenty-four  hours,  as  determined  by 
the  Pettenkofer-Voit's  respiration  apparatus,  amounts,  on  an  average, 
to  410  litres  (25,625  cub.  in.,  or  14  cub.  feet)  in  twenty-four  hours. 


454 


ABSORPTION  OF  OXYGEN,   ETC. 


Tabulated  Results  of  Experiment  with  the  Pettlnkofer-Voit 
Respiration  Appai:.uts  upon  a  Dog. 


Determination  of  Carbonic  Acid 

Determination 
op  Water. 

Amount  of  air 
investigated. 

Baryta  water  tubes. 

Carb. 
.i.  id  '.r 
air  in- 
vesti- 
gated. 

Carb. 

acid  of 

1000 

litres  of 

air. 

Water 
of  air 
investi- 
gated 

Differ- 
ence. 

0.7682 
0  7670 

O.G947 
0.8135 

Water 

Gas 
Meters. 

Volumes  in 
c.c. 

Cubic  cent.of  oxalic 

acid  for  25  c.c.  of 

baryta  water. 

in  1000 

litres  "f 

air. 

Revolu- 
tions. 

Litres. 

Before 

After. 

Differ- 
ed :e. 

No.  1       ) 
Outer  air.  J 

No.  2.      } 
Outer  air.  j 

20.380 
26.657 

22,985 

25.577 

67.108  | 
67.024  | 

5(1.044 1 
64  981 1 

Large  240  c.c. 
Small     50   " 

Large  240  c.c. 
Small     50   " 

Large  240  c.c. 
Small     50    " 

Large  249  c.c. 
Small    50   " 

33.8  cc. 
33.8    " 

]33.8c.c. 
33.8    '• 

72.4  c.c. 
33.8    " 

72  4  c.c. 
33.8    " 

29  8  c.c.  1 
33.5    "    j 

29.8  c.c.  "1 
33  5    "    / 

61  8  c.c.  1 
33.5    "    j 

60.3  c.c.  1 
33.7   "   ; 

0.03900 
003900 

0.10236 
0.11636 

0.5811 

0.5819 
2)1.1630 

1.1447 

1.1444 

2)2.2891 

No.  3.      1 
Inner  air.   j 

No.  4.      I 
Inner  air.  } 

0.5815 
1.82G4 

1.7907 
2)3.0171 

1.1445 
1.2395 

1.2519 

2)  2.4914 

1.8085 

1.2457 

Calculation  for  Carbonic  Acid  and  Water. 


Carbonic  acid. 


Water. 


In  1000  litres  of  inner  air 
In  1000  litres  of  outer  air 

Difference 


In  11600.5  litres  of  large  meter  .  14.23 
In  66.55  litres  chamber  and  tube  0.11 
In      121.02  3d  and  4th  meters         .     0.15 


Total 


1.8085  grammes.      1.2457  grammes. 
0.5815         "  1.1445 

1.2270         "  0.1012 

11.74 
0.07 
0.12 

14.49  "  11.93 


Calculation  for  Oxygen  Absorbed. 

Before  experiment.  After  experiment. 

Weight  of  animal  3001.3  grms.     Weight  of  animal  .         .  2987.80  grms. 


Inaresta 


0.0 


Egesta 


Total     3001.8 


urine     .         .         0.0  '" 

feces      .         .         0.0  " 

water    .         .       11.93  " 

carbonic  acid       14.49  " 

Total       3014.22  " 

3001.30  " 


The  quantity  of  oxygen  absorbed  equals  the  difference,  viz.     12.92     " 
The  proportion  of  carbonic  acid  to  oxygen,  100   :    89. 


AMOUNT    OF    CARBONIC    ACID    EXHALED.  455 

This  estimate  is  intermediate  between  that  of  Andral  and  Gavarret,1 
468  litres  (29,238  cubic  inches),  and  that  of  Edward  Smith,2  387  litres 
(24,208  cubic  inches),  for  the  same  period  of  time.  The  experiments  of 
these  observers  were  made  with  the  object  of  determining  only  the 
carl  tonic  acid  exhaled,  and  the  apparatus  consisted  in  both  instances  of 
a  mask  closely  fitting  the  face,  having  two  openings  provided  with 
valves  for  the  entrance  and  exit  of  the  air,  the  carbonic  acid  exhaled 
in  the  experiments  of  Andral  and  Gavarret  being  determined  by  means 
of  a  solution  of  potash  contained  in  U  tubes,  and  in  those  of  Smith  by 
a  solution  of  potash  arranged  in  numerous  layers.  The  mechanical 
details  of  the  apparatus  made  use  of  by  these  observers,  as  well  as 
by  their  predecessors,  Lavoisier  and  Seguin,  Prout,  Davy,  Dumas, 
Allen  and  Pepys,  Scharling,  and  others,  not  being  as  perfect  as  those 
of  the  Pettenkofer-Voit  respiration  apparatus,  just  described,  it  would 
be  superfluous  to  dwell  further  upon  them.  In  this  connection,  how- 
ever, it  is  proper  that  some  allusion  at  least  be  made  to  the  indirect 
method  of  determining  the  amount  of  carbonic  acid  exhaled  in  a  given 
time,  so  successfully  applied  in  the  case  of  large  animals  by  Boussin- 
gault.3  This  method  consists  of  so  regulating  the  diet  of  the  animal 
experimented  upon,  a  horse  or  cow,  for  example,  that  there  is  no  loss 
of  weight  during  the  experiment,  and  of  weighing  everything  introduced 
as  food,  solid  and  liquid,  and  all  discharged  as  urine  or  feces.  Knowing 
the  quantity  of  carbon  entering  the  body  in  the  food,  and  leaving  it 
in  the  urine  and  feces,  the  difference  between  the  carbon  of  the  latter 
and  the  former  (that  of  the  food  being  in  excess)  will  be  the  amount  of 
carbon  leaving  the  body  by  the  lungs  and  skin.  As  regards  the  carbon 
excreted  by  the  skin,  it  can,  for  such  approximate  determinations,  be 
neglected,  since,  as  we  shall  see,  when  the  skin  is  considered  as  a 
respiratory  surface,  the  carbonic  acid  exhaled  does  not  amount  to  more 
than  between  -^th  and  Tj^-g-th  of  the  total  amount  excreted. 

1  Ann.  <ie  Chimie  <-t  <le  Physique,  3iue  serie,  t.  viii.  p.  129. 

2  Phil.  Trans  ,  1859,  p.  681. 

8  Mem.  de  Chimie  agricole  et  de  Physiolugie,  pp.  1-12.     Paris,  1854. 


CHAPTER    XXX. 

CONDITIONS  INFLUENCING  PRODUCTION  OF  CARBONIC  ACID, 
EXHALATION  OF  WATERY  VAPOR.  ORGANIC  MATTER,  AND 
VENTILATION. 

The  amount  of  carbonic  acid  exhaled  in  a  given  period,  like  that  of 
oxygen  absorbed,  is  greatly  influenced  by  various  conditions.  Of  the 
most  important  of  these  may  be  mentioned,  the  influence  of  the  rapidity 
of  the  respiratory  movements,  sex,  age,  food,  digestion,  sleep,  exercise, 
fatigue,  temperature,  moisture,  barometric  pressure.  Let  us  consider 
the  influences  exerted  by  the  above  somewhat  in  detail.  The  osmosis 
of  the  oxygen  of  the  air  and  the  carbonic  acid  of  the  blood  within  the 
pulmonary  capillaries  not  being  a  sudden  action,  but  a  continuous  one, 
the  amount  of  the  gases  so  interchanged  will  naturally  depend  on  the 
length  of  time  during  which  the  air  remains  in  contact  with  the  respira- 
tory surface;  thus,  Vierordt,1  in  the  experiments  performed  upon 
his  own  person,  found  that,  when  he  breathed  as  slowly  as  possible,  6 
per  cent  of  C02  was  exhaled  in  each  expiration,  but  that  when  he 
breathed  as  rapidly  as  possible  only  3  per  cent.  According  to  the  same 
authority,  if  an  expiration  be  divided  into  two  equal  parts,  the  first 
part  will  contain,  on  an  average,  3.72  per  cent,  of  carbonic  acid,  the 
second  5.44  per  cent.,  the  air  exhaled  during  the  first  period  of  the 
expiration  containing  less  carbonic  acid  than  that  exhaled  during  the 
second  period.  Vierordt  further  believes  that  he  has  discovered  the 
law  by  which  to  calculate  the  per  cent,  of  carbonic  acid  contained  in  an 
expiration  of  longer  duration,  if  the  duration  of  the  shortest  possible 
expiration,  and  the  per  cent,  of  carbonic  acid  that  it  contains  are  given. 
Thus,  supposing  that  the  duration  of  the  shortest  expiration  was  0.3125 
second,  the  respirations  being  192  per  minute,  and  that  this  expiration 
contained  2.8  per  cent,  of  carbonic  acid,  then  an  expiration  lasting  ten 
seconds,  the  respirations  being  six  per  minute,  will  contain  5.9  per 
cent,  of  carbonic  acid.  The  formula  by  which  this  result  is  obtained  is 
as  follows : 

10  minus  0.3125  equals  9.6875 

9.6875  ,    Q  , 

equals  3.1 

3.125       * 

3.1  plus  2.8  equals  5.9 

9.6875  being  the  difference  between  the  duration  of  the  long  and 
short  expirations,  3.125  the  product  of  the  duration  of  these  two 
expirations,  3.1  the  quotient  of  the  difference  of  the  two  expirations 
divided  by  the  product  of  the  duration  of  the  two  expirations,  and  2.8 

1  Physiologie  des  Athmens,  p.  102.     Karlsruhe,  1845. 


PER    CENT.    OF    CARBONIC    ACID    IN    EXPIRED    AIR.    457 

the  per  cent,  of  carbonic  acid  contained  in  the  short  expiration.  The 
quantity  of  carbonic  acid  is  2.8  per  cent,  when  the  number  of  respi- 
rations is  192  per  minute.  The  latter,  when  added  to  the  quotient, 
3.1,  gives  5.9  as  the  per  cent,  of  carbonic  acid  contained  in  the  long 
expiration.  Table  LXIL,  synoptically  arranged,  illustrates  the  inverse 
relation  existing  between  the  per  cent,  of  carbonic  acid  in  the  expired 
air  and  the  number  of  expirations. 

Table  LXIT. 

Per  cent,  of  C02  in  expired  air.  No.  of  expirations  per  minute. 

5.9  6 

4.3  12 

3.5  24 

3.1  48 

2.9  96 

2.8  150 

It  does  not  follow,  however,  that  because  the  per  cent,  of  carbonic 
acid  contained  in  each  expiration  is  greater  during  slow  than  in  rapid 
breathing  that  more  carbonic  acid  is  expired  in  a  given  period  in  the 
former  case  than  the  latter.  On  the  contrary,  the  reverse  obtains, 
since  the  small  per  cent,  of  carbonic  acid  that  each  expiration  contains 
during  rapid  breathing  is  more  than  compensated  for  by  the  greater 
number  of  expirations.  Thus,  suppose,  for  example,  that  250  c.  cm.  of 
air  are  expired  six  times  in  a  minute,  then,  as  each  100  c.  cm.  contain 
5.9  c.  cm.  of  carbonic  acid:  5.9  X  2.5  X  6,  or  88.50  c. cm.,  will 
be  the  amount  of  carbonic  acid  expired  in  the  given  time.  On  the 
other  hand,  if  the  same  quantity  of  air  be  expired  twelve  times  in  a 
minute,  each  expiration  will  contain  only  4.3  per  cent,  of  carbonic  acid, 
and  yet  129  c.  cm.  of  carbonic  acid  will  be  expired  in  the  given  time, 
since  4.3  X  2.5  X  12  equals  129.  The  amount  of  carbonic  acid 
exhaled  by  an  individual  depends  also  upon  the  sex. 

Thus  it  was  shown  by  Andral  and  Gavarret1  that  a  litre  (2  pints) 
more  carbonic  acid  was  exhaled  per  hour  by  the  male  than  by  the 
female.  Indeed,  the  difference  amounted  in  some  instances  to  even  as 
much  as  7  litres.  The  difference  in  the  weight  of  the  body  was  not 
taken  into  consideration  in  tbe  observations  of  Andral  and  Gavarret, 
Scharling2,  however,  found  that  more  carbonic  acid  was  exhaled  by  the 
male  than  the  female,  even  when  this  was  estimated  writh  reference  to 
the  body-weight.  Apart  from  the  greater  muscular  activity  of  the 
male,  as  compared  with  the  female,  being  sufficient  to  account  for  the 
difference  in  the  amount  of  carbonic  acid  exhaled  by  the  sexes,  other 
conditions  peculiar  to  the  female  exert  an  influence  in  this  respect 
which  must  not  be  overlooked.  Thus  it  was  shown  by  the  experi- 
ments of  Andral  and  Gavarret,  that  as  long  as  the  menses  succeeded 
each  other  regularly,  the  average  amount  of  carbonic  acid  exhaled 
remained  about  the  same,  being  on  the  average  11.7  litres  per  hour, 
with  their  cessation  the  amount  increased  to  about  15  litres,  while  from 
60  to  82  years  of  age  it  diminished  from  13  to  11  litres.  Temporary 
cessation  of  the  menses,  whether  due   to  pregnancy  or  other  causes,  is 

1  Op.  cit.  -  Ann.  de  Chimie,  tome  viii.  p.  486. 


458  PRODUCTION    OF    CARBONIC    ACID,    ETC. 

also  accompanied    by   an    increase  of   the  amount    of   carbonic    acid 
exhaled. 

As  is  well  known,  during  the  first  few  hours  and  days  after  birth, 
the  infant  making  little  or  no  movement,  sleeping  most  of  the  time, 
generates  but  little  heat,  and  must,  therefore,  be  carefully  guarded 
against  changes  in  the  external  temperature.  At  this  early  period  of 
life  the  amount  of  carbonic  acid  exhaled  must  be  very  small.  With 
the  thorough  establishment  of  respiration,  this  amount  is  increased,  and 
from  the  fact  of  the  number  of  respirations  being  greater  in  early  than 
in  later  life,  it  is  probable  that  the  amount  of  carbonic  acid  exhaled, 
considered  with  reference  to  the  body-weight,  is  greater  in  the  infant 
than  in  the  adult.  The  necessary  data  essential  for  such  a  comparison 
are,  however,  too  insufficient  to  admit  of  more  than  the  general  state- 
ment just  made.  From  the  observations  of  Andral  and  (/avarret1, 
based  upon  the  examination  of  numerous  individuals  between  the  ages 
of  12  and  102  years,  we  learn  that  from  the  age  of  12  to  32,  there  is 
an  absolute  increase  in  the  amount  of  carbonic  acid  exhaled,  from  32 
to  00  years  old  a  slight  diminution,  and  from  60  to  102  years,  a  very 
considerable  one.  The  results  of  the  observations  of  Andral  and  Gavar- 
ret  are  synoptically  arranged  in 

Table  LXIII.2 

Males.  Carbonic  acid  exhaled  per  hour. 

12  to  16  years  of  age.  15  litres  (915  cubic  inches). 

17   "   19       "        "  20       " 

25   "   32       "         "  22       " 

32   "   60       "        "  20       " 

63   "   82       "        "  15.3    " 

102  "        "  11       " 

When  these  observations  are  supplemented  by  those  of  Scharling,3 
we  also  learn  that  the  amount  of  carbonic  acid  exhaled  in  youth,  rela- 
tive to  the  weight  of  the  body,  is  greater  than  that  in  the  adult,  being 
in  the  case  of  a  boy,  for  example,  twice  as  much  as  in  a  man.  The 
results  of  Scharling's  experiments  might  be  inferred  from  those  of 
Andral  and  Gavarret,  since  the  absolute  increase  in  the  amount  of 
carbonic  acid  exhaled  between  the  period  of  childhood  and  adult  life, 
is  small,  as  compared  with  the  increase  in  the  weight  of  the  body 
within  the  same  period. 

As  regards  the  influence  of  the  food  upon  the  exhalation  of  car- 
bonic acid,  the  extended  series  of  experiments  performed  by  Dr. 
Edward  Smith4  upon  himself  and  friends,  are  very  conclusive.  Food, 
with  reference  to  the  exhalation  of  carbonic  acid,  can  be  divided, 
according  to  Dr.  Smith,  into  two  classes,  respiratory  excitants,  which 
increase  the  exhalation  of  carbonic  acid,  and  non-exciters,  wdiich 
diminish  it.  The  excito-respiratory  foods  include  the  nitrogenous 
articles  of  diet,  milk,  sugar,  rum,  beer,  stout,  the  cereals,  and  potato ; 
the  non-exciters,  starch,  fat,  certain  alcoholic  compounds,  the  volatile 
element  of  wines   and  spirits,  and  coffee   leaves.     The   most  powerful 

1  Op.  cit.,  p.  129.  '2  Andral  and  Gavarret,  op.  cit.,  p.  129. 

3  Op.  cit.,  p.  486.  *  Phil.  Trans.,  1859,  p  715, 


EXHALATION    OF    CARBONIC    ACID.  459 

respiratory  excitants  are  tea  and  sugar,  coffee,  rum,  milk,  cocoa,  ales 
and  chickory  come  next,  then  casein  and  gluten,  and  lastly  gelatin 
and  albumen.  The  effect  of  taking  respiratory  excitants  is  soon  ex- 
perienced by  the  system,  the  maximum  effect  being  usually  attained 
within  an  hour ;  their  action  is  of  a  temporary  character,  and  the 
effect  is  not  proportional  to  the  quantity  taken.  Certain  respiratory 
excitants,  like  tea  and  coffee,  cause  an  exhalation  of  carbon  in  excess 
of  that  supplied  by  these  foods,  while  others,  like  sugar,  cause  an 
evolution  less  in  amount  than  that  supplied.  In  this  connection  it 
may  be  mentioned  that  the  soothing  influence  experienced  by  persons 
suffering  from  depression  of  spirits  by  drinking  tea  is  probably  due  to 
the  exhalation  of  carbonic  acid  being  increased,  an  excess  of  carbonic 
acid  in  the  system  giving  rise  to  such  feelings.  According  to  Dr. 
Smith,  brandy,  whiskey,  and  gin,  the  volatile  elements  of  alcohol,  gin, 
rum,  sherry,  and  port  wine,  when  inhaled  diminished  the  quantity  of 
carl  ionic  acid  exhaled,  while  rum  and  malt  liquors,  on  the  contrary, 
increased  the  exhalation.  While  the  effect  of  pure  alcohol,  according 
to  Prout,  Horn,  and  Vierordt,1  is  to  diminish  the  exhalation  of  carbonic 
acid,  just  the  opposite  effect  is  attributed  to  it  by  Hervier  and  St. 
Leger  and  Smith.  The  difference  in  the  result  of  the  effect  of  alcohol 
upon  the  exhalation  of  carbonic  acid  observed  by  the  e  experimenters 
may  be  due  to  the  proportion  of  carbonic  acid  in  the  expired  air  being 
only  considered,  and  not  the  absolute  quantity  exhaled,  as  was  the  case 
in  the  experiments  of  Prout,  or  to  the  alcohol  being  administered  with 
or  Avithout  food,  or  even  to  individual  peculiarities. 

It  might  be  supposed  from  the  fact  of  the  absorption  of  oxygen 
being  increased  during  digestion,  that  the  same  would  prove  to  be  the 
case  with  the  exhalation  of  carbonic  acid.  Such  was  shown  to  be  the 
case  by  the  experiments  of  Lavoisier  and  Seguin,2  and  in  modern 
times  by  those  of  Vierordt.3  Thus,  while  during  repose  and  fasting 
1210  cubic  inches  of  carbonic  acid  were  exhaled  per  hour,  during 
digestion  this  amount  increased  to  1800  and  1900  cubic  inches. 
Vierordt  observed  that  while,  before  eating,  he  exhaled  258  c.  cm.  of 
carbonic  acid,  after  eating  he  exhaled  295  c.  cm.,  or  37  c.  cm.  more. 
The  reverse  effect,  or  the  diminution  in  the  exhalation  of  carbonic  acid 
in  the  absence  of  digestive  activity  through  the  depriving  one's  self,  or 
an  animal,  of  food,  was  also  shown  by  Vierordt  in  his  own  person, 
and  by  Spallanzani  in  the  case  of  snails  and  silk  worms,  Marchand 
in  frogs,  and  Bidder  and  Schmidt  on  cats.4  It  has  been  shown  by 
numerous  observers  that  muscular  exertion  increases  the  exhalation  of 
carbonic  acid.  The  experiments  of  Vierordt,  and  Edward  Smith,  in 
this  respect,  are  especially  worthy  of  mention.  According  to  Vierordt,5 
during  moderate  exercise  the  carbonic  acid  exhaled  was  increased  in 
amount  1.197  cubic  inches  per  minute,  while  Dr.  Smith6  found  that  in 
walking  at  the  rate  of  three  miles  an  hour,  the  exhalation  of  carbonic 
acid  in  one  hour  was  equal  to  that  exhaled  during  two  and  three- 
quarters  hours  of  repose  with,  and  three  and  one-half  hours  of  repose 

i  Milne  Edwards:  Pliyaiologic,  tome  ii.  p.  5:3ii.  2  Mem.  de  l'Acad.  des  Sciences,  1789. 

3  Op.  cit  ,  S.  98.  *  Milne  Edwards,  op.  cit.,  pp.  538,  540. 

1  Cyclopaedia  of  Anat.  ami  IMivs.,  vol.  iv.  p.  .'AS.  «  Op.  cit.,  p.  713. 


460  PRODUCTION    OF    CARBONIC    ACID. 

without  food.  According  to  the  same  authority  the  amount  of  carbonic 
acid  exhaled  during  one  hour's  work  on  a  tread-wheel,  was  equal  to 
four  and  one-half  hours  of  rest  with,  and  six  hours  without  food.  It 
should  be  mentioned  that  whenever  the  muscular  exertion  is,  however, 
excessive,  producing  fatigue  and  exhaustion,  that  the  amount  of 
carbonic  acid  exhaled  is  diminished,  and  the  same  holds  true  of  severe 
mental  as  well  as  of  physical  work. 

A  natural  inference  from  that  which  has  just  been  stated  with  refer- 
ence to  muscular  exertion  increasing  the  amount  of  carbonic  acid  exhaled, 
Avould  be  that  during  sleep  the  exhalation  of  carbonic  acid  should  be 
diminished.  The  experiments  of  many  observers  show  that  such  is  in 
fact  the  case  ;  thus,  according  to  Dr.  Edward  Smith,1  the  amount  of 
carbonic  acid  exhaled  during  the  night,  as  compared  with  that  exhaled 
during  the  day,  was  in  the  ratio  of  10  to  18.  The  experiments  of 
Vierordt  show  that  with  slight  diminution  in  the  external  temperature 
the  amount  of  carbonic  acid  exhaled  by  man  is  increased  about  one- 
sixth.  Thus  the  external  temperature  being  between  3  and  15  degrees 
C.  (37.4°  and  59°  F.),  the  absolute  amount  of  carbonic  acid  exhaled 
per  minute  was  299.33  c.  cm.  (about  18  in.),  while  with  the  external 
temperature  between  16  and  24  degrees  the  amount  exhaled  was  only 
257.81  c.  cm.  (15  inches).  The  result  of  Vierordt's  experiments  might 
have  been  anticipated,  since  a  fall  in  the  external  temperature  necessi- 
tates a  greater  production  of  heat,  the  high  temperature  of  the  body 
being  maintained,  and  this  implies  a  greater  absorption  of  oxygen  and 
consequently  a  greater  exhalation  of  carbonic  acid.  When  we  come  to 
study  the  production  of  animal  heat  we  shall  see  that  one  of  the  most 
striking  contrasts  between  mammals  and  birds,  as  compared  with  re- 
maining animals,  is  the  power  the  former  possess  of  generating  heat 
to  replace  that  lost  through  a  fall  in  the  external  temperature.  On  the 
same  principle  as  that  just  mentioned  we  should  expect  to  find  also  that 
more  carbonic  acid  is  exhaled  in  winter  than  in  summer,  there  being  a 
greater  demand  for  the  production  of  heat  in  the  former  case  than  in 
the  latter.  This  has  been  shown  to  be  the  case  more  particularly  by 
the  researches  of  Dr.  Edward  Smith.  Thus  the  maximum  amount  of 
carbonic  acid  is  exhaled  in  January,  February,  and  March,  the  mini- 
mum amount  in  July,  August,  and  part  of  September;  June  and  July 
being  months  of  gradual  diminution,  October,  November,  and  December 
of  gradual  increase.  It  should  be  mentioned  in  this  connection,  how- 
ever, that  animals,  and  probably  also  man,  cannot  at  once  adapt  them- 
selves as  regards  their  respiration  to  sudden  changes  in  temperature. 
Thus  it  was  shown  many  years  ago  by  W.  Milne  Edwards2  that  birds, 
for  example,  in  winter  would  still  consume  the  same  amount  of  oxygen 
and  exhale  the  same  amount  of  carbonic  acid  as  usual,  though  the 
external  temperature  was  artificially  raised  to  that  of  summer  heat. 

It  has  been  shown,  especially  by  Lehmann,3  that  the  exhalation  of 
carbonic  acid  is  greater  in  a  moist  than  in  a  dry  atmosphere.  This 
conclusion  was  based  upon  a  number  of  experiments  upon  birds  and 

1  Op.  cit.,  S   79.  -  De  l'lnfluence  lies  Agens  Physiques  snr  la  Vie. 

3  Physiological  Chemistry,  vol.  ii.  p.  444.     Philadelphia,  1855. 


PRODUCTION    OF    CARBONIC     ACID.  -161 

rabbits.  Thus  rabbits  exhaled  in  a  moist  air,  the  temperature  being 
100°  F.,  '1-  cubic  inches  of  carbonic  acid,  while  in  a  dry  air,  the  tem- 
perature being  the  same,  the  animals  exhaled  only  about  15  cubic 
inches. 

Finally,  it  is  evident  that  an  increase  or  diminution  in  the  density 
of  the  air  inspired,  increasing  or  diminishing  the  amount  of  oxygen  ab- 
sorbed, must  sooner  or  later  influence  the  amount  of  carbonic  acid  exhaled. 
Thus,  in  the  experiments  performed  many  years  ago  by  Hervier  and  St. 
Leger,1  it  was  shown  that  with  a  slight  augmentation,  at  least  of  atmos- 
pheric pressure,  the  amount  of  carbonic  acid  exhaled  was  increased. 
When  the  pressure,  however,  exceeds  twenty  atmospheres  the  production 
of  carbonic  acid  is  diminished  correspondingly  to  the  diminished  oxida- 
tion, and  with  still  higher  pressure  it  is  entirely  arrested,  oxidation, 
according  to  Bert,2  as  we  have  seen,  ceasing  then  altogether.  With  a 
diminution  of  atmospheric  pressure  the  amount  of  carbonic  acid  produced 
is  also  diminished. 

Having  now  considered  the  amount  of  carbonic  acid  exhaled  and  the 
various  influences  modifying  the  same,  let  us,  in  conclusion,  study  the 
relation  of  the  carbonic  acid  exhaled  to  the  oxygen  absorbed.  Oxygen, 
as  is  well  known,  in  combining  with  carbon  to  form  carbonic  acid  gas 
does  not  change  in  volume — that  is,  the  volume  of  carbonic  acid  gas 
formed  is  equal  to  the  volume  of  oxygen  entering  into  its  composition  :  it 
follows,  therefore,  that  if  all  the  oxygen  absorbed  in  inspiration  combines 
with  carbon  to  form  carbonic  acid,  the  volume  of  the  air  expired  ought  to 
be  equal  to  that  inspired.  We  have  seen,  however,  that  the  expired  air 
is  from  g^th  to  y^o"th  less  than  the  inspired  air,  the  difference  amounting 
usually  to  between  2  and  1  per  cent.,  or,  as  we  have  also  expressed  it, 
of  100  parts  of  air  respired  5  parts  of  oxygen  are  absorbed  and  4  parts 
of  carbonic  acid  are  exhaled.  It  is  evident,  therefore,  that  1  part  of 
the  5  of  oxvuen  absorbed  does  not  combine  with  carbon  to  form  carbonic 
acid.  What  becomes,  then,  of  this  one  part  of  oxygen  ?  With  what  does 
it  combine?  Under  what  form  does  it  leave  the  body?  In  speaking  of 
the  composition  of  the  carbohydrates,  it  will  be  remembered  that  attention 
was  called  to  the  fact  of  the  hydrogen  present  being  in  the  proportion  to 
form  with  the  oxygen  water.  Suppose  now  that  starch,  a  carbohydrate, 
be  oxidized,  the  result  would  be  the  formation  of  carbonic  acid  gas  and 
the  setting  free  of  the  water,  the  reaction  being  as  follows : 

C6H10O5    +     012    =    6(C02)     +     5(H20). 

In  an  animal  fed  exclusively  on  starch  the  volume  of  carbonic  acid 
exhaled  would,  therefore,  be  equal  to  the  volume  of  oxygen  ab- 
sorbed, since  all  of  the  oxygen  combines  with  carbon  and  reappears  as 
carbonic  acid.  If,  however,  the  same  animal  be  fed  upon  a  fat  in 
which  the  hydrogen  is  in  excess,  being  more  than  sufficient  to  form 
water  with  the  oxygen  present,  the  absorption  of  oxygen  and  the  oxida- 
tion of  the  fat  would  result  in  the  formation  of  carbonic  acid  and  the 
setting  free  of  the  water,  as  in  the  first  case;  but  as  part  of  the  oxygen 
absorbed  *vould  also  combine  with  that  part  of  the  hydrogen  in  excess 

1  Gazette  des  hupitanx,  1849,  :ime  serie,  t.  i.  p.  .'iT4. 
-  La  Pressiou  Baromutrique,  p.  1152.     Paris,  1878. 


462  PRODUCTION    OF    CARBONIC    ACID. 

to  form  water,  necessarily  some  of  the  oxygen  absorbed  would  not  reap- 
pear as  carbonic  acid  in  the  expired  air,  but  as  water.  The  reaction 
would  be  as  follows,  supposing  olein  to  be  the  fat  used  : 

C57H92  +  2(H6Os)  +  O160  -  57(C02)  +  2(H603)  +  46(H20). 
We  would  find  the  same  to  be  the  case  were  the  animal  fed  upon  meat, 
since  after  the  urea  was  separated  from  the  albumen  the  remainder  of 
the  meat  would  contain  an  excess  of  hydrogen,  as  in  the  case  of  fat, 
hence  part  of  the  oxygen  absorbed  in  respiration  would  not  reappear  as 
carbonic  acid  but  as  water,  part  of  the  oxygen  combining  with  the 
carbon  to  form  carbonic  acid  and  part  combining  with  the  hydrogen  to 
form  water.  These  theoretical  considerations  are  fully  justified  by  the 
experiments  of  Regnault  and  Reiset.  Making  use  of  the  respiration 
apparatus,  it  was  found  by  these  observers  that  in  animals  fed  upon 
starch  the  difference  between  the  amount  of  oxygen  absorbed  and  ex- 
haled in  the  form  of  carbonic  acid,  was  far  less  in  the  case  of  animals 
fed  upon  starch  than  when  fed  upon  fat  or  meat.  Both  theory  and 
experiment  agree,  therefore,  in  showing  that  of  the  oxygen  absorbed, 
that  part  of  it  not  reappearing  as  carbonic  acid  combines  with  hydrogen 
and  leaves  the  body  as  water.  On  the  other  hand,  when  it  is  remem- 
bered that  carbonic  acid  is  produced  in  the  system  through  the  decom- 
position of  the  carbonates  of  the  blood  by  the  pneumic  acid  of  the  lungs 
by  fermentation,  and  that  in  certain  kinds  of  vegetable  food,  fruits,  etc., 
the  oxygen  present  is  in  excess,  being  more  than  sufficient  to  form  with 
the  hydrogen  water,  it  is  to  be  expected  that  under  such  circumstances 
more  oxygen  will  be  exhaled  as  carbonic  acid  than  can  be  accounted  for 
by  that  absorbed  in  inspiration,  as  seen,  for  example,  in  the  oxidation 
of  tartaric  acid : 

C4H606    +     05    =    4(C02)     +     3H20. 

The  relation  of  the  oxygen  absorbed  to  the  carbonic  acid  exhaled  in 
respiration  is  a  very  complex  one,  depending  upon  the  nature  of  the 
food,  the  habit  of  the  animal,  and  various  other  conditions.  While  the 
production  of  carbonic  acid,  like  that  of  urea,  etc.,  is,  undoubtedly,  to 
a  great  extent,  a  process  of  oxidation,  it  must  be  admitted  that,  as  yet, 
the  exact  nature  of  the  process  has  not  been  determined.  It  evidently 
does  not  take  place  in  the  alimentary  canal,  lungs,  or  blood,  a  readily 
oxidizable  substance,  for  example,  like  pyrogallic  acid,  remaining 
unaffected  in  the  latter,  and  from  the  fact  that  the  tissues  exhale 
carbonic  acid  in  an  atmosphere  of  hydrogen  or  nitrogen,  that  the 
formation  of  the  latter  is  not  due  to  the  immediate  combination  of 
the  oxygen  of  the  air  with  the  carbon  of  the  tissues,  the  oxygen 
apparently  entering  into  some  molecular  combination  after  absorption 
by  the  latter.  It  can,  however,  be  positively  stated  that,  while  food 
enters  the  body  as  such,  it  leaves  it  oxidized  as  carbonic  acid,  water, 
urea,  etc.,  and  that  the  oxidation  takes  place  in  the  tissues,  though 
exactly  how,  we  know  not.  Some  of  the  intermediate  stages  in  the 
metamorphosis  of  food  into  carbonic  acid,  urea,  etc.,  have  been  made 
out,  many  yet  remain  unknown,  while  the  exact  reactions  and  nature 
of  the  chemical  changes  taking  place  in  the  tissues  are  still  very 
obscure. 


EXHALATION   OF  WATER.  463 

That  the  expired  air  is  laden  with  aqueous  vapor  becomes  evident  to 
every  one  in  cold  weather,  for,  when  the  external  temperature  is  about 
40°  a  distinct  cloud  is  produced  by  the  condensation  of  the  vapor  of 
the  breath.  Again,  the  ordinary  tarnishing  of  a  surface  breathed  upon 
is  due  to  the  condensed  moisture.  It  is  not  to  be  supposed,  however, 
that  the  water  exhaled  from  the  lungs  is  entirely  due  to  the  combination 
of  hydrogen  with  oxygen  within  the  system  in  the  manner  which  we 
have  just  described.  On  the  contrary,  the  greater  part  of  the  water 
exhaled  was  previously  absorbed  as  such  in  the  form  of  drinks,  etc. 
Admitting  that  the  part  of  the  oxygen  which  is  absorbed  in  inspiration, 
and  does  not  reappear  in  the  carbonic  acid  exhaled,  combines  with 
hydrogen  to  form  water  within  the  economy,  the  quantity  so  formed 
and  exhaled  is  small  as  compared  with  the  water  taken  in  as  drink. 
For,  supposing  that  the  oxygen  not  reappearing  as  carbonic  acid  in 
expiration  amounted  in  twenty-four  hours  to  about  120  litres,  or  168 
grammes,  the  water  formed  through  the  combination  of  the  oxygen 
with  the  hydrogen  of  the  food,  supposing  the  latter  to  amount  to  about 
12  grammes,  would  be  108  grammes,  or  about  1540  grains  : 

H,0      .  H        H20        H 

18      :     2    :  :      x       :     12    x  =  108  grammes. 

whereas  the  water  exhaled  from  the  lungs  of  a  man  may  amount,  in 
twenty-four  hours,  to  as  much  as  1200  grammes,  or  18000  grains,  and 
more,  if  exercise  be  taken.  If,  however,  the  available  hydrogen  of  the 
food  amounts  to  34  grammes,  as  is  supposed  by  Dalton,1  then  about 
300  grammes  of  water  will  be  produced  in  twenty-four  hours  through 
oxidation  of  the  former. 

It  will  not  be  necessary  to  explain  again  the  manner  in  which  the 
amount  of  water  exhaled  by  a  man  or  animal  is  determined  at  the 
present  day,  the  process  having  been  already  explained  in  our  account 
of  the  respiration  apparatus  made  use  of  for  that  purpose.  It  may  be 
mentioned,  however,  that  Valentin's2  results,  which  are  often  quoted, 
were  obtained  by  breathing  into  a  curved  tube,  terminating  in  Liebig's 
bulbs,  filled  with  sulphuric  acid  and  pumice  stone  for  the  absorption  of 
the  water,  the  increased  weight  giving  the  amount  of  water  exhaled. 
The  mean  of  this  experimenter's  observations  gave  a  daily  exhalation  of 
540  grammes  (8333  grains,  equal  to  about  1.2  pounds)  of  water,  a 
rather  low  estimate,  but  the  one  usually  accepted. 

The  amount  of  water  exhaled  from  the  respiratory  tract  will  be 
influenced,  as  in  the  case  of  inert  bodies,  by  the  amount  of  water 
present  in  the  atmosphere,  the  temperature,  and  the  pressure.  Hence, 
the  dryness  of  the  throat  and  fauces  experienced  by  persons  ascending 
into  high  altitudes  through  the  loss  of  water  due  to  the  diminished 
pressure  and  great  cold.  The  extent  of  the  respiratory  surface  will 
influence  also  the  amount  of  aqueous  vapor  exhaled.  This  is  well  seen 
in  the  diminution  of  the  exhalation  in  old  age,  as  shown  by  Barral,3 
the  pulmonary  cells  becoming  larger,  a  less  extent  of  respiratory 
surface  is  offered.     Finally,  the  amount  of  water  exhaled  is  increased 

1  Physiology,  1882.  p   37.  -  Lehrbuch,  Band  i.  S.  527. 

3  Ann.  de  Cliimie,  18W,  3me  ser   t.  xxv.  p.  1GG. 


464 


PRODUCTION    OF    CARBONIC    ACID. 


Pig.  254. 


-J<= 


by  the  quantity  of  water  taken  in  as  drink,  etc.,  and  by  the  frequency 
of  the  respiration.  In  conclusion,  it  should  be  remembered  that,  if  the 
ordinary  conditions  prevailing  be  reversed,  water  may  be  absorbed  by 
the  respiratory  surface  instead  of  being  exhaled.  The 
sudden  gain  in  weight  frequently  observed  in  indi- 
viduals who  had  not  partaken  of  solid  or  liquid  food, 
often  referred  to  by  writers  on  physiology1  is  due,  no 
doubt,  to  absorption  by  the  lungs  of  the  watery  vapor 
of  the  atmosphere,  rather  than  to  cutaneous  absorp- 
tion, as  sometimes  supposed. 

It  has  already  been  mentioned  that  the  expired  dif- 
fers from  the  inspired  air,  not  only  in  containing 
carbonic  acid  and  water,  but  in  being  warmer,  and 
containing  small  quantities  of  ammonia,  nitrogen,  and 
organic  matters.  Thus,  according  to  Grehant2,  one  of 
the  latest  observers,  the  temperature  being  at  72° 
Fahr.,  and  the  air  inspired  by  the  nares,  that  exhaled 
by  the  mouth  had  a  temperature  of  95°  Fahr.,  as 
determined  by  a  thermometer  (Fig.  254,  C)  placed 
within  the  apparatus  A,  through  which  the  air  was 
expired,  and  which  was  uninfluenced  by  the  external 
temperature.  When  the  air  was,  however,  inspired  by 
the  mouth,  the  air  expired  had  a  temperature  of  only 
93°.  The  result  of  Grehant's  observations  differ  a 
little  from  those  of  Valentin,3  previously  made.  Ac- 
cording to  the  latter  observer,  the  external  temperature 
being  at  68°,  that  of  the  expired  air  was  99°.  The  tem- 
perature of  the  surrounding  atmosphere  has  an  im- 
portant influence  on  that  of  the  expired  air,  thus, 
according  to  Valentin,  in  winter,  the  external  tem- 
perature being  at  18°,  that  of  the  expired  air  was 
only  85.5°. 

Ammonia  is  undoubtedly  exhaled  from  the  lungs, 
being  almost  invariably  found  in  the  expired  air.  In 
fact,  it  is  only  absent  at  certain  periods  of  the  day, 
or  during  cold  weather,  as  noticed  by  Richardson.4  In 
certain  conditions  of  the  system,  as  in  cases  of  ursemic  poisoning,  the 
amount  of  ammonia  in  the  expired  air  is  so  great  as  to  become  very 
perceptible  to  the  patient.5  At  one  time  a  difference  of  opinion  pre- 
vailed among  physiologists  as  to  whether  nitrogen  was  absorbed  or  exhaled 
during  respiration.  The  researches  of  Regnault,6  Boussingault,7  and 
Barral,8  leave  no  doubt,  however,  that,  in  mammals  and  birds  at  least, 
under  ordinary  circumstances,  a  small  quantity  of  nitrogen  is  exhaled  in 
respiration,  equal  to  about  one-fiftieth  by  weight  of  the  oxygen  absorbed. 
The  reverse,  however,  appears  to  be  the  case  with  fishes,  according  to 


Apparatus  for  de- 
termining tempera- 
ture of  expired  air. 


1  Carpenter's  Physiology,  p.  404. 

-  Journal  de  1'A.uat.  et  de  la  Phys.,  1804,  tome  i.  p.  5415. 

*  The  Cause  of  the  Coagulation  of  the  Blood,  p.  360.     London,  1857. 

5  Lehmanu:  Phys.  Chem.,  vol.  ii.  p.  4:54.     Philadelphia,  1855. 

"  Chimie  Agricole,  pp.  1-24.     Paris,  1854. 


Physiologie,  Band  i.  S.  533. 

«  Op.  cit .,  p.  510. 
8  Op.  cit.,  p.  129. 


ORGANIC    MATTER    EXHALED.  465 

Humboldt  and  Provencal,1  nitrogen  being  absorbed  by  those  animals. 
In  speaking  of  nitrogen,  it  may  be  incidentally  mentioned  that  its 
mixture  with  oxygen  as  the  air  we  breathe  is  obviously  of  advantage, 
since,  on  account  of  its  great  diffusibility,  the  air  vitiated  with  carbonic 
acid  is  readily  renewed  during  respiration.  A  small  quantity  of  organic 
matter,  the  nature  of  which  is  not  thoroughly  known,  but,  as  we  shall 
see,  is,  to  a  great  extent,  poisonous  in  character,  is  constantly  present 
in  the  expired  air.  The  presence  of  this  organic  matter  can  be  shown 
through  the  putrefaction  of  the  aqueous  products  of  the  expired  air 
when  condensed  in  a  cool  receiver,  or  through  the  putrefaction  of  a 
sponge  saturated  with  the  vapors  exhaled  by  the  lungs. 

Many  articles  of  food,  like  onions,  garlic,  alcohol,  spirits  of  turpen- 
tine, drugs  like  camphor,  musk,  asafoetida,  wdien  absorbed  by  the  blood 
and  vaporized  in  the  system,  are  exhaled  by  the  lungs,  being  readily 
recognized  by  their  odor  in  the  expired  air.  That  poisonous  gases  are 
also  exhaled  by  the  lungs  is  rendered  very  probable  by  the  experiments 
of  Bernard2  and  Xysten,3  in  which  sulphuretted  hydrogen  and  carbonic 
oxide,  so  fatal  when  inhaled,  were  injected  into  the  veins  without  bad 
eifect,  being  eliminated  by  the  lungs  as  rapidly  as  they  Avere  taken  up 
by  the  venous  blood. 

Many  animals  in  which  the  respiration  is  of  a  feeble  character,  such 
as  slugs,  snails,  certain  kinds  of  fish,  frogs,  etc.,  continue  to  live  in  air 
from  which  the  oxygen  has  been  removed  to  a  considerable  extent.* 
Such,  however,  is  not  the  case  with  animals  whose  respiration  is  very 
active,  as  in  man.  Any  considerable  diminution  in  the  amount  of 
oxygen  in  the  surrounding  air  soon  causes  death.  Just  as  a  lamp  goes 
out  when  the  air  feeding  it  does  not  contain  more  than  about  17  per  cent, 
of  oxygen,  so  with  the  lamp  of  life  is  its  flame  too  dying  out,  respiration 
soon  ceasing,  if  the  amount  of  oxygen  usually  present  in  the  atmosphere 
be  diminished  by  absorption,  or  through  dilution  with  some  indifferent 
gas.  In  fact,  air  which  has  been  breathed  by  man  once  should  not  be 
breathed  again  ;  such  air  having  lost  5  per  cent,  of  oxygen  and  gained  4 
per  cent,  of  carbonic  acid,  if  breathed  twice,  will  give  up  but  little 
oxygen  to  his  economy.  Indeed,  as  shown  by  Lavoisier,5  air,  having 
lost  about  10  per  cent,  of  oxygen,  becomes  absolutely  irrespirable. 
Such  is  found  to  be  the  case  in  certain  parts  of  mines  where  the  air 
contains  only  that  amount  of  oxygen.  It  is  well  known,  also,  that  birds 
and  mammals  will  suffocate  in  an  atmosphere  in  which  the  amount  of 
oxygen  has  been  diminished  to  that  extent.  Thus,  a  mouse  will  die  in 
six  minutes,  if  confined  in  such  an  atmosphere,  and  a  sparrow  in  an  hour, 
if  the  oxygen  be  diminished  to  half  that  amount,  or  5  per  cent.  It  is 
not,  however,  the  want  of  oxygen  alone  that  causes  death  in  breathing 
bad  air,  but  the  simultaneous  increase  of  carbonic  acid  as  well.  The 
effects  of  an  accumulation  of  carbonic  acid  in  the  air,  while  no  doubt 
often  exaggerated,  are  nevertheless  injurious  in  many  ways  indirectly, 
since  the  oxygen  to  be  absorbed  will  be  diluted  by  it,  and  the  exhalation 
of  the  carbonic  acid  will  be  interfered  with,  a  condition  of  equilibrium 

1  Milne  Edwards :  Physiologie,  tome  ii.  p.  599,  note.       -  Substances  Toxiques,  p.  58.     Paris,  1857. 

3  Recberches  de  Physiologie,  p.  81.  4  Milne  Edwards:  Physiologie,  tome  ii.  p.  626. 

5  Deuxienie  Memorie  sur  la  respiration  mem.  de  Chimie,  t.  iv.  p.  'It. 

30 


466  PRODUCTION    OF    CARBONIC    ACID. 

being  brought  about,  and  directly  by  its  effects  upon  the  economy  giving 
rise  to  malaise,  headache,  a  sense  of  oppression,  and  even  stupor.1  The 
ill  effects  of  breathing  vitiated  air  appear,  however,  in  many  cases  to  be 
due  not  so  much  to  the  carbonic  acid  as  to  the  organic  matter  that  it 
contains,  and  to  which  we  have  already  referred.  According  to  Foster,2 
while  an  atmosphere  containing  simply  1  per  cent,  of  carbonic  acid,  the 
oxygen  being  diminished  to  the  same  extent,  has  little  or  no  effect  upon 
the  economy,  air  containing  1  per  cent,  of  carbonic  acid  and  organic 
matter  that  has  been  exhaled  is  highly  injurious ;  in  fact,  according  to 
Pettenkofer,3  such  air  becomes  unendurable.  As  we  have  already  seen, 
the  amount  and  nature  of  this  organic  matter  are  comparatively  unknown, 
the  per  cent,  of  carbonic  acid  exhaled  with  it  is  conveniently  taken  as  its 
measure.  Good  air,  in  fact,  should  never  contain  more  than  one-fifth  of 
one  per  cent,  of  carbonic  acid ;  and  indeed,  if  the  air  is  to  be  kept  per- 
fectly wholesome,  the  amount  of  carbonic  acid  should  never  be  allowed 
to  exceed  even  one-tenth  of  one  per  cent. ;  the  air  of  chambers  in  which 
animals  have  breathed  beginning  to  smell  even  when  the  carbonic  acid 
present  amounts  to  so  little  as  one  part  in  a  thousand  of  air. 

On  the  supposition  that  each  human  being  exhales  20  litres  of  car- 
bonic acid  in  an  hour  (Pettenkofer),  it  is  obvious  that  if  the  carbonic 
acid  of  the  surrounding  air  is  not  to  exceed  one-tenth  per  cent,  in 
amount,  that  at  least  20,000  litres,  or  20  cubic  metres,  of  air  must  be 
supplied  for  each  person  in  that  period  of  time,  or  480  cubic  metres — 
about  16,800  feet  in  twenty-four  hours. 

While  a  room  having  a  capacity  of  343  cubic  feet,  as  we  have  seen, 
contains  about  enough  air  to  supply  the  oxygen  required  by  a  man  in 
twenty-four  hours  confined  in  it,  such  a  room  would  evidently  not  contain 
enough  air  to  keep  the  proportion  of  carbonic  acid  exhaled  into  it  in 
that  time  in  the  proportion  of  one-tenth  per  cent.  A  room  25  feet  long, 
wide,  and  deep — that  is,  with  a  capacity  of  15,000  cubic  feet  at  least — 
is  necessary. 

In  breathing  in  the  open,  where  the  atmospheric  air  is  out  of  all  pro- 
portion to  that  expired  by  any  one  individual,  at  no  moment  is  any  want 
of  fresh  air  experienced.  In  our  dwellings  also,  if  properly  constructed, 
a  due  supply  of  fresh  air  is  maintained  by  the  opening  of  windows  and 
doors,  and  the  entrance  of  the  outside  air  through  the  cracks,  crevices, 
etc.  In  churches,  theatres,  lecture-rooms,  barracks,  prisons,  hospitals, 
etc.,  however,  where  large  numbers  of  people  are  congregated  together, 
the  proper  supply  of  fresh  air  should  never  be  left  to  chance.  Indeed, 
tli is  is  now  so  well  understood  that  in  the  ventilation  of  such  buildings  as 
the  Chamber  of  Deputies  and  many  of  the  hospitals  in  Paris,  in  the  House 
of  Commons  in  London,  in  the  Philadelphia  Academy  of  Music,  etc., 
the  air  is  continually  renewed  by  means  of  fans  worked  by  engines,  etc., 
regard  being  paid  to  the  fact  that  the  air  supplied  is  in  reference  not  only 
to  the  amount  of  oxygen  to  be  inspired,  but  also  to  the  carbonic  acid, 
organic  matter,  etc.,  exhaled  to  be  carried  away,  care  being  taken  that 
the  expired  air  does  not  mix  with  that  to  be  inspired,  and  at  the  same 

1  Milne  Edwards,  op.  cit.,  p.  639.  Physiology,  1879,  p.  309. 

3  Med.  Times  and  Gazette,  1862,  p.  459. 


ASPHYXIA.  467 

time  that  drafts  be  avoided,  the  velocity  with  which  the  air  passes 
through  the  chambers  not  being  greater  than  from  two  to  three  feet  per 
second.  That  it  is  the  want  of  oxygen,  however,  and  not  the  excess 
of  carbonic  acid,  that  constitutes  the  natural  stimulus  to  healthy  respi- 
ratory movement  can  be  shown  in  two  different  ways. 

First.  If  an  animal  be  made  to  breathe  an  atmosphere  of  nitrogen 
into  which  the  carbonic  acid  exhaled  will  readily  diffuse,  the  blood  being 
rid,  therefore,  of  any  excess  of  carbonic  acid,  the  breathing,  neverthe- 
theless,  at  once  .becomes  difficult,  dyspnoea  sets  in,  and  death  from 
asphyxia,  preceded  by  convulsions,  soon  follows. 

Second.  If  the  blood  of  the  animal  be  saturated  with  oxygen,  which 
can  be  readily  done  by  artificial  respiration,  apncea  results — that  is, 
all  respiratory  movements  cease,  the  condition  of  the  animal,  however, 
in  other  respects,  being  perfectly  normal.  It  is  evident,  therefore,  that, 
in  the  first  case,  it  is  the  want  of  oxygen  that  gives  rise  to  the  dyspnoea, 
respiratory  movements,  etc. ;  whereas,  in  the  second  case,  the  oxygen 
being  in  excess,  no  necessity  exists  for  such  respiratory  movements, 
hence  their  absence ;  or,  on  the  other  hand,  if  an  animal  be  made  to 
breathe  an  atmosphere  containing  an  excess  of  carbonic  acid,  but,  at 
the  same  time,  plenty  of  oxygen,  though  the  breathing  becomes 
deeper  and  quicker,  and  while  there  is  an  excess,  even  of  carbonic  acid, 
in  the  blood,  nevertheless  no  convulsive  asphyxia  follows.  On  the  con- 
trary, the  breathing  soon  becomes  slower,  a  state  of  unconsciousness 
sets  in,  and  death  takes  place,  as  if  caused  by  narcotic  poisoning.  There 
can  be  no  doubt,  therefore,  that  the  violent  respiratory  movements 
preceding  death  from  asphyxia  are  due  primarily  to  the  blood  being 
insufficiently  oxygenated,  and  not  to  an  excess  of  carbonic  acid,  any 
influence  exerted  in  this  respect  by  the  latter  being  of  a  secondary 
character,  mechanically,  for  example,  in  preventing  the  access  of  the 
oxygen,  etc.  As  dyspnoea,  apnoea,  and  asphyxia  are  rather  subjects 
of  study  for  the  pathologist  than  for  the  physiologist,  I  have  only  inci- 
dentally alluded  to  those  conditions  so  far  as  they  seem  to  elucidate  the 
relative  role  that  oxygen  and  carbonic  acid  play  as  stimuli  to  the  respi- 
ratory movements.  Inasmuch,  however,  as  the  condition  of  asphyxia 
is  an  interesting  and  important  one  from  many  points  of  view,  a  brief 
description  of  it  may  not  appear  inappropriate. 

Asphyxia,  from  a,  primitive,  and  s<pv!jig,  the  pulse,  literally  a  state  of 
being  without  pulse,  the  condition  brought  about  when  the  system  is 
deprived  of  a  due  supply  of  air,  whether  suddenly  by  occlusion  of  the 
trachea,  as  in  strangulation,  or  by  slow  suffocation  through  breathing 
in  a  confined  space,  manifests  itself  first  by  the  breathing,  both  inspira- 
tory and  expiratory,  becoming  more  frequent  and  deeper.  This  exag- 
geration of  the  breathing,  or  hypernoea,  is  soon  succeeded  by  a  con- 
dition of  difficult  breathing,  or  dyspnoea,  the  respiratory  movements,  at 
the  same  time,  having  become  almost  entirely  expiratory  in  character, 
every  muscle  being  brought  into  play  that  can  contribute  in  any  way 
to  this  effect.  Sooner  or  later,  the  muscles  of  the  whole  body  become 
involved  in  the  convulsive  expiratory  movements  that  follow.  General 
convulsions  then  set  in,  which,  after  lasting  a  short  time,  are  followed 


468  PRODUCTION    OF    CARBONIC    ACID. 

by  a  stage  of  tranquillity  due  to  exhaustion.  At  this  stage  the  pupil  is 
insensible  to  light,  the  cornea  fails  to  respond  to  touch,  breathing  has 
become  almost  entirely  inspiratory,  and  occurs  only  at  long  intervals. 
Finally,  with  a  long  and  deep  gasp  death  takes  place,  with  the  head 
thrown  back,  nostrils  dilated,  opened  mouth,  straightened  trunk,  and 
extended  limbs.  That  the  convulsions,  which  occur  as  dyspnoea  passes 
into  asphyxia,  are  due  to  the  stimulation  of  the  respiratory  centre  of 
the  medulla  oblongata  by  the  insufficiently  arterialized  blood  circulating 
through  it,  is  proved  from  the  fact  of  such  convulsions  being  absent  if 
the  spinal  cord  has  been  previously  divided  below  the  medulla,  but 
being  present  if  the  part  of  the  brain  lying  above  the  medulla  only  be 
removed.  That  these  convulsions  are,  in  fact,  due  to  influences  ema- 
nating from  the  medulla  is  still  further  shown  by  the  rise  in  blood 
pressure  that  occurs  during  the  development  of  asphyxia,  and  which  is 
due  to  the  constriction  of  the  arterioles  through  the  stimulation  of  the 
vasomotor  centre  by  the  excessively  venous  blood,  and  by  the  fact  that 
if  the  supply  of  blood  to  the  brain  be  cut  off  by  ligation  of  the  vessels, 
convulsions,  similar  to  those  observed  in  asphyxia,  follow.  The  facts 
just  mentioned  will  become  more  significant,  however,  when  the  struc- 
ture of  the  medulla,  and  its  influence  upon  the  respiration  and  the 
circulation,  have  been  considered. 

Owing  to  the  constriction  of  the  vessels  at  the  periphery  that  obtains 
in  asphyxia,  offering  an  obstacle  to  the  flow  of  the  blood  from  the  heart, 
while  the  increased  respiratory  movement  favors  the  flow  toward  it,  the 
heart  soon  becomes  distended,  and,  finally,  exhausted,  though  continuing 
to  beat  for  a  few  moments  after  respiration  has  ceased.  During  the 
latter  stage  of  asphyxia  the  blood  pressure,  therefore,  not  only  falls, 
but  the  heart  is  weakened — that  is,  unable  to  empty  itself  of  its 
contents.  Hence,  in  post-mortem  examinations  of  cases  of  death  from 
asphyxia,  if  made  before  rigor  mortis  has  set  in,  all  the  cavities  of  the 
heart  will  be  found  choked  with  blood.  With  the  setting  in  of  rigor 
mortis,  however,  the  blood  is  expelled  from  the  left  side  of  the  heart, 
the  right  remaining  gorged  with  venous  blood.  The  difference  of  opinion, 
that  sometimes  prevails,  as  to  whether  all  the  cavities  of  the  heart  are 
filled  with  blood  in  death  from  asphyxia,  may  be  due,  therefore,  to  the 
length  of  time  intervening  between  death  and  the  making  of  the  post- 
mortem examination,  having  been  different  in  the  cases  investigated. 
In  this  connection  it  may  not  be  without  interest  to  mention  that 
Harvey1  notices  that,  in  cases  of  death  from  ordinary  causes,  the  left 
side  of  the  heart  and  arteries  are  found  empty ;  whereas,  in  sudden 
death,  as  from  syncope  or  drowning,  the  arteries,  as  well  as  the  veins, 
are  found  full  of  blood.  The  duration  of  asphyxia  varies  very  much 
in  different  animals,  and  according  to  the  age  of  the  animal.  Thus,  a 
dog  will  be  asphyxiated  by  occlusion  of  the  trachea  in  four  or  five 
minutes,  a  rabbit  in  three  or  four  minutes ;  whereas,  as  shown  long  ago 
by  Buffon,2  puppies  just  born  can  be  submerged  in  Avarm  milk  for  half 
an  hour  at  a  time,  several  times  in  succession,  and  yet  recover ;  while, 

l  Works,  p.  115.     Loudon,  1847.  2  Natural  History,  vol.  iii.  p.337.  London,  1797. 


ASPHYXIA.  469 

according  to  Legallois,'  newborn  rabbits  lost  consciousness  only  after 
having  been  kept  thirteen  minutes  under  water.  Milne  Edwards2 
refers  to  cases,  interesting  from  a  medico-legal  point  of  view,  where 
infants  born  asphyxiated  were  revived  seven  and  even  twenty-three 
hours  afterward.  The  remarkable  power  that  animals  just  born  exhibit 
in  resisting  asphyxia  depends  principally  upon  the  demand  for  oxygen 
being  so  slight  at  this  time.  In  fact,  at  this  early  period  of  existence 
the  newborn  mammal  is  essentially  a  cold-blooded  animal,  it  depending 
for  its  heat  almost  entirely  on  external  warmth,  the  blood  is  still  mixed 
through  the  foramen  ovale  being  open,  the  circulation  and  respiration 
have  not  assumed  the  important  role  that  they  play  in  the  adult,  little 
or  no  muscular  exercise  is  taken,  most  of  the  time  being  passed  in  sleep, 
hence  but  little  oxygen  is  required.  The  connection  between  the 
deficiency  in  the  circulation  and  the  want  of  aeration,  just  referred  to, 
is  also  seen  in  cases  of  syncope  in  the  adult,  it  being  well  known  that  a 
person  in  that  condition  can  resist  for  some  time  the  effects  of  asphyxia, 
the  amount  of  oxygen  consumed  bv  the  tissue  being;,  of  course,  less  in 
proportion  as  the  circulation  is  slowed,  the  oxygen  inspired  will  last, 
therefore,  longer  than  usual. 

1  (Euvres,  tome  premier,  p.  58.     Paris,  1850  2  Op  cit.,  p.  559, 


CHAPTER    XXXI. 

ANIMAL  HEAT. 

One  of  the  most  striking  phenomenon  in  the  life  of  man,  and  in  that 
of  the  hot-blooded  animals  generally  (mammals  and  birds),  and  of 
plants,  also,  to  a  certain  extent,  which  did  not  escape  the  attention 
of  the  ancients,  is  the  almost  constant  temperature  maintained  by  the 
body,  notwithstanding  the  great  extremes  in  temperature  to  which  it 
may  be  subjected.  Thus,  whether  one  lives  in  a  changeable  climate, 
or  passes  from  the  genial  atmosphere  of  the  temperate  regions  into  the 
extreme  heat  of  the  tropics,  53.3°  C.  (130°  F.),1  on  the  one  hand,  or 
into  the  intense  cold  of  the  arctics,  — 57.7°  C.  ( — 72.5°  F.)2  on  the  other, 
the  temperature  of  the  body  varies,  as  we  shall  see,  but  little.  If,  how- 
ever, the  so-called  cold-blooded  animals,  frogs,  for  example,  be  observed 
in  this  respect,  a  most  notable  difference  becomes  at  once  apparent,  their 
temperature  being,  according  to  the  circumstance,  higher  or  lower  than 
that  of  the  surrounding  water  or  air,  and  any  rise  or  fall  in  it  depending 
upon  that  of  the  latter.  Thus,  according  to  Landois,3  the  temperature  of 
the  water  in  which  the  frog  is  immersed  being;  successivelv  2.8°,  20.6°, 
and  41°  C,  that  of  the  stomach  of  the  animal  will  be  respectively 
5.8°,  20.7°,  38.0°  C,  while  if  the  animal  be  living  in  air  at  a  temper- 
ature of  5.9°,  19.8°,  and  40.4°  C,  that  of  the  stomach  will  be  at 
18.6°,  15.6°,  31.7°  C.  Thus,  as  Hunter  expressed  it,  warm-blooded 
animals  have  a  certain  permanent  heat  in  all  atmospheres,  while  the 
temperature  of  cold-blooded  ones  is  variable  with  every  atmosphere, 
hence  the  distinction  of  pomiothermal  and  poikilothermal  animals  intro- 
duced by  Bergman4,  and  which  being  based  upon  the  relation  of  the 
temperature  of  the  body  to  that  of  the  surrounding  medium  is  a  better 
one  than  that  of  hot-  and  cold-blooded  animals,  and  which  we  have  just 
incidentally  alluded  to. 

The  following  table  Avas  drawn  up  from  the  observations  of  Davy,5 
Martine,6  Prevost,7  and  Dumas  de  la  Roche,s  Jones9,  Valentin,10 
Hunter,11  and  of  the  author.  When  not  otherwise  mentioned,  the 
temperature  in  the  vertebrates  was  taken  in  the  rectum. 

As  the  temperature  differs  often  in  individuals  of  the  same  species, 
and  according;  to  the  biological  conditions  influencing  the  animal  at 
the  moment  of  observations,  and  further,  as  the  number  of  observations 
are  comparatively  limited,  any  results,  such  as  exposed  in  Table  LXIV., 
can  only  be  accepted  as  approximately  giving  the  average  temperature 
in  animals. 

1  Jameson  :  British  India,  vol.  iii.  p.  170.  -  Erman  :  Siberia,  vol.  ii.  p.  369. 

3  Physiologie,  S.  393.     Wien,  188  5.  *  Gottinger  Studien,  Abth.  i.  S.  595. 

5  Researches  Phy-i.  ami  An  it.,  p.  161.     London,  1839.        ''■  Essays,  Medical  and  Philos.,  1740,  p.  337. 

7  Annates  de  chim.  et  de  phya.,  2e  serie,  t.  xxiii.  p.  64,  1823. 

8  Journal  de  physique,  Ixxi.  p.  298,  1810. 

9  Investigations,  Cliem.  and  Physiol.,  Smith.  Contrib.,  1856. 

i°  Repertorium  fur  Aimt.  und  I'iiys.,  Vierter  Bin  I,  S.  359.    Bern,  1839. 
11  Works,  ed.  by  Palmer,  vol.  iv.  p.  147.     London,  1835. 


TEMPERATURE    OF    ANIMALS. 


471 


Table  LXIV.1 — Temperature  of  Animals. 


Name  of  auimal. 

Temperature. 

Observer. 

A  ves— 

Chicken, 

Ill"  F.  (43.8°  C.) 

Davy. 

Guinea  fowl, 

110 

n 

Thrush, 

109 

it 

Sparrow, 

108 

a 

Goose, 

107 

!< 

Screech  owl, 

106 

a 

Mammalia — 

Hog, 

105          (40.3°  C.) 

" 

Manatee, 

li '4  abdomen, 

Martine. 

Rabhit, 

104  to  100, 

Prevost  a 

de  la  ] 

Sheep, 

104 

Davy. 

Goat, 

104 

it 

Eat, 

102 

a 

Squirrel, 

102 

c< 

Cat, 

102 

a 

Panther, 

102 

a 

Dog, 

102 

it 

Monkey, 

101 

a 

Porpoise, 

100  liver, 

a 

Ox, 

100 

a 

Elephant, 

99.5 

ft 

Horse, 

99.5 

a 

Reptilia — 

Green  snake, 

88.5 

a 

Tortoise, 

87     oesophagus, 

.. 

Iguana, 

82.5 

■' 

Alligator, 

69 

Jones. 

Amphibia — 

Frog, 

64 

Davy. 

Pisces — 

Trout, 

58 

u 

Eel, 

51 

.. 

Articulata — - 

Beetle, 

77     surrounding  air  76°, 

it 

Cockroach, 

-  \                               It                                   11         -7  AO 
1  ->                                                                                   t-±     , 

" 

Mollusca — 

( >yster, 

Temp,  same  as  sea,  82°. 

(( 

Snail, 

76.5  surrounding  air.  76.2* 

;,° 

(( 

Echinodermata — 

Star  fish, 

6-10°  F.  above  temp,  of  sea 

(66.3°) 

Valentin 

Sea  urchin, 

5-10 

(66.7  ) 

a 

Sea  cucumber, 

6-10 

(67.6   ) 

" 

Vermes — 

Leech, 

1            "          "      of  air 

(56.     ) 

Hunter. 

Ccelenterata — 

Anemone, 

5-10            "          "     of  sea 

(69.4   | 

Valentin 

Jelly  fish, 

7-10 

(72.5 

n 

Ponfera — 

Sponge, 

Same  as  sea  (68. 3^  F.) 

it 

472  ANIMAL    HEAT. 

Of  ;ill  animals,  birds  have  the  highest  temperature,  that  of  the 
chicken,  for  example,  according  to  Davy1  being  as  high  as  111°  F., 
(43°  C),  a  slightly  higher  temperature,  according  to  Pallas,2  even  being 
found  in  certain  small  birds.  Among  mammals  the  temperature  of  the 
rabbit  is  noteworthy,  amounting  to  40°  C.  (105.8°  F.j.  On  the  other 
hand  the  temperature  of  fishes,  with  some  exceptions,  is  not  usually 
more  than  0.5°  C.  (0.9°  F.)  higher  than  that  of  the  water  in  which 
they  live,  whilst  among  the  invertebrata,3  as  in  the  case  of  mollusks, 
star  fish,  jelly  fish,  anemone,  the  excess  of  the  temperature  over  that 
of  the  surrounding  medium  may  be  even  less,  amounting  often  to  no 
more  than  0.2°  C.  As  an  exception  to  the  last  statement  and 
interesting  in  this  connection  may  be  mentioned  the  considerable 
amount  of  heat  developed  by  bees  and  ants  when  swarming.  Although 
a  great  number  of  observations  have  been  made,  some  difference  of 
opinion  still  prevails  as  to  what  constitutes  the  average  normal  temper- 
ture  in  man.  This,  however,  is  readily  understood  when,  as  we  shall 
presently  see,  the  temperature  of  the  body  not  only  varies  considerably 
in  different  situations,  but  according  to  numerous  circumstances ;  among 
others  may  be  here  very  appropriately  mentioned  especially  the  manner 
in  which  the  thermometrical  observations  should  be  made.  It  is  of  the 
highest  importance,  not  only  that  the  part  of  the  body  selected  for 
taking  the  temperature  should  be  mentioned,  but  that  the  thermometer 
used  in  making  the  observation  should  be  a  standard  one. 

The  exact  date  of  the  invention  of  the  thermometer  as  well  as  of 
that  of  the  microscope  is  not  exactly  known,  and  in  both  instances 
there  is  also  doubt  as  to  whom  the  merit  of  these  inventions  should  be 
accorded.  At  the  present  moment,  for  example,  the  invention  of  the 
thermometer  is  attributed  on  the  one  hand  by  Rosenthal4  to  Galileo, 
and  on  the  other  by  Wunderlich5  to  Sanctorius.  It  is  probable  that  it 
was  invented  by  Galileo  (1603),  but  first  made  use  of  in  the  study  of 
the  temperature  of  man  in  fever  by  Sanctorius  (1626).  While  it  is 
true  that  Galileo  is  mentioned  in  the  preface  to  his  works,6  and  is 
referred  to  by  his  biographer  Viviani,7  as  the  inventor,  nevertheless, 
that  Sanctorius  considered  himself  as  the  inventor,  there  can  be  no 
doubt ;  since  he  himself  distinctly  says  so,8  and  it  may  be  mentioned 
in  this  connection  that  this  claim  is  admitted  without  reserve  by  both 
Borelli9  and  Malpighi.10  Other  claims,  however,  like  those  in  favor 
of  Galileo,  of  a  posthumous  character,  have  been  advanced  by  Boer- 
haave,11  who  attributed  the  invention  to  his  countryman  Drebbel,  and 
by  Fulgentius12  to  his  compatriot,  the  great  Venetian  Father  Paul 
Sarpi. 

The  metastatic  thermometer  of  Walferdin  (Fig.  255),  is  very  useful 
since  by  means  of  it  a  variation  of  the  Yorjth  of  a  degree  Cent,  (corre- 

1  Researches,  Phys.  and  Anat.,  p.  186.     London,  1839. 

-  Gavarret,  De  la  Chalenr  Prouduite  par  les  Etres  Vivants,  p.  94.     Paris,  1855. 

3  Milne  Edwards:  PhysiolOgie,  tome  neuvieme,  18fi:i,  p.  13. 

*  Hermann  :  Handbuih  der  Pliysiologrie,  Vierter  Band,  Zweiter  Theil,  S.  294 

5  Das  Verhalten  der  Eigenwiirwe  in  Kranklieiten,  2  And.  1870,  S.  34. 

6  Opere  di  Galilei,  p.  47.  7  Vita  de  1'Galilei,  p.  67. 

8  Com.  in  Galen,  Art.  Med.,  p.  736.     Com.  in  Avicen,  i.  p.  22,  78,  219. 
o  De  Motu  Animal,  11  Prop.  175.  '0  Opera  Posth.,  p.  30. 

"  Elem.-iita  Chenriae,  p.  152,  156.     Lugd.  Bat.,  1732. 
!2  Opere  del  Padre,  Vita  del  Padre,  p.  158.     Paola,  K'87. 


METASTATIC    THERMOMETER. 


473 


Pig. 255 


Fig.  256. 


Walferdin's 

metastatic 

thermometer. 


sponding  to  a  millimetre  in  length  of  the  mercury)  can  be 
accurately  determined,  and  that  however  excellent  the 
instrument  may  be  at  the  time  obtained,  it  should  be 
constantly  tested.  Further,  in  using  the  thermometer  it 
should  be  so  applied  that  the  part  whose  temperature  is  to 
be  determined  completely  surrounds  the  bulb  of  the  instru- 
ment, hence,  of  all  parts  of  the  body,  the  rectum  is  that 
which  is  best  adapted  for  thermometrical  observations,  the 
instrument  being  inserted  to  a  depth  of  at  least  5  cm.  (2  in ). 
On  account,  however,  of  being  more  convenient,  the  axilla 
is  frequently  made  use  of  in  determining  the  temperature 
of  the  human  body.  It  must  be  remembered  in  that  case 
then  that  the  temperature  is 
usually  Y5(j-th  to  1  degree 
lower  than  that  of  the  rec- 
tum. The  tongue  and  va- 
gina are  also  frequently 
made  use  of  in  taking  the 
temperature.  Apart  from 
individual  idiosyncrasies,  to 
neglect  of  the  precautions 
just  referred  to  is  undoubt- 
edly due  much  of  the  dif- 
ference of  opinion  that  has 
prevailed  more  particularly 
among  the  older  physiolo- 
gists with  reference  to  the 
temperature  of  man.  If. 
from  the  nature  of  the  case, 
on  account  of  the  size  of 
the  cavity  to  be  examined, 
etc.,  the  application  of  a 
thermometer  is  inadmissi- 
ble, thermo-electric  needles 
are  then  made  use  of  in  de- 
termining the  temperature. 
Even  greater  precautions 
must  be  taken  than  when  the 
observation  is  made  in  the  usual  way  on  account  of  the  deli- 
cacy of  the  apparatus,  as  slight  a  variation  as  the  T qVo^1  °f 
a  degree  having  been  determined  by  such.  Thermo-electric 
needles  (Fig.  256,  Af,  f  A)  are  usually  made  of  iron  and 
German  silver,  each  needle  consisting  of  iron  (f)  and  silver 
(A),  soldered  together  at  and  near  their  points,  and  the  two 
so  disposed  as  to  constitute  together  an  element.  The 
iron  wires  being  in  the  middle,  and  the  silver  ones  exter- 
nally, if  the  latter  are  connected  with  each  other  through 
a  galvanometer  (M),  a  circuit  is  formed.  The  deviation 
of  the   needle  will   then   indicate   the   temperature  of  the 


Thermo-electric  needles. 


474  ANIMAL    HEAT. 

part  examined  through  the  electricty  developed  by  the  contact  of  the 
needles  with  the  heated  surface.  The  wires  are,  of  course,  except 
where  soldered  together,  carefully  isolated,  and  where  held,  are  covered 
with  silk  and  varnish.  When  the  difference  in  the  temperature  of  two 
parts  of  the  body  is  to  be  determined,  the  two  needles  are  imbedded  in 
the  parts,  and  the  intensity  of  the  current  measured  and  the  amount  of 
heat  determined,  the  relation  between  the  deviation  of  the  needle  and  the 
amount  of  heat  producing  it  having  been  previously  experimentally  de- 
termined. This  can  be  accomplished  by  immersing  the  needles  with  deli- 
cate thermometers  attached,  in  oil  baths  differing  in  temperature,  for  ex- 
ample, by  one  degree  C.  The  deviation  of  the  galvanometer  needle  will 
then  indicate  a  difference  in  temperature  of  one  degree  C.  Suppose, 
further,  that  as  measured  by  the  scale  the  deviation  of  the  galvanometer 
needle  amounts  to  150  mm.,  then  yJ-jjth  of  a  degree  C.  of  temperature  is 
indicated  by  a  deviation  of  1  mm.  of  the  needle.  If  absolute  tempera- 
ture be  required,  then  one  needle  is  applied  to  a  surface  maintained  at  a 
known  temperature,  and  the  other  to  that  whose  temperature  is  to  be  de- 
termined, or  the  known  temperature  can  be  gradually  reduced  until  there 
is  no  deviation  of  the  needle.  The  opposite  currents  being  then  equal 
the  heat  producing  them  must  be  equal — that  is,  the  unknown  heat  is 
equal  to  the  known.  It  was  by  means  of  the  thermo-electric  apparatus 
that  Becquerel,1  and  Breschet  determined  the  temperature  of  the  biceps 
muscle  under  different  external  conditions  to  be  referred  to  in  a  moment, 
and  Nobili2  and  Melloni  proved  that  the  internal  temperature  of 
insects  was  slightly  higher  than  that  of  the  surrounding  atmosphere. 
Among  the  most  reliable  observations  that  have  been  made  with  refer- 
ence  to  determining  the  average  temperature  of  the  human  body  may 
be  mentioned  those  of  Hunter,3  37.2°  C.  (98.9°  F.),  Daw.4  37.3°  C. 
(99.1°  P.),  Wunderlich,5  37°  C.  (98.6°  F.),  Jurgensen^6  37.2°  C. 
The  mean  of  Jurgensen's  observations,  it  will  be  observed,  is  the  same 
as  that  of  Hunter,  a  confirmation  of  the  accuracy  with  which  that 
great  physiologist  investigated  the  subject  of  animal  heat  as  all  other 
biological  phenomena.  The  results  of  Jurgensen's  experiments  are 
most  important,  both  on  account  of  their  number  and  the  length  of 
time  over  which  they  extended.  They  consisted  in  reading  off  at 
intervals  of  five  minutes  the  indications  of  a  thermometer  permanently 
retained  in  the  rectum,  and  extended  over  three  days.  The  mean 
obtained  by  Jurgensen  was  37.2°  C.  (08.9°  F.),  which  we  will  consider 
as  being  the  average  normal  temperature  of  the  human  body,  although 
variations  between  37°  and  38°  C.  (98.6°  and  100.4°  F.)  may  occur 
within  the  limits  of  health. 

Among  the  various  conditions  that  modify  the  normal  temperature 
may  be  mentioned,  in  addition  to  the  influence  of  the  part  of  the  body 
examined,  to  which  we  have  already  incidentally  alluded,  that 
exerted  by  age,  sex,  the  time  of  day,  food,  muscular  and  mental  work, 

1  Ann.  des  Sciences  Xaturelles,  2d  ser.,  183n,  t.  iii.  p.  269. 

*  Ann.  de  Chiniie  et  de  Physique,  1831,  t.  xlviii.  ).   208. 

8  Works  of . John  Hunter,  ed.  by  J.  F.  Palmer   vol.  i.  p.  280.    London,  1S35.    Phil.  Trans.,  1844,  p.  61. 
4  Researches,  I'liys.  and  Anat.,  lSiD,  vol.  i.  p.  162. 

*  Op.  eit.,  S.  92.  >'  Deutsche  Archiv  klin.  Med.,  Band  iii.  S.  166. 


DAILY    VARIATIONS.  -475 

external  temperature,  etc.     To  the  consideration  of  these  let  us  now 
turn. 

Age  and  Sex. 

According  to  Andral,1  Barensprung,2  and  others,  the  temperature 
before  birth,  as  well  as  immediately  afterward,  is  slightly  higher  than 
that  of  the  mother ;  but  as  the  newborn  child  possesses  but  little  power 
of  resisting  external  cold,  its  temperature  soon  falls,  within  two  hours, 
perhaps,  from  37.8°  to  35.2°  C.  (100.04°  to  95.2°  P.).  Hence  the 
importance  of  providing  for  the  infant  sufficient  warmth  by  suitable 
means,  and  to  the  neglect  of  which  the  death  in  many  instances  is 
undoubtedly  due.  Immediately  after  birth  the  temperature  of  the 
infant  taken  in  the  rectum  is  between  37.5°  and  37.8°  C.  (99.5°  and 
100.04°  R),  falling  after  the  first  bath  to  37°  C.  (98.6°  F.)  and  even 
lower,  while  during  the  next  ten  days  it  varies  between  37.25°  and 
37.6°  C.  (98.9°  and  99.6°  R),  being  notably  increased  by  screaming, 
etc.  During  the  period  intervening  between  early  infancy  and  the  age 
of  puberty  the  temperature  falls  about  0.2°  C.  (3.6°  R),  and  from  there 
on  till  adult  life  falls  about  0.2°  C.  still  more,  the  normal  temperature  or 
37.2°  C.  (98.9°  F.)  being  then  reached.  After  sixty  years  of  age  the 
temperature  begins  to  rise  again,  and  at  eighty  years  has  again  reached 
that  of  the  newborn  child.  This  rise  in  temperature  in  old  age  is  prob- 
ably due  to  the  diminished  circulation  of  the  anaemic  skin,  since  it 
cannot  be  supposed  that  the  production  of  heat  has  been  increased.  As 
a  general  rule,  sex  has  no  appreciable  influence  upon  the  temperature  of 
the  body.  According  to  Ogle,3  however,  the  temperature  of  the  female 
appears  to  be  slightly  higher  than  that  of  the  male. 

Daily  Variations. 

The  temperature  of  the  body,  like  the  frequency  of  the  pulse,  respira- 
tion, and  exhalation  of  carbonic  acid,  exhibits  periodical  variations. 
From  the  numerous  observations  of  Davy,  Hallmann,  Gierse,  Baren- 
sprung, Lichteufels,  Frohlich,  Damrosch,  Ogle,  Liebermeister,  Jurgen- 
sen,4  it  appears  that  the  temperature  of  the  body  increases  very  quickly 
from  6  a.m.  to  11  a.m.,  but  from  that  time  forward  increases  more 
slowly,  reaching  a  maximum  between  5  and  6  p.m.  About  7  in  the 
evening  the  temperature  begins  to  fall,  reaching  the  minimum  about  5 
a.m.,  the  difference  being  in  24  hours  usually  about  1°  C.  (1.8°  F.), 
though  it  may  amount  to  as  much  as  2°  C.  (3.6°  F.). 

Climate  seems  to  influence  the  time  of  day  at  which  the  maximum 
and  minimum  temperatures  occur,  the  minimum  being  reached,  according 
to  Davy,  in  England  by  midnight,  but  in  the  tropics  not  before  6  or 
7  A.M." 

1  Compt.  Rend  ,  t.  lxx.  p.  825.  -  V.  Barensprung,  Arch.  f.  Anat.  u.  Phys.,  1851,  S.  138. 

::  Kirke'8  Physiology,  10th  ed.,  p.  255.    Phila.,  1881. 

4  Rosenthal  die  Physiologie  der  thierlschen  Warme  in  Hermann,  op.  cit,  Vierter  Band,  S.  322. 


476 


ANIMAL    HEAT. 


Table  LXV.1 

II. .ur 

Be  rensprung. 

Davy. 

Jurgensen. 

5 

....  Cent. 

36.7 

36.6 

(i 

36.68 

36.7 

36.4 

7 

36.94* 

36.*63 

36.98 

36.7* 

36.5* 

A.  M.      8 

:;7."l6* 

36.80* 

37.08* 

36.8 

36.7 

9 

36.89 

36.9 

36.8 

10 

:;7.2ii 

37.*36 

37.*23 

37.0 

37.0 

11 

36.*89 

•S7.2 

37.2 

M.    12 

36.87 

37.3* 

37.3* 

1 

36.83 

37.13 

37.3 

37.3 

2 

37.05 

37.21 

37.50*- 

37.4 

37.4 

3 

37.15- 

M7.43 

37.4* 

37.3* 

4 

37.17 

37.5 

37.5 

5 

37. 48 

37.05* 

37.31 

.".7.4:; 

37.5 

37.5 

6 

36.83 

37.29 

37.5 

37.6 

7 

37.43 

36.50* 

37.31  i 

30.00 

37.5* 

37.6* 

P.  M.      8 

37.4 

37.7 

9 

37.02* 

37.4 

37.5 

10 

37.29 

37.3 

37.4 

11 

36.85 

36.72 

36.70 

36.81 

37.2 

37  1 

12 

37.1 

37.4 

1 

36.85 

3C..44 

37.0 

36.9 

2 

36.9 

36.7 

3 

36.8 

36.7 

4 

3G.7 

36.7 

Asterisk  signifies  that  food  was  taken. 

Supposing  with  Jurgensen,  Table  LXV.,  that  the  day  temperature 
begins  at  6  a.m.  with  36.4°  C,  and  ends  at  8  p.m.  with  37.7°,  the 
duration  of  the  former  with  a  usually  mean  temperature  of  37.3°, 
exceeds  the  latter  with  a  mean  of  36.9°  by  four  hours,  the  average  tem- 
perature for  the  whole  day  being,  as  already  mentioned,  about  37.2°  C. 
(98.9°  F.).  As  might  be  expected,  Debczynski2  finds  that  persistent 
night  work  reverses  the  rhythm  of  the  variations  of  temperature,  the 
thermometer  standing  highest  in  the  morning  (37.8°),  instead  of  in  the 
evening  (35.3°). 

Food. 


As  in  the  long  run  the  heat,  as  we  shall  see,  is  due  to  the  combustion 
of  substances  taken  into  the  body  as  food,  it  follows  that  the  production 
of  heat  is  intimately  associated  with  that  of  nutrition.  Inasmuch,  how- 
ever, as  it  is  not  until  the  last  stage  of  inanition  in  the  starving  man  or 
animal  that  the  temperature  notably  falls,  it  having  been  previously 
maintained  in  the  absence  of  food  through  the  combustion  of  the  tissues, 
it  is  not  to  be  expected  that  in  health  the  mere  taking  of  food  will 
influence  the  temperature  to  any  great  extent,  since  the  fuel,  so  to 
speak,  is  ordinarily  consumed  as  rapidly  as  supplied,  and  when  deficient 
is  made  up  at  the  expense  of  the  tissues.  For  example,  very  hot  drinks 
increase  the  temperature  but  little.  Suppose,  for  example,  a  man 
weighing  60  kilo.  (132  lbs.)  drinks  a  kilo.  (2.2  lbs.)  at  50°  C.  (122° 
F.),  the  temperature  of  the  whole  body  (supposing  it  to  be  37.2°  C. 


1  Landois,  op.  cit.,  S.  406. 


"-  Virchow  u.  Hirsch  :  Jahresber.,  1875,  Band  i.  S.  248. 


CONDITIONS    INFLUENCING    PRODUCTION    OF    HEAT.     477 

and  having  the  same  specific  heat  as  water)  would  be  increased  only 
about  0.2  of  a  degree  C.  It  must  be  remembered  in  this  instance,  as  in 
many  others,  that  the  effect  of  taking  a  hot  drink  is  not  so  simple  as 
may  at  first  appear,  since  the  circulation  being  increased  by  it  the  loss 
of  heat  through  evaporation  will  be  increased.  The  one  effect  neutraliz- 
ing to  a  certain  extent  the  other,  the  full  effect  of  the  drink  as  regards 
elevation  of  the  temperature  is  not  therefore  experienced.  Even  if  the 
drinks  contain  specific  substances  such  as  tea,  coffee,  alcohol,  etc.,  the 
temperature  of  the  body  is  diminished  only  two  or  three  tenths  of  a 
degree  C.  It  is  possible  that  the  loss  of  heat  experienced  in  the  taking 
of  alcohol  is  not  only  due  to  the  quickened  circulation,  but  to  a  para- 
lyzing effect  exerted  upon  the  vasomotor  nerves  of  the  skin,  whereby  a 
greater  quantity  of  blood  being  conveyed  to  the  surface  than  usual,  more 
heat  is  consequently  given  off  and  so  lost.  On  the  other  hand,  while 
the  effect  of  cold  drinks,  etc.,  is  to  diminish  the  temperature  of  the  body, 
the  diminution  is  also  very  slight,  amounting  usually  to  but  a  few  tenths 
of  a  degree  C.  Thus,  according  to  Lichteufels  and  Frolich,  Winter- 
nitz,  and  others,1  drinks  at  a  temperature  of  18°,  16.3°,  and  4.6°  C, 
reduced  that  of  the  body  in  the  first  two  instances  within  6  minutes 
after  taking  them  0.1°,  0.4°,  and  in  the  last  in  70  minutes  1.4°  C.  Fur- 
ther, as  in  the  digestion  of  solid  foods  heat  is  required  to  assist  the 
chemico-physical  changes,  it  might  be  expected  that  as  part  of  the  heat 
becomes  latent  the  temperature  of  the  body  would  be  slightly  diminished 
temporarily  after  taking  the  food,  even  though  the  temperature  should 
be  increased  later  through  further  oxidation.  That  such  is  the  case 
seems  to  be  shown  by  the  experiments  of  Vintschgau  and  Dietl,2  made 
upon  a  dog  with  gastric  fistula,  in  which  the  temperature  of  the  food  in- 
troduced, and  which  differed  but  little  from  that  of  the  body,  first  fell  and 
then  rose.  From  what  has  just  been  said,  however,  of  the  compensating 
power  exercised  by  the  economy  whether  food  be  taken  or  withheld,  it 
would  be  inferred  that  the  influence  exerted  by  the  taking  of  food  upon 
the  daily  variations  must  be  very  slight,  if  any.  Indeed,  the  variations 
in  temperature  that  are  observed  after  meals,  as  a  matter  of  fact,  occur 
whether  food  be  taken  or  not.  The  most,  indeed,  that  can  be  said  is 
that  if  a  meal  be  taken  late  in  the  day  the  diminution  in  temperature, 
characteristic  of  that  period,  is  somewhat  put  off.  Indeed,  it  is  not 
until  shortly  before  death  caused  by  inanition  or  starvation,  for  the 
reasons  already  given,  that  the  temperature  is  notably  diminished. 

Muscular  and  Mental  and  Glandular  Action. 

We  shall  soon  see,  in  our  study  of  muscular  action,  that  at  the  moment 
of  muscular  contraction  a  considerable  amount  of  heat  is  set  free — indeed, 
probably  three-fourths  of  the  heat  developed  is  produced  in  the  muscles. 
Thus,  according  to  Davy,3  the  temperature  of  the  room  being  66°  F,, 
that  of  the  feet  66°,  under  the  tongue  98°,  and  of  the  urine  100° ;  after 
a  walk  in  the  open  air  at  40°  the  temperature  of  the  feet  was  96.5°  and 

1  Rosenthal,  op.  rit.,  S.  325. 

2  Sitz.  d.  Wiener  Acad.  Math-Natur  u.  CI.  2  Abth,  lx,  S.  697,  1870. 

3  Phil.  Trans.,  1844,  p.  03. 


478  ANIMAL    HEAT. 

the  urine  101°,  that  under  the  tongue  being  unchanged.  Indeed,  daily 
observation  as  well  as  special  experiments  teaches  us  that  our  whole  body 
is  wanned  by  muscular  exercise.  Further  consideration,  however,  will 
show  that  the  body  is  not  as  much  heated  as  one  would  be  led  to  expect 
from  the  amount  of  heat  developed  under  the  circumstances,  and  from 
the  rapidity  with  which  the  temperature  of  the  body  falls  to  the  normal 
with  the  cessation  of  the  exercise,  it  is  evident  that  as  fast  as  the  heat  is 
developed  it  is  as  rapidly  radiated  away  or  lost  as  some  other  mode  of 
force.  The  influence  of  muscular  exercise  in  elevating  the  temperature 
of  the  body  is  also  well  seen  under  certain  pathological  conditions ;  the 
temperature  in  tetanus,  for  example,  rising,  according  to  Wunderlich, 
as  high  as  44.75°  C.  (112.5°  F.).  It  should  be  mentioned,  however, 
that  this  great  rise  in  temperature  can  hardly  be  attributed  entirely  to 
muscular  action,  since  in  all  probability  at  the  same  time  other  influences 
come  into  play,  such  as  the  acting  of  the  vasomotor  nerves,  which  in 
constricting  the  vessels  of  the  skin  will  diminish  the  usual  loss  of  heat 
due  to  radiation  and  evaporation. 

Nervous-like  muscular  activity  is  also  accompanied  with  the  production 
of  heat.  Thus,  according  to  Davy,2  in  England,  during  the  reading  of 
a  work  demanding  attention  the  temperature  of  the  body  was  increased 
0.5°  F.  Mental  effort  in  the  tropics  is  accompanied  by  a  still  greater 
production  of  heat,  amounting,  in  some  instances,  to  more  than  2°  F., 
as  in  the  giving  of  a  lecture,  for  example;  in  the  latter  case  some  of  the 
heat  was  probably  due  to  the  muscular  action  involved.  Lombard3  has 
also  determined,  by  means  of  delicate  thermo-electric  apparatus,  local 
increase  of  temperature  in  the  head  resulting  from  mental  effort. 
Schiff4  has  also  shown  that  the  action  of  the  nerves,  as  well  as  that  of 
the  brain,  is  accompanied  with  the  production  of  heat.  In  all  instances, 
however,  the  amount  of  heat  produced,  at  least  that  appearing  as  such, 
is  a  small  part  of  the  heat  produced,  as  in  the  case  of  muscle  being  con- 
verted, as  we  shall  see  hereafter,  into  other  modes  of  force. 

Glandular  action  is  also  accompanied  with  the  production  of  heat  due 
to  the  chemical  activity  incidental  to  secretion.  Thus,  according  to 
Ludwig  and  Spiess,5  the  temperature  of  the  saliva  secreted  during  stim- 
ulation of  the  chorda  tympani  is  1  to  1.5°  (J.  higher  than  that  of  the 
blood  of  the  carotid  artery  of  the  same  side.  We  have  already  called 
attention  to  the  fact  of  the  temperature  of  the  blood  of  the  hepatic 
vein  being  higher  than  that  of  any  other  part  of  the  body,  due, 
in  part  at  least,  to  the  size  and  constant  activity  of  the  liver. 

Surrounding  Temperature. 

Any  consideration  as  to  the  temperature  of  man  or  animal  would 
naturally  suggest  the  influence  exerted  by  that  of  the  surrounding  atmos- 
phere, and  concerning  which  there  was,  during  the  last  century,  differ- 
ence of  opinion.     So  distinguished  a  teacher  as  Boerhaave,  for  example, 

1  Op.  cit.,  S.  400.  -  Phil,  Trans.,  1845,  p.  443. 

3  Experimental  Researches  on  the  Regional  Temperature  of  the  Head.     London,  1879. 

<  Archiv  de  phy.  normal  et  path.,  1870,  pp.  5,  198,  323,  421.  ■"■  Wien.  Sitzb.,  Bd.  25,  1857. 


INFLUENCE    OF    SURROUNDING    TEMPERATURE.       479 

observing1  that  no  body  can  endure  an  air  heated  to  90°  F.,  and 
that  we  are  always  warmer  than  the  surrounding  air,  supported 
this  view  by  experiments  performed  at  his  request,2  by  Fahrenheit  and 
Provost,  which  consisted  in  placing  a  sparrow,  a  cat,  and  a  dog  in  a 
sugar-baker's  oven,  heated  to  146°  F.,  and  in  which  it  was  found 
they  soon  died.  Notwithstanding  the  result  of  these  experiments,  the 
great  Haller,  basing  his  opinion  upon  the  testimony  of  Lining  Adam- 
son,  and  other  travellers,  as  to  the  intense  heat  that  prevailed  in  certain 
parts  of  this  country,  South  Carolina,  Senegal,  and  elsewhere,  held3 
in  opposition  to  the  view  entertained  by  Boerhaave  that  man  could  not 
only  live  in  an  atmosphere  16°,  but  even  28°  F.,  higher  than  that 
of  the  blood.  About  this  time  important  observations  bearing  upon 
this  question  were  made  by  Franklin  and  Governor  Ellis.  In  a  letter 
dated  London,  June  IT,  1758,  in  referring  to  a  hot  Sunday  passed  in 
Philadelphia,  in  June,  1750,  Franklin4  recalls  that,  during  the  day,  when 
the  thermometer  was  at  100°  F.,  in  the  shade,  his  body  never  grew  so  hot 
as  the  air  surrounding  it,  or  the  inanimate  bodies  immersed  in  the  same  air, 
and,  with  his  usual  acuteness,  accounts  for  the  body  being  kept  cool  under 
such  circumstances  by  continual  sweating,  and  by  the  evaporation  of  that 
sweat. 

Within  a  month  of  the  same  year — that  is,  in  July  17,  1758 — 
Governor  Ellis,  in  a  letter  to  his  brother  in  London,  called  attention 
particularly  to  the  fact  that,  while  in  Georgia,  a  thermometer  suspended 
from  under  an  umbrella  which  he  carried  during  a  walk  of  one  hundred 
yards  registered  105°  F.,  the  temperature  of  his  body  was  only  97°. 
The  letter  of  Governor  Ellis  being  communicated  to  the  Royal  Society5 
was  thereby  at  once  insured  a  wide  circulation ;  that  of  Franklin, 
though  written  first,  was  not  made  public,  however,  till  afterward.6 
Shortly  after  the  observation  of  Ellis,  just  referred  to,  it  was  ascer- 
tained by  Tillet,7  in  experimenting  with  a  baker's  oven,  that  the  young 
women  in  attendance  were  accustomed  to  remain  in  it  for  a  few  minutes 
even  when  at  a  temperature  of  260°  F.- (126.6°  C).  In  one  in- 
stance Tillet,  anxious  for  the  safety  of  the  woman,  requested  her  to 
come  out,  but  she  assured  him  she  felt  no  inconvenience,  and  remained 
in  the  oven  for  ten  minutes,  the  latter  having  a  temperature  of  280°  F. 
(169°  C),  indeed,  on  her  coming  out,  beyond  the  flushing  of  the 
face,  there  was  nothing  especially  noticeable.  While  the  facts  just 
referred  to  excited  considerable  interest  at  the  time,  it  was  not  till  some 
years  later,  however,  that  any  further  experiments  were  performed  with 
the  object  of  ascertaining  the  effect  of  heated  air  upon  the  temperature 
of  the  body.  In  1774,  the  subject,  however,  was  taken  up  again  by 
Fordyce,  who,  together  with  Blagden,  Solander,  Banks,  and  others, 
experimented  upon  themselves,  either  in  a  room  heated  with  flues,  and 
upon  the  floor  of  which  boiling  water  was  poured,  or  in  rooms  heated 

i  Element*  Chemise,  p.  192.     Lugd.  Bat.,  MDCCXXXII. 

-  Idem  opus,  p.  275. 

s  Elementa  Physiologiae,  p  37.    Lausanne,  MDCCLX. 

4  Works,  vol.  iii.  p.  301.    Phila.,  L809.  ''  Phil.  Trans.,  1759,  vol.  1.  p.  755,  Part  ii. 

6  Journal  de  Physique,  177:;,  tome  ii.  p.  45.S. 

i  Mem.  de  l'Acad.  'Irs  Sciences,  1764,  to:ne  lxxxi.  p.  188. 


480  ANIMAL    HEAT. 

with  flues   only.     The  result   of    these   experiments,  as   described   by 
Blagden,1  may  be  summed  up  as  follows  : 

In  the  room  containing  vapor  Fordyce  was  able  to  bear  for  10  min- 
utes a  temperature  of  110°  F.  (4:-3.3°"  C),  20  minutes  120°  F.  (48.8° 
C),  and  for  15  minutes  a  heat  gradually  increasing  from  119°  to  130° 
F.  (48.3°  to  54°  C).  In  these  experiments,  it  is  said,  that  the  tem- 
perature under  the  tongue  and  of  the  urine  did  not  rise  higher  than 
100°  F.  (37.7°  C).  In  the  room  heated  with  flues  only,  and  con- 
taining dry  air,  Fordyce,  together  with  Blagden  and  Banks  in  the 
room,  could  stand,  however,  a  higher  heat  than  in  the  former  instance, 
supporting  for  ten  minutes  a  temperature  of  198°  F.  (92°  C).  Shortly 
after  these  experiments  it  was  ascertained  by  Dobson,2  from  observa- 
tions made  in  the  sweating-room  of  the  Liverpool  Hospital,  that  indi- 
viduals could  stand  for  periods  between  10  and  20  minutes  a  temper- 
ature, if  the  air  be  dry,  of  between  ^02°  and  224°  F.  (94.4°  and  106.6° 
C.)  Fordyce,  himself,  as  mentioned  in  a  subsequent  paper  by  Blag- 
den,3 was  able  to  endure  for  8  minutes  even  as  high  a  temperature  as 
260°  F.  (127°  C),  the  uncomfortable  feelings  experienced  quickly 
passing  away  with  the  breaking  out  of  a  profuse  sweat.  The  immunity 
possessed  by  persons  habitually  exposed  from  time  to  time  to  a  dry 
atmosphere,  having  a  temperature  even  higher  than  that  to  which  For- 
dyce, Blagden,  etc.,  were  subjected,  is  undoubtedly  due,  in  a  great 
measure  at  least,  as  Franklin  supposed,  to  the  cold  produced  through 
the  evaporation  of  the  cutaneous  perspiration  and  pulmonary  exhalation. 
In  this  way  can  be  explained  how  the  workmen  of  the  sculptor  Chantry 
wrent  into  a  furnace  having  a  temperature  of  340°  F.  (182°  C),  and 
Chabert,  the  fire  king,  into  one  at  between  400°  and  600°  F.  (226° 
and  315.5°  C).  Indeed,  the  salutary  effect,  under  such  circumstances, 
of  keeping  the  temperature  down  by  evaporation  was  fully  recognized 
by  Fordyce  and  Blagden,4  and  proved  by  them  in  the  following  way  : 
Two  similar  earthen  vessels,  one  containing  water  only  and  the  other 
an  equal  quantity  of  water,  with  a  bit  of  wax,  were  put  upon  a  piece 
of  wood  in  the  heated  room.  In  an  hour  and  a  half  the  pure  water  was 
heated  to  140°  F.,  while  that  containing  the  wax  had  acquired  a  tem- 
perature of  152°  F.,  as  the  wax  in  melting  had  formed  a  film  upon  the 
surface  of  the  water,  and  thereby  had  prevented  evaporation.  Fur- 
ther, it  was  observed  that  the  pure  water  never  came  near  the  boiling- 
point,  but  if  a  small  quantity  of  oil  was  dropped  into  it,  as  had  been 
done  before  with  the  wax,  finally  the  water  in  both  vessels  boiled  briskly. 
The  effect  of  sweating  in  keeping  down  the  bodily  temperature  is  daily 
seen  in  the  taking  of  Turkish  as  compared  with  Russian  baths,  an 
equally  high  temperature  being  much  better  borne  in  the  former,  on 
account  of  the  air  being  dry,  than  in  the  latter,  where  the  air  is  moist. 
The  profuse  perspiration  induced  through  hot  baths  has  long  been  a 
matter  of  comment ;  as  early  as  the  first  half  of  the  last  century  Le  Mon- 
nier,5  in  speaking  of  the  natural  hot  baths  at  Baregas,  with  a  temperature 
in  the  hottest  part  of  112°  F.  (44.4°  C),  observes  that  the  sweat  poured 

i  Phil.  Trans.,  vol.  lxv.,  1775,  Part  i.  p.  111.  2  Idem,  p.  4G3.  3  Idem,  p.  484. 

4  Op.  cit.,  p.  491. 

6  Mem.  de  1' Acad,  des  Sciences,  1747,  tome  lxiv.  p.  271. 


INFLUENCE    OF    BATHS    UPON    BODILY    TEMPERATURE.      -181 

down  from  his  face  after  remaining  in  it  8  minutes,  and  that  after  that 
time  he  was  obliged  to  leave  the  bath,  with  reddened  and  swollen  skin, 
and  greatly  increased  pulse  through  violent  attacks  of  vertigo.  The 
conclusion  drawn  from  the  different  experiments  of  Fahrenheit  and 
Provost,  Tillot,  Fordyce,  and  Blagden,  etc.,  that  we  have  just  described, 
was  that  man  could  not  only  exist  in  an  atmosphere  having  a  higher 
temperature  than  that  of  his  own  body,  but  that  the  latter  remained 
unchanged,  even  when  that  of  the  surrounding  atmosphere  was  greatly 
increased,  notwithstanding  that  in  an  experiment  with  a  dog  the  tem- 
perature was  found  by  Fordyce  to  increase.  It  would  appear,  however, 
without  doubt,  from  later  observations,  that  with  an  increase  in  the 
temperature  of  the  surrounding  air  there  is  an  increase  in  that  of  the 
body.  Thus,  in  the  experiments  made  by  De  la  Roche1  and  Berger, 
it  was  found  that,  after  remaining  15  minutes  in  a  vapor  bath,  with  a 
temperature  varying  between  37.5°  and  48.8°  C.  (99.5°  and  119.6°  F.), 
the  temperature  in  the  mouth  was  increased  3.1°  C.  (5.5°  F.),  while  in 
dry  air,  but  at  a  temperature  of  80°  C.  (174°  F.),  the  temperature  was 
increased  about  5°  C.  (9°  F.).  According  to  Davy,2  also,  who  made  a 
great  number  of  observations  in  different  parts  of  the  world,  the  mean 
temperature  of  the  body  in  the  tropics  is  about  1°  F.  higher  than  in 
England.  Such  a  variation  has  been  held  by  Boileau,3  for  example,  as 
abnormal,  and  as  an  indication  of  a  slight  disturbance  in  the  system 
due  to  change  of  climate,  and  to  which  certain  delicate  persons  are  liable. 
The  observations  of  Eydoux4  and  Souleyet,  made  during  the  voyage  of 
the  "  Bonite,"  and  of  Brown-Sequard,5  to  the  Isle  of  France,  though  less 
in  number  than  those  of  Davy,  so  far  as  they  go,  confirm  the  result 
obtained  by  that  reliable  observer.  Davy6  also  showed,  from  a  number 
of  observations,  that  the  mean  temperature  of  the  air  being  00°  F. 
(15.5°  C),  that  of  the  body  was  98.28°  F.  (36.7  C,),  whereas,  if  the 
temperature  of  the  air  rose  to  80°  F.  (26.6°  C),  the  temperature  of  the 
body  rose  to  99.67°  F.  (37.5°  C). 

The  temperature  of  individual  portions  of  the  body  has  been  shown 
to  increase  with  that  of  the  surrounding  medium,  as  well  as  that  of 
the  whole*  body.  In  an  experiment  of  Becquerel  and  Breschet,7  for 
example,  where  the  biceps  muscle  was  surrounded  for  15  minutes  by 
water  at  a  temperature  of  42°  (109°  F.),  the  temperature,  as  deter- 
mined by  their  thermo-electric  apparatus  was  increased  two-tenths  of  a 
degree.  Tbe  rise  in  temperature,  through  increase  of  heat  in  the  sur- 
rounding atmosphere,  can  be  well  shown  in  animals.  Thus,  according 
to  Rosenthal,8  the  temperature  of  a  rabbit  rose  from  the  normal,  38°  C. 
(104.4°  F.)  to  45°  C.  (113°  F.).  while  the  external  temperature  was 
increased  from  32°  to  40°  C.  (89.6°  to  104°  F.),  death  taking  place  at 
the  latter  temperature.  Essentially  the  same  result  was  obtained  in 
the  experiments  of  De  la  Roche  and  Berger  with  a  guinea-pig.  Ac- 
cording to  these  observers,  as  well  as  Rosenthal,  an  increase  in  the  tem- 
perature of  6°  to  7°  C.  (10.8°  to  12.6°  F.)  above  the  normal,  however 

1  These?  de  l'ecole  de  mfidecine  de  Paris,  1806,  No.  11.     Journal  de  physique,  1776,  tome  vii.  p.  57. 

2  Philus.  Transact,  L830,  \>.  437.  ■       3  Lancet,  1878,  p.  413. 

4  Conip   Rend.,  1838,  tome  vi.  p.  456.  ■'■  Journal  tie  Physiology,  t.  ii.  p.  554. 

6  Researches,  Phys.  and  Anat.,  p.  163.  "  Ann.  des  Sciences  Nat.,  1838,  p.  271. 

8  Op.  cit.,  S.  337. 

31 


482  ANIMAL     IIK  AT. 

brought  about,  is  fatal  to  all  animals.  It  would  appear  from  these  ex- 
periments as  well  as  the  earlier  ones  of  Provost  and  Fahrenheit,  that 
large!  animals  bear  a  high  temperature  better  than  small  ones,  probably 
because,  in  the  latter,  a  greater  quantity  of  heat  is  produced  relatively 
and  more  quickly.  Thus,  in  the  experiments  of  Fahrenheit,  already 
referred  to,  of  the  three  animals  placed  in  the  oven  the  sparrow 
died  in  8  minutes,  whereas  the  dog  and  the  eat  survived  28  minutes. 
According  to  De  la  Roche  and  Berger,  a  mouse  died  in  32  minutes,  the 
temperature  being  increased  from  57.5°  to  63.7°  C.  (135°  to  146.0°  P.), 
■while  a  guinea-pig  survived  1  hour  and  25  minutes,  the  temperature 
rising  from  62°  to  80°  C.  (143.6°  to  177°  F.);  a  young  ass,  however, 
though  weak  at  the  end  of  the  experiment,  successfully  resisted  for 
nearly  three  hours  a  temperature  increased  from  60°  to  75°  C.  (140° 
to  107°  F.).  In  the  case  of  man,  in  certain  pathological  conditions,  as 
in  typhoid  and  typhus  fever,  the  temperature  of  the  body  may  rise  to 
40.5°  and  41.1°  C.  (105°  and  106°  F.),  and  yet  recovery  take  place. 
The  highest  temperature  yet  observed  in  man,  and  ending  in  recovery, 
was  in  a  case  of  injury  to  the  spine,  reported  by  Dr.  J.  Teale,1  in 
which  the  thermometer  registered  122°  F.  (50°  C).  The  elevation  in 
temperature  in  sunstroke,  104°  to  112°  F.  (40°  to  44.4°  C),  is  also 
very  considerable ;  in  such  cases,  however,  the  high  temperature  is  to 
be  attributed,  in  part  at  least,  not  only  to  the  effect  of  exposure  to  the 
sun's  heat,  but  also  to  the  exercise  taken  incidental  to  the  character  of 
the  occupation  of  those  usually  attacked,  such  as  field  and  street 
laborers,  soldiers,  etc. 

Inasmuch,  as  we  have  seen,  through  the  free  action  of  the  skin,  and 
with  proper  precautions  taken  as  regards  exercise,  food,  clothing,  etc., 
man  can  live  in  an  atmosphere  the  temperature  of  which  is  much  higher 
than  that  of  his  body,  it  might  naturally  be  supposed  that  through 
similar  compensating  agencies  intense  cold  can  be  equally  well  resisted, 
if  not  better  than  intense  heat.  Such,  indeed,  experience  proves  to  be 
the  case,  the  temperature  of  the  body  of  man,  even  when  exposed  to  the 
intense  cold  of  the  Arctic  regions,  is  almost  the  same  as  in  the  tem- 
perate ones,  since  the  amount  of  heat  generated  absolutely  is  greater  on 
account  of  the  quantity  and  quality  of  food,  and  relatively  so  from  the 
fact  of  the  clothing,  etc.,  being  of  such  a  character  as  to  retain  the  heat 
produced.  In  animals  the  latter  protective  effect  is  provided  for  by 
their  fur,  wool,  feathers,  etc.,  as  the  case  may  be. 

A  glance  at  Table  LXVI.  will  show  how  little  the  temperature  of  the 
body  in  Arctic  animals  differs  from  that  of  the  animals  in  temperate 
regions,  though  the  difference  in  the  temperature  of  the  former,  as  com- 
pared with  that  of  the  surrounding  atmosphere,  may  amount  to  as  much 
as  76.7°  C.  (138°  F.). 

1  Lancet,  March  6,  187o. 


INFLUENCE    OF    ATMOSPHERE. 

Table  LXVI.1 

—Observations  of  Parry. 

Animal. 

Tiiuji.  of  animal. 

Temp,  of  air. 

Difference. 

Arctic  fox 

.     41.5- 

C  (106. 

r°F. 

)     —25.6°  C. 

67.1°  C 

i            it 

.     38.5 
.     37.8 
.     38.5 

—20.6 
—19.4 
—29.4 

59.1 
57.2 

67.9 

t            << 

.     37.6 

—26.2 

63.8 

.     36.6 
.     37.6 

—23.3 
—23.3 

59.9 
60.9 

a             << 

.     40.3 

—20  3 

7u. 7 

White  hare 

.    38.3 

—29.4 

67.7 

Fox      . 

.    37.8 
.     41.1 

—26.2 
—35.6 

64.0 

76.7 

a 

.     39.4 
.     38.9 

.     38. 3 

— 32.S 
—31.7 
—35.6 

72.2 

70.6 
73.9 

W 

olf    . 

.     40.5 

—32.8 

73.3 

483 


On  account  of  water  being  a  better  conductor,  and  having  also  a 
greater  capacity  for  heat  than  air,  the  temperature  of  the  body  will  fall 
more  rapidly  if  exposed  to  cold  water  than  to  air  at  the  same  tempera- 
ture :  hence  the  great  effect  of  cold  baths  in  the  treatment  of  fevers  so 
much  in  vogue,  particularly  in  Germany,  in  late  years,  and  the  great 
benefit  derived  from  the  application  of  ice  in  the  treatment  of  sunstroke. 
While  man  and  animals  can  resist  the  most  intense  Arctic  cold  by  the 
agencies  just  referred  to,  nevertheless  a  far  less  degree  of  cold,  if  sud- 
denly and  directly  applied  to  the  body,  will  soon  prove  fatal.  Thus, 
according  to  Rosenthal,2  animals  die  if  the  temperature  of  their  bodies 
be  reduced  to  24°  C.  (15.2°  F.),  and  such  is  usually  the  case  in  man 
also,  as  shown  by  the  clinical  cases  referred  to  by  the  same  high 
authority  ;  as  well  known,  however,  the  temperature  in  cholera  may  fall 
as  low  as  18.3°  C.  (67°  F.).  There  are  some  other  conditions  in  addi- 
tion to  those  already  mentioned  which  may  affect  the  temperature  of  the 
body.  Of  such  are  the  effects  exerted  by  race,  country,  labor,  sea-sick- 
ness, and  barometrical  variations.  As  such  influences  are,  however, 
either  exceptional  or  temporary  in  their  character,  we  will  not  dwell 
further  upon  them,  merely  mentioning  that,  according  to  the  late  dis- 
tinguished Professor  Dunglison,3  the  temperature  of  the  uterus  during 
labor  may  rise  as  high  as  106°  F.  (41.1°  C),  that  of  the  vagina  at  the 
same  time  being  105°  F.  (40.5°  C). 


I  Gavarret,  op.  cit.,  p.  101. 

-  Op.  <  it..  S.  133. 


Parrj  'e  Journal,  p.  130. 


Philadelphia,  1821  . 

::  Physiology,  1856,  Sth  ed.,  vol. 


p.  602. 


CHAPTER    XXXII 


PRODUCTION  OF  ANIMAL  HEAT. 

Having  considered  the  temperature  of  the  body,  and  the  various 
modifying  conditions,  it  now  remains  to  account  for  the  production  of 
this  heat,  and  the  manner  in  which  the  latter  is  regulated.  Notwith- 
standing that  a  certain  amount  of  heat  is  produced  through  the  double 
decompositions  and  hydrations  continually  taking  place  in  the  economy,1 
there  can  be  no  doubt  that,  by  far,  the  greatest  amount  of  heat  pro- 
duced is  due,  as  Lavoisier  supposed,  to  the  slow  combustion  continually 
o-oing  on  within  the  body  of  the  animal,  caused  by  the  absorption  of  oxygen, 
the  interchanging  of  which  with  carbonic  acid,  etc.,  we  have  seen,  consti- 
tutes the  essence  of  respiration.  The  various  theories  as  to  the  cause 
of  animal  heat  put  forward  at  different  times  before,  and  even  after,  the 
errand  generalizations  of  Lavoisier2  had  been  made  known,  have, 
therefore,  for  us,  now  only  an  historical  interest.  We,  therefore,  merely 
allude  in  a  passing  way  to  the  views  that  attributed  animal  heat  to  the 
reaction  of  certain  of  the  fluids  of  the  body,3  to  an  archaeus  vital 
spirit  or  kindred  fetiches,4  to  fermentation,5  movement  of  the  blood  in 
the  vessels,6  etc.,  recalling,  however,  the  very  remarkable  work  of  Mayo,7 
and  noting  that  Crawford8  still  maintained  his  view  that  animal  heat 
was  the  latent  heat  of  the  inspired  air,  which,  set  free  in  the  lungs,  is 
taken  up  by  the  blood  and  carried  thence,  latent,  to  all  parts  of  the 
body,  becoming  free  heat  again  in  the  capillaries,  even  after  the  theory 
of  Lavoisier  had  been  developed.  In  our  account  of  the  progress  in 
discovery  by  which  the  theory  of  respiration  was  slowly  established  we 
had  occasion  to  refer  to  the  great  works  of  Lavoisier,  in  which,  not 
only  was  the  view  of  respiration  essentially  as  we  now  understand  it 
first  distinctly  enunciated,  but  the  inference  also  drawn,  which  was  later 
fully  confirmed  by  experiment,  that  respiration  was  essentially  the 
cause  of  animal  heat.  In  the  paper  on  the  calcination  of  metals,  brought 
before  the  Academy  of  Sciences,  in  1775,  Lavoisier  had  shown 
that  in  the  decomposition  of  mercuric  oxide  by  heat  the  principle 
(oxygen)  so  obtained  supported  both  combustion  and  respiration,  wdiereas, 
when  the  same  substance  was  reduced  by  carbon  the  principle  then 
obtained  (carbonic  acid  gas)  supported  neither.  These  fundamental 
facts  having  been  established,  two  years  later  Lavoisier9  further  showed 
that  animals  absorb  oxygen  and  exhale  carbonic  acid,  and  during  the 

1  D'Arsonval,  Comptes  Rendus,  Aout  25th,  1879.  2  Mem.  de  1'Acad.  des  Sciences,  1775-1789. 

3  Sylvius :  Disput.  med.  cap   vii.   1879. 

4  Van  Helmiiut :  Opera  Omnia,  Anno  1707,  pp.  174  ami  734. 

s  Descartes  (Euvres,  ed   de  Cousin,  t.  iv.  p.  437.  6  Haller :  Elementa  Physiol.,  t.  ii.  p.  286. 

1  Tractatus  de  Kespiratione,  1668. 

8  Experiments  and  Observations  on  Animal  Heat,  London,  1788. 

9  Mem.  de  l'Acad.  des  Sciences,  1775,  p.  520 


THE    CALORIMETER.  485 

same  year1  formulated  a  view  on  combustion  in  general  in  which 
respiration  was  regarded  as  a  slow  process  of  combustion,  oxygen  being 
absorbed  and  carbonic  acid  and  heat  given  off  just  as  in  the  burning  of 
coal.  As  might  have  been  expected  from  the  methods  of  investigation 
so  characteristic  of  the  great  chemist  and  physiologist,  Lavoisier  did  not 
long  rest  satisfied  with  the  establishing  of  a  generalization  as  to  the  nature 
of  respiration  and  heat  as  important  as  that  just  referred  to,  but  soon 
instituted  a  series  of  experiments  with  the  view  of  ascertaining  whether 
the  amount  of  carbonic  acid  exhaled  and  heat  produced  by  an  animal  in 
a  given  time  was  such  as  ought  to  be  expected  on  the  supposition  that 
a  certain  amount  of  carbon  had  been  burned  in  the  body  of  the  animal, 
the  amount  of  carbonic  acid  given  off  and  heat  produced  by  the  combus- 
tion of  a  similar  amount  of  carbon  outside  of  the  body  having  been  pre- 
viously determined,  and  of  so  establishing  the  truth  of  his  theory  by 
experimental  demonstration.  For  this  purpose,  in  conjunction  with 
Laplace,  he  invented  the  ice  calorimeter.2  This  consisted  essentially  of 
three  chambers,  concentrically  disposed,  and  which  could  be  thoroughly 
closed  above,  two  of  the  chambers  opening  below  the  stopcocks.  In 
the  innermost  chamber  was  placed  the  substance  whose  heat  was  to  be 
determined,  in  the  middle  one  ice,  the  melting  of  which  was  the  measure 
of  the  heat  produced,  it  having  been  previously  determined  how  much  heat 
is  required  to  melt  a  given  quantity  of  ice,  while  in  the  outer  chamber 
ice  was  also  placed  in  order  to  shield  that  in  the  middle  chamber  from  the 
external  temperature.  Having  concluded  from  their  experiments  with 
the  ice  calorimeter  that  a  pound  of  carbon,  when  burned,  would  produce 
heat  enough  to  melt  95.6  pounds  of  ice,3  Lavoisier  and  Laplace  then 
placed  a  guinea-pig  in  the  innermost  chamber  of  their  ice  calorimeter, 
so  modified  as  to  permit  of  the  free  passage  of  a  current  of  air,  so  that  the 
respiration  of  the  animal  should  not  be  interfered  with,  and  found  that 
in  ten  hours  402.7  grammes  ((3043.9  grains)  of  ice  had  been  melted. 
But,  of  the  heat  given  out  during  the  experiment,  and  to  the  effect  of 
which  the  melting  of  this  amount  of  ice  was  due,  part  only  evidently 
could  have  been  produced  by  the  guinea-pig,  since,  as  Lavoisier 
observes,  the  animal  must  have  lost  heat  through  exposure  to  the  sur- 
rounding cold ;  further,  the  ice  would  have  been  melted  to  a  certain  extent 
by  the  cooling  of  the  watery  vapor  exhaled  by  the  animal,  while,  finally, 
the  amount  of  the  melted  water,  measuring  the  heat  produced  by  the 
animal,  would  have  been  increased  by  the  admixture  of  the  condensed 
water.  Lavoisier  felt  himself,  therefore,  warranted  in  deducting  from  the 
402.7  grammes  of  ice  actually  melted  61.19  grammes  as  representing 
the  ice  melted  by  the  heat  due  to  the  extraneous  sources  just  mentioned, 
and  not  actually  produced  by  the  animal  during  the  experiment,  the 
latter  being,  of  course,  the  difference,  and  amounting  to  341.07 
grammes.  But,  the  amount  of  carbon  burned  by  the  guinea-pig  while 
in  the  calorimeter,  as  deduced  from  the  carbonic  acid  exhaled,  as 
determined  by  previous  experiments,  would  have  been  only  sufficient  to 

1  Ibid.,  1777,  p.  183.  ;  Mem.  do  I' Acad,  dea  Sciences,  1780,  p.  355. 

3  Or,  as  we  would  now  express  it,  a  pound  (if  carbon  when  burned  in  the  calorimeter  produced  3740 
calories  or  heat  units — that  is,  heat  enough  to  raise  the  temperature  of  1  kilo  of  water  3740°  C.  or  3740 
kilo  of  water  1°  C. 


486  PRODUCTION    OF    ANIMAL    HEAT. 

have  incited  826.75  grammes  of  ice,  whereas,  as  we  have  just  seen,  at 

least  341.07  grammes  must  have  been  actually  produced  by  the  animal, 

it  is  evident  that  some  of  the  heat  produced  by  the  guinea-pig  must 

have    been   due  to   the  combustion   of  some   other  substance  than  its 

/326  75  \ 

carbon,  as  only  96-100th  (  ' --    — -  =0.'JG  )  of   the   heat  could    be  ac- 
J  V341.07  / 

counted  for.1  This  fact,  together  with  another  one  observed  at  the 
time,  namely,  that  all  the  oxygen  absorbed  did  not  return  in  the 
carbonic  acid  exhaled,  led  Lavoisier2  afterward  (1785)  to  the  conclu- 
sion that  of  the  oxygen  inspired  part  combined  with  hydrogen  to  form 
water  and  that  the  heat  developed  by  the  combustion  of  the  hydrogen, 
if  added  to  that  due  to  the  combustion  of  the  carbon,  would  account 
for  the  heat  produced  by  an  animal,  as  in  the  experiment  with  the 
guinea-pig,  just  described,  and  which  could  not  be  accounted  for  by  the 
combustion  of  the  carbon  alone.  The  final  conclusion  of  Lavoisier  as 
to  the  nature  of  respiration  and  calorification,  based  upon  the  closest 
reasoning,  observation,  and  experiments,  extending  over  many  years, 
is  best  expressed  in  his  own  words:3  "  Respiration  is  only  a  slow  com- 
bustion of  carbon  and  hydrogen,  and  which  resembles  in  every  respect 
that  which  goes  on  in  a  lighted  lamp  or  candle,  and,  from  this  point  of 
view,  animals  which  respire  are  true  combustibles,  which  form  and  con- 
sume themselves.  In  respiration,  as  in  combustion,  it  is  the  atmos- 
pheric air  which  furnishes  the  oxygen  and  caloric,4  but,  as  in  respira- 
tion, it  is  the  substance  itself  of  the  animal ;  it  is  the  blood  which 
furnishes  the  combustible.  If  animals  do  not  repair  habitually  by  food 
that  which  they  lose  in  respiration,  the  oil  will  soon  give  out  in  the 
lamp,  and  the  animal  would  perish,  as  a  lamp  extinguishes  itself 
through  want  of  feeding.  The  proof  of  this  identity  of  effects  between 
respiration  and  combustion  is  immediately  furnished  by  experiment. 
In  fact,  the  air  which  has  maintained  respiration  does  not  contain  any 
longer,  at  its  exit  from  the  lungs,  the  same  quantity  of  oxygen ;  it 
contains  not  only  carbonic  acid,  but,  in  addition,  more  water  than  it 
contained  before  inspiration.  But,  as  the  vital  air  can  convert  itself 
into  carbonic  acid  only  by  the  addition  of  carbon,  and  into  water  only 
by  the  addition  of  hydrogen,  and,  as  this  double  combination  can  not 
take  place  without  the  vital  air  losing  a  part  of  its  specific  caloric,  it 
results  that  the  effect  of  respiration  is  to  extract  from  the  blood  a  por- 
tion of  carbon  and  hydrogen,  and,  to  replace  them,  a  portion  of  its 
specific  heat,  which,  during  circulation,  distributes  itself  with  the  blood 
in  all  parts  of  the  animal  economy,  and  maintains  there  that  constant 
temperature  observed  in  all  animals  that  breathe." 

It  would  appear  that  this  analogy,  which  exists  between  respiration 
and  combustion,  had  not  escaped  the  poets,  or  rather  the  philosophers 

1  The  amount  of  ice  actually  melted  was,  according  to  Lavoisier  (op.  cit.,  p.  405),  l.i  oz.,  and  that  esti- 
mated from  the  combustion  of  the  carbon,  10.38  oz.  The  numbers  given  in  the  text  are  those  of  Gavarret, 
op.  cit.,  p.  174. 

2  Hist,  de  la  Societe  Royale  de  Medecine,  17S7,  568. 

3  Mem.  de  l'Acad.  des  Sciences,  1789,  p.  570. 

*  To  appreciate  this  passage  it  must  be  borne  in  mind  that  at  the  date  when  it  was  written  oxygen  was 
supposed  to  be  composed  of  oxygen  united  with  caloric,  the  principle  of  heat  or  fire,  and  that  during  the 
formation  of  carbonic  acid  through  the  combination  of  oxygen  with  carbon  the  caloric  was  set  free. 


THE    CALORIMETER.  487 

of  antiquity,  of  which  they  were  the  interpreters  and  the  organs.  The 
fire  snatched  from  Heaven,  the  flame  of  Prometheus,  is  not  merely  an 
ingenious  and  poetical  idea,  it  is  a  faithful  picture  of  the  operations  of 
nature,  at  least  for  animals  which  breathe.  We  can  only  say  with  the 
ancients  that  the  flame  of  life  is  lit  at  the  moment  that  the  infant 
breathes  for  the  first  time,  and  that  it  is  only  extinguished  with  its 
death.  In  considering  relations  so  happily  we  are  sometimes  led  to 
believe  that,  in  fact,  the  ancients  had  penetrated  further  than  we  think 
in  the  sanctuary  of  knowledge,  their  fables  being  truly  only  allego- 
ries, under  which  they  concealed  the  great  truths  of  medicine  and  of 
physics. 

And  now,  after  a  lapse  of  more  than  a  century,  the  only  essential 
criticism  that  we  can  make  upon  the  magnificent  views  so  poetically 
expressed,  apart  from  the  theory  of  caloric  implied,  is  as  to  the  part  of 
the  body  where  the  combustion  was  supposed  to  take  place,  Lavoisier 
regarding  the  lungs  as  the  seat  of  the  combustion;  whereas,  we  know 
now  that  it  is  going  on  in  all  parts  of  the  body.  But,  even  while 
holding  this  view,  Lavoisier  showed  his  profound  appreciation  of  the 
phenomena,  since  he  distinctly  states,  in  a  previous  communication,1 
that  possibly  the  carbonic  acid  is  not  produced,  but  only  exchanged 
with  oxygen  in  the  lungs.  However  important  his  generalizations  as 
to  the  matter  of  respiration  and  animal  heat,  nevertheless,  dying  on  the 
scaffold  a  victim  to  the  fury  of  the  French  Revolution,  Lavoisier  left 
his  work  unfinished.  With  the  view  of  settling,  if  possible,  some  of 
the  questions  left  undetermined  by  their  great  chemist,  the  Paris 
Academy  offered,  in  1821,  a  prize  for  the  best  essay  on  the  origin  of 
animal  heat.  The  prize  being  awarded  to  Depretz,  his  essay  was 
shortly  afterward  published,2  that  of  the  unsuccessful  competitor, 
Dulong,3  not,  however,  until  several  years  afterward — in  fact,  after  the 
death  of  its  author.  To  avoid  repetition,  we  will  consider  the  appa- 
ratus and  results  of  these  experimenters  together. 

The  calorimeter  of  Dulong  and  Depretz  did  not  differ  in  principle 
essentially  from  the  water  calorimeter  previously  made  use  of,  for  the 
same  purpose,  by  Crawford.4  It  consisted  essentially,  like  the  latter, 
of  two  chambers,  an  inner  one,  in  which  the  animal  within  a  willow 
cage  was  placed,  and  an  outer  one,  containing  the  distilled  water,  the 
elevation  of  whose  temperature  was  taken  as  the  measure  of  the  heat 
produced  by  the  animal.  In  the  calorimeter  of  Crawford,  however, 
while  the  air  of  the  inner  chamber  was  gradually  diminished,  and  at 
the  end  of  the  experiment  was  transferred  to  an  eudiometer  for  analysis, 
in  that  of  Dulong  and  Depretz  the  air  in  the  inner  chamber  was  con- 
tinually renewed  by  air  from  a  gasometer,  and  being  transmitted  from 
the  inner  chamber  through  a  spiral  tube  placed  within  the  water  of  the 
outer  chamber,  passed  thence  into  a  water  gasometer,  where  it  could  be 
measured  and  analyzed,  the  air,  in  the  mean  time,  as  it  passed  through 
the  spiral  tube,  giving  off  the  heat  (communicated  by  the  animal)  to 
the  surrounding  water,  and  so  elevating  its  temperature.     The  amount 

1  Mem.  de  1'Acad.  des  Sciences,  1777,  p.  191.         2  Ann.  de  Chimie  et  de  Physique,  1824,  t.  xxvi.  p.  337. 
3  Ibid.,  3ienie  aerie,  1841,  t.  i.  p.  440.  4  Op.  cit.,  p.  315. 


488  PRODUCTION    OF    ANIMAL    HEAT. 

of  heat  produced  by  the  animal,  as  determined  by  the  elevation  of  the 
temperature  of  the  water,  being  expressed  in  calories,  or  heat  units,  ;i 
heat  unit  being  the  amount  of  heat  necessary  to  elevate  the  temperature 
of  a  pound  of  distilled  water  one  degree  Cent,  or  Fahr.,  according  to 
the  thermometer  used,  or,  as  is  more  usually  understood  at  the  present 
day,  the  amount  of  heat  necessary  to  elevate  the  temperature  of  one 
kilo.  (±2  lbs.)  one  degree  Cent.  The  amount  of  heat  produced  by  the 
animal  expressed  in  heat  units  while  in  the  calorimeter  is  then  obtained 
by  multiplying  the  weight  of  the  water  by  the  number  of  degrees  by 
which  the  temperature  of  the  water  has  been  increased.  Suppose,  for 
example,  that  the,  water  in  the  calorimeter  weighed  20  kilo.,  and  its 
temperature  had  been  elevated  as  shown  by  the  thermometers  two 
degrees  Cent.,  then  40  calories,  or  heat  units,  would  have  been  produced 
during  the  experiment  by  the  animal,  the  latter  having  neither  gained 
nor  lost  heat,  since,  if  the  animal  gained  heat,  it  is  evident  that  all  of 
the  heat  produced  was  not  given  off'  to  the  water,  and  if  it  lost  heat  the 
latter  was  not  produced  during  the  experiment,  but  simply  radiated 
away  from  it,  as  would  have  been  the  case  with  any  heated  body.  In 
the  first  case,  the  heat  retained  by  the  animal  must  be  added  to  the 
heat  as  determined  by  the  calorimeter ;  and,  in  the  second  case,  the 
heat  lost  by  the  animal  must  be  subtracted.  In  making  calorimetrical 
experiments,  therefore,  the  temperature  of  the  animal  must  be  taken  at 
the  beginning  and  the  end  of  the  experiment.  It  must  be  also  remem- 
bered, however,  that  the  materials  entering  into  the  composition  of  the 
calorimeter,  such  as  copper,  iron,  brass,  etc.,  absorb  heat,  even  if  in 
less  amount  than  the  water,  and  this  heat  also  expressed  in  heat  units 
must  be  added  to  that  absorbed  by  the  water.  This  can  be  readily 
estimated,  the  weight  of  the  materials  and  their  specific  heat,  or  capacity 
for  heat,  being  known,  the  capacity  for  heat  of  water  being  taken  as 
unity.  Suppose,  for  simplicity,  that  the  calorimeter  is  made  out  of 
copper,  much  like  the  one  we  shall  use,  and  that  it  weighs  10  kilo. ; 
now  the  specific  heat  of  copper  being  0.09  that  of  water,  it  is  evident 
that  if  the  10  kilo,  of  copper  be  multiplied  by  0.09,  the  product  0.90, 
or  the  water  equivalent,  when  multiplied  by  the  two  degrees  Cent, 
equals  1.8,  which  will  be  the  amount  of  heat  expressed  in  heat  units 
absorbed  by  the  copper,  and  which  must  be  added  to  the  40  heat 
units  already  obtained ;  or,  what  is  the  same  thing,  if  the  water  equiv- 
alent of  the  copper,  0.9,  be  added  to  the  20  kilo,  of  water,  and  the 
result  20.9  be  multiplied  by  2,  the  quotient  will  be  the  same  as  before — 
that  is,  41.8  heat  units  produced  by  the  animal.  In  other  words,  each 
kilo,  of  copper,  having  0.09  the  capacity  of  heat  of  a  kilo,  of  water,  10 
kilo,  of  copper  may  be  regarded  as  equivalent  to  0.9  kilo,  of  water, 
which,  when  added  to  the  20  kilo,  of  water  and  multiplied  by  2,  or 
the  temperature  gained,  gives  41.8  heat  units.  It  is  hardly  necessary 
to  add,  after  Avhat  has  just  been  said,  that  of  the  other  metals  usually 
entering  into  the  construction  of  the  calorimeter  the  heat  absorbed  by 
them,  as  well  as  that  retained  or  given  off  by  the  animal,  which,  as  we 
have  seen,  must  be  added  to  or  subtracted  from  the  41.8  heat  units, 
for  example,  according  as  the  animal  has  gained  or  lost  heat  during  the 
experiment,  is  determined  in  exactly  the  same  way  as  in  the  case  of 


SPECIFIC    HEAT    OF    TISSUES.  489 

the  copper.  As  regards  obtaining  the  water  equivalent  of  the  animal — 
that  is,  its  weight  multiplied  by  its  specific  heat — a  difficulty  presents 
itself,  since  the  specific  heat  of  the  animal  has  not  been  absolutely  deter- 
mined. The  latter  is  usually  accepted  as  being  0.8, l  the  mean  specific 
heat  of  the  tissues  so  far  determined,  that  of  water  being  1.  In  deter- 
mining the  amount  of  heat  given  off  by  an  animal  in  a  calorimeter 
there  is  another  consideration  which  must  not  be  overlooked,  and  which 
is  a  slight  source  of  error  even  in  the  best  constructed  calorimeters. 
That  is  the  slight  loss  of  heat  due  to  conduction  and  radiation  from 
the  instrument,  and  which  cannot  be  entirely  prevented.  The  loss  of 
heat  from  this  cause,  hoAvever,  can  be  reduced  to  a  very  small  amount 
by  proper  precautions,  such  as  surrounding  the  calorimeter  with  down, 
etc.,  as  was  done  by  Crawford,  or  by  lowering  the  temperature  of  the 
water  in  the  calorimeter  some  degrees  below  that  of  the  surrounding 
atmosphere,  the  supposition  being  that  the  heat  absorbed  by  the  sur- 
rounding air  during  the  first  half  of  the  experiment  would  be  radiated 
back  again  during  the  latter  half,  and  that  this  source  of  error  could, 
therefore,  be  neglected,  as  was  admitted  in  the  experiments  of  Dulong 
and  Depretz.  The  loss  of  heat  due  to  radiation,  etc.,  can  be  also  deter- 
mined experimentally,  and  can  be  then  taken  into  account  in  the  final 
calculation ;  or,  by  self-regulating  gas-jets,  heat  can  be  supplied  to 
restore  that  which  is  lost.  Further,  it  is  important  that  the  heat  should 
be  thoroughly  diffused  through  the  water  in  the  calorimeter ;  this  can 
be  accomplished  by  the  stirrers,  as  in  the  apparatus  of  Dulong  and 
Depretz,  or  by  any  other  suitable  mechanical  arrangement.  The  great 
improvement  in  the  experiments  of  Dulong  and  Depretz,  however,  as 
compared  with  those  of  their  predecessors,  consisted  in  comparing  the 
expired  air  with  the  inspired  air,  and  determining  the  amount  of  heat 
produced  and  carbonic  acid  exhaled  simultaneously ;  whereas,  in  the  ex- 
periments of  both  Lavoisier  and  Crawford,  this  was  done  with  the  same 
animal,  but  at  different  times.  Notwithstanding  the  great  number  of 
experiments  performed  by  Dulong  and  Depretz,  and  the  general  accept- 
ance with  which  their  views  were  received,  not  much  importance  can  be 
attached  to  them  at  the  present  day  on  account  of  the  following  reasons : 
First.  That  the  temperature  of  the  animal  within  the  calorimeter  was 
assumed  to  remain  unchanged  during  the  experiment,  although  Lavoi- 
sier had  distinctly  called  attention  to  the  improbability  of  such  being 
the  case.  Second.  Of  the  amount  of  carbonic  acid  exhaled  by  the 
animal  being  underestimated,  part  of  it  being  absorbed  by  the  water  of 
the  gasometer  into  which  it  passes.  Third.  Of  the  amount  of  heat,  as 
deduced  from  the  carbonic  acid  exhaled,  being  also  underestimated, 
both  on  account  of  the  estimate  of  Lavoisier  of  the  heat  produced  by  the 
combustion  of  carbon  and  hydrogen  obtained  with  an  ice  calorimeter, 
being  accepted  as  the  basis  of  comparison  with  the  heat  produced  by  an 
animal  in  a  water  calorimeter,  and  because  the  heat-producing  power  of 
the  carbon  and  hydrogen  burned  even,  as  determined  by  Lavoisier,  is 
manifestly  too  low  as  shown  by  the  later  and  accurate  experiments  of 
Fabre  and  Silberman;-  and  further,  that  no  account  was  taken  of  the 

1  Liebermeister :  Handbuch  der  Pathologic  u.  Therapie  des  Fiebers,  p.  147.     Leipzig,  1875.     Rosen- 
thal :  Archiv  f.  Anat..  etc.,  1878,  p.  215. 
'-'  Ann.  do  Chimie  et  de  Physique,  3ieme  ser.,  t.  xxxiv.  p.  357  ;  t.  xxxvi.  p.  51  ;  t.  xxxvii.  p.  405. 


490  PRODUCTION     OF    ANIMAL     HEAT. 

heat  produced  by  the  burning  of  the  sulphur  and  phosphorus  in  the 

animal  economy.  Fourth.  That  the  ratio  of  the  carbon  to  the  hydrogen 
was  erroneously  estimated,  an  important  source  of  error,  since  far  more 
heat  is  produced  by  the  combustion  of  hydrogen  than  by  an  equal  weight 
of  carbon.  Fifth.  From  the  carbon  and  hydrogen,  to  whose  combustion 
is  the  heat  principally  due,  being  supposed  to  exist  in  the  free  con- 
dition, which  they  evidently  do  not.  Sixth.  From  the  fact,  to  a  cer- 
tain extent,  of  the  exhalation  of  carbonic  acid  and  water  not  being  a 
measure  of  the  heat  produced,  some  heat  being  evolved  through  double 
decomposition  and  hydration,  etc.,  without  carbonic  acid  and  water 
being  necessarily  exhaled  and  of  carbonic  acid  and  water  being  exhaled 
through  the  decomposition  of  the  principles  containing  these  substances, 
without  the  heat  being  evolved.  This  last  objection  applies  to  all  calori- 
metrical  experiments  in  which  the  heat  produced  by  the  living  body  is 
estimated  from  the  carbonic  acid  and  water  exhaled.  It  is  true,  that 
later  investigators  have  endeavored  to  utilize  the  results  of  Dulono;  and 
Depretz  in  considering  them  as  influenced  by  the  conditions  just  referred 
to,  since  the  attempts,  however,  have  been  far  from  satisfactory,  it  is 
not  necessary  for  me  to  dwell  upon  them.  While  the  results  of  Dulong 
and  Depretz,  even  when  so  corrected,  cannot  be  accepted,  nevertheless 
the  conclusion  arrived  at  by  these  experimenters  exercised  a  most  impor- 
tant and  beneficial  influence  upon  the  progress  of  physiology,  since  it 
was  shown  by  them  that  the  experimental  method  was  the  only  one  by 
which  the  phenomena  of  animal  heat  could  be  successfully  studied,  that 
so-called  vital  phenomena  are  physico-chemical  phenomena,  and  must 
be  investigated  in  exactly  the  same  manner  as  the  latter,  a  view  wdiich 
had  fallen  entirely  into  disrepute  in  France  since  the  death  of  Lavoisier, 
the  influence  of  Bichat  being  so  preeminent.  In  the  words  of  that  other- 
wise profound  thinker,1  "let  us  leave  to  chemistry  its  affinity,  as  to 
physics  its  elasticity,  its  gravity — let  us  employ  for  physiology  only 
sensibility  and  contractility." 

To  the  deus  ex  machina,  the  vital  force,  that  physiological  fetich,  then 
as  even  now  every  unexplained  phenomenon  was  attributed.  Indeed, 
it  may  yet  be  asked  how  long  will  it  be  before  such  an  idea  as  a  vital 
force  acting  as  an  entity  is  entirely  banished  to  that  obscurity  where 
such  a  conception  similar  to  that  of  nature  abhorring  a  vacuum,  etc., 
has  long  since  been  relegated.  During  late  years  a  number  of  investi- 
gations have  been  made  calorimetrically,  with  the  object  of  determining 
the  heat  produced  by  an  animal  in  a  given  time.  Among  these  may 
be  mentioned  especially  those  of  Senator2  upon  dogs.  The  calorimeter 
used  in  these  experiments  was  essentially  the  same  as  that  of  Dulong's, 
the  only  difference  being  that  it  was  usually  filled  with  warm  water  in 
order  to  prevent  the  animal  losing  heat.  The  ventilation  of  the  chamber 
in  which  the  animal  was  placed  was  maintained  by  aspiration,  the  cur- 
rent of  air,  before  entering  the  calorimeter,  being  freed  from  its  carbonic 
acid  by  passing  it  through  potash,  and  the  carbonic  acid  exhaled  into  it 
by  the  animal  being  determined  after  it  left  it  by  Pettenkofer's  method. 
In  the  final  estimation  of  the  heat  produced  by  the  animal  in  addition 
to  that  taken  up  by  the  calorimeter,  the  heat  absorbed  by  the  air  passing 

i  Anatomie  Generale,  tome  i.  p.  16.    Paris,  1818.        2  Archiv  f.  Anat.  u.  Phys.,  1872,  S.  1 ;  1874,  S  18. 


THE   CALORIMETER. 


491 


through  as  well  as  that  lost  through  conduction  and  radiation,  was  also 
taken  into  consideration.  Senator  found,  as  the  mean  of  his  experi- 
ments, that  a  dog  fed  daily  produced  16.5  calories  or  heat  units  per 
hour,  with  an  exhalation  during  the  same  time  of  4.4  grammes  of  car- 
bonic acid,  as  a  general  rule,  there  being  produced  2.5  calories  for  every 
kilo.  (2.2  lbs.)  of  weight.  In  order  to  obtain  the  amount  of  heat  pro- 
duced in  twenty -four  hours,  it  is  usual  to  multiply  the  16.5  calories, 
e.  //..  by  24,  but  as  it  is  uncertain  whether  the  production  of  heat  is 
constant,  this  is  hardly  admissible.  The  general  conclusion  to  be  drawn 
from  the  experiments  of  Senator  is,  that  there  is  no  constant  relation 
existing  between  the  production  of  heat  and  the  exhalation  of  carbonic 
acid,  and  while  during  digestion  the  production  of  both  is  increased,  in 
starvation  both  are  diminished. 

The  calorimeter  (Fig.  257)  that  we  make  use  of  consists  of  two  copper 
cylinders  concentrically  disposed,  the  outer  space  a,  or  the  space  between 

Fig.  257. 


Calorimeter. 


the  cylinders  being  closed  at  both  ends  with  copper,  the  inner  space  b, 
or  the  space  within  the  cylinder,  being  closed  at  one  end  by  copper 
and  at  the  other  end  by  an  annular  door  consisting  of  brass  and  glass, 
and  which  can  be  hermetically  closed  by  the  brass  clamps  and  rubber 
facing  soldered  to  the  brass  rim  internally.  The  outer  chamber  a  is 
filled  with  distilled  water  by  means  of  a  funnel  introduced  through  the 
opening/',  and  when  full  contains  18.1  kilo.  (40  lbs.)  of  water.  The 
inner  chamber  b,  at  the  end  opposite  the  door,  communicates  by  a  stop- 
cock (d)  with  the  external  air.  and  through  the  opening  h  in  its  roof 
with  a  copper  spiral,  which,  after  making  a  dozen  turns  around  the  inner 
cylinder  within  the  water  of  the  outer  chamber,  terminates  in  the  open- 
ing k  of  the  latter.  By  means  of  the  mercurial  pump  (already  described) 
the  ventilation  of  the  inner  chamber  can  be  thoroughly  maintained, 


492  PRODUCTION    OF    ANIMAL    HEAT. 

the  air  entering  the  latter  through  the  opening  at  d  and  passing  thence 
by  the  opening  h  into  the  spiral  i  and  out  by  the  opening  k  with  the 
same  temperature  at  which  it  entered,  the  heated  air  being  gradually 
cooled  as  it  passes  through  the  spiral,  the  heat  being  absorbed  by  the 
surrounding  water.  If  it  is  desired  to  compare  the  expired  with  the  in- 
spired air,  the  air  freed  from  its  water  and  carbonic  acid  by  Voit's  method 
is  made  to  pass  through  a  meter,  before  it  enters  the  calorimeter  and 
through  one  after  it  leaves  it,  being  previously  freed  from  its  water  and 
carbonic  acid  in  the  same  manner  as  was  the  inspired  air.  Fitting  in  the 
floor  of  the  inner  chamber  of  the  calorimeter  is  a  movable  copper  pan 
with  a  sieve-like  cover  on  which  the  animal  rests,  the  object  of  the  cover 
being  that  the  urine  of  the  animal  can  trickle  into  the  pan  and  insure 
cleanliness.  Ventilation  having  been  assured  by  the  action  of  the  pump, 
and  the  temperature  of  the  water  in  the  outer  chamber  noted  by  introduc- 
ing a  thermometer  into  the  opening/  and  that  of  the  animal  taken,  the 
latter,  having  been  previously  weighed,  is  placed  within  the  chamber  on 
the  tray  and  the  door  securely  closed.  Suppose  the  experiment  has  lasted 
one  hour,  and  it  be  admitted  that  the  heat  lost  by  radiation  and  conduc- 
tion from  the  calorimeter  be  replaced  by  that  furnished  by  the  gas  jets, 
the  flow  of  gas  being  regulated  by  the  valve  V,  which  with  the  heating 
of  the  water  is  pressed  outward  (through  the  pressure  of  the  column  of 
water  in  the  tube  t,  replacing  the  thermometer)  against  the  opening 
transmitting  the  gas  and  thereby  diminishing  its  flow,  and  which  with 
the  cooling  of  the  water,  is  drawn  back  again  from  the  opening,  thereby 
increasing  it  again.  To  determine  the  calories  or  heat  units  produced 
by  the  animal,  a  rabbit,  for  example,  during  the  time  mentioned,  we 
have  only  now  to  multiply  the  number  of  degrees  by  which  the  tempera- 
ture of  the  water  has  been  increased  by  its  weight,  to  which  has  been 
added  the  water  equivalent  of  the  copper,  brass,  glass,  rubber,  and  solder 
entering;  into  the  construction  of  the  calorimeter,  and  adding  or  subtract- 

©  © 

ing  the  heat  gained  or  lost  by  the  animal  as  determined  immediately  at 
the  conclusion  of  the  experiment.  Suppose  that  the  temperature  of  the 
water  in  the  calorimeter  has  increased  0.5°  C,  the  temperature  at  the 
beginning  of  the  experiment  being  15°  C.  (59°  F.),  and  at  the  end 
15.5°  C.  (59.9°  F.),  and  the 


'ate 

r  equivalent. 

copper 

= 

21  lbs. 

X 

0.095 

= 

1.995 

It 

" 

brass 

= 

23.25  lbs. 

X 

0.093 

;= 

2.162 

tl 

" 

iron 

= 

0.09     " 

X 

0.11 

= 

0.009 

it 

" 

glass 

= 

1.25     " 

X 

0.19 

= 

0.237 

it 

a 

rubber 

= 

0.6       " 

X 

(1) 

= 

0. o1 

11 

a 

tin 

= 

0.5       " 

X 

0.05 

= 

0.025 

it 

a 
a 

leaH 

= 

0.5      " 

X 

0.03 

= 

0.015 

it 

materials 

= 

4.443 

x\dding  the  water  equivalent  of  the  materials  used,  4.4  lbs.,  to  the 
weight  of  the  water,  40  lbs.,  making  44.4  lbs.,  or  20.1  kilo.,  and  multi- 
plying the  latter  by  0.5°  C,  the  number  of  degrees  gained  by  the  water, 
the  product,  10.05,  will  be  the  number  of  calories  or  heat  units  produced 

1  Specific  heat  of  rubber  slip  not  being  determined,  the  heat  actually  produced  was  slightly  greater 
than  that  given  in  text.     The  amount,  however,  would  be  so  small  that  it  may  be  neglected. 


HEAT     PRODUCED    IN     TWENTY-FOUR    HOURS.  -193 

by  the  animal,  supposing  the  temperature  of  the  latter  to  have  remained 
unchanged.  Suppose  the  animal,  however,  lost  0.9°  C,  its  temperature 
being  39.2°  C.  at  the  beginning  of  the  experiment  and  38.3°  C.  at  the 
end,  then  there  must  be  subtracted  from  the  10.05  calories  2.16 — that 
is,  the  product  of  the  weight  of  the  rabbit,  6.6  lbs.  or  3  kilo.,  by  its  spe- 
cific heat,  0.8°  by  0.9°  (3  X  0.8  X  0.9  =  2.16):  the  total  number  of 
heat  units  produced  by  the  rabbit  in  the  hour  would  then  be  7.8  calories. 
If  the  rabbit  gains  the  same  number  of  degrees,  then  the  2.16  calories 
must  be  added  to  instead  of  being  subtracted  from  the  10.05  heat  units. 
Calorimetrical  investigations  have  been  made  also  upon  man  by  Schar- 
ling,1  Vogel,2  and  Hirn,3  but  with  rather  unsatisfactory  results.  The 
apparatus  made  use  of  by  these  experimenters  was  essentially  the  same, 
consisting  of  a  chamber  in  which  the  man  was  placed  and  which  was 
kept  in  a  room  maintained  at  a  temperature  as  constant  as  possible, 
the  increase  in  the  temperature  of  the  chamber,  together  with  the  heat 
lost  through  cooling,  being  regarded  as  produced  by  the  man  during  the 
experiment.  Since  the  temperature  of  the  chamber  after  being  some- 
what elevated  after  that  remains  constant,  the  heat  as  produced  being 
radiated  away,  according  to  the  Xewtonian  law  of  cooling,  the  amount 
of  heat  produced  will  be  equal  to  the  difference  between  the  constant 
temperature  and  the  initial  temperature  multiplied  by  the  coefficient  of 
cooling,  the  latter  being  determined  experimentally.  In  the  experiments 
of  Scharling  and  Yogel  this  was  accomplished  by  placing  a  vessel  filled 
with  hot  water  in  the  chamber  and  comparing  the  loss  of  heat  with  the 
increase  of  the  chamber,  and  in  those  of  Hirn  by  burning  hydrogen  and 
comparing  the  actual  result  Avith  that  obtained  by  calculation.  On 
account  of  the  many  sources  of  error  incidental  to  such  a  crude  method 
of  experimentation  as  that  just  described,  an  approximate  value  only  can 
be  attached  to  the  results  so  obtained,  and  the  same  may  be  said  of  the 
estimates  of  the  amount  of  heat  produced  based  upon  the  rise  in  the 
temperature  of  the  water  of  a  bath  in  which  a  man  is  immersed,4  or  of 
that  of  a  calorimeter  inclosing  only  a  part  of  a  person,  a  limb,  for  ex- 
ample.5 Nevertheless,  it  should  be  mentioned  that  the  estimates  of  these 
observers  of  the  heat  produced  by  a  man  in  twenty-four  hours  do  not 
differ  as  much  as  might  be  supposed,  amounting,  according  to  Scharling, 
Vogel,  Hirn,  Liebermann,  and  Leyden,  to  3168,  2400,  3720,  3525,  and 
2376  calories  respectively,  allowance  being  made  for  the  size  and  weight 
of  the  individual  experimented  upon. 

Since  the  heat  produced  by  an  animal  is  due  to  the  combustion  of 
its  food,  it  might  appear  at  first  sight  that  it  would  be  only  necessary  to 
determine  the  amount  of  combustible  materials,  carbon,  hydrogen,  sul- 
phur, phosphorus,  etc.,  in  the  food,  and  the  products  of  its  combustion 
carbonic  acid,  water,  urea,  etc.,  in  the  excreta  in  order  to  determine 
the  amount  of  heat  produced,  on  the  principle  of  the  heat  produced  by 
the  animal  depending  upon  the  fuel  supplied  and  consumed,  the  calori- 
meter being  used  as  a  test  of  the  accuracy  of  the  results  so  obtained. 

1  Journal  fiir  pract.  Chemie,  xlviii.  S.  435,  1849. 
-  Arcliiv  (1.  ver.  !'.  Wiss.  Heilk.  Neue  folge,  Band  i.  S.  441.     1865. 

3  Kecherches  sur  1' equivalent  mecanique  de  la  chaleur,  Oolmar,  1858.     Exposition  analytique  et  ex- 
perimentale  de  la  theorie  mecanique  tie  la  chaleur,  3d  ed.,  t.  i.  p.  27.     Paris,  1st.",. 
•  Liebermeister,  >>\>.  >it.,  p.  239.  »  Leyden  :  Deutseh.  Arcliiv  f.  klin.  med.,  1869,  S.  273. 


494  PRODUCTION    OF     ANIMAL     HEAT. 

It  must  be  borne  in  mind,  however,  that  to  effect  the  combustion  of  the 
food — that  is,  its  transformation  into  carbonic  acid,  water,  etc.,  a  certain 
amount  of  beat,  or  an  equal  amount  of  force  of  some  kind,  is  required, 
since  the  carbon,  hydrogen,  and  other  combustible  matters  do  not 
exist  in  the  food  in  the  free  gaseous  state,  but  in  a  state  of  molecular 
combination.  A  certain  unknown  amount  of  heat  would  have  to  be 
deducted  therefore  from  the  amount  estimated  if  based  upon  an 
analysis  of  the  food  and  the  excreta.  In  other  words,  the  heat  pro- 
ducing power  of  food,  or  any  fuel,  cannot  be  estimated  from  the 
amount  of  combustible  matters  it  may  contain,  since  the  heat  to  be 
expended  in  breaking  up  the  chemical  combinations  constituting  these 
matters,  and  of  setting  free  the  heat  previously  locked  up  in  them  is 
practically  unknown.  It  is  for  the  reasons  just  given,  as  well  as  for 
the  further  one  of  the  accepted  estimates  of  Dulong  of  the  amount 
of  heat  produced  by  the  combustion  of  a  given  weight  of  carbon, 
hydrogen  being  too  low,  that  the  calculation  of  Helmholtz1  of  the 
amount  of  heat  produced  by  a  man  weighing  82  kilo,  in  twenty-four 
hours,  viz.,  2731.2  calories,  can  only  be  accepted  as  approximating 
the  truth.  And  while  the  calculation  of  Ludwig,2  of  a  daily  produc- 
tion on  the  average  of  3191.9  calories  is  free  from  the  last  source  of 
error  mentioned,  being  based  upon  the  data  of  Barral  and  the  higher 
estimates  of  Fabre  and  Silberman  of  the  heat  value  of  the  carbon  and 
hydrogen  burned,  nevertheless,  as  it  also  assumes  that  the  combustion 
of  the  carbon  and  hydrogen  of  the  food  develops  as  much  heat  as  if 
existing  in  the  free  condition,  it  is  open  to  the  same  objection  as  the 
calculation  of  Helmholtz.  In  fact,  the  only  way  in  which  the  amount 
of  heat  produced  through  the  combustion  of  food  can  be  actually  deter- 
mined, is  by  burning  it  in  a  calorimeter,  as  was  done  by  Frankland,3 
and  of  so  obtaining  its  heat  value  by  direct  experimentation.  The 
instrument  we  make  use  of  for  this  purpose,  the  same  as  that  of  Frank- 
land,  of  the  convenient  form  devised  by  Thompson,  consists  of  a  copper 
cylinder  with  a  capacity  of  120  c.  cm.  open  below,  and  with  the  rim 
perforated  by  a  small  opening,  but  closed  above,  and  with  the  cavity  of 
the  cylinder  prolonged  into  a  narrow  tube  provided  with  a  stopcock 
near  its  end,  and  of  a  smaller  cylinder  with  a  capacity  of  15  c.  cm. 
open  above,  but  closed  below,  the  lower  portion  of  the  cylinder  fitting 
into  the  little  cup  of  the  stand,  the  latter  being  provided  with  three 
elastic  springs  which  securely  hold  the  large  cylinder  when  the  latter 
encloses  the  small  one  Within  the  small  cylinder  is  placed  the 
substance  to  be  burned  with  a  small  fuse  attached  with  a  combustible 
whose  heat  values  are  known.  The  latter  being  lighted,  the  large 
cylinder  is  immediately  placed  over  the  small  one,  the  elastic  springs 
holding  it  fast,  and  the  instrument  so  put  together  at  once  plunged  into 
a  long,  narrow  vase  containing  a  known  quantity  of  distilled  water 
whose  temperature  has  been  accurately  determined  by  a  specially 
constructed  thermometer  graduated  into  tenths.  In  a  few  moments 
fumes  will  be  seen    to   issue  from  the   holes   in   the  rim  of  the  outer 

1  Encyl.  Worterbnch  der  Med.  Wissen,  Band  xxxv.  S.  55.5      Berlin,  1846. 

2  Lebrbuch  der  Physiologie  des  Menschen,  Zweiter  Auflage,  Zweite  Band,  S.  749.     Leipzig,  1861. 

3  Pbilos.  Mag.,  1866,  xxxii.  p.  182. 


HEAT  VALUE  OF  FOODS.  495 

cylinder  into  the  surrounding  water.  The  deflagration  being  ended, 
and  the  stopcock  opened,  the  water  will  rise  through  the  holes  into 
the  cylinders.  The  instrument  being  moved  up  and  down,  the  heat 
given  out  will  soon  diffuse  itself  equally  throughout  the  water,  the 
amount  of  heat  produced  by  the  food  burned  being  determined  by 
the  elevation  of  the  temperature  of  the  latter,  due  allowance  being 
made  on  the  one  hand  for  the  heat  absorbed  by  the  copper,  etc.,  and 
on  the  other  for  that  produced  by  the  burning  of  the  fuse  and  com- 
bustible used.  The  other  sources  of  error  incidental  to  the  working;; 
of  the  apparatus  are  so  slight  that  they  may  be,  according  to  Frank- 
land,  neglected.  It  was  by  means  of  the  calorimeter  just  described 
that  Frankland  determined  by  actual  experiment  the  amount  of  heat 
developed  by  the  combustion  of  different  kinds  of  food.  It  will  be  seen, 
however,  at  a  glance  at  Table  LXYIL,  drawn  up  from  the  results 
obtained  by  this  observer,  that  the  fatty  and  carbohydrate  foods  are  as 
thoroughly  burned  in  the  body  as  out  of  it,  though  more  slowly, 
whereas  the  albuminous  substances  are  but  imperfectly  so.  This  is  as 
might  have  been  expected,  since,  as  Ave  have  already  mentioned,  except 
in  certain  temporary  conditions  in  a  state  of  health,  fat  and  starch  are 
never  found  in  the  excreta,  these  substances  passing  out  of  the  body  as 
carbonic  acid  and  water,  being  as  thoroughly  oxidized  within  the  svstem 
as  if  burned  in  pure  oxygen  outside  of  it,  whereas,  as  we  shall  presently 
see,  uric  acid  and  urea  are  normal  constant  ingredients  of  the  excreta, 
these  substances  representing  so  much  unburned  albumen  which  passes 
out  of  the  system  in  this  form. 

Table  LXVII.1 — Heat  developed  by  burning  1  gramme  (15.4  gr.)  of 

DIFFERENT  ARTICLES  OF  FOOD  EXPRESSED  IN  HEAT  UNITS. 

A  heat  unit  is  equal  to  the  amount  of  heat  necessarv  to  raise  the  temperature 
of  1  kilo.  (2.2  lbs.)  of  distilled  water  1°  Cent.  (1.8°  F.). 


When  oxidized  outside  of  body.        When  oxidized  inside  of  body. 


Cod-liver  oi  1 
Fat  of  beef 

Butter 

Guiness'  stout    . 

Arrowroot 

Lump  sugar 

Grape  sugar 

Yelk  of  egg 

Hard  boiled  egg 

Cheese 

Mackerel 

Lean  of  beef 

Milk. 

White  of  egg     . 

Veal  . 

Ham  (boiled)     . 

Bread  (crumb)  . 

Flour 

Rice  (ground)    . 

Cabbage     . 

Potatoes     . 


Dry. 

Natural  condition. 

Dry. 

Natural  condition. 

9.107 

9.107 

9.069 

9.069 

7.264 

7.264 

6.401 

1.076 

6.401 

1.076 

3.912 

3.912 

3.348 

3.348 

3.227 

3.227 

6.460 

3.423 

6.24 ' 

3.30 

6.321 

2.383 

6.05 

2.2S 

6.114 

4.647 

•">.74 

4  36 

6.064 

1.789 

5.71 

1.61 

5.313 

1.567 

4.S."> 

1.42 

5.093 

0.662 

5.07 

0.62 

4.896 

0.671 

4.21 

0.57 

4.514 

1.314 

4.02 

1.11 

4.343 

1.980 

3.68 

1.68 

3.984 

2.231 

3.84 

1 .45 

3.936 

3.84 

3.813 

3.76 

3.776 

0.434 

3.65 ' 

0.42 

3.752 

1.013 

3.69 

0.99 

1  Frank  1 

and,  op.  cit. 

496  PRODUCTION    OF    HEAT. 

According  to  Frankland,  while  1  gramme  of  ox  flesh  and  of  albumen 
will  produce,  when  burned  out  of  the  body,  5.103  and  4.988  heat 
units,  the  same  amount  of  these  substances  when  burned  in  the  body 
will  produce  only  4.368  and  4.263  heat  units  respectively,  the  differ- 
ence of  <>.73.r)  heat  unit  being  due  to  that  amount  of  heat  passing  out 
of  the  system  latent  locked  up — so  to  speak — in  the  urea  or  theunburned 
albumen,  1  gramme  of  urea  producing,  when  burned  outside  of  the 
body,  2.206  bent  units.  In  estimating  the  amount  of  heat  produced 
by  the  burning  of  albumen  within  the  body,  as  based  upon  that  pro- 
duced when  burnt  outside  of  it,  about  one-third  must  therefore  be 
deducted  as  representing  so  much  incombustible  matter.  Thus  1 
gramme  of  albumen,  when  burned  outside  of  the  body,  will  give  4.998 
heat  units,  of  which  albumen  and  urea  constitute  about  one-third ;  deduct- 
ing 0.735  heat  unit,  or  the  heat  that  would  be  produced  were  the 
urea  burned  in  the  system,  there  remain  4.263  heat  units  as  the  actual 
amount  of  heat  produced  when  the  albumen  is  burned  in  the  system. 

Having  learned  the  amount  of  heat  developed  in  the  burning  of  a 
given  weight  of  sugar,  fat,  albumen,  etc.,  out  of  the  body,  it  still 
remains,  knowing  by  analysis  how  much  of  such  substances  is  con- 
tained in  the  food,  to  determine  from  the  carbonic  acid,  water,  and  urea  in 
the  excreta,  or  the  products  of  the  combustion  of  such  substances,  the 
amount  actually  burned  in  the  body,  and  of  so  estimating,  by  means  of 
the  above  data  of  Frankland,  the  amount  of  heat  developed  within  the 
body  on  a  normal  diet,  or  otherwise.  In  other  words,  the  ingesta  or  the 
food  must  be  compared  with  the  egesta  or  the  excretions.  The  subject 
of  the  observation  must  be  weighed  at  the  beginning  and  the  end  of  the 
experiment  to  learn  whether  the  weight  has  remained  unchanged,  since, 
if  the  individual  loses  weight,  the  food  has  been  deficient,  the  body 
wasting  to  supply  it ;  and,  if  the  reverse  is  the  case,  the  food  has  been 
in  excess,  the  body  fattening.  Further,  the  experiment  should  extend 
over  a  period  of  twenty-four  hours,  and  longer,  when  possible,  in 
order  to  avoid  the  usual  source  of  errors  incidental  to  all  experiments 
of  such  a  character  if  lasting  for  shorter  periods  of  time.  It  was  on 
such  prineiples  that  the  admirable  experiments  of  Ranke,  performed  upon 
himself,  were  conducted,  and  it  may  be  mentioned,  incidentally,  in  this 
connection,  that  at  that  time  the  distinguished  physiologist  was  twenty- 
four  years  old,  six  feet  high,  weighed  one  hundred  and  fifty-four  pounds 
(70  kilos.),  was  in  perfect  health,  and  that  the  apparatus  made  use  of 
was  the  Pettenkofer  respiration  apparatus  that  we  have  already  referred 
to.  The  results  obtained  by  Ranke,  by  means  of  the  method  just 
described,  may  be  seen  from  Table  LXVIII. 


HEAT    VALUE    OF    FOODS. 


497 


Table  LXVIII.1 — Heat  produced  in  24  hours  by  the  combustion  of 

FOOD    WITHIN    THE    BODY    AS    ESTIMATED   FROM   THE   EGESTA,    AND    EX- 
PRESSED IN  HEAT  UNITS. 

Nitrogenous  Diet. 

Ingesta. 

Meat.  1832  grammes, 

1300     "    consume 
Fat  of  meat,  70     " 
Salts,  31     " 

Water,        3371  c.c. 
Fat  of  body,  75.14  grammes, 
Water     "  *    71.00 


Initial  weight 
Terminal  weight 


Heat  units  produced 


Ingesta. 

Body  consumed. 

Albumen,       54.45  grammes. 

Fat,  195.94 


N 

0 

Egesta.                   N 

c 

G2.29 

229.3(3 

Urea,        86.3     40.28 

17.26 

44.19 

162.75 

Uric  acid,  1.9       0.65 

0.70 

0.00 

50.27 

Salts,         26.6 
Urine,  2073  c.c. 

b.'ob 

54.02 

Feces,       99.0       3.26 

14.88 

Respiration, 

44.19 

231.20 

44.19 

267.04 

267.04 

.     72.927  Ml. 

.     72.781    " 

0.146  gramme. 

2779.5 

Starvation  Diet. 

Heat  units  produced    .... 

Non-nitrogenous  Diet 
Ingesta. 

Starch,  300  grammes.  Urea, 

Sugar,  100  Uric  acid, 

Fat,  150         "  Feces, 

Albumen  of  body,  51.55       "  Respiration, 


Egesta. 

Urea,  18.3    grammes. 

Uric  acid,  0.24         " 

Respiration,  180.00  cubic  metres. 

.     2012.8 


Heat  units  produced 


Heat  units  produced 


Mixed  Diet. 


Egesta. 

17.1 

0.54 
90.00 
200.00  cubic  metres. 

.     2059.5 


2200 


It  Avill  be  observed  by  looking  at  the  table  that  the  greatest  amount 
of  heat  was  produced  on  a  nitrogenous,  or  a  very  abundant  meat  diet, 
but  that  this  was  accomplished  at  the  expense  of  the  body,  Ranke  losing 
14(3  grammes  in  weight,  his  body  supplying  75.14  grammes  of  fat  in 
addition  to  the  70  grammes  of  roast  meat  and  71  grammes  of  water, 
and  that  of  the  1832  grammes  of  meat  eaten  only  1300  grammes  wrere 
burned,  as  shown  by  the  amount  of  urea  excreted.  It  follows,  there- 
fore, that,  so  far  as  the  production  of  heat  was  concerned,  the  same 
result  might  have  been  obtained  with  532  less  grammes  of  meat,  but 
with  71  more  grammes  of  fat.  On  the  other  hand,  as  Ranke  mentions 
in  speaking  of  the  heat  produced  on  a  non-nitrogenous  diet,  of  the  150 
grammes  of  fat  eaten  only  68.5  grammes  could  have  been  burned,  81.5 
grammes  having  been  deposited  in  the  body.  On  such  a  diet,  there- 
fore, more  than  half  the  fat,  if  taken  with  the  view  of  producing  heat, 
would  be  superfluous.  While  the  heat  developed  on  a  mixed  diet,  as 
may  be  seen  from  Table  LXVIII.,  amounts,  according  to  Ranke,  to  2200 


i  Ranke  :  Physiologic  Dritte  Aufl.,  S.  196,  S.  5G6.     Leipzig,  1875. 
32 


49"  PRODUCTION    OF    ANIMAL    HEAT. 

heat  units,  Vierordt1  estimates  it  at  2497,  and  Voit2  even  still  higher 
(3066).  It  should  be  mentioned,  however,  that  the  food,  at  the  expense 
of  which  the  latter  amount  of  heat  is  produced,  contains  far  more 
albumen,  fat,  starch,  sugar,  etc.,  than  that  taken  by  Ranke 3  in  his 
experiments,  as  may  be  seen  from  the  following  : 


Table 

lxix. 

Albumi  n. 

(•'at.              St 

iireh  or  sugar. 

Total. 

Ranke 

.      100 

100 

240 

440  grammes, 

Vierordt 

.     120 

90 

330 

.".40 

Voit       . 

.     118 

50 

500 

668 

Let  us  take,  however,  the  lowest  estimate,  that  of  Ranke,  and  sup- 
pose that  the  heat  produced  by  the  burning  of  the  food  will  produce 
2200  heat  units — that  is,  an  amount  of  heat  that  will  elevate  the  tem- 
perature of  2200  kilo,  of  distilled  water  one  degree  Cent.,  that  is,  70 
kilo.  31.4°  C,  or,  what  is  the  same  thing,  154  pounds  of  water  56.5° 
F. :  such  an  amount  of  heat,  if  applied  to  the  heating  of  the  human 
body,  would  elevate  its  temperature  1.7°  C,  or  3°  F.  higher,  since 
a  human  being  weighing  70  kilo.  (154  pounds)  consists  of  only  three- 
fifths  water,  the  remaining  two-fifths  being  tissue,  and  the  specific  heat 
of  the  latter  being  less  (0.8)  than  that  of  the  water,  the  same  amount 
of  heat,  namely,  2200  heat  units,  when  applied  to  the  heating  of  a 
body  weighing  70  kilo.,  consisting  of  44.1  kilo,  of  water  and  25.9 
of  tissue,  must  naturally  elevate  its  temperature  higher  than  if  the 
70  kilo,  to  be  heated  consisted  of  water  alone,  as  shown  by  the  fol- 
lowing :  25.9  kilo,  of  tissue  multiplied  by  its  specific  heat,  0.8,  gives 
20.7  kilo,  to  be  added  to  the  44.1  kilo,  of  water,  making  64.8  kilo,  of 
water  to  be  heated  instead  of  70  kilo. ;  dividing  the  2200  kilo,  by  the 
former  number,  64.8,  the  quotient,  33.1°  C.  (59.5°  F.),  is  the  number  of 
degrees  to  which  the  temperature  of  a  man  weighing  70  kilo.  (154 
pounds)  would  be  elevated  by  the  burning  of  his  food.  In  other  words, 
the  tissue  of  the  human  body,  from  this  point  of  view,  bears  the  same 
relation  to  its  water  as  the  brass,  copper,  etc.,  do  to  the  water  of  the 
calorimeter,  the  human  body,  in  fact,  serving  as  a  calorimeter  for  the 
determination  of  the  heat  value  of  foods  when  burned  within  the  body. 
Suppose  the  temperature  of  the  human  body,  for  example,  was  reduced 
to  70°  F.,  or  lower,  as  is  the  case  in  cholera,  it  is  evident  on  the  above 
supposition  that,  upon  a  normal  diet,  the  temperature  would  be  elevated 
within  twenty-four  hours  to  about  131°  F.  On  the  other  hand,  suppose 
the  temperature  of  the  body  was  normal,  the  heat  of  the  food  would 
elevate  it  from  98.9°  F.  to  nearly  160°  F.,  and  yet,  as  we  have  already 
seen,  the  temperature  of  the  human  body  varies  but  little. 

It  now  remains  for  us,  in  conclusion,  to  endeavor  to  account  for  this 
constant  temperature  somewhat  more  in  detail  than  we  have  already 
done,  and  that  leads  us  to  the  consideration  of  the  expenditure  of  the 
heat  produced. 

1  Physiologic  Vierte  Aufi.  S.  257.     Tub.,  1871. 

3  Ueber  ie  Kost  iu  einig.  offent  AnstalteD,  1877.  3  Ranke,  op.  cit.,  p.  207. 


CHAPTER    XXXIII. 

EXPENDITURE  AND  REGULATION  OF  HEAT. 

We  have  seen  that  there  are  produced  within  the  human  body  in 
twenty-four  hours  between  2200  and  2300  calories,  or  heat  units;  that 
is,  heat  enough  to  raise  the  temperature  of  2300  kilo,  of  water  1°  C, 
or  23  kilo.  100°  C,  or,  what  is  the  same  thing,  about  50  pounds   of 
water  from  the  freezing  to  the  boiling  point.     It  is  very  evident,  there- 
fore, that  were  such  a  production  of  heat  kept  up,  and  the  heat  developed 
not  dissipated,  but  retained  in  the  body,  that  the  latter,  in  the  course 
of  tAvo  days,  would  boil.    A  little  reflection  will  show,  however,  that,  in 
addition  to  the  heat  given  off  through  radiation  and  conduction,  if  the 
temperature  of  the  body  be  higher  than  that  of  its  surroundings,  that 
a  certain  amount  of  heat  leaves  the  body  in  a  latent  condition,  so  to 
speak,  locked  up  in  the  watery  vapor  exhaled  from  the  lungs  and  skin, 
and  from  the  fact  of  the  solid  and  liquid  food,  and  the  air  breathed 
entering  the  body  at  a  lower  temperature,  15°  C.  (69°  R),  for  example, 
than  that  of  the  latter,  and  leaving  it  at  the  same  temperature,  38°  C. 
(100.4°  F.),  heat  must  also  be  absorbed,  and  that  there  must  be  a  still 
further  expenditure  of  heat  in  the  accomplishing  of  bodily  and  mental 
work,  since  there  can  be  no   doubt  that,  whatever  be  the  nature  of 
muscular  and  mental  force,  the  latter  is  correlated  in  some  way  with 
heat,  the  disappearance  of  the  one  being  coincident  with  the  appearance 
of  the  other.     Now,  from  the   very   nature   of  the   case,  the  relative 
amounts  of  heat  expended  in  the  ways  mentioned  must  vary  very  much, 
according  to  the  character  of  the  climate,  of  the  quantity  and  quality  of 
air  breathed,  of  food  taken,  of  the  amount   of  muscular  and   mental 
work  performed.     It  is  therefore  impossible,  if  for  these  reasons  only, 
to  indicate  exactly  what  becomes  of  the  heat  developed  in   the   body. 
Further,  however,  too  much   importance  must  not  be  attached  to  the 
following  table,  since  the  data  upon  which  such  a  table  must  be  based 
are,   to    a  certain   extent,  assumed,   or,  as   will  be  seen,  are,  indeed, 
entirely  wanting.     It  is  only  offered  as  illustrating  in  a  more  detailed 
way  the  general  observations  regarding  the  expenditure  of  the   heat 
just  made,  and  as  also  showing  the  manner  in  which  such  a  table  could 
be   drawn  up  if  all   the  data  had  been  without  cavil  experimentally 
determined.      It   should   be    mentioned,   however,   that    this   criticism 
applies   only  to  the  relative  amounts  of  expenditure  of  the  heat,  the 
total  amount  of  heat  leaving  the  body  being,  of  course,  that  produced 
if  the  temperature  of  the  body  remains  constant.     With  these  qualifi- 
cations, before  calling  attention    to  Table  LXX.,  one   or   two  points 
should  be  mentioned  in    order   to    understand  the  manner    in    which 
the  results  so  tabulated  were  obtained. 

We  will   suppose   that   the   food   of  a  man  weighing  60   kilo.  (132 


500 


EXPENDITURE    OF    HEAT 


pounds)  produces  in  twenty-four  hours  2300  calories,  or  heat  units; 
that  the  food  of  such  a  man,  including  the  air  breathed,  be  known; 
that  the  specific  heat  of  the  food  be  accepted  as  being  0.8,  and  that  of 
the  air  0.26;  that  the  amount  of  watery  vapor  exhaled  from  the  lungs 
and  skin  has  been  determined;  that  it  be  admitted  that  it  requires 
582  heat  units  to  vaporize  1  kilo,  of  water  ;  that  the  work  incidental 
to  the  circulation  and  respiration  be  known,  and,  further,  that  the 
muscular  work  performed  by  the  man  during  a  day  be  considered  as 
amounting  to  112,397  kilogramme-metres,  that  is  to  say,  the  man 
does  an  amount  of  work  equivalent  to  lifting  112^397  kilo.  (247,273.4 
pounds),  or,  110.8  tons  1  metre  (3.2  feet)  high,  or,  what  is  the  same 
thing,  354  tons  through  one  foot,  and  that  the  amount  of  heat  necessary 
to  raise  the  temperature  of  one  kilo.  (2.2  pounds)  of  water  1°  C. 
(1.8°  F.),  or  a  heat  unit,  if  applied  mechanically,  would  raise  423  kilo. 
(930  pounds)  1  metre  (3.2  feet)  high,  or  2977.9  pounds,  or  1.4  ton, 
through  one  foot.  The  above  being  admitted,  it  follows  that  the  heat 
produced  is  expended  somewhat  as  follows  : 


Table  LXX. — Expenditure  of  Heat. 

1.5  kil.  (  3.3  lbs.)  water 
1.5    "     solid  food,  raised  23°  C  (73°  F.) 
16.0    "     (35.2  lbs.)  air  inspired       . 

19.0  kil.  (41.8  lbs.) 

0.4  kil.  (  8172  grs.)  water  evap.  from  lungs     232.8 
0.6   '•     (10183  era.)       "         "  "      skin 


1.0  kil.  (18355  grs.) 
Radiation  and  conduction 


Work 


circulation,    43917  kil.  138  ft.  tons 

respiration,      1590    "  25 

nervous, 

muscular,     112397    "  354 


157904 


517 


34.5  beatui 

27.6  " 
95.6     " 

n'ts.     1.50  percent. 
1.20     "     " 
4.15     "     " 

157.7     " 

6.85     "     " 

s     232.8     " 
384.1     " 

'       10.12     "     " 
16.70     "     " 

616.9     " 

'       26.82     "     " 

.  1156.3     " 

'       50.27     "     " 

s       98.5     " 
17.8     " 

4.28     "     " 
0.77     "     " 

252.8     " 

'       10.99     "     " 

369.1     " 

'       16.04     "     " 

Ratio  of  work  to  beat    . 

Ratio  of  muscular  work  to  beat 


to  6 
to  9 


It  will  be  observed  from  Table  LXX.,  that  of  the  2300  heat  units 
produced  in  twenty-four  hours,  about  7  per  cent,  are  expended  in 
warming  the  food,  including  the  water  and  air  breathed;  26  per  cent, 
in  evaporating  the  water  from  the  lungs  and  skin  ;  50  per  cent,  in 
radiation  and  conduction  from  the  general  surface  of  the  body,  and 
about  16  per  cent.,  or  one-sixth  of  the  Avhole  heat  produced  in  the  per- 
formance of  work.  It  must  be  borne  in  mind,  however,  that  the  116.3 
heat  units,  or  5.05  per  cent,  of  the  whole  heat  produced,  and  at  the 
expense  of  which  the  work  of  maintaining  the  circulation  and  respira- 
tion is  maintained,  are  only  temporarily  converted  into  mechanical  energy, 
the  latter  being  almost  entirely  reconverted  into  heat  again,  owing  to 
the  various  obstructions  that  are  offered  to  the  movement  of  the  blood 
and  respiratory  organs.       The  5.05  per  cent,  heat  units  leaving  the 


CORRELATION    OF    HEAT    AND    MECHANICAL    WORK.      501 

body  as  heat,  must  be  added,  therefore,  to  the  50.5  per  cent,  expended 
in  radiation  and  conduction,  making  the  latter  really  amount  to  55.55 
per  cent.  While  no  numerical  estimate  can  be  given,  as  yet,  of  the 
relation  existing  between  heat  and  nervous  force,  there  can  be  no  doubt, 
however,  that  the  latter,  like  all  other  kinds  of  energy,  must  be  de- 
veloped out  of  some  equivalent  amount  of  force,  and  leaves  the  body 
as  such,  or  as  some  other  mode  of  motion.  That  nervous  force  is 
developed  out  of  heat  appears  very  probable  from  the  experiments  of 
Lombard,  already  referred  to,  and  by  which  it  was  shown  that,  while 
all  mental  action  was  accompanied  with  the  production  of  heat,  that 
more  heat  disappeared  during  deep  thought  than  during  reading  to 
one's  self,  for  example,  of  emotional  poetry  ;  further,  it  was  shown  by 
the  same  experimenter  that  more  heat  disappeared  than  when  the 
reading  was  aloud — that  is,  had  a  muscular  expression,  part  of  the  heat 
produced  in  the  latter  case  being  applied  to  making  the  oral  or  muscular 
effort.  It  is  a  matter  of  daily  observation  that  silent  grief  is  deepest, 
that  pent-up  emotion  finds  relief  in  physical  action.  This  is  in  accord- 
ance with  the  results  of  the  experiments  just  mentioned,  since  the  heat 
that  is  transformed  into  emotions  or  ideas,  in  the  one  case,  becomes 
muscular  action  in  the  other,  and  just  in  proportion  as  there  is  more  of 
the  one,  so  there  is  less  of  the  other.  Hirn1  endeavored  to  determine, 
experimentally,  the  exact  quantity  of  heat  expended  in  the  performance 
of  mechanical  work  by  comparing  the  heat  produced  within  a  definite 
time  with  the  work  done,  the  latter  consisting  in  a  man  raising  his  own 
weight  through  a  given  height,  the  man  walking  upon  the  circum- 
ference of  a  tread-wheel  rotating  in  the  opposite  direction  to  himself. 
According;  to  Hirn,  a  man  weighing  75  kilo.,  during  an  hour's  work 
upon  the  tread-wheel,  placed  within  the  calorimeter,  produced  430  heat 
units,  whereas,  judging  from  the  amount  of  oxygen  absorbed  and 
carbonic  acid  exhaled,  500  heat  units  were  produced.  What,  then, 
became  of  the  70  extra  heat  units?  According  to  Hirn,  it  was  at  the 
expense  of  this  amount  of  heat  that  the  20,610  kilogramme-metres  of 
work  were  accomplished — that  is,  of  raising  75  kilo,  through  nearly  400 

metres  (423x70= =  394  V     On  account,  however,  of  the 

v  75  / 

errors  incidental  to  the  construction  of  the  apparatus,  and  of  the  amount 
of  heat  produced  as  determined  from  the  oxygen  absorbed  being  esti- 
mated as  too  high,  the  results  of  Hirn,  as  just  given,  cannot  be  accepted ; 
nevertheless,  the  difference  between  the  amount  of  heat  that  appeared, 
as  such,  and  that  which  ought  to  have  appeared,  can  only  be  accounted 
for  on  the  supposition  that  part  of  the  heat  produced  was  expended  in 
the  performance  of  mechanical  work,  and,  as  a  corollary,  it  follows  that 
less  heat  appears  during  a  muscular  contraction,  when  accompanied 
with  work,  than  when  without,  and  which  accords  with  daily  experience. 
The  relation  that  has  been  shown  to  exist  between  food,  heat,  and 
mechanical  work,  is  not  merely  one  of  theoretical  interest,  but  of  prac- 
tical importance.  Suppose,  for  example,  we  wish  to  determine  how 
much  food — bread,  for  instance — is  required  to  supply  the  force  that  will 

1   Theurie  mecaniqne  ile  la  Chaleur,  3d  ed..  i.  p.  35.     Paris. 


502  EXPENDITUKE    OF    HEAT. 

enable  a  man  weighing  7"  kilo.  (154  pounds)  to  raise  himself  to  about 
the  top  of  Mont  Blanc,  a  height  of  4929  metres  (15,774  feet),  or  to 
accomplish  any  other  physical  feat  involving  an  equal  expenditure  of 
force.  From  the  data  given  above  such  an  estimate  can  be  made,  and 
in  the  following  way :  It  being  admitted  that  1  heat  unit,  when 
applied  mechanically,  will  raise  1  kilo,  through  423  metres,  it  will 
require  11.6  times  as  much  heat  or  11.6  heat  units  to  raise  1  kilo.  11.6 
times  us  high,  or  4906  metres  (423x11-6=4906),  and  812  heat  units 
(70x11-6=812)  to  raise  70  times  that  weight,  or  70  kilo,  to  the  same 
height,  4906  metres  (15,699  feet),  or  about  that  of  Mont  Blanc.  That 
is,  it  is  required  to  determine  how  much  bread  must  be  burned  in  the 
body  to  furnish  812  heat  units,  or  the  heat  necessary  when  applied 
mechanically,  to  raise  70  kilo.  (154  pounds)  through  4906  metres 
(15,699  feet) — that  is  of  doing  an  amount  of  mechanical  work  ecjual  to 
343,476  kilogramme-metres  (1077  foot  tons).  By  looking  at  Table 
LXVIIL,  it  will  be  observed  that  while  1  gramme  of  dry  bread  crumb 
when  burned  out  of  the  body  produces  3.9  heat  units,  when  burned  in  the 
body  it  produces  3.8  heat  units  ;  and  when,  further,  it  is  remembered  that 
of  the  heat  produced  by  the  burning  of  the  food,  only  about  one-ninth  is 
expended  in  muscular  work,  the  mechanical  value  of  the  3.8  heat  units 

(38  \ 

-1   =  0.4):  1  gramme  of 

dry  bread  crumb  when  burned  in  the  body  furnishing  then  0.4  heat 
unit  for  the  production  of  muscular  force,  and  812  heat  units  being 
required,    it    is    evident  that   2030   grammes  or  4  pounds    of   bread 

(  — -=2030  grs.=4  lbs.  )  must  be  eaten  to  supply  the  necessary  force 

of  raising  70  kilo,  through  4906  metres;  an  estimate  which  agrees 
closely  with  that  of  Frankland,1  according  to  that  experimenter,  2.3 
pounds  of  bread  being  required  when  oxidized  in  the  body  to  raise 
63.5  kilo.  (140  pounds)  through  3125  metres  (10,000  feet)  or  3.8 
pounds  of  bread  to  raise  70  kilo.  4906  metres.  It  may  appear  at  first 
sight  strange  that  such  an  amount  of  muscular  work  can  be  performed 
upon  a  vegetable  diet,  but  on  reflection  it  will  be  remembered  that  the 
strongest  men  are  not  always  meat  eaters,  and  that  among  animals 
noted  for  their  strength  are  the  elephant  and  rhinoceros,  strictly 
vegetable  feeders.  The  heat  developed  during  muscular  contraction 
and  its  probable  source  will  be  considered  more  fully  hereafter;  the 
above  examples  will  suffice,  however,  for  the  present,  to  illustrate  the 
general  relation  existing  between  the  loss  of  heat  and  the  production 
of  work. 

It  will  be  seen  from  Table  LXX.  that  over  ten  per  cent.,  or  about 
one-ninth,  of  the  heat  produced  is  expended  in  muscular  work,  and  it 
might  appear  at  first  sight  that  there  would  be  no  heat  left  available 
for  the  production  of  nervous  force,  as  in  mental  effort.  Apart,  how- 
ever, from  the  fact  of  the  nervous  and  muscular  force  not  being  pro- 
duced necessarily  at  the  same  time  the  estimates  of  the  latter  of  354 

1  Op.  cit.,  Table  iv.  p.  11)7. 


CONDITIONS    INFLUENCING    EXPENDITURE    OF    HEAT.      503 

foot  tons  is  too  high,  being-  equal  to  walking  twenty  miles  a  day.  If, 
however,  such  an  amount  of  exercise  be  taken,  either  little  mental 
work  can  be  done,  or  more  food  must  be  furnished  than  is  ordinarily 
allowed  a  laboring  man.  It  has  already  been  mentioned  that  the 
temperature  of  the  rectum  is  higher  than  that  of  the  axilla,  and  from 
what  has  been  said  of  the  production  and  expenditure  of  heat  it  might 
be  supposed  that  equal  difference  in  temperature  must  prevail  in  other 
parts  of  the  body,  for  although  the  circulating  blood  tends  to  equalize 
the  temperature,  nevertheless,  on  account  of  the  radiation  and  conduc- 
tion of  the  heat  from  the  general  surface  varying  so,  the  temperature  can 
not  be  the  same  throughout  the  body.  Such  has  been  shown  to  be  the 
case,  experimentally.  Thus,  according  to  Davy,1  while  the  temperature 
of  the  axilla,  for  example,  was  36.6°  C.  (97.8°  F.),  that  of  the  lower  part 
of  the  leg,  and  of  the  hollow  of  the  foot  amounted  to  onlv  34.4°  C. 
(93.9°  F.),  and  32.2°  C.  (89.9°  F.),  respectively. 

Having  studied  the  manner  in  which  animal  heat  is  produced  and 
expended,  there  remains  now  for  our  consideration  the  way  in  which 
animal  heat  is  regulated,  of  determining  as  far  as  possible  in  detail 
the  means  by  which  the  temperature  of  a  hot-blood  animal  is  main- 
tained nearly  constant,  notwithstanding  the  variations  in  that  of  its 
surroundings.  Among  the  conditions  regulating  animal  heat  may  be 
mentioned  the  taking  of  solid  and  liquid  food,  the  character  of  the 
respiration  and  circulation,  the  action  of  the  skin,  the  influence  of 
bodily  size. 

While  the  amount  of  heat  produced  will  depend  on  the  quality  and 
quantity  of  the  food,  the  mere  taking  of  the  latter  in  the  form  of  hot 
or  cold  drinks,  for  example,  with  the  view  of  increasing  or  diminishing 
the  general  temperature  of  the  body,  as  is  so  commonly  done,  has 
already  been  mentioned  as  having  really  but  little  effect.  In  fact,  as 
we  have  seen,  about  2.7  per  cent,  of  the  heat  produced  is  expended  in 
warming  all  the  solid  and  liquid  food  taken.  The  effect  of  cold  drinks 
in  lowering  the  general  temperature  of  the  body  must  therefore  be  but 
slight  and  temporary.  On  the  other  hand  the  effect  of  a  hot  drink, 
as  we  have  seen,  may  be  exactly  opposite  to  what  might  have  been 
expected,  not  only  through  the  cooling  effect  due  to  the  evaporation  as 
in  the  drinking  of  hot  tea,  but  on  account  of  the  specific  substance  of 
which  the  hot  drink  consists.  Thus,  for  example,  if  hot  spirits  be 
taken,  while  at  first  a  sense  of  warmth  is  experienced  with  the  paralysis 
of  the  vaso-motor  nerves  by  the  alcohol,  a  greater  quantity  of  blood 
flowing  to  the  skin  than  usual,  a  proportionally  larger  quantity  of  heat 
will  be  lost  from  the  general  surface,  and  the  effect  of  the  hot  drink 
will  be  in  the  long  run,  therefore,  to  lower  the  temperature  of  the 
body  rather  than  to  raise  it.  It  has  already  been  mentioned  that 
about  4.1  per  cent,  of  the  heat  produced  is  expended  in  warming  the 
inspired  air,  and  it  might  naturally  be  supposed  that  if  the  respiration 
be  quickened  and  the  amount  of  air  inspired  increased,  that  a  propor- 
tionally greater  quantity  of  heat  would  then  be  expended  in  warming 
it.      Such  would  appear  to  be  the  case,  dogs  and  other  animals  panting 

i   Phil.  Trans.,  1814,  civ.  p.  359. 


504  EXPENDITURE    OF    HEAT. 

when  overheated.  Not  sweating  except  in  those  parts  destitute  of  fur 
or  hair,  and  the  cooling  effect  of  the  perspiration  being  ahsent,  the 
excess  of  heat  developed  is  carried  away  in  the  expired  air.  The 
respiration  when  quick,  will  be  more  efficient,  therefore,  in  lowering 
the  general  temperature  of  the  body  than  when  slow.  Hence,  also, 
the  condition  of  heat  dyspnoea  or  the  rapidity  of  the  breathing  inci- 
dental to  the  exposure  of  the  body  to  a  high  temperature.  While  no 
doubt  under  such  circumstances  a  certain  amount  of  heat  is  carried 
away  in  the  expired  air,  and  the  temperature  of  the  body  prevented 
from  rising  as  high  as  it  otherwise  would,  it  must  be  borne  in  mind 
that  the  quickened  respiration  in  heat  dyspnoea  may  be  as  much 
regarded  as  due  to  increased  oxidation  owing  to  the  high  external 
temperature  as  an  effort  of  nature  to  prevent  the  temperature  of  the 
body  rising  too  high.  In  other  words,  the  cooling  effect  of  the 
respiration  is  to  be  considered  rather  an  incidental,  not  an  invariable 
effect  due  to  the  activity  of  the  oxidation  caused  by  the  external  heat. 
In  considering  the  cooling  effect  of  respiration,  it  will  be  remembered, 
also,  that  4.1  per  cent,  of  the  heat  produced  is  expended  in  warming 
the  inspired  air.  On  account  of  so  much  heat  being  given  off  from 
the  skin  amounting  through  radiation,  conduction,  and  evaporation,  to- 
nearly  eighty  per  cent,  of  the  heat  produced,  any  change  in  the  condi- 
tion of  the  latter,  as  regards  its  structure  or  the  amount  of  blood  circu- 
lating through  it,  etc.,  will  materially  influence  the  general  temperature 
of  the  body.  Were  the  temperature  of  the  skin  constant,  the  amount 
of  heat  given  off  or  taken  up  by  it  would  depend  simply  upon  that  of 
the  surrounding  atmosphere,  the  skin  losing  heat  if  the  temperature 
of  the  air  was  lowered,  and  gaining  heat  when  that  of  the  air  was 
elevated.  As  a  matter  of  fact,  however,  when  the  body  is  exposed  to 
a  temperature  cooler  than  its  own,  the  vessels  of  the  skin  contracting, 
the  general  surface  becomes  cooler,  the  difference  between  the  temper- 
ature of  the  body  and  the  surrounding  air  being  diminished,  the 
loss  of  heat  is  correspondingly  diminished  ;  on  the  other  hand,  when 
the  body  is  exposed  to  a  higher  temperature  than  its  own,  the  vessels  of 
the  skin  expanding,  the  general  surface  becomes  warmer,  and  a  corre- 
spondingly greater  amount  of  heat  is  lost. 

It  is  a  cause  frequently  of  surprise  to  most  persons  to  learn  that,  no 
matter  how  hot  or  cold  they  may  feel,  the  temperature  of  their  body 
nevertheless  remains  practically  the  same.  From  what  has  just  been 
said,  however,  as  regards  the  action  of  the  skin  in  regulating  the  tem- 
perature of  the  body,  it  is  obvious  that  in  the  cooling  of  the  body  through 
evaporation  from  the  cutaneous  surface,  when  exposed  to  a  higher  ex- 
ternal temperature,  the  greater  quantity  of  hot  blood  then  circulating 
through  the  cutaneous  vessels  will,  in  impressing  the  sensory  nerves,  give 
rise  to  a  general  sense  of  warmth,  so  that  while  we  feel  warmer  our  body 
is  actually  getting  cooler  through  the  loss  of  heat  involved  in  the  evapora- 
tion. On  the  other  hand,  when,  through  the  exposure  to  extreme  cold, 
the  cutaneous  vessels  are  diminished  in  size,  the  smaller  quantity  of  hot 
blood  circulating  through  them  will  give  rise  to  a  sense  of  coolness,  so 
that  while  we  feel  cool  our  body  is  actually  becoming  warmer  through 
retention  of  the  heat  of  the  blood  within  it.     The  feeling  warm  or  cold 


INFLUENCE    OF    BATHS    AND    CLOTHING.  505 

depends,  then,  simply  upon  the  relative  amounts  of  blood  circulating  in 
the  skin. 

The  effect  of  the  successive  exposure  of  the  body  to  cold  and  heat,  as 
just  described,  is  well  seen  in  the  taking  of  cold  baths.  While  in  the  bath, 
the  vessels  of  the  skin  being  contracted,  the  latter  is  pale  and  cold,  the 
heat  is  retained,  on  emerging  from  the  bath  the  vessels  being  dilated, 
the  skin  is  red  and  warm,  and  heat  is  then  given  off  from  the  surface. 
When  we  come  to  study  the  structure  of  the  skin  somewhat  in  detail,  we 
shall  see  that  its  adipose  tissue,  being  a  bad  conductor,  prevents  any 
great  amount  of  heat  from  being  given  off  from  the  inner  parts  of  the 
body  to  the  surface,  and  so  lost.1  This  effect  being  especially  Avell- 
marked  in  those  cases  where  the  difference  in  temperature  on  both  sides 
of  the  skin  does  not  amount  to  more  than  about  9°  C.  (16°  F.),  the  sig- 
nificance of  the  good  effect  of  wearing  clothing  becomes  apparent,  since 
under  such  circumstances  the  body  of  a  man  is  surrounded  by  a  layer 
of  air  having  a  temperature  of  about  30°  C.  (86°  F.),  the  temperature 
under  the  skin  being2  36°  C.  (96.8°  F.),  this  difference  amounting,  there- 
fore, to  only  6°  C.  (12.8°  F.)  Clothing  in  man  plays  the  same  part 
as  hair,  fur,  and  feathers  in  animals,  the  air  inclosed  within  the  latter, 
through  being  a  bad  conductor,  practically  prevents  any  great  loss  of 
heat  from  the  general  surface.  Man,  however,  is  far  better  able  to 
adapt  himself  to  changes  in  climate  than  most  animals,  since  through 
change  of  clothing,  food,  etc.,  and  free  action  of  the  skin,  he  is  able  to 
live  in  tropical  or  temperate  regions  as  well  as  in  arctic  ones. 

It  has  already  been  mentioned  that  through  the  evaporation  of  the 
water  from  the  skin  as  sweat  about  sixteen  per  cent,  of  the  heat  pro- 
duced is  expended,  and  that  the  amount  of  water  evaporated  will  depend, 
among  other  conditions,  upon  the  amount  of  water  already  existing  in 
the  atmosphere.  It  is  very  evident,  therefore,  that  the  regulation  of  the 
temperature  of  the  body  and  the  heat  that  a  person  can  endure  must 
soon  reach  a  limit,  since  if  the  temperature  of  the  surrounding  air  keeps 
continually  rising,  becomes  saturated  with  watery  vapor  and  is  un- 
changed, the  body,  notwithstanding  what  has  just  been  said  of  the  action 
of  the  lungs,  skin,  etc.,  will  become  as  hot  as  its  surroundings.  It  is 
easier  to  keep  out  cold — that  is,  to  keep  in  the  bodily  heat  by  proper 
food,  clothing,  and  active  exercise — than  to  keep  out  heat.  Travellers, 
when  well  equipped,  complain  less  of  the  cold  of  the  arctic  regions  than 
of  the  heat  of  the  tropics — indeed,  the  officers  of  the  Austrian  steamers 
say  that  while  crossing  the  Red  Sea.  at  certain  seasons  of  the  year,  with 
all  precautions  taken,  they  at  times  fear  they  will  lose  their  reason,  the 
heat  being  so  unendurable. 

An  important  condition  in  the  regulating  of  animal  heat,  and  which 
may  here  lie  appropriately  considered,  is  the  influence  of  the  size  or  bulk 
of  the  body  of  an  animal  as  compared  with  its  surface  area;  for  the 
ratio  of  the  bulk  to  the  surface  area  being  proportional  to  the  size  of  the 
animal,  and  the  heat  produced  being  proportional  about  to  the  bulk,  and 
the  heat  lost  to  the  surface  area,  it  follows  that  of  two  animals  of  similar 

i  King  :  Zcits.  ftir  Biologic,  x   S.  73. 

-   Becquerel  ami  Breschet      Inn.  di  -  Sciences  Nut.,  2ieme  ser.  t.  iii.  p.  257;  t.  iv.  p   243 


50(5  EXPENDITURE    OF     HEAT. 

shape  but  of  different  sizes,  that,  other  things  being  equal,  the  larger 
animal  of  the  two  will  lose  relatively  the  least  heat.  Suppose,  for  ex- 
ample, of  two  animals  of  similar  shape,  that  one  be  ten  times  as  long  as 
the  other,  then,  while  the  loss  of  heat  in  the  larger  animal  will  be  as  its 
surface  area  102,  or  100  times  as  great  as  the  small  one,  the  heat  pro- 
duced by  the  larger  animal  will  be  at  its  bulk  103,  or  1000  times  as 
great.  It  follows,  therefore,  that  if  two  such  animals  have  the  same 
temperature  that  the  small  animal  either  retains  its  heat  much  better 
than  the  large  one  or  that  it  produces  heat  far  more  actively.  That  the 
latter  is  the  case  appears  from  the  fact  of  a  small  animal  taking  more  food 
relatively  than  a  large  one,  and  of  its  circulation  and  respiration  being 
absolutely  more  frequent.  What  has  just  been  said  of  the  laws  of  heat, 
as  compared  with  its  production,  is  further  illustrated  by  a  number  of 
well-known  facts.  Thus  small  animals  are  more  readily  affected  by 
changes  in  the  external  temperature  than  large  ones,  the  temperature 
of  a  rabbit,  for  example,  under  such  circumstances,  varying  more  than 
that  of  a  dog,  that  of  a  young  animal  more  than  that  of  an  old  one  of 
the  same  kind,  as  that  of  the  young  child,  as  compared  with  that  of  the 
adult.  Large  animals,  like  the  whale  or  hippopotamus,  live  either 
habitually  or  temporarily  in  the  water,  the  latter  being  a  better  con- 
ductor of  heat  than  air.  On  the  other  hand,  the  smallest  homiothermal 
animals  live  in  the  tropics,  while  of  animals  of  the  same  kind  the  largest 
ones  live  in  temperate  or  cold  regions.  Of  course,  what  has  just  been 
said  with  reference  to  the  bulk  and  surface  area  in  the  production  and 
loss  of  heat  is  not  inconsistent  with  what  daily  observation  teaches  when 
man  or  animal  changes  the  position  of  the  body,  for  as  the  external  tem- 
perature varies  if  the  body,  when  cold,  be  contracted,  less  surface  being 
then  exposed  less  heat  will  be  lost,  whereas,  if,  Avhen  overheated,  the 
body  and  limbs  be  stretched  to  the  utmost,  more  surface  being  exposed, 
then  more  heat  will  be  lost. 

The  influence  exerted  by  the  nervous  system  in  the  production  and 
expenditure  of  animal  heat,  so  far  as  known,  will  be  considered  hereafter. 
In  concluding  this  part  of  our  subject,  however,  it  may  be  here  said 
that,  however  accomplished,  there  undoubtedly  exists  some  mechanism 
by  which  the  production  of  heat  in  man  and  animals  is  adapted  to  that 
lost  through  the  means  already  indicated.  In  addition  to  what  has 
already  been  said,  as  a  further  confirmation  of  the  existence  of  some 
regulating  mechanism,  may  be  mentioned  the  well-known  facts  already 
alluded  to,  of  the  diet  of  the  inhabitants  of  cold  countries  being  so  dif- 
ferent from  that  of  those  of  hot  ones,  the  amount  of  food  consumed 
by  the  former  not  only  being  greater,  but  the  food  consisting  largely  of 
fat  and  oil,  substances  eminently  suitable  for  the  production  of  heat.  A 
corresponding  difference  in  diet  is  also  made  use  of  by  the  inhabitants 
of  temperate  regions  in  winter,  as  compared  with  summer,  and  with  the 
same  effect  of  increasing  the  production  of  heat  in  cold  and  of  diminish- 
ing it  in  hot  weather.  It  might  be  supposed  that  such  a  regulation  of 
the  heat  produced  and  expended,  of  a  loss  of  heat  inducing  an  increased 
production,  would  be  shown  from  the  amount  of  oxygen  absorbed  and 
carbonic  acid  exhaled,  and  notwithstanding  the  numerous  difficulties 
incidental  to  such  an  experimental  investigation,  it  may  be  said  that  the 


REGULATION  OF  HEAT  PRODUCED  AND  EXPENDED.   507 

general  result  obtained  by  Lavoisier,  Crawford,  and  De  la  Roche,1  as 
well  as  by  modern  experimenters,  as  Roliring  and  Zuntz,2  Colasanti,3 
Pfliiger,4  Prince  Theodore,5  Voit,6  etc.,  was,  as  a  rule,  that  the  con- 
sumption of  oxygen  and  exhalation  of  carbonic  acid  increased  with  a 
fall  in  the  external  temperature  and  diminished  with  a  rise  in  it,  though, 
under  certain  circumstances,  hot-blooded  animals  behaved  as  cold-blooded 
ones — that  is,  the  absorption  of  oxygen  and  exhalation  of  carbonic  acid 
increase  with  a  rise  in  the  external  temperature  and  diminish  with  a 
fall  in  it.  Within  certain  limits  at  least,  it  may  be  said  that,  when  a 
man  or  animal  is  exposed  to  cold,  the  production  of  heat  is  increased, 
as  shown  by  the  greater  amount  of  oxygen  absorbed  and  carbonic  acid 
exhaled,  but  when  exposed  to  heat  the  reverse  is  the  case  and  less  heat 
is  produced. 

1  Op.  cit.  2  pfluger's  Arctaiv,  1871,  iv   S.  57. 

3  Ebentia,  xiv.  S.  92.  *  Ebenda,  1878,  xviii.  S.  247. 

5  Zeitschrift  f.  Biol.,  1878,  xiv.  S.  51.  '•  Ebenda,  S.  57. 


C  HAPTER    X  X  X  I  V. 

THE  KIDNEYS  AND  URINE. 

We  have  seen  that  during  digestion  the  food  is  transformed  into 
albuminose,  glucose,  emulsified  fats,  etc.,  that  through  absorption  and 
the  circulation  the  latter  are  carried  to  the  tissues,  supplying  the  cells 
of  the  same  with  materials,  which,  either  in  being  assimilated  serve  for 
repair,  growth,  or  development,  or  in  being  destroyed  are  a  source  of 
heat  and  force  ;  and  that  the  destructive  metamorphosis  going  on  in  the 
body  caused  by  fermentation,  hydration,  oxidation,  etc.,  incidental  to 
life,  the  final  outcome  of  which,  at  least,  is  the  production  of  carbonic 
acid,  water,  and  urea,  is  due,  to  a  far  greater  extent,  to  the  destruction  of 
the  food  by  the  cells  of  the  tissues  than  to  the  destruction  of  the  tissues 
themselves ;  that,  by  means  of  the  lungs,  oxygen  is  introduced  into  the 
system,  and  carbonic  acid  and  water  removed,  the  skin,  as  we  shall  see, 
in  the  latter  respect,  acting  also,  to  a  certain  extent,  in  the  same  way. 
In  concluding  now  our  account  of  nutrition,  it  remains  for  us  still  to 
consider  the  structure  of  the  kidneys,  and,  so  far  as  is  known,  the 
manner  in  which  the  urea,  etc.,  are  excreted  by*  them  from  the  system. 
It  will  be  observed  that  we  speak  of  the  urea,  etc.,  as  being  excreted 
by  the  kidneys,  and  it  may  be  appropriately  mentioned  here  that,  while 
it  would  be  equally  correct  to  refer  to  the  secreting,  as  well  as  to  the 
excreting  of  the  urine ;  the  word  secretion,  however,  is  usually  made  use 
of  in  referring  to  a  glandular  product  of  some  use,  such  as  the  saliva, 
gastric  juice,  etc.,  the  term  excretion  being  confined  to  products  of  no 
use,  to  be  gotten  rid  of,  such  as  the  urine.  In  this  sense,  the  bile,  as 
we  have  seen,  is  both  an  excretion  and  a  secretion. 

A  kidney  may  be  regarded,  functionally,  as  consisting  essentially  of 
one  or  more  tubes,  opening  externally  at  one  end,  but  terminating  inter- 
nally at  the  other  end  in  blind,  sac-like  capsules.  The  tubes  and  their 
capsules  are  lined  with  an  epithelium,  and  covered  more  or  less  exte- 
riorly with  bloodvessels,  the  latter  supplying  the  tubes  with  blood,  from 
which  are  excreted,  by  the  cells  of  their  lining  epithelium,  the  urea,  water, 
etc.,  constituting  the  urine  ;  elaborated  and  transported  by  the  cells  into 
the  interior,  or  lumen  of  the  tubes,  the  urine  passes  finally  thence  out  of 
the  body.  Such  a  disposition  as  that  just  described,  obtains  in  the 
kidneys  of  the  lower  vertebrates.  In  bdellostoma,  for  example,  one  of 
the  cyclostomous  fishes,  the  kidney  consists  (Fig.  258,  A)  of  a  ureter 
(a),  from  which  are  given  off,  at  right  angles,  short  uriniferous  tubules 
(b,  b),  terminating  in  capsular-like  Malpighian  bodies  (<?),  lined  with 
an  epithelium,  and  supplied  externally  with  bloodvessels  (Fig.  258, 
d,  e).  The  kidneys  in  man,  smooth,  dark  red,  compressed,  oval  bodies, 
deeply  set  in  the  lumbar  region,  opposite  the  last  dorsal  and  two  or 
three  upper  lumbar  vertebme,  measuring,  on  an  average,  4  in.  (10  cm.) 


STRUCTURE    OF    KIDNEY. 


509 


in  length,  2J  in.  (6  cm.)  in  breadth,  and  1J  in.  (3  cm.)  in  thickness, 
and  weighing  about  4|  ounces  (121  grammes),  present  such  a  charac- 


Fio.  258. 


Fig.  259. 


Kidney  of  bdellostoma. 


Longitudinal  section  of  a  kidney  1.  Cortical  sub- 
stance. 2.  Kenal  pyramid.  3  Renal  papilla;.  4.  Pelvis. 
5.  Ureter.  6.  Renal  artery.  7.  Renal  vein.  8  Branches 
of  the  latter  vessels  in  the  sinus  of  the  kidney.   (Leidy.) 


The  same  magnified.     I  Muller.) 


teristic  form  through  the  presence  of  a 
deep  notch  on  their  inner  side  that  the 
term  reniform  or  kidney  form,  derived 
from  them,  is  often  conveniently  made 
use  of  in  describing  various  other  natu- 
ral objects.  If  a  kidney  be  divided  lon- 
gitudinally through  its  breadth  (Fig. 
259),  it  will  be  observed  that  the  hilus  or  notch  leads  into  a  cavity, 
the  sinus  of  the  kidney,  which  is  filled  in  the  natural  condition  with 
the  pelvis  (4),  or  expanded  upper  portion  of  the  ureter  (5),  and  the 
renal  vessels  (6,  7)  and  nerves.  Such  a  section  further  shows  that 
the  kidney  consists  apparently,  at  least,  of  two  distinct  substances,  an 
internal  striated  portion,  the  medullary  substance  (2),  and  an  external 
granular-looking  portion,  the  cortical  substance  (1).  This  distinction 
is,  however,  a  purely  artificial  one,  being,  in  reality,  due  to  the  urini- 
ferous  tubule  (Fig.  260),  coursing,  in  its  beginning  (9,  8),  through  the 
medullary  or  interior  portion  in  a  straight  manner,  but  at  its  termi- 
nation (5,  8),  in  the  cortical  or  external  portion  in  a  convoluted  one. 
Theoretically,  at  least,  if  the  uriniferous  tubules,  of  which  the  kidney 
largely  consists,  could  be  unravelled  and  straightened  out,  the  distinction 
of  medullary  and  cortical  substance  would  then  cease  to  exist.  It  is, 
also,  very  apparent,  as  observable  in  a  longitudinal  section  (Fig.  259), 
that  the  interior,  or  so-called  medullary  portion  of  the  kidney,  is  dis- 
posed in  from  ten  to  fifteen  conical  masses,  the  pyramids  of  Malpighi 
(2),  so  named  after  the  celebrated  anatomist  of  that  name,  the  bases  of 
which  are  imbedded  in  the  cortical  substance,  while  the  free  summits, 


510 


THE    KIDNEYS. 


or  papilla  (3),  of  the  same  project  into  the  sinus  of  the  kidney.  It 
may  be  mentioned  in  this  connection  that  the  Malpighian  pyramids, 
together  with  the  cortical  substance  enveloping  each  of  their  bases,  the 
coliinime,  or  septa  Bertini,1  correspond  to  the  distinct  lobules  of  which 
the  human  kidney  consists  in  the  foetal  state,  and  while  becoming  indis- 


Fro.  260. 


Diagram  and  course  of  two  uriniferous  tubules.     A.  Cortex.     B.  Boundary  zone.     c.  Papillary  zone  of 
the  medulla,     a,  a'.  Superficial  and  deep  layers  of  cortex,  free  from  glomeruli. 

solubly  blended  as  development  advances  in  man,  remain  quite  distinct 
throughout  life  in  many  of  the  mammalia,  as  in  the  otter  and  bear 
among  the  carnivora,  and  in  the  cetacea — whales,  dolphins,  for  example. 
If  now  the   apex   or  summit  of  one   of  the   Malpighian  pyramids,  or 


1  Mem.  de  l'Acad.  des  Sciences,  1741,  p.  77. 


STRUCTURE    OF    KIDNEY. 


511 


Fig.  261. 


papillae,  be  examined  microscopically,  very  minute  orifices  (between 
200  and  500)  will  be  observed,  each  of  which  is  the  beginning  of  a 
uriniferous  tubule  (Fig.  260),  and  which  will  be  seen,  if  followed  in 
longitudinal  section,  to  pursue,  as  a  tube  of  Bellini,1  a  nearly  straight 
course  through  the  medullary  portion,  as  already  mentioned,  each 
Bellinian  tubule,  however,  soon  dividing  and  subdividing  the  bundle 
formed  by  the  division  of  the  latter,  at  the  beginning  of  the  cor- 
tical substance,  constituting  the  pyramids  of  Ferrein.2  The  uriniferous 
tubule  followed  thence  outwardly  toward  the  cortical  substance,  then 
turns  back  upon  itself  toward  the  medullary  portion,  and  turning  once 
more  toward  the  cortical  portion  as  the  ascending  and  descending  loops 
of  Henle3  becomes  quite  convoluted,  constituting  the  cortical  tubules  of 
Ferrein,*  terminating,  finally,  in  a  pouch-like  dilatation,  the  capsule  of 
Muller,5  the  latter,  as  we  shall  see,  being  inflected  over  the  so-called 
Malpighian  vascular  glomerulus,  the  capsule  and  glomerulus  together 
constituting  a  Malpighian  corpuscle,  as  first  described  by  Malpighi.6 

The  uriniferous  tubules,  held  together  by  connective  tissue,  the  stroma 
about  2  inches  in  length,  and  with  a  diameter  varying  between  the 
-2^jth  and  g-^-g-th  of  an  inch,  the  Bellinian 
tubules  being  the  largest,  consist  of  basement 
membrane  lined  with  epithelium  ;  the  latter, 
however,  like  the  diameter  of  the  tube,  differing 
considerably  according  to  the  part  examined, 
being,  for  example,  distinct  and  columnar,  with 
a  wide  lumen  in  the  straight,  or  Bellinian 
tubules,  but  indistinct  granular,  with  little  or  no 
lumen  in  the  convoluted  tubules,  or  tubules  of 
Ferrein. 

The  kidneys  are  very  vascular,  the  arteries 
being  large  vessels  in  proportion  to  the  size  of 
the  organs  which  they  supply.  The  renal  artery, 
Fig.  259,  6,  as  it  approaches  the  hilus  of  the 
kidney  subdivides  into  four  or  five  branches, 
which,  entering  the  sinus,  pass  thence  between 
the  pyramids  into  the  substance  of  the  kidney, 
dividing  and  subdividing  as  they  ramify  through 
the  cortical  substance,  each  branch  finally  ter- 
minating in  an  afferent  vessel  (Fig.  261,  a'), 
leading  to  a  Malpighian  glomerulus,  so  called 
after  their  discoverer,  Malpighi,  around  which, 
as  already  mentioned,  as  first  shown  by  Bow- 
man,7 is  inflected  the  capsule  of  Muller,  the 
beginning  or  end,  as  you  will,  of  the  uriniferous  tubule. 
Malpighian  glomerulus  (Fig.  261),  about  the  ^th  of  a  mm.  (y^-Tjth 


ur^ 


Diagram  showing  the  rela- 
tion of  the  Malpighian  hody  to 
the  uriniferous  ducts  and  blood- 
vessels, a.  One  of  the  inter- 
lobular arteries,  a'.  Afferent 
artery  passing  into  the  glomer- 
ulus, c.  Capsule  of  the  Mal- 
pighian body.  t.  Uriniferous 
tube,  e'  e'.  Efferent  vessels 
which  subdivide  in  the  plexus 
p,  surrounding  the  tube,  and 
finally  terminate  in  the  branch 
of  the  renal  vein,  e.   (Bowman.) 


Each 
of  an 


1  Lauri-ntii  Bellini  Exercitatio  anatomica  de  structura  et  usu  renum,  pp.  64-72,  Fig.  x.    Amstelodami, 
16C5. 

-   Mem.  de  PAcad.  des  Sciences,  1740,  p.  284,  pi.  14  and  15. 

3  Abhand.  d.  K.  Ges.  d.  Wiss.  zu  Gottingen,  1862,  x.  4  Op.  cit. 

Di   glandularum  secernentium  structura  penitiore,  p.  101.     Lepsiae,  1830. 

8  Marcelli  Malpighi   Philosophii  et  Med.  Bon  E.  Soc.  Reg.   Operum,  torn.  sec.     Loudini,  168(i      I  i 
Renibus. 

"  Phil.  Trans.,  1842,  p.  57. 


512  THE     KIDNEYS. 

inch)  in  diameter,  including  the  investing  capsule,  consists  of  a  close-set, 
spheroidal,  knot-like  net  of  capillaries,  from  which  emerge  an  efferent 
vessel  ef,  which,  together  with  other  efferent  vessels,  forms  a  capillary 
network  (/>)  along  and  between  the  uriniferous  tubules.  From  this 
nt't  work  the  renal  veins  (V)  originate,  which,  converging,  form  the 
external  surface  of  the  kidney  toward  the  bases  of  the  pyramids,  pass 
through  the  sinus,  and,  becoming  confluent,  emerge  as  one  trunk  (Fig. 
259,  7)  from  the  hilus.  The  water,  urea,  etc.,  having  been  excreted  by 
the  epithelial  cells  lining  the  uriniferous  tubules  from  the  blood  brought 
to  them  by  the  renal  artery,  elaborated  as  the  urine-,  passes  down  through 
the  uriniferous  tubules,  finally  dribbling  out  of  their  orifices  situated, 
as  already  mentioned,  at  the  apices  or  summits  of  the  Malpighian  pyra- 
mids (Fig.  259,  3),  one  or  more  of  the  latter  projecting  into  one  of 
the  calices  or  infundibula,  into  which  the  pelvis  or  upper  expanded  por- 
tion  of  the  ureter  (4)  (within  the  sinus),  is  subdivided,  a  further  passage- 
way  is  provided  by  which  the  urine  is  conveyed  to  a  temporary  reser- 
voir— the  bladder — a  musculo-membranous  sac,  from  which  it  is  finally 
eliminated  during  micturition  from  the  body.  The  calices,  pelvis  of  the 
ureter,  and  the  ureter  proper  consist  externally  of  a  fibrous  coat,  of  a 
middle  unstriated  muscular  one,  and  internally  of  a  lining  mucous  mem- 
brane. The  fibrous  layer  of  the  calices  at  the  base  of  the  pyramid 
becomes  continuous  with  that  investing  the  sinus  of  the  kidney,  the  latter, 
in  turn,  being  a  continuation  of  its  external  fibrous  capsule  ;  the  middle 
muscular  layer  thinning  awray  at  the  pelvis,  disappears  altogether  at 
the  base  of  the  pyramids,  while  the  mucous  membrane  of  the  calyx  is 
reflected  upon  the  pyramids,  becoming  continuous  at  the  orifice  with 
that  of  the  urinifeiT>us  tubule.  It  is  eivident,  therefore,  that  leaving  out 
of  consideration  the  anatomical  details  just  described,  that  a  kidney, 
physiologically,  may  be  regarded  as  consisting  essentially  of  one  or 
more  uriniferous  tubules,  supplied  with  blood,  a  uriniferous  tubule  con- 
sisting of  basement  membrane  separating  blood  on  the  one  side  from 
a  secreting  cell  on  the  other.  When  reduced,  therefore,  to  its  simplest 
expression,  the  structure  of  the  kidney  does  not  differ  in  any  way  from 
that  of  glands  in  general. 

The  Urine. 

The  urine  is  a  clear,  amber-colored  fluid,  of  a  watery  consistence,  con- 
taining a  little  mucus,  saltish  in  taste,  with  a  characteristic  though  not 
disagreeable  odor,  acid  in  reaction,  and  with  a  specific  gravity  varying 
between  1.020  and  1.025.  The  color  of  the  urine  appears  to  be  due  to 
a  substance  not  yet  satisfactorily  isolated,  but  which,  when  slightly 
modified,  gives  rise  to  the  substances  variously  known  as  urochrome, 
urosin,  urosacin,  htemaphaelin,  urohsematin,  uroxanthin,  urobilin,  and 
hydrobilirubin,  the  latter  terms  indicating  the  affinity  evidently  ex- 
isting between  the  coloring  matter  of  the  bile  and  that  of  the  urine, 
whatever  the  latter  may  be,  as  seen  by  the  readiness  with  which,  by 
the  addition  of  water  and  abstraction  of  oxygen,  the  coloring  matter  of 
the  bile  is  transformed  into  that  of  the  urine,  or  one  of  its  modifications, 
as  shown  by  the  following  formula : 

Bilirubin  Urobilin. 

2(C16H18N203)  +  2(H20)  -  O  =  C32H40N4O7. 


THE    URINE, 


513 


Fig.  262. 


In  all  probability  the  coloring  matter  of  the  urine  is  derived  from 
that  of  the  bile,  the  varying  tints  often  observed,  from  an  amber  color 
to  red,  being  due  to  the  oxidation  of  the  former  substance.  The  acidity 
of  the  urine  is  not  due  to  free  acid,  as  can  be  shown  by  there  being  no 
precipitate  formed  on  the  addition  of  sodium  hypophosphite,  but  to  the 
presence  of  the  acid  sodium  phosphate,  NaH2P04,  the  latter  salt  being 
probably  formed  by  the  reduction  of  the  basic  sodium  phosphate, 
Na2HP04,  of  the  blood  by  abstraction  of  one  equivalent  of  its  sodium  by 
uric,  hippuric,  or  carbonic  acid,  and  sodium  urate,  hippurate,  or  car- 
bonate, formed,  as  may  be  seen  from  the  following  formula,  for  example  : 

Sodium  phosphate.        Uric  acid.        Acid  sodium  phosp.  Sodium  urate. 

2Na2HP04  +  C5H4N403  =  2Na  H2P04  +  Na2C5H2N403. 

The  acidity  of  the  urine,  due  to  acid  sodium  phosphate,  as  measured 
by  the  amount  of  a  standard  solution  of  caustic  soda  necessary  to 
neutralize  it,  is  equivalent  to  about  three  grammes  of 
oxalic  acid  in  twenty-four  hours,  supposing  the  urine 
voided  in  that  time  to  amount  to  1200  c.  cm.  The 
solution  of  soda,  of  such  a  strength  that  each  cubic 
centimetre,  containing  0.0031  gramme  of  soda,  exactly 
neutralizes  0.0063  gramme  of  oxalic  acid,  is  added, 
drop  by  drop,  to  a  given  quantity  of  urine — say  100  c.cm., 
until  litmus  paper  changes  violet  in  color,  i.  e.,  neither 
to  red  nor  blue.  The  number  of  cubic  centimetres  of  the 
soda  solution,  as  read  off  on  the  burette,  say  30,  when 
multiplied  by  0.0063,  Avill  give  then  the  amount  of 
acidity,  or  0.1890,  in  100  c.  cm.  of  urine,  as  measured 
in  grammes  of  oxalic  acid,  and,  consequently,  of  2.2. 
grammes  in  1200  c.  cm. 

The  specific  gravity  of  the  urine,  a  matter  of  great 
importance  practically,  is  readily  determined  by  the 
urinometer  (Fig.  262),  the  stem  of  which  is  so  graduated 
that  when  immersed  in  water  the  level  of  the  latter 
stands  at  that  portion  of  the  stem  marked  conveniently 
1000,  the  level  at  which  the  urine  stands,  as  read  off  on 
the  urinometer  when  the  latter  is  immersed  in  the  urine 
giving  the  specific  gravity  sought.  A  convenient 
method  of  determining  the  solids  of  the  urine,  approxi- 
mately, at  least,  is  by  means  of  what  is  generally  known 
as  Trapps,  or  Christison's  formula,  based  upon  the 
fact,  as  empirically  shown  by  that  chemist,  of  the  specific 
gravity  of  the  urine  bearing  generally  a  close  relation 
to  the  solid  matters  which  it  contains  in  solution.  The 
rule  is  as  follows:  Multiply  the  last  two  figures  (22) 
of  a  given  specific  gravity  expressed  in  four  figures — 
say  1.022,  by  2.33;  the  result,  22  X  2.33  =  51.26 
grammes,  will  be  the  amount  of  solids  contained  in  1000  (lanbois.) 
parts  of  urine  having  a  specific  gravity  of  1.022,  and  if  the 
urine  passed  in  twenty  four  hours  amounts  to  1200  c.  cm.,  then  the 
solids  will  be  increased  proportionally,  1000  :  1200  :  :  51.26  :  x  =  61.51 

33 


1000 


.1010 


1020 


1030 


—1040 


514  THE    KIDNEYS 

grammes.     If  the  specific  gravity  of*  the  urine  be  below  1.018,  greater 
accuracy  will  be  obtained  by  multiplying  by  2  instead  of  2.33. 

The  daily  quantity  of  mine  excreted  amounts  in  the  adult  man,  on 
the  average,  according  to  Parkes.1  who  has  compared  the  observations 
of  manv  observers,  to  about  fifty-two  and  a  half  fluid  ounces.  As  little  as 
thirty-five  ounces,  and  a-  much  as  eighty-one  ounces  may,  however,  be 
voided  within  the  limits  of  health,  and  it  may  lie  added  that  almost  every 
intervening  number  between  these  limits  has  been  given  as  the  usual 
average,  the  very  greatest  difference  prevailing  in  this  respect.  Apart, 
however,  from  personal  peculiarities,  the  amount  of  urine  excreted  is 
also  influenced  by  sex,  age,  and  season  of  the  year.  Thus,  more  urine 
is  excreted  by  women  than  men,  more  by  children,  relatively  to  their 
weight,  than  by  adults;  more  in  winter,  the  skin  being  then  less  active, 
than  in  summer.  When  it  is  considered  that  the  quantity  and  quality 
of  the  urine,  as  we  shall  see,  are  influenced  by  such  conditions  as  wake- 
fulness, sleep,  rest,  exercise,  solid  and  liquid  food,  it  might  be  naturally 
supposed  that  considerable  differences  would  present  themselves  in  the 
urine  passed  at  different  times  during  the  day.  usually  five  or  six  times 
within  the  twenty-four  hours.  As  a  matter  of  fact,  diurnal  variations  do 
succeed  each  other  quite  regularly.  Thus,  the  urine  collected  during 
the  night  and  voided  early  in  the  morning,  is  strongly  colored,  distinctly 
acid,  and  of  a  high  specific  gravity  :  toward  noon  it  becomes  paler,  less 
dense  (1.003  to  1.008).  and  less  acid,  the  acidity  even  disappearing 
altogether:  during  the  afternoon  and  evening,  the  color,  density,  ami 
acidity  increase,  while  by  night  it  has  become  again  highly  colored, 
markedly  acid,  and  with  a  specific  gravity  of  1.028  or  even  1.030.  As 
these  diurnal  variations  are.  however,  increased  or  diminished  by  the 
amounts  of  liquids  taken,  and  as  the  acidity  of  the  urine  is  inversely 
as  that  of  the  stomach,  and  may  be  more  or  less  neutralized  by  fruits, 
vegetables,  etc.,  the  lactates,  malates,  and  tartrates  of  the  same  being 
replaced  within  the  system  by  carbonates,  and  reappearing  in  that 
form  in  the  urine,  it  is  evident  that  if  the  acidity  and  specific  gravity 
are  to  be  determined,  one  sample  voided  will  not  suffice,  but  that  the 
entire  quantity  passed  in  twenty-four  hours  should  be  examined,  and 
the  mean  result  taken.  It  is  worth  while  mentioning  that  with  refer- 
ence to  the  liquids  absorbed  by  the  system  or  lost,  that  under  normal 
conditions  the  relation  of  the  specific  gravity  of  the  urine  to  that  of 
the  liquids  is  an  inverse  one.  Thus,  if  a  great  quantity  of  liquid  be 
taken,  or  the  perspiration  be  diminished,  the  amounts  of  solids  remain- 
ing the  same,  the  specific  gravity  of  the  urine  will  be  diminished, 
whereas,  if  drinks  be  abstained  from,  or  the  perspiration  be  increased, 
the  specific  gravity  will  be  increased.  If,  however,  notwithstanding 
that  a  great  quantity  of  liquid  be  absorbed,  the  specific  gravity  still 
remains  high,  or  with  a  diminution  in  the  liquid  the  specific  gravity 
remains  low,  there  would  be  reason  to  suspect  disease  through  the 
increase  or  diminution  respectively  in  the  solid  constituents  of  the 
urine,  and  such  would  also  be  the  case  if,  the  specific  gravity  remaining 
constant,  the  quantity  of  urine  increased  or  diminished,  and  vice  versa. 

1  On  the  Urine   p.  5.     London,  1860. 


CONSTITUENTS    OF    THE    URINE 


515 


Table  LXXI.1- 


-CONSTITUENTS  OF  UrIaME  AND  AMOUNTS  EXCRETED  IN 

Twenty-four  Hours. 


Urea 

Uric  acid 

Allantoin 

Hippuric  acid 

Kreatinin 

Sugar    . 

Xanthin 

Paraphanic 

Kryptophanie 

Phenylic 

Taurylic 

Damaluric         \-  acids 

Damolic 

Fatty 

Oxaiuric 

Oxalic 

Pigment 

Mucus  .... 

Inorganic  salts,  composed 


Average  quantity 

Average  quantity  excreted 

excreted  in 

24 

in  24  hrs.  in  grs.  for  each 

^hours  in 

1  lb.  of  body 

*  grains. 

weight  (150). 

512 

3.5 

8.5 

0.057 

Trace. 

15 

o.i ' 

15 

0.1 

Traces. 


of 


Sulphuric 

Phosphoric 

Nitric 

Silicic 

Chlorine 

Potassium 

Sodium 

Calcium 

Ammonium 

Magnesium 

Iron 


1 


acids . 


140.00  to  380.00 

17.34  to    41.14 

31 .00  to    79.00 

Traces. 

Traces. 

51.87  to  173.2 

26.36  to  107.7 

79.75  to  171.0 

2.33  to      6.36 

Trace. 
2.53  to      4.21 
Trace. 


0.933  to  2.53 
0.115  to  0.27 
0.207  to  0.526 


0.345  to  1.154 
0.175  to  0.718 
0.531  to  1.14 
0.015  to  0.042 


0.016  to  0.028 


The  urine  conveying  out  of  the  body,  as  we  have  seen,  many  of  the 
proximate  principles  to  their  derivatives,  the  latter  having  played  their 
part  in  the  economy,  must  necessarily  be  a  highly  complex  fluid  con- 
sisting of  both  organic  and  inorganic  principles.  That  such  is  the  case 
is  evident  from  the  composition  of  the  urine  as  given  in  Table  LXXL, 
after  Carpenter,  based  principally  upon  the  works  of  Parkes,2  Thudi- 
chum,3  Neubauer,4  and  Vogel.  Of  the  various  constituents  of  the 
urine,  whether  organic  or  inorganic,  urea  existing  in  about  2.6  parts 
per  hundred,  about  half  the  solid  matters  of  the  urine,  is  the  most  im- 
portant. Urea  consists  of  carbon,  oxygen,  nitrogen  and  hydrogen 
united  in  the  proportions  shown  in  the  formula  CON2H4,  and  is 
isomeric,  therefore,  with  ammonium  cyanate,  NH4CNO.  Urea  is,  how- 
ever, regarded  by  chemists  as  being  carbamide  or  the  diamide  of  carbonic 

acid  as  expressed  in  the  formula  CO  <  ^ttt2   Urea  is  a  colorless  neutral 

substance,   very  soluble  in  water  and  boiling  alcohol,  but  insoluble  in 
ether,  and  crystallizing   in  four-sided  prisms  (Fig.  2t}3).      Urea  can  be 


1  Carpenter's  Physiology,  1881,  p.  468. 

1  On  the  Pathologj  ofthe  Urine.     London,  1858. 

*  On  the  Urine,  Nev  Syd.  Soc.  Trans.     London,  1S63. 


2  Op.  cit. 


516 


THE     KIDNEYS 


readily  obtained  from  the  urine  in  the  following  manner.  Add,  say, 
half  a  drachm  of  pure  nitric  acid  to  a  drachm  of  concentrated  urine  in  a 
watch  glass  and  set  aside  to  cool.  The  nitrate  of  urea  then  formed  will 
be  precipitated  as  a   yellow  crystalline  mass.     The  insoluble  nitrate 


Fig.  263. 


Urea,  prepared  from  urine,  and  crystallized  by  slow  evaporation.     (Lehmann.) 


caught  on  a  filter,  dried,  and  dissolved  in  boiling  water,  is  mixed  with 
animal  charcoal  to  remove  coloring  matters  and  filtered  while  hot. 
The  filtrate  being  then  allowed  to  cool,  colorless  crytals  of  nitrate  of 
urea  will  be  deposited.  The  latter  being  dissolved  in  boiling  water 
and  barium  carbonate  added  as  long  as  effervescence  takes  place, 
barium  nitrate  and  urea  will  be  produced,  from  which  after  evaporating 
to  dryness  the  urea  can  be  extracted  with  absolute  alcohol.  On  evaporat- 
ing the  alcoholic  solution  of  urea  crystals  of  pure  urea  are  obtained. 
As  may  be  seen  from  Table  LXXL,  as  much  as  512  grains  of  urea  are 
excreted  on  an  average  daily,  which,  consisting  of  46.6  per  cent.,  or  235 
grains,  nitrogen,  may  be  regarded  as  the  chief  especial  product  of  the 
oxidation  of  the  nitrogenous  food  or  tissue,  or  both,  and  to  a  great  extent 
taken  as  the  measure  of  the  disintegration  of  the  same,  since  with  the 
above  amount  of  urea,  the  amount  of  nitrogen  excreted  by  the  skin 
and  in  the  feces  would  amount  to  only  about  0.6  grain  and  18  grains 
respectively.  It  is,  therefore,  of  great  importance  that  we  should  have 
some  ready  method  of  determining  the  amount  of  urea  present  in  a  given 
quantity  of  urine.  Of  the  different  methods  in  use  none  is  more 
convenient  or  more  accurate  than  that  of  Davy,  based  upon  the  decom- 
position of  urea  by  sodium  hypobroniite — the  nitrogen  of  the  urea  being 
set  free,  and  with  caustic  soda  in  excess,  the  carbonic  acid  developed 
combines  with  the  soda,  the  water  being  retained  in  the  mixture ;  the 
amount  of  urea  is  determined  by  the  amount  of  nitrogen  evolved.  The 
experimental  procedure  is  as  follows  :  A  given  quantity  of  urine,  say 
4  c.  cm.,  is  placed  within  the  vessel,  and  about  25  c.cm.  of  a  solution  of 
sodium  hypobromite  freshly  made  by  dissolving  100  grammes  of  caustic 
soda  in  250  c.  cm.  of  water,  to  which  are  added  25  c.  cm.  of  bromine  in 


DETERMINATION    OF    UREA.  517 

the  vessel.     The  immediate  effect  of  the  mixing  of  the  urine  with  the 
hypobromite  is  the  development  of  N,  as  seen  from  the  following  reaction : 

CON./H,  +  3(NaBrO)  +  2(NaOH)  =  3NaBr  +  Na,C03  +  3H20  +  2N. 

The  free  nitrogen  passing  into  and  being  collected  by  the  graduated 
tube  standing  over  mercury,  will  be  found  to  amount  to  30  c.  cm., 
supposing  at  the  moment  of  the  experiment  the  thermometer  registers 
15°  C.  (59°  ¥.),  and  the  barometer  740  mm.  (29.6  in.),  or  27.6  c.  cm. 
if  the  volume  of  30  c.  cm.  be  corrected  for  temperature  and  pressure 
by  the  methods  already  explained.  Now,  since  100  grammes  of  urea 
contain  46.6  gr.  of  nitrogen,  1  gramme  of  urea  will  contain  0.466 
of  a  gramme  of  nitrogen,  and  as  1000  c.  cm.  of  nitrogen  weigh  1.252 
grammes,  372  c.  cm.  of  nitrogen  will  weigh  proportionally  0.466  of  a 
gramme;  but  as  0.466  of  a  gramme  of  nitrogen  corresponds  to  1  gr.  of 
urea,  the  latter  will  give  off  372  c.  cm.  of  nitrogen,  and  the  0.0027  of  a 
gramme  of  urea  proportionally  1  c.  cm.  of  nitrogen.  If  now  the  27.6 
c.  cm.  of  nitrogen  collected  in  the  graduated  tube  given  off  from  the 
urine  be  multiplied  by  1.0027,  or  the  amount  of  urea  in  grammes 
corresponding  to  a  cubic  centimetre  of  nitrogen  at  standard  tempera- 
ture and  pressure,  the  product,  0.0745  gramme,  will  be  the  amount 
of  urea  in  4  c.  cm.  of  urine,  and  consequently  34  grammes  (524  grains) 
in  1300  c.  cm  of  urine,  or  the  amount,  say,  passed  in  twenty-four 
hours.  Such  a  rough  and  ready  method  for  the  determination  of  urea 
as  that  just  given,  like  all  other  similar  ones,  is  open  to  some  criticism, 
the  most  important  of  which  is,  that  uric  acid  and  other  nitrogenous 
principles  present  in  the  urine,  like  urea,  are  also  decomposed  by 
hypobromites  or  hypochlorites,  the  latter  being  used  as  well  as  the 
former  to  free  the  nitrogen.  The  quantity  of  such  nitrogenous  princi- 
ples is,  however,  so  small  that  the  error  introduced  can  be  neglected 
without  materially  affecting  the  accuracy  of  the  result. 

While  the  urea  excreted  by  an  adult  amounts  on  an  average  in  24 
hours,  as  has  already  been  mentioned,  to  about  512  grains,  it  must  be 
mentioned  that  the  quantity  eliminated  varies  very  considerably  with 
the  age,  weight  of  body,  sex,  period  of  the  day,  season,  and  kind  of 
food.  Thus  children  of  from  three  to  seven  years  of  age,  weighing  say, 
30  lbs.,  in  daily  excreting,  may  be,  240  grs.  of  urea,  eliminate  more  than 
half  that  excreted  by  an  adult,  459  grains,  weighing,  however,  153 
pounds,  or  more  than  five  times  as  heavy.  In  other  words,  while  an 
adult  man  excretes  for  each  pound  of  body  weight  about  3  grs.  of  urea, 
a  boy  excretes  7.5  grs.,  or  more  than  twice  as  much.  As  might  be 
expected,  therefore,  the  amount  of  urea  excreted  continues  to  diminish 
as  age  advances.  It  would  appear  that  less  urea  is  excreted  by  the 
female  than  the  male  in  the  proportion,  perhaps,  of  about  half  a  grain 
less  in  the  female  for  each  pound  of  body  weight,  and  that  the  amount 
is  diminished  during  menstruation.  The  hour  of  the  day  apparently 
also  exerts  an  influence  upon  the  excretion  of  urea,  the  greatest  amount 
being  eliminated  after  breakfast  and  tea,  the  least  during  the  night.  The 
increase  or  decrease  observed  may  be,  however,  due,  to  a  certain  extent, 
as  we  shall  see,  to  the  taking  of  or  the  abstaining  from  food.  Like  the 
urine,  more  urea  is  probably  eliminated  in  cold  than  in  warm  weather. 


518  THE    KIDNEYS. 

It  is  difficult,  if  not  impossible,  to  give  exact  numerical  estimates. 
According  to  Dr.  E.  Smith,1  the  daily  variations  in  himself  amounted  in 
a  year  from  between  219  to  700  grains,  the  average,  on  the  whole,  being, 
however,  510  grains.  Of  the  conditions  influencing  the  production  of 
urea,  none  is  so  important  as  that  of  the  taking  of  food.  This 
becomes  at  once  evident  when  the  amount  of  urea  excreted  upon  a 
vegetable  or  mixed  diet  is  compared  with  that  of  a  highly  animal  one. 
Thus  while  the  urea  excreted  by  Ranke,2  during  24  hours  on  a  vegetable 
diet,  amounted  to  only  264  grains,  and  on  a  mixed  to  between  463  and 
617  grains,  on  a  highly  animal  diet  it  was  increased  to  as  much  as  1332 
grains,  or  nearly  three  times  as  much  as  normal.  From  such  facts  as 
that  nearly  all  of  the  nitrogen  of  the  food  consumed  passes  out  of  the 
body  in  the  form  of  urea  in  the  urine,  each  grain  of  urea  implying  the 
disintegration  of  3  grains  of  albuminous  matter,  or  about  15  grains  of 
meat,  and  that  the  amount  of  urea  excreted  attains  its  maximum  within 
five  to  seven  hours  after  the  taking  of  food,  it  would  appear  that  by  far 
the  greatest  amount  of  the  urea  produced  must  be  derived  directly  from 
the  disintegration  of  the  albuminous,  nitrogenous  food  brought  about 
through  fermentation,  oxidation,  etc.,  as  already  mentioned,  it  being 
absurd  to  suppose  that  of  the  five  pounds  of  meat  eaten  by  a  large  dog, 
to  take  an  extreme  instance,  the  albuminous  matter  of  the  same  should 
be  first  transformed  into  tissue,  then  decomposed  into  urea,  and  elimi- 
nated by  the  kidneys  within  the  short  space  of  24  hours.  It  appears 
to  us  at  least  more  reasonable  to  suppose  that  the  albumen  of  the  food 
goes  through  the  system  like  a  dose  of  salts,  so  to  speak,  with  the  dif- 
ference, however,  that  the  albumen  entering  the  body  as  such  in  the 
food,  leaves  it  in  the  excreta  as  urea,  carbonic  acid,  and  water.  If  the 
above  view  of  urea  being  derived  from  nitrogenous  food  rather  than 
nitrogenous  tissue  be  accepted,  it  is  readily  understood  why  muscular 
exertion  does  not  increase,  as  was  once  supposed,  the  production  of  urea, 
for  muscular  force,  being  like  all  other  kinds  of  so-called  vital  force, 
transformed  heat,  and  the  latter  being  developed,  if  not  exclusively, 
at  least  to  a  greater  extent  out  of  fats  and  carbohydrate  than  albu- 
minous food,  it  follows  that  muscular  activity  will  be  measured  not  by 
the  amount  of  urea  but  by  that  of  the  carbonic  acid  produced.  Such 
theoretical  considerations  are  fully  borne  out  by  the  experiments  of 
Smith,  Lehmann,  and  Voit.  In  the  celebrated  ascension  of  the  Faul- 
horn  by  Fick  and  Wislicenus,3  in  1866,  involving  considerable  muscular 
exertion,  as  may  be  imagined,  it  will  be  seen  from  Table  LXXII.  that 
so  far  from  the  urine  being  increased  during  the  period  of  ascent,  lasting 
8  hours  and  10  minutes,  and  the  6  hours  immediately  following,  as 
measured  by  the  nitrogen  eliminated,  it  was  actually  diminished,  since 
while  during  the  12  hours  preceding  the  ascent  the  urea  excreted  by 
Fick,  for  example,  measured  by  the  106.7  grs.  of  nitrogen  eliminated, 
would  amount  to  about  228  grs.  during  the  period  of  14  hours,  includ- 
ing not  only  the  8  hours  of  work  in  the  ascent  but  the  succeeding  6 
hours  of  rest,  it  would  amount  to  only  190  grs.,  as  measured  by  the 
88.6  grs.  of  nitrogen  eliminated. 

i  Proc.  of  Royal  Soc,  May  30,  1861.     Carpenter's  Physiology,  1881,  p.  470. 

2  Physiologie,  1872,  S.  509.  3  London  Phil.  Magazine,  1806,  p.  485. 


INFLUENCE    OF    MUSCULAR    EXERCISE.  519 

Table  LXXII.1 — Ascent  of  the  Faulhorx  (6417.5  feet). 

Weight  of  Fick.  L45.5  lbs.  X  6417.5  =    933746  foot  pounds. 

"   Wislicenus,  167.5  lbs.  X  6417.5  =  1074931     " 

Grains  of  nitrogen  excreted  bj 

Night  urine  previous  to  ascent 
Work  8  hours  10  min.    . 

After  work  6      " 

Night  (after  a  meal)  10.]  hours 

88.6  grs.  X  of  Fiek  derived  from  575.0  grs.  of  muscle. 

85.6     "      "      Wislicenus         "  "     555.5       "  " 

575.0  grs.  of  muscle  of  Fick  burned  raised  498525  lbs.  1  foot. 

555.5        "        "        "   Wislicenus        "  "      481618     "     " 


Fick. 

w 

isliceuus. 

106.7 

103.2 

51.1 

48.3 

37.5 

88.6 

37.3 

74.3 

82.5 

Fick. 

Wislicenus. 

tVork  of  ascending  mountain 
"     "    circulation 
"     "    respiration 

.     933746 
.     183348 
.       37620 

1074!  131 
213906 

43890 

"    foot  pounds       ....  1154714  1332727 

done  from  burned  muscle      .         .     498525  481618 


"        "     unaccounted  for    .         .         .     656189  851109 

It  being  borne  in  mind  that  no  albuminous  food  had  been  taken  for 
seventeen  hours  previous  to  the  ascent  by  Fick  or  Wislicenus,  their  diet 
consisting  of  cakes  made  out  of  fat,  starch,  and  sugar,  it  is  not  strange 
that  the  amount  of  urea  excreted  should  have  been  small,  it  being; 
derived  from  the  albuminous  tissues  of  the  body;  the  latter  supplying 
the  albuminous  food  that  would  have  been  otherwise  present  had  the 
diet  been  a  mixed  one.  It  is  well  known  that,  even  in  starvation,  more 
urea  is  excreted  than  on  a  diet  consisting  of  sugar,  fat,  etc.,  since  the 
latter  substances,  in  supplying  ready  materials  for  combustion,  spare  the 
tissues  of  the  body. 

That  there  is  an  enormous  amount  of  potential  force  locked  up  latent, 
so  to  speak,  in  sugars,  etc.,  is  made  evident  in  the  extreme  weakness 
and  emaciation  so  noticeable  in  diabetes,  since  the  sugar  in  that  disease, 
instead  of  being  burned,  and  constituting  as  normally  a  source  of  heat 
and  force,  passes  unoxidized  out  of  the  body.  The  amount  of  force 
lost  to  the  system  under  such  circumstances  may  be  judged  of  when  it 
is  remembered  that  in  extreme  cases  of  diabetes  as  much  as  40  ounces 
of  sugar  are  passed  in  the  urine  in  twenty-four  hours,  and  that  if  the 
16  ounces  of  carbon  contained  in  such  an  amount  of  sugar  were  oxi- 
dized, heat  enough  would  be  produced,  if  applied  mechanically,  to  raise 
20  millions  of  pounds  1  foot  high,2  or  carry  a  man  weighing  130 
pounds  on  a  level  66  miles.  The  system  being  deprived,  therefore,  in 
this  disease  of  such  a  source  of  force,  draws  upon  the  albuminous  tissues, 
hence  the  characteristic  emaciation  and  weakness.  It  is  evident,  also, 
as  may  be  seen  from  Table  LXXII.,  on  the  supposition  that  the  com- 
bustion of  muscle  is  the  source  of  its  power,  that  the  burning  of  575 

i  Letheby  On  Food,  p.  64.     London,  1872. 

2  H.  Bence  Junes  :  Pathology  and  Therapeutics,  p.  73.     London,  1867. 


520  THE    KIDNEYS. 

grains  of  the  muscular  tissue  of  Fick's  body,  as  implied  in  his  elimina- 
tion of  88.6  grains  of  nitrogen,  would  not  suffice,  in  his  case,  to  account 
for  the  work  actually  performed  by  him  in  ascending  the  Faulhorn  by 
650,189  foot-tons,  and  the  same  is  true  by  almost  as  large  an  amount 
in  the  case  of  Wislicenus,  the  work  unaccounted  for  being  evidently 
due  to  the  heat  developed  through  the  combustion  of  the  starch,  sugar, 
and  fat.  Essentially  the  same  result  was  obtained  more  recently  by 
Haughton,1  who  found,  while  walking  five  miles  a  day,  that  the  urea  elimi- 
nated amounted  to  501.28  grains ;  that  when  the  walk  was  increased  to 
20.74  miles  a  day,  and  kept  up  for  five  consecutive  days,  the  urea  elimi- 
nated amounted  to  only  501.16  grains,  or  actually  less.  Parkes2  found, 
also,  that  in  the  case  of  two  soldiers,  who  walked  in  two  days  56  miles 
on  a  non-nitrogenous  diet,  that  the  total  increase  of  nitrogen  eliminated 
amounted,  in  the  one  case,  to  only  about  3  grains ;  and,  in  the  other, 
15  grains;  corresponding  to  an  increase  of  6.4  grains,  and  32.1  grains 
of  urea,  respectively,  in  forty-eight  hours.  The  case  of  Weston,  who 
walked  over  300  miles  in  five  consecutive  days,  cited  by  Flint3  as  an  illus- 
tration of  urea  being  increased  by  muscular  exercise,  illustrates  really 
only  what  we  have  already  seen  to  be  the  case,  that  the  amount  of  urea 
excreted  is  greatly  increased  upon  a  highly  nitrogenous  diet,  and  that 
heat,  the  ultimate  source  of  muscular  force,  can  be  developed  through 
the  combustion  of  albuminous,  as  well  as  of  fatty  or  carbohydrate 
foods,  the  former  means  of  obtaining  the  necessary  heat  being,  however, 
a  far  more  expensive  way  than  the  latter,  and  entailing  greater  work 
upon  the  system.  It  is  true  that,  if  the  coal  gives  out,  the  steamer 
can  be  supplied  with  fuel  from  its  masts,  shrouds,  etc.,  and  other  integral 
parts  of  its  structure ;  one  does  not  resort,  however,  save  in  dire  neces- 
sity, to  such  a  source  of  fuel.  The  facts  of  the  case  of  Weston,  just  referred 
to,  are  essentially  as  follows :  Weston  walked  in  five  consecutive  days 
310  miles,  losing  in  weight  3J  pounds.  1173.80  grains  of  nitrogen  were 
taken  into  the  system  in  the  food,  and  1807.60  grains  were  eliminated 
from  it  in  the  excreta,  leaving  633.80  grains  of  nitrogen  to  be  accounted 
for,  which  were  evidently  derived  from  the  3  pounds  of  tissue  lost, 
the  latter  containing  633.80  grains  of  nitrogen  ;  the  remaining  quarter 
of  a  pound,  lost  in  weight,  corresponded,  probably,  to  the  produc- 
tion of  water  or  fat.  Such  being  the  case,  and  Weston  being  trained 
down,  and  having,  therefore,  little,  if  any,  superfluous  fat  or  carbo- 
hydrate matter  at  disposal  for  the  production  of  heat  or  force,  it 
would  appear,  from  the  large  quantity  of  nitrogen  eliminated,  that  his 
albuminous  tissues  were  largely  drawn  upon  to  supply,  through  com- 
bustion, the  heat  incidental  to  the  production  of  such  a  muscular  effort. 
The  3  pounds  of  muscular  tissue  lost  by  Weston  during  the  walk, 
supplied,  therefore,  the  body  with  3  pounds  of  albuminous  food,  which, 
in  being  consumed,  accounted  for  the  elimination  of  633.80  grains  of 
nitrogen,  corresponding  to  1124  grains  of  urea,  just  as  if  he  had  eaten 
3  pounds  of  butcher's  meat,  instead  of  the  same  amount  of  his  own  body. 
That  this  conclusion  is  not  merely  a  theoretical  one  is  shown  by  the 

i  British  Medical  Association,  1868.  -  Proc.  Royal  Soc,  1867,  No.  89,  94. 

3  New  York  Medical  Journal,  1871,  p.  687. 


OEIGIN    OF    UREA.  521 

fact  of  Rubner,1  weighing  158  pounds,  being  able  to  consume  2.87 
pounds  of  meat,  of  which  2.84  were  perfectly  destroyed  in  the  system, 
giving  rise  to  a  corresponding  quantity  of  urea  and  nitrogen. 

Not  only  has  it  been  held  that  muscular  activity  increases  the  amount 
of  urea,  but  mental  and  sexual  activity  as  well.  Even  if  such  is  shown, 
hereafter,  to  be  the  case,  apart  from  the  influence  exerted  by  nitrogenous 
food,  the  facts  are,  at  present,  too  few  to  offer  any  exact  numerical  esti- 
mate. It  would  appear,  from  what  has  just  been  said  with  reference  to  the 
production  of  urea,  that,  to  a  large  extent  at  least,  it  is  derived  directly 
from  the  nitrogenous  principles  of  the  food  without  the  latter  becoming 
first  tissue ;  and  while,  in  all  probability,  such  is  the  case,  it  must  be 
admitted  that  exactly  how  or  where  the  transformation  of  food  into  urea 
takes  place  has  not,  as  yet,  been  posith  ely  established.  It  will  be  remem- 
bered, however,  that,  in  speaking  of  intestinal  digestion,  leucin  and 
tyrosin  were  mentioned  as  being  among  the  products  of  the  action  of 
the  pancreatic  juice  upon  the  albuminous  principles  of  the  food,  and 
that,  together  with  the  latter,  the  glycin  of  the  decomposed  glycocholic 
acid  of  the  bile  was  reabsorbed.  Now  leucin,  C6Hu(H2N)02,  being 
amido-caproic  acid — that  is,  caproic  acid,  C6H1202,  in  which  an  atom 
of  hydrogen  is  replaced  by  the  residue  of  ammonia,  H2N,  and  tyrosin, 
CrII5(C2H5HN)03,  being  amido-ethyl  salicylic  acid — that  is,  salicylic 
acid,  CrH603,  in  which  an  atom  of  hydrogen  is  replaced  by  the  residue 
of  ethylamin.  or  C2H5HN  ;  glycin,  C2H3(H2N)02,  being  amido-acetic 
acid — that  is,  acetic  acid,  C2H402,  in  which  an  atom  of  hydrogen  is 
replaced  by  the  residue  of  ammonia;  it  is  readily  conceivable  how, 
through  the  disintegration  of  these  substances,  leucin,  tyrosin,  and 
glycin,  urea  could  be  formed  by  simply  supposing  that  the  residue  of 
ammonia,  NH2,  or  of  ethylamin,  C2H5HN,  entering  into  their  compo- 
sition, is  set  free,  becomes  NH3,  or  ammonia,  and  then  combines  with 
carbamic  acid,  C02XII3,  with  subsequent  dehydration,  as  follows  : 

Ammonium  carbamate.       Water.  Urea. 

C02X2H6    —    H,0    =    CON2H4 

the  caproic,  salicylic,  and  acetic  portions  of  the  leucin,  tyrosin,  and  glycin 
respectively  being  oxidized  into  water,  or,  in  the  case  of  the  caproic 
acid,  into  fat.  Or  what  is  also  probable,  that  ammonium,  NH4,  being 
developed  in  the  disintegration  of  the  albuminous  food  in  combining 
with  a  carbonic  acid  radical,  C03,  with  subsequent  dehydration,  would 
give  rise  to  urea  as  follow  s  : 

Ammonium  carbonate.  Water.  Urea. 

(NH4)2C03    -     2H.2<>     =     CON2H4 

or  with  that  of  cyanic  acid,  CNO,  to  form  ammonium  cyanate,  NH4CNO, 
which  is  isomeric  witli  urea.  As  a  confirmation  of  the  view  that  leucin 
and  glycin  are  antecedents  of  urea,  it  may  be  mentioned  that  feeding- 
dogs2  with  the  same  increases  the  amount  of  urea. 

There    being    no    difficulty    in    comprehending    how    urea    may    be 

i  Zeitschr.  ftlr  Biologie,  1879,  xv.  S  1-22. 

-  Schultzen  and  Nencki  :  /tit.  fur  Biologie,  1872. 


522  THE    KIDNEYS. 

developed  out  of  the  albuminous  principles  of  the  food  or  their  ammo- 
niated  derivatives — it  remains,  therefore,  only  to  show  where  the  trans- 
formation takes  place.  Now,  from  such  facts  as  that  of  the  liver 
containing  more  urea  than  any  other  gland  in  the  body,  as  shown  by 
Meisner,1  of  the  albuminous  principles  of  the  food,  of  the  glycin  of  the 
decomposed  bile,  of  the  leucin  and  tyrosin  of  the  spleen  being  carried 
by  the  portal  circulation  to  the  liver,  of  leucin  and  tyrosin  replacing 
urea  in  the  urine  in  acute  atrophy  of  the  liver,  the  conclusion  forces 
itself  upon  us  that  it  is  the  liver  that  elaborates  the  urea  out  of  the 
albuminous  principles  of  the  food,  etc.,  brought  to  it  by  the  portal  cir- 
culation. Admitting  that  by  far  the  greatest  quantity  of  urea  is 
derived  from  the  transformation  of  albuminous  food  in  the  liver,  it 
must  be  remembered  that  urea  is  not  only  found  in  the  liver,  but  in 
many  other  parts  of  the  system — in  the  chyle,  saliva,  blood,  serous 
fluids,  etc.,  and  that  in  starvation  in  the  absence  of  all  food,  though  the 
amount  of  urea  is  gradually  diminished,  it  is  nevertheless  present,  even 
to  the  last.  Of  course,  in  such  cases,  as  already  mentioned,  one  part 
of  the  body  being  nourished  at  the  expense  of  another,  the  nitrogenous 
tissues,  instead  of  food,  supply  the  materials  for  the  development  ot 
urea.  Urea  being  found  under  normal  circumstances  in  many  parts 
of  the  system,  and  being  derived  in  starvation  from  the  tissues,  it  is 
reasonable  to  suppose  that  part  of  the  urea  is  also  derived  from  the 
latter  even  when  nitrogenous  food  is  taken,  and  since  leucin  and  tyrosin 
are  found  in  the  thyroid,  thymus,  parotid,  and  submaxillary  glands, 
kidney,  liver,  and  suprarenal  capsules,  as  well  as  in  the  pancreas  and 
spleen,  analogy  would  lead  us  to  suppose  that  they  may  be  antecedents 
of  the  urea  derived  from  tissue,  as  we  have  supposed  them  to  be  of 
the  urea  derived  from  food.  In  this  connection  it  is  an  interesting 
fact  that  while  urea  is  not  found  in  the  muscles,  spleen,  or  nervous 
tissue,  kreatin,  C4H9N302,  enters  into  the  composition  of  muscles  to  the 
extent  of  two  per  cent.,  and  into  that  of  the  spleen  and  probably  of 
nervous  tissue  also.  Now  since  kreatin,  through  dehydration,  readily 
becomes  kreatinin,  C4H7N30,  and  the  latter  through  oxidation,  urea, 
CON2H4,  it  is  quite  probable  that  kreatin  may  be  an  antecedent  of 
urea  arising  out  of  the  disintegration  of  the  muscular  tissues,  etc.,  but 
converted  into  urea  elsewhere.  It  should  be  mentioned,  however,  that 
the  kreatin,  or  rather  kreatinin,  normally  found  in  the  urine  is  not 
that  of  the  muscular  tissue,  etc.,  just  alluded  to,  but  is  probably  derived 
from  the  food,  since  it  varies  in  quantity,  increasing  with  a  meat  diet, 
but  not  with  exercise,  and  is  absent  in  starvation.  On  the  supposition 
that  urea,  whether  derived  from  food  or  tissue,  is  not  elaborated  by  the 
kidneys,  but  simply  excreted  out  of  the  blood  brought  to  them,  we 
might  expect  to  find  that  the  blood  of  the  renal  artery  contained  more 
urea  (0.03  per  cent.)  than  that  of  the  renal  vein  (0.01  per  cent.),  but 
also  with  the  extirpation  of  the  kidneys,  or  the  ligation  of  the  ureters, 
which  has  practically  the  same  effect,  that  the  urea  would  accumulate  in 
the  blood,  and  such  has  been  found  to  be  the  case  according  to 
Grehant2  and   Gscheidlen3,  the  amount  being  increased  from  0.020  to 

l  Centralblatt  mod.  Wiss.,  1870,  S.  249.  2  Zeits.  fur  nat.  med.,  xxxi.  S.  144. 

3  Studieu  u.  d.  Ursprung  d.  Harnstoffs,  Leipsic,  1871 ;  also  Centralblatt,  1871,  p.  630. 


ORIGIN"    OF     UREA.  523 

206  percent,  in  twenty -four  hours,  while  Voit3  obtained  after  extirpation 
of  the  kidneys  in  an  animal  5.3  grammes  of  urea,  or  almost  the  same 
amount  as  would  have  been  normally  excreted  (5.8  grammes)  in  the 
same  time.  It  may  be  mentioned  that  the  toxic  effects  appearing  under 
such  circumstance  appear  to  be  due,  not  so  much  to  the  accumulation 
of  a  great  quantity  of  urea  as  to  the  retention  within  the  system  of  other 
undefined  albuminous  substances. 

1  Centralblatt,  1868,  p.  4GS. 


CHAPTER    X  X  X  V. 

THE  URINE. 

Of  the  remaining  constituents  of  urine,  next  in  importance  to  urea, 
as  representing,  like  it,  the  result  of  the  metamorphosis  of  nitrogenous 
food  and  tissue,  is  uric  acid,  C5H4N403.  Chemically,  uric  acid  may 
be  regarded  as  imperfectly  oxidized  urea,  a  molecule  of  uric  acid,  through 
oxidation  in  presence  of  water,  being  transformed  into  two  molecules  of 
urea  and  three  molecules  of  carbonic  acid,  the  carbonic  oxide  con- 
stituent of  the  uric  acid  being  oxidized  as  follows  : 

Uric  acid.  Water.  Oxygen.  Urea.         Carbonic  acid  gas. 

C5N4H403  +  2(H20)  +  03  =  2CON2H4  +  3C02. 

It  does  not,  however,  follow  that  uric  acid  is  invariably  an  antecedent  of 
urea.  Indeed,  the  production  of  uric  acid  and  urea  does  not  depend, 
according  to  many  physiologists,  so  much  upon  the  presence  of  oxygen 
as  upon  the  structure  of  the  uriniferous  tubules,  and  the  amount  of  water 
absorbed,  the  physical  conditions  involved  in  some  animals  being  better 
adapted  to  the  excretion  of  uric  acid,  and  in  others  to  that  of  urea.  That 
the  amount  of  uric  acid  and  ui'ea  respectively  produced  does,  however, 
depend  to  a  great  extent  upon  the  amount  of  oxygen  absorbed,  appears 
from  the  striking  contrast  offered  by  reptiles  and  mammals  when  con- 
sidered in  this  respect.  Thus,  while  in  reptiles,  in  which  respiration  is 
inactive,  uric  acid  is  the  principal  nitrogenous  constituent  of  the  urine, 
urea  being  absent ;  in  mammals,  on  the  contrary,  in  which  respiration 
is  active,  urea  is  the  most  important  of  the  nitrogenous  constituents, 
uric  acid  being  found  in  small  quantities,  both  absolutely  and  relatively 
with  reference  to  the  urea ;  in  man,  for  example,  about  8.5  grains  of 
uric  acid  only  being  excreted  in  twenty-four  hours,  or  one  part  of  uric 
acid  to  about  sixty  parts  of  urea,  as  may  be  seen  from  Table  LXXI. 
The  view  of  the  production  of  uric  acid  instead  of  urea  being  due  to 
defective  oxidation,  has  been  held,  however,  by  many  physiologists  to 
be  inconsistent  with  the  fact  that,  while  the  respiration  in  birds  is  more 
active  even  than  that  of  mammals,  the  urine  of  these  animals,  never- 
theless, contains  uric  acid  and  urates  instead  of  urea,  as  in  reptiles.  A 
little  consideration  will  show,  however,  that,  notwithstanding  the 
activity  of  their  respiration,  their  economy  is  such  that  it  is  an  advan- 
tage to  birds,  this  retention  of  the  ancestral  trait  (birds  being  only 
highly  specialized  reptiles)  of  producing  uric  acid  and  urates  instead  of 
urea.  Thus,  as  urged  by  Odling,1  while  the  respiration  of  birds  is  very 
active,  it  is  not  excessive,  when  considered  with  reference  to  the  great 

1  Animal  Chemistry,  p.  142.     London,  18G6. 


ORIGIN    OF    URIC    ACID.  525 

deed  of  oxygen  experienced  by  these  animals,  birds  being  more  depen- 
dent on  a  constant  supply  of  pure  air  than  any  other  animals.  Their 
organization  is.  therefore,  such  that,  while,  on  the  one  hand,  the  respira- 
tory surface  is  increased  in  every  possible  way,  notably  so  in  the  pre- 
datory birds,  on  the  other  hand,  through  the  excretion  of  uric  acid, 
instead  of  urea,  the  demand  for  fresh  air  is  diminished,  less  oxygen 
being  required  for  the  conversion  of  the  carbon  of  the  food  or  tissue 
into  the  carbonic  oxide  (CO)  constituent  of  hydrated  uric  acid, 
C3032(C]''s2OH4),  than  into  carbonic  acid,  3(C02),  and  urea,  2(COX2H4), 
which  hydrated  uric  acid  becomes  through  oxidation,  and,  consequently, 
less  heat  or  force  is  lost  in  elevating  the  temperature  of  the  inspired  air 
to  that  of  the  body,  an  additional  advantage.  It  might  appear  at  first 
sight,  though,  that  the  heat  developed  through  the  oxidation  of  carbon 
into  carbonic  oxide  (CO)  would  be  only  one-half  that  developed  in  the 
production  of  carbonic  acid  (C02).  It  must  be  remembered,  however, 
that  the  heat  absorbed  in  the  conversion  of  carbon  into  carbonic  acid 
gasis  lost  to  the  economy,  and  that,  therefore,  the  difference  in  the  heat 
developed  (about  25  per  cent.)  in  the  two  cases  is  not  as  great  as  might 
have  been  supposed,  and  that  the  amount  of  oxygen  is  also  employed 
with  far  less  econoni}7  in  the  production  of  C02,  than  in  that  of  CO, 
the  ratio  being  as  1  to  1J.1  Further,  the  proportion  of  nitrogen  to 
carbon  in  ammonium  urate,  C5X5H703,  being  as  1  to  1,  whereas,  in 
urea,  CON2H4,  it  is  as  1  to  2,  it  follows  that  the  amount  of  carbon  elimi- 
nated by  the  kidneys,  in  combination  with  nitrogen,  is  greater  if 
excreted  in  the  form  of  ammonium  urate,  as  in  birds,  than  in  that  of 
urea,  as  in  mammals,  obviously  an  advantage,  since  the  excretory  work 
of  the  respiratory  organs  is  relieved  to  a  corresponding  extent.  That 
the  production  of  uric  acid  is  due  to  imperfect  oxidation  appears,  also, 
from  what  one  daily  observes  in  cases  of  gravel  and  gout  diseases,  in 
which  the  characteristic  accumulation  of  uric  acid  or  urate  of  sodium  is 
without  doubt,  due  to  either  albuminous  food  being  continually  taken 
in  excess,  or  to  the  imperfect  combustion  of  the  albumen  of  ordinary 
diet,  or  of  that  resulting  from  the  disintegration  of  the  tissues.  As  in 
all  probability  albumen,  whether  derived  from  food  or  tissue,  in  being 
transformed  into  carbonic  acid  and  urea,  passes  through  a  uric  acid 
stage,  just  as  starch  passes  through  the  stage  of  sugar,  it  follows  that, 
if  oxidation  be  arrested  at  a  certain  stage,  uric  acid,  or  urates,  will 
accumulate  in  the  system,  and  give  rise  to  gravel  or  gout.  An  attack 
of  gout  being,  chemically,  a  sudden  oxidation  of  sodium  urate  into 
urea  and  carbonic  acid,  enabling  the  system,  thereby,  to  rid  itself  of  at 
least  the  mechanical  effects  of  the  disease,  the  best  preventive  to  such 
an  attack  is  to  eat  as  little  food  of  any  kind,  and  breathe  as  much  fresh 
air  as  possible.2  The  good  effect  of  diet,  accompanied  with  active 
exercise  in  the  open  air,  horseback  riding,  etc.,  to  increase  the  respira- 
tion, and  the  taking  of  alkalies  and  iron,  to  promote  oxidation  indirectly, 
experienced  by  those  who  .  are  habitually  high  livers,  and  subject  to 
gout,  etc.,  is  too  well  known  to  need  further  comment. 

1  For  the  heat  developed  in  the  production  of  CO  b-'ing  %,  that  of  C02  =  1,  that  developed  in  the  pro- 
duction of  C202  equals  1J£  that  of  C02. 
-  Beuce  Jones,  op.  cit.,  p.  126. 


526 


THE     URINE- 


That  uric  acid,  like  urea,  is  derived  almost  entirely  from  the  nitro- 
genous food,  appears  from  the  amount  of  it  excreted  being  dependent 
upon  the  kind  of  food  taken,  rising  to  over  thirty-two  grains  in  twenty- 
four  hours  on  a  full  meat  diet,  sinking  to  about  three  grains  during 
abstinence,  in  the  latter  case  the  body  supplying  the  nitrogenous  food. 
Uric  acid  appears  to  be  very  generally  present  when  active  changes  are 
taking  place,  being  found  in  the  spleen  pulp,  in  the  lungs,  liver, 
pancreas,  brain,  and  muscles.  As  already  mentioned,  the  acidity  of  the 
urine  is  indirectly  due  to  uric  acid  through  its  combining  with  the  sodium 
of  the  basic  phosphate,  and  so  reducing  the  latter  to  the  acid  phosphate, 
upon  which  the  acidity  of  the  urine  directly  depends.  Uric  acid 
existing  in  the  urine  in  the  form  of  urates,  usually  as  a  brownish, 
yellowish,  powdery  substance,  ammonium  or  sodium  urate  (Fig.  264), 


Fig.  264. 


Fig.  265. 


Uric  acid,  deposited  from  urine.   (Dalton.) 


Sodium  urate  from  urinary  deposit.  (Dalton.) 


may  be  readily  obtained  by  the  decomposition  of  the  same.  Thus,  if 
nitric  or  hydrochloric  acid  be  added  to  freshly  filtered  urine  in  the 
proportion  of  about  two  per  cent,  by  volume,  and  the  mixture  be 
allowed  to  remain  at  rest,  within  twenty-four  hours  uric  acid  will  be 
deposited  as  thin  crystals  on  the  sides  of  the  vessel.  These  crystals 
(Fig.  265)  are  usually  transparent,  yellowish,  rhombic  plates,  with  the 
angles  rounded  off,  and  are  frequently  collected  together  in  rosette, 
star-like  clusters  and  spheroidal  masses.  If  uric  acid  be  boiled  with 
nitric  acid  it  dissolves  with  a  yellow  color,  and  with  an  abundant 
liberation  of  gas  bubbles.  If  the  solution  be  now  evaporated  a  brilliant 
red  stain  is  left,  which,  by  the  addition  of  aqua  ammonia,  becomes 
purple.  The  presence  of  uric  acid  and  urates  can  be  readily  determined 
by  this  procedure,  which  is  usually  known  as  the  murexide  test.  It 
has  already  been  mentioned  that  kreatinin  (C4H7N30)  (Fig.  266), 
usually  found  in  small  quantities  in  the  urine — about  fifteen  grains  being 
excreted  daily — is  probably  not  derived  from  the  kreatin  (C4H9N302), 
(Fig.  267)  of  the  muscle,  but,  rather,  from  that  of  food,  probably  by 
dehydration,  and  may  be  regarded,  chemically,  as  imperfectly  oxidized 


ORIGIN    OF    HIPPURIC    ACID. 


527 


albumen,  intermediate  between  the  latter  and  urea,  the  disintegration 
of  food  or  tissue  albumen  leading  through  kreatin,  kreatinin,  uranin, 
guanin,  allantoin,  xanthin,  hypoxanthin,  all  nitrogenous  products,  to 
uric  acid,  which,  as  we  have  seen,  is  finally  transformed  into  urea  and 
carbonic  acid. 


Fig.  266. 


Ptg.  267. 


M$d* 


Kreatin,  crystallized  by  hut  water. 
(Leiima.nn.) 


Kreatinin,  crystallized  from  hot  water. 

(Lehmasn.) 


Hippuric   acid,    C9H9N03  (Fig.  268),   excreted   in   about  the  same 
amount  as  kreatinin,  like  the  latter,  is  also  a  very  imperfectly  oxidized 


Fig.  268. 


Hippuric  acid.     (Laxdois.) 

nitrogenized  principle.  Chemically  it  may  be  regarded  as  being  a 
residue  of  benzoic  acid  and  glycin — that  is,  a-  formed  through  the  con- 
jugation of  these  principles  with  dehydration,  as  follows: 

Benzoic  acid.  Glycin.  Water.         Hippuric  acid. 

C7H602  +  C2H5N02  —  H,0  =  09H9X0, 

That  hippuric  acid  actually  arises  in  the  bod)-  through  the  combina- 
tion of  glycin  with  benzoic  acid  appears  from  the  fact  that,  if  the  latter  be 


528  THE    URINE. 

taken  internally,  the  amount  of  hippuric  acid  excreted  is  increased,1  and 
thai  a  benzoic  acid  residue  naturally  exists  in  the  fodder  of  ruminants, 
which  accounts  for,  on  the  above  supposition,  hippuric  acid  replacing 
uric  acid  in  the  urine  of  herbivorous  animals.2  Since,  in  jaundiced 
patients,  and  in  animals  in  which  the  liver  is  extirpated,  or  the  ductus 
communis  is  ligated,  the  benzoic  acid  administered  passes  out  of  the 
body  as  such,  one  would  be  led  to  suppose  that  the  synthesis  with 
glycin  takes  place  in  the  liver.  That  hippuric  acid  is  also  formed  in 
the  kidneys  appears  from  the  fact  that  if  arterialized  blood,  containing 
benzoic  acid,  be  passed  through  the  bloodvessels  of  a  freshly  excised 
kidney,  hippuric  acid  will  be  found  in  the  perfused  blood.  With  refer- 
ence to  the  plausible  hypothesis,  just  given,  of  the  origin  of  the  hippuric 
acid  in  the  herbivora,  it  should  be  mentioned,  however,  that  it  is  found 
in  the  urine  of  man  when  on  an  animal  diet,  though  in  less  quantity 
than  when  on  a  vegetable  or  mixed  one,  and  that  benzoic  acid  is  not  a 
constituent  of  his  food. 

Indican,  also  known  as  uroxanthin,  C26H3IN017,  a  yellowish  sub- 
stance, usually  present  in  the  urine  of  man,  and  in  greater  quantity  in 
that  of  the  horse,  is  probably  derived  from  indol,  one  of  the  products  of 
pancreatic  digestion ;   through  oxidation  it  becomes  indigo  blue. 

The  presence  of  the  volatile  acids,  phenylic,  C6H602,  taurylic,  C14Hs02, 
and  damaluric,  C14H1304,  appears  to  give  rise  to  the  odor  of  the  urine. 

In  addition  to  its  organic  constituents,  amounting  to  about  550 
grains  in  twenty-four  hours,  the  urine  contains,  as  may  be  seen  from 
Table  LXXL,  a  number  of  inorganic  saline  ones.  These  salts, 
amounting,  in  twenty-four  hours,  to  perhaps  300  grains,  though  varying 
on  a  mixed  diet  between  140  and  378  grains,  and  in  women  between 
158  and  303  grains,  are  taken  into  the  body  with  the  food,  and  pass 
out  of  it  as  such  in  the  urine  unchanged,  or  they  are  produced  within 
the  system  through  the  oxidation  of  the  sulphur  and  phosphorus,  either 
of  the  food  or  tissue,  the  sulphuric  and  phosphoric  acids  so  formed  (a 
source  of  heat)  combining  with  alkaline  and  earthy  bases,  the  latter 
being  in  combination  with  weaker  acids.  While  it  is  impossible,  as 
yet,  to  determine  exactly  the  manner  in  which  the  bases  are  related  to 
the  acids,  and  in  the  salines  of  the  urine,  since  the  composition  of  the 
ash  corresponds  almost  exactly  with  the  direct  analysis  of  the  urine,  it 
would  appear  that  the  phosphoric  acid  exists  in  the  urine  in  combina- 
tion with  sodium  and  potassium  as  alkaline,  and  with  lime  and  magne- 
sium as  earthy  phosphates,  the  sulphuric  acid  with  sodium  and  potas- 
sium as  alkaline  sulphates,  the  sodium  as  sodium  urate,  phosphate, 
and  chloride,  etc.  The  latter  constitutes  by  far  the  greater  part  of  the 
inorganic  constituents  of  the  urine,  as  much  as  250  grains  and  more  of 
sodium  chloride  being  excreted  in  twenty-four  hours,  being  derived 
principally  from  the  food;  the  amount  will  vary,  however,  considerably. 
Some  part  of  the  sodium  chloride  introduced  into  the  system  as  food, 
appears  to  be  the  source  of  the  hydrochloric  acid  of  the  gastric  juice, 
and  of  the  soda  of  the  bile.    It  appears  probable  that,  after  being  decom- 

i  Matschersky  :  Virchow's  Archiv,  1863,  S.  528. 

-  Meissner  and  Shepard  :  Centralblatt,  18UC,  Nos.  43  and  44. 


EXCRETION    OF    URINE.  529 

posed,  it  is  recomposed  again  within  the  system,  and  as  such  eliminated. 
The  alkaline  sulphates,  amounting  to  10  per  cent,  of  the  solid  matter 
of  the  urea,  are  derived  from  the  food  and  the  disintegration  of  the 
albuminous  tissues,  the  greater  part  of  the  sulphur  not  eliminated  in 
the  feces  as  taurin  becoming  sulphuric  acid,  and  combining  with  the 
sodium  and  potassium  supplied  by  the  alkaline  carbonates  and  phos- 
phates of  the  blood,  about  4  grammes  (60  grains)  are  excreted  daily. 
The  phosphoric  acid  of  the  urine  is  excreted  principally  in  the  form  of 
potassium  and  sodium  phosphate.  Being  readily  soluble,  these  salts 
are  not  precipitated,  and  therefore  do  not  affect  the  transparency  of  the 
urine.  The  amount  of  alkaline  phosphates  excreted,  about  4  grammes 
(60  grains)  in  twenty-four  hours,  varies  with  the  kind  of  food  taken, 
being  greater  on  an  animal  than  on  a  vegetable  diet,  the  former  being- 
richest  in  soluble  phosphates,  or  substances  yielding  readily  phosphoric 
acid.  Phosphoric  acid,  like  sulphuric,  being  produced  in  the  system 
through  oxidation  of  the  phosphorus  of  the  muscular  and  nervous  tissues, 
the  amount  of  alkaline  phosphates  excreted,  like  the  sulphates,  will 
depend,  to  a  certain  extent,  upon  the  amount  of  tissue  disintegrated.  The 
earthy  phosphates,  magnesium  and  calcium  phosphate,  are  usually  ex- 
creted in  less  quantity  than  the  alkaline  phosphates,  the  average  daily 
quantity  of  the  latter  being  about  1  gramme  (16.43  grains),  or  about 
one-fourth  of  the  former.  They  are  not  the  less  important,  however, 
from  a  pathological  point  of  view,  since  their  solubility,  like  the  urates, 
depending  upon  the  acid  sodium  phosphate,  they  will  be  precipitated 
if  the  latter  be  absent,  and  the  urine  be  consequently  alkaline.  The 
earthy  phosphates,  while  derived  principally  from  the  food,  are,  no 
doubt,  formed  within  the  system,  through  the  decomposition  of  sodium 
chloride,  calcium  carbonate,  etc.,  the  bases  combining  with  the  phos- 
phoric acid.  It  is  in  this  way,  probably,  that  the  calcium  carbonate  of 
the  food,  or  that  resulting  from  the  disintegration  of  osseous  tissue,  is 
eliminated  as  calcium  phosphate  in  the  urine.  It  is  worthy  of  mention, 
in  this  connection,  that  on  a  vegetable  diet  the  excess  of  alkali  in  the 
food  reappears  in  the  urine,  while  on  an  animal  diet  it  is  the  excess  of 
the  earthy  base  that  becomes  conspicuous.  In  addition  to  the  impor- 
tant organic  constituents  just  mentioned,  the  urine  contains,  usually, 
traces  of  nitric  and  silicic  acids,  ammonia,  and  iron,  and  small  quantities 
of  nitrogen  (0.8  per  cent.)  and  carbonic  acid  (7  per  cent.),  about  one- 
third  of  the  latter  being  in  a  state  of  combination,  the  remaining1  two- 
thirds  free ;  oxygen,  however,  is  usually  absent. 

Having  considered  the  composition  of  the  urine,  it  remains  for  us 
now  to  describe,  as  far  as  possible,  the  manner  in  which  it  is  excreted. 
That  the  urine  is  excreted  by  the  kidneys,  but  not  elaborated  by  them, 
appears  not  only  from  what  has  been  said  of  the  origin  of  its  constituents 
and  of  their  accumulation  after  ligation  of  the  renal  arteries,  extirpation 
of  the  kidneys,  etc.,  but  from  the  fact,  also,  that  in  certain  cases  referred 
to  by  Ilaller,2  Nysten,3  Burdach,4  and  Lay  cock,5  in  which  the  kidneys 

1  Gorup  Besanez  :  Physiol.   Chemie,  18G2,  S.  520.    Bernard  :  Liquides  de  l'Organisme,  1869,  tome  i. 
p.  347. 

-  Elementa  Physiologa,  tome  ii.  p.  370.  3  Recherches  de  la  Phys.  et  de  Chimin,  p.  265. 

4  Physiologie  (Jourdain),  tome  viii.  p.  248.  '  Edin.  Sled,  and  Sur£.  Journal,  1838. 

34 


530  THE     URINE. 

were  either  congenitally  absent  or  not  acting,  the  urine,  or  fluid  closely 
resembling  it  at  least,  was  vicariously  excreted  by  the  skin,  pleura,  peri- 
toneum, mucous  membrane  of  the  intestinal  canal,  salivary,  lachrymal, 
and  mammary  glands,  ears,  nose,  etc.     Such  being  the  case,  the  question 

reduces  itself  to  the  consideration  of  the  manner  in  which   the  different 
constituents  of  the  urine  are  separated  by  the  renal  epithelium  from  the 
blood  supplying  the  kidney.    Now,  we  have  seen  that  the  urine  consists 
of  water  holding  in  solution  urea,  etc.,  and  that  the  kidney  is  made  up 
of  uriniferous  tubules,  each  tubule  consisting  of  two  distinct  portions,  a 
tubular  part  and  a  capsular  part,  both  lined  with  epithelium  and  supplied 
with  bloodvessels.     The  bloodvessels  invaginated  by  the  capsular  portion 
being,  however,  disposed  in  a  capillary  knot  of  far  greater  aggregate 
capacity  than  the  branch  of  the  renal  artery  from  which  it  originates, 
and  of  the  single  exit  vessel  in  which  it  terminates,  the  blood  must  be, 
therefore,  retarded  as  it  flows  within  the  capsule,  and  the  escape  of  its 
water  much  favored  by  such  a  disposition.      That  the  function  of  the 
capsular  part  of  the  uriniferous  tubule,  as  shown  by  Bowman,1  is  to 
filter,  drain  off  the  water  from  the  blood,  the  urea,  etc.,  being  excreted 
by  the  tubular  part  and  then  washed  out,  so  to  speak,  by  the  water,  is 
confirmed  by  what  is  seen  in  reptiles.     Thus,  in  the  boa  uric  acid,  the 
equivalent  of  the  urea  of  mammals,  excreted  in  a  solid  state  is  only  found 
in  the  tubular  portion  of  the  uriniferous  tubule.      The  excretion  of  the 
urine  will  then  depend  essentially  upon  the  relation  of  the  pressure  of 
the  blood  in  the  renal  arteries,  120  to  140  mm.  mercury,  to  that  of  the 
fluid  within  the  tubules  and  ureter,  10  to  40  mm.,  the  amount  of  urinary 
materials  in   the  blood,  and  the  activity  of  the  renal  epithelium.      The 
influence  of  the  blood  pressure  is  shown  from  the  fact  that  the  excretion 
of  urine  is  diminished  with  the  lowering  of  the  pressure  of  the  blood 
whether  brought  about  generally  or  locally,  as  by  constriction  of  the 
renal  artery — in  fact,  if  the  blood  pressure  be  as  low  as  40  mm.  the  ex- 
cretion of  the  urine  ceases.      On  the  other  hand,  with  an  elevation  in 
the  blood  pressure,  whether  induced  generally  or  locally,  the  excretion 
of  the  urine  is  increased.     That  the  renal  epithelium,  however,  exerts 
an  excretory  activity  independent  of  the  influence  of  the  blood  pressure, 
is  shown  by  the  experiments  of  Heidenhain2  upon  animals  in  which, 
after  the  flow  of  urine  had  ceased  through  section  of  the  spinal  cord 
below  the  medulla,   sodium   sulphoindigotate  being  injected    into  the 
veins  was  found,  after  death,  in  the  renal  epithelium  or  the  interior  of 
uriniferous  tubules  according  to  the  length  of  time  elapsing  between  the 
injection  and  killing  of  the  animals,  proving  that  the  renal  epithelium 
had  excreted  the  sulphoindigotate  from   the  blood.     By  varying  the 
quantity  of  the  salt  injected  and  the  time  elapsing  between  the  experi- 
ment and  the  subsequent  examination,  Heidenhain  was  able  to  follow 
step  by  step  the  salt  as  it  passed  from  the  blood  into  the  cells,  thence 
through  the  latter  into  the  tubules  for  some  little  distance.    There  being- 
no  fluid  passing  along  the  uriniferous  tubules  to  wash  away  the  sulpho- 
indigotate, the  latter  remained  about  where  it  had  been  excreted.     Not 
a  trace  of  the  salt  injected  could  be  found  in  the  epithelium  or  within 

1  Op.  cir.  -  Hermann  :  Physiologie,  Fnnfter  Band,  Erster  Theil,  S.  345. 


EXCRETION    OF    URINE. 


531 


the  capsular  portion  of  the  tubule,  the  cells  excreting  the  sodium 
sulphoindigotate  being  of  the  kind  described  by  Heidenhain  as  rod- 
shaped,  more  especially  found  in  the  intercanalary  portion  of  the  urinif- 
erous  tubule.  It  was  also  shown  by  these  experiments,  as  might  have 
been  expected,  that  there  was  a  limit  to  the  excreting  capacity  of  the 
renal  epithelium,  the  excretion  of  a  second  quantity  of  sulphoindigotate 
injected  soon  after  the  first  being  very  imperfect.  It  might  be  supposed 
that  the  experiments  of  Heidenhain  with  sulphoindigotate  could  be 
repeated  with  urea,  uric  acid,  etc.,  with  the  view  of  showing  that  these 
suiistances  are  excreted  by  the  cells  lining  the  tubular  and  not  by  those 
lining  the  capsular  portion  of  the  tubule.  Inasmuch,  however,  as  the 
injection  of  urea,  etc.,  gives  rise  to  a  copious  flow  of  urine,  even  after 
section  of  the  spinal  cord  below  the  medulla,  which  is  not  the  case  with 
the  sulphoindigotate,  the  urea  will  be  washed  along  the  tubules  as  fast 
as  it  is  excreted,  which  makes  it  impossible,  therefore,  to  say  by  what 
part  of  the  renal  epithelium  it  has  been  excreted.  It  is  Avell  known, 
however,  that  in  birds,  reptiles,  and  fishes,  branches  from  the  mesenteric, 
femoral  veins,  etc.,  pass  to  the  kidneys  (Fig.  269),  and  after  ramifying 
through  the  latter  converge  and  finally  terminate 
in  the  vena  cava,  the  veins  being  known  collectively  Fig.  269, 

as  the  renal  portal  system,  or  the  system  of  Jacob- 
son,1  after  their  discoverer.  The  blood  Hows  through 
the  kidneys  in  these  animals,  therefore,  very  much 
as  it  does  through  the  liver  in  man.  Now  the 
branches  of  this  renal  portal  system,  together  with 
the  efferent  vessels  from  the  glomeruli,  constitute 
the  capillary  plexus  surrounding  the  tubular  portion 
of  the  uriniferous  tubules,  the  glomeruli  themselves, 
however,  being  supplied  exclusively  by  branches  of 
the  renal  artery.  It  is  obvious,  therefore,  that  if  the 
renal  artery  be  ligated  the  blood  will  be  entirely 
cut  off  from  the  glomerulus,  while  that  supplying 
the  remaining  portion  of  the  uriniferous  tubule  will 
be  unaffected.  Such  being  the  case,  it  follows  that 
if  urea  still  appears  in  the  urine  after  ligation  of  the 
renal  arteries,  it  must  be  excreted  by  the  epithelium 
of  the  tubular  and  not  by  that  of  the  capsular  por- 
tion of  the  uriniferous  tubule.  These  theoretical 
considerations  are  fully  borne  out  by  the  experiments  of  Nussbaum,2 
who  has  shown  that  while  sugar,  peptones,  and  albumen  are  excreted 
by  the  glomeruli,  these  substances  not  appearing  in  the  urine  after  liga- 
tion of  the  renal  arteries,  urea  is  excreted  by  some  part  of  the  remaining 
portion  of  the  tubule,  urea,  when  injected  into  the  blood,  giving  rise  to 
a  How  of  urine  even  after  ligation  of  the  arteries.  The  urine,  like  the 
bile,  is  excreted  continuously,  and  while  the  flow  may  be  increased  or 
diminished,  it  never  absolutely  ceases  in  health  for  any  length  of  time. 
The  urine  trickling  through  the  mouth  of  the  uriniferous  tubules  into 


c  i.  Vena  cava.  R.  Kid- 
neys, r  r.  Vena  reveh ens. 
r  «  Vena  advehens.  a. 
Vena  epigastrica.  h.  Vena 
hypogastrica.  i.  Vena  is- 
chiada.     (Gagenbaub.) 


1  De  svstemate  venoso  peculiar!  in  penultia  animalibua  observatio 
-  Pfliiger's  Archiv,  1877,  xvi.  S.  139  ;  1878,  xvii.  S.  580. 


Copenhagen,  1821. 


532 


THE    URINE. 


the  calices,  passes  thence  by  the  ureters  into  the  bladder,  its  return  from 
the  Latter  during  micturition  being  prevented  by  the  obliquely  disposed 
valvular-like  orifices  of  the  ureters. 

The  bladder  is  a  musculo-membranous  sac,  the  muscular  fibres,  chiefly 
of  the  involuntary  character,  being  disposed  in  a  longitudinal  and  circu- 
lar manner,  the  former  constituting  the  detrusor,  the  latter  the  sphincter 
vesicae,  by  the  contraction  of  which  the  urine  is  either  expelled  or 
retained  within  the  bladder.  Micturition  appears  to  be  brought  about 
essentially  as  follows : 

During  the  intervals  in  which  the  urine  is  not  voided  the  sphincter 
vesicae  is  in  a  state  of  tonic  contraction  ;  if,  however,  the  urine  be  re- 
tained for  some  time  the  contraction  of  the  sphincter  alone  is  insufficient 
to  resist  the  outflow,  and  the  action  of  the  adjacent  muscles  is  called 
upon  to  assist  it.  The  disposition  to  urinate  after  a  time  becoming  very 
great  a  few  drops  of  urine  pass  into  the  urethra,  the  impression  so  pro- 
duced then  calls  into  play  the  action  of  the  detrusor  and  ejaculator 
urin83,  the  sphincter  being  simultaneously  relaxed,  and  the  bladder  is 
emptied.  Ordinarily  the  voiding  or  the  retaining  of  the  urine  is  a  vol- 
untary act,  but  that  the  urine  can  be  voided  at  regular  intervals  inde- 
pendent of  the  will  is  shown  by  the  regularity  with  which  the  action  is 
performed  in  animals  in  which  the  spinal  cord  has  been  divided,  and  in 
human  beings  in  which  it  has  been  injured.  The  mechanism  by  means 
of  which  the  muscular  contractions  are  brought  about  in  response  to 
stimuli,  the  result  of  which  is  the  voiding  of  the  urine,  will  be  better 
appreciated  after  the  subject  of  reflex  action  has  been  considered. 

Finally,  in  concluding  our  account  of  the  urine,  the  changes  produced 
by  standing  may  here  be  briefly  alluded  to.     The  urine  when   first 


Fig 


Fig.  271. 


Calcium  oxalate.  Deposited  from  healthy  urine, 
during  the  acid  fermentation.     (Dalton.) 


Ammoniom  magnesium  phosphate.  Deposited 
from  healthy  urine,  during  alkaline  fermentation. 
(Dalton.) 


passed,  it  will  be  remembered  is  acid,  the  acidity  being  due  to  the  acid 
phosphate  of  sodium.  Within  about  twelve  or  twenty-four  hours  after  being 
passed,  however,  free  acid  makes  its  appearance,  lactic  acid  being  that 


FORMATION    OF     ALKALINE    URINE.  533 

usually  developed,  probably  from  some  of  the  organic  principles  of  the 
urine  by  the  fermentative  action  of  fungi,  and  perhaps  of  the  mucus 
usually  present  in  small  quantities  in  the  urine;  oxalic  acid  is  also  fre- 
quently produced,  probably  in  the  same  manner,  and  in  decomposing 
the  salts  of  lime  give  rise  to  the  formation  of  crystals  of  oxalate  of 
calcium  (Fig.  270).  After  a  few  days  this  acid  fermentation  ceases, 
through  the  conversion  of  urea  by  the  addition  of  water  into  carbonate 
of  ammonium,  the  change  being  brought  about  by  the  development  of 
the  micrococcus  urese,  one  of  the  simplest  of  living  beings,  as  follows : 

Urea.  Water.  Ammonium  carbonate. 

CON,H,  2(H20)     =     (NH4)2CO, 

and  the  neutralization  of  the  acid  sodium  phosphate  by  the  ammonium 
carbonate,  as  shown  by  the  following  reaction  : 

Acid  sodium  phosphate.  Amnion,  carb.       Amnion,  sodium  phosphate.         C'arb.  acid. 

2NaH2P04    +     (NH4)2C03    =    2NaNH4HP04    +     H2C03 

the  urine  becomes  alkaline.  With  the  alkalinity  of  the  urine,  the  earthy 
phosphates  being  only  soluble  in  acid  fluids,  are  precipitated,  and  in 
combining  with  the  ammonia  give  rise  to  the  formation  of  the  triple 
phosphate  or  ammonium  magnesium  phosphate  (Fig.  271),  as  follows  : 

Magnesium  phosphate.  Amnion,  carb.  Amnion,  mag.  phosphate.  Carb.  acid. 

2MgHP04      +      (NH4)2C03      =      2MgNH4P04      +      H2C03. 

As  decomposition  goes  on,  the  ammonium  carbonate,  after  saturating 
the  elements  with  which  it  is  capable  of  uniting,  is  given  oft*  free,  giving 
rise  to  the  ammoniacal  odor  of  the  urine,  and  this  continues  until  all  of 
the  urea  has  disappeared. 


CHAPTER    XXXVI. 

STRUCTURE  OF  THE  NERVOUS  SYSTEM. 

In  describing  the  mariner  in  which  food  is  digested,  absorbed,  and 
circulated  through  the  economy  as  blood,  supplying  the  material  for  the 
repair  of  the  tissues  and  the  production  of  heat  and  force;  of  the 
absorption  of  oxygen,  and  exhalation  of  carbonic  acid,  water,  urea,  etc.,  the 
influence  exerted  by  the  nervous  system  upon  these  processes  has  only 
been  alluded  to,  if  at  all,  in  an  incidental  manner.  That  the  phenomenon 
of  nutrition  is  not  dependent  upon  the  nervous  system,  however  much  it 
may  be  influenced  by  the  latter,  is  shown  from  the  fact  that  the  nutrition 
of  the  lower  animals,  in  which  the  nervous  system  is  but  little  developed, 
and  of  plants,  in  which,  with  but  few  exceptions,  so  far  as  is  known, 
it  is  altogether  absent,  does  not  differ  from  the  higher  forms  of  animal 
life.  Indeed,  the  essential  difference  between  the  nutrition  of  plants, 
as  compared  with  animals,  consists  of  the  deoxidation  by  plants  of  the 
water,  carbonic  acid,  and  ammonia  constituting  their  food  into  starch, 
sugar,  fats,  albumen,  and  the  storing  up  of  force,  and  the  oxidation  by 
animals  of  the  latter  substances  constituting  their  food  into  carbonic 
acid,  water,  and  ammonia,  and  the  expenditure  of  force.  But  while 
such  a  broad  distinction  exists  between  plants  and  animals,  as  com- 
pared, on  the  whole,  nevertheless,  it  must  not  be  lost  sight  of  that 
oxidations,  analytical  processes,  are  going  on  in  the  economy  of  plants 
incidental  to  the  elaboration  and  circulation  of  the  sap,  the  production 
of  heat,  in  budding,  flowering,  etc.,  and  deoxidations,  synthetical  pro- 
cesses, in  the  economy  of  animals.  Indeed,  as  has  already  been  men- 
tioned, no  sharp  line  of  demarcation  can  be  drawn  between  vegetable 
and  animal  life.  While  nutrition  is  not  actually  dependent  upon  the 
nervous  system  therefore,  nevertheless  every  one  is,  however,  conscious 
of  the  extent  to  which  it  influences  nutritive  processes.  The  sudden 
manner  in  which  digestion  is  brought  to  a  stop  by  a  piece  of  bad  news,  of 
the  weakness  of  the  heart  induced  by  nervous  shock,  of  the  sudden  blush 
or  pallor  due  to  emotion,  are  familiar  illustrations.  The  flow  of  the 
secretions  into  the  alimentary  canal  in  response  to  food,  the  rhythmical 
action  of  the  heart  and  lungs,  though  unconsciously  brought  about,  are 
due  equally  to  the  action  of  the  nervous  system.  The  influence  of  the 
nervous  system  upon  nutrition  has  often  been  compared  to  that  exer- 
cised by  the  rider  upon  the  movements  of  a  horse,  the  force  being  put 
forth  by  the  latter,  but  controlled  by  the  bit  and  spur.  Man,  like  other 
animals,  is,  however,  something  more  than  a  mere  nutritive  machine, 
becoming  conscious,  through  his  nervous  system,  of  an  external  world. 
Impressions  made  upon  sensory  nerves  by  heat,  light,  sound,  etc.,  when 
conveyed  to  the  sensorium,  give  rise  there  to  sensations  out  of 
which  are  developed  in  still  higher  centres,  emotions,  desires,   ideas, 


MEDULLATED    NERVE     FIBRES, 


535 


while  through  the  influence  exerted  by  the  motor  nerves  in  the  reverse 
direction  upon  the  muscles  the  mandates  of  the  will  are  obeyed.  In  a 
word,  it  is  by  means  of  the  nervous  system  that  the  various  nutritive 
processes  that  we  have  studied  are  brought  into  relation  with  each 
other — are  coordinated — that  we  feel,  think,  will. 

The  nervous  system,  or  the  apparatus  by  which  the  different  por- 
tions of  the  body  are  brought  into  such  intimate  sympathy,  by  which 
one  sees,  hears,  thinks,  wills,  consists,  structurally,  of  fibres  and  cells, 
the  former  being  found  in  all  parts  of  the  nervous  system,  the  latter 
confined,  in  a  great  measure,  however,  to  the  cerebro-spinal  axis  and 
ganglia.  The  fibres  are  principally  of  two  kinds,  the  white  tubular 
medullated,  dark  bordered,  and  the  gray,  pale  non-medullated  ;  the 
latter,  however,  only  differ  from  the  former,  as  we  shall  see,  in  not 
having  the  white  substance  of  Schwann,  and  are  much  less  abundant 
than  the  medullated  kind,  being  found  principally  in  the  sympathetic, 
though.  also,  to  a  considerable  extent,  in  the  cerebro-spinal  nerves. 
The  white  medullated  nerve  fibres  constitute  the  white  parts  of  the 
brain,  spinal  cord,  and  the  cerebro-spinal  nerves.  If  one  of  the  latter 
be  examined,  the  median  nerve,  for  example,  it  will  be  found  to  consist 
of  bundles  or  funiculi  of  ultimate  nerve  fibres  (Fig.  272),  supported 
(Fig.  273)  by   a  framework   of  connective  tissue,  the    epineurium   ep, 


Fig.  273. 


| 


Division  of  a  nerve,  showing 
portion  of  nervous  trunk  (a), 
funiculus,  and  the  separation  of 
its  filaments  (6,  c,  d,  e).  (Dalton.) 


Transverse  section  of  part  of  the  median  nerve,  ep.  Epineurium. 
;  Perineurium.  e<l.  Eudotieurium.  (After  Eichhorst.)  a,  a. 
Funiculus.     (Landois.) 


each  of  the  bundles  being  surrounded  by  its  special  sheath  of  connective 
tissue,  the  perineurium  pe,  the  ultimate  nerve  fibres,  varying  in 
diameter  from  the  12o0otn  to  tne  T3~Yi)tu  °^  an  incni  of  which  the 
bundle  or  funiculus  (Fig.  272,  a)  consists,  being  separated   from  each 


;,:;i; 


STRUCTURE    OF    THE    NERVOUS    SYSTEM. 


other  by  a  more  or  less  homogeneous  substance,  containing  connective 
tissue,  capillaries,   etc. — the    endoneurium    ed.      The  ultimate  nerve 


Fig.  274. 


Fig.  275. 


White  or  medullated  nerve  fibres,  showing  the'siriuons 

outline  and  double  contour.  (After  Bidder  and  Volkmann.) 

Fig.  276. 


a 


Nerve  fibre  from  the  sciatic  nerve  of  the  rabbit  after 
the  action  of  nitrate  of  silver  ".  Ring  formed  by 
thickened  membrane  of  Schwann,  m.  White  substance 
of  Schwann  rendered  transparent  by  glycerine.  cry. 
Axis-cylinder,  which  just  above  and  below  the  level  of 
the  annular  constriction  presents  the  strife  of  From- 
mann.     (Carpenter.) 


".  Axis-cylinder  showing  its  fibrillar 
structure  ;  at  the  upper  part  x,  X,  it  is  seen 
to  arise  from  a  ganglion  cell  only  par- 
tially represented,  and  to  become  incrusted 
by  a  medullary  sheath  at  a',  b.  Naked 
axis-cylinder,  from  the  dorsal  region  of 
the  spinal  cord  of  the  ox.  The  medullary 
sheath  has  been  removed.  (Carpenter.) 


fibres,  when   perfectly   fresh  (Fig.  274),  appear  as  transparent,  clear, 
sinuous,  double  contoured,  beaded,  or  varicose,  hio-hlv  refractive  threads; 


AXIS-CYLINDER    OF    NERVES.  537 

after  exposure,  however,  to  the  action  of  air  or  water,  through  a  pro- 
cess of  coagulation,  possibly,  the  ultimate  nerve  fibre  is  seen  to  consist 
of  three  distinct  parts,  a  central  axis,  an  intermediate  white 
substance,  and  an  external  tubular  sheath.  The  central  axis,  or  axis- 
cylinder,  with  a  diameter  of  about  one-fourth  that  of  the  nerve  fibre 
itself,  is  a  pale,  homogeneous,  or  finely  granular,  usually  cylindrical 
cord,  and,  though  soft  and  delicate,  is,  to  a  certain  extent,  elastic.  In 
its  intricate  structure  the  axis-cylinder  is  fibrillar  in  character,  the 
fibres  being  disposed  longitudinally  (Fig.  275)  ;  transverse  strise  can, 
however,  be  also  shown  by  appropriate  treatment  with  silver  nitrate 
(Fig.  276).  As  a  general  rule,  the  axis-cylinder  cannot  be  distinguished 
in  the  natural  condition  of  the  nerve,  owing;  to  its  refracting  light  in 
the  same  manner  as  the  intermediate  white  substance,  nor  after  coagu- 
lation, usually  on  account  of  the  opacity  developed;  if  the  nerve  fibre, 
however,  be  treated  with  strong  acetic  acid,  the  divided  ends  retracting, 
the  protruding  axis-cylinder  will  present  the  appearance  just  described. 
The  axis-cylinder,  further,  by  staining  with  carmine  and  gold  chloride, 
can  be  readily  distinguished  in  sections  from  the  intermediate  surround- 
ing white  substance.  The  axis-cylinder,  chemically,  appears  to  be 
albuminous  in  character;  it  is  insoluble  in  water,  alcohol,  and  ether,  but 
soluble  in  a  boiling  solution  of  sodium  hydrate.  Through  the  action  of 
concentrated  acetic  acid  it  becomes  pale  and  swollen.  From  the  fact  of 
the  axis-cylinder  being  the  only  constant  portion  of  the  ultimate  nerve 
fibre,  the  intermediate  white  substance  and  external  sheath  being  absent 
at  the  origin  (Fig  275,  a)  and  termination  of  the  latter,  there  can  be  no 
doubt  that  it  is  the  most  important,  indeed,  the  essential,  portion, 
functionally,  of  the  nerve  fibre,  the  remaining  portions  having  accessory 
functions,  as  will  be  explained  presently. 

The  intermediate  portion  of  the  nerve  fibre — that  is,  the  part  imme- 
diately surrounding  the  axis-cylinder,  commonly  known  as  the  white 
substance  of  Schwann,  but  also  as  the  medullary  sheath  or  myelin, 
consists  of  a  transparent  highly  refractive  oleaginous  material,  and  to 
which  the  white  glistening  aspect  of  the  nerve  fibre  is  due.  The 
characteristic  double  contour,  the  two  parallel  lines  on  each  border  of 
the  ultimate  nerve  fibre,  indicates  the  external  and  internal  limits  of 
the  intermediate  layer,  or  white  substance  of  Schwann.  Owing  to  the 
fact  of  the  latter  becoming  swollen  through  the  imbibition  of  water,  and 
exuding  from  the  divided  ends  of  the  nerve  in  the  so-called  myelin 
forms,  and  from  the  after  obscurity  arising  through  the  changes  in- 
duced in  these  forms  by  water,  and  which  extend  into  the  fibre,  it  is 
more  advantageous  to  study  the  white  substance  of  Schwann  by  harden- 
ing and  staining.  Thus,  when  treated  with  perosmic  acid,  the  white 
substance  of  Schwann  becomes  blackened,  the  axis-cylinder,  however, 
remaining  clear.  If  a  transverse  section  of  the  nerve  fibre  be  examined 
when  so  treated,  it  will  be  seen  to  consist  of  two  concentric  zones,  an 
inner  clear  one,  the  axis-cylinder,  an  outer  dark  one,  the  white  sub- 
stance of  Schwann.  The  white  substance  of  Schwann  appears  to  serve 
both  as  a  protective  envelope  to  the  axis-cylinder,  and  as  an  insulator, 
so  to  speak,  of  the  latter,  so  that  the  nerve  force  in  its  transmission 


538  STRUCTURE    OF    THE    NERVOUS    SYSTEM. 

may  nol  be  diffused.  The  external  investing  portion  of  the  nerve 
fibre,  or  the  neurilemma,  also  known  as  the  sheath  of  Schwann,  the 
limiting  membrane  of  Valentin,  the  primitive  sheath  or  tubular  membrane, 
a  colorless  transparent,  almost  homogeneous  membrane,  somewhat 
elastic,  bears  to  the  nerve  fibre  in  its  general  properties  very  much 
the  same  relation  that  sarcolemma  does  to  muscular  fibre,  and  serves, 
"without  doubt,  as  a  protective  covering  to  the  white  substance  of 
Schwann,  and  the  axis-cylinder  enclosed  by  the  forme]'.  Although,  as 
already  mentioned,  in  a  perfectly  fresh  nerve  the  neurilemma  cannot 
be  distinguished  from  the  remaining  white  substance  of  Schwann, 
and  the  axis-cylinder  of  which  the  ultimate  nerve  fibre  consists,  it 
can  be  demonstrated  by  treating  the  nerve  with  fuming  nitric  acid, 
and  then  with  caustic  potash,  the  axis-cylinder  being  dissolved,  and 
the  fatty  matters  being  discharged,  the  neurilemma  remains  as  an 
empty  tubular,  swollen,  turgid,  yellow  membrane,  or  the  neurilemma 
can  be  isolated  by  treating  the  nerve  with  cold  caustic  soda,  and 
then  boiling  for  a  moment  in  the  same  fluid.  At  regular  intervals, 
along  the  neurilemma,  may  be  observed  indentations,  the  so-called 
constrictions,  or  nodes  of  Ranvier.  At  these  nodes  the  white  sub- 
stance of  Schwann,  or  medullary  sheath,  is  indented  to  such  an 
extent  that  the  neurilemma  or  sheath  of  Schwann,  comes  in  contact  with 
the  axis-cylinder.  From  the  fact  that  a  substance  like  picro-carmine 
diffuses  into  the  axis-cylinder  only  at  the  nodes,  but  not  into  the  whole 
substance,  it  is  possible  that  it  is  at  such  points  that  nutritive  material 
finds  its  way  into  the  axis-cylinder  and  effete  matter  a  way  out.  Each 
interannular  segment  of  that  part  of  the  nerve  fibre  below  the  nodes 
exhibits  when  stretched  oblique  lines  running  across  the  white  substance, 
and  known  as  the  incessures  of  Lautennann.  Corpuscles  may  also  be 
seen  at  intervals  between  the  neurilemma  and  the  white  substance  of 
Schwann.  Finally  the  nerve  sheaths  are  supplied  with  special  nerve 
fibres,  the  nervi  nervorum  to  which  their  sensibility  is  due. 

Non-medullated  nerve  fibres  differ  from  the  medullated  ones  in  not 
having  the  wdiite  substance  of  Schwann,  presenting  a  grayish,  semi- 
transparent  appearance  instead  of  the  white  glistening  appearance  of 
the  medullated  ones.  The  nerve  fibres  of  the  invertebrata  are  exclu- 
sively of  the  non-medullated  variety  ;  in  those  of  the  vertebrates,  how- 
ever, non-medullated  fibres  are  often  found  mixed  with  medullated 
ones ;  they  are  very  abundant  in  the  sympathetic,  and  constitute  for 
example  solely,  the  fibres  of  which  the  olfactory  nerve  consists.  As, 
however,  the  medullated  nerve  fibres,  as  already  mentioned,  lose  their 
white  substance  of  Schwann,  becoming,  therefore,  non-medullated  at 
their  origin  or  termination  in  the  gray  matter  of  the  brain  and  spinal 
cord,  or  in  sensory  organs  or  muscles,  the  distinction  between  the  two 
kinds  of  nerve  fibres  is  not  a  very  essential  one.  In  addition  to  the 
medullated  and  non-medullated  nerve  fibres  described  there  are  also 
found  in  the  nervous  system  entirely  another  kind  of  nerve  fibres, 
indeed  differing  so  from  those  just  described  as  to  have  been  held 
by  competent  histologists  to  be  a  variety  of  connective  rather  than 
nervous   tissue.     Such    are    the    gelatinous    nerve   fibres   or  fibres    of 


GELATINOUS    NERVE    FIBRES 


539 


Remak,  pale,  flattened,  granular,  gray  fibres,  presenting  well-marked, 

longitudinal,  oval  nuclei  (Fig.  277),  the  presence  of  the  latter  giving 

rise    to  the   name  of   nucleated  nerve  fibres.     The 

gelatinous    nerves   fibres    are  chiefly   found    in    the  FlG-  -""• 

sympathetic,  and  particularly  in   such  portions  of  it 

influencing  the  involuntary  muscular  fibres.     They 

have  a   diameter   of  about   the   8  Q\  0 th  of  an  inch, 

and  while  rendered  pale  by  the  action  of  acetic  acid, 

do  not  swell  up  to  anything   like   the   extent   that 

connective  tissue   does  under  similar  circumstances. 

Inasmuch  as  up  to  the  fifth  month  of  intrauterine 

life  the  nerves  generally  have  essentially  the  same 

structure   as  the   so-called  gelatinous  fibres    of   the 

adult,  and  as  during  the  regeneration  of  nerves  after 

injury  or  division   the   new   elements  pass   in   their 

development  through  a  transitory  stage   comparable 

in  structure  to  that    of    the  gelatinous    fibres,    the 

latter  may  be  regarded  perhaps,  morphologically,  as 

undeveloped  medullated  or  non-medullated  fibres. 

Neither  in  their  course  as  nerve  cords,  nor  through 
the  white  part  of  the  nervous  axis  are  the  nerve 
fibres  ever  observed  uniting  or  anastomosino;  nor 
dividing  into  branches,  except  at  their  peripheral 
termination.  Though  the  nerve  fibres  may  exist  in 
great  numbers,  bound  up  as  a  nerve  cord,  neverthe- 
less, like  the  threads  in  a  skein  of  silk,  they  main- 
tain their  individual  distinctness  from  their  origin 
to  their  termination.  When  an  anastomosis  of  nerve 
trunks  apparently  exists,  it  is  due  in  reality  to  the  nerve  fibres  of  which 
the  trunks  consist,  simply  crossing  over  each  other,  the. fibres  from 
one  trunk  running  in  opposition  to  those  of  the  other,  each  nerve 
fibre,  however,  preserving  its  own  individual  action.  As  the  nerve 
fibres  can  be  traced  on  the  one  hand  into  the  cells  of  the  gray  matter 
of  the  nervous  system,  and,  on  the  other,  into  muscles,  glands,  and 
sensory  organs,  let  us  consider  them  now  in  these  relations. 

The  nerve  cells  (Fig.  278),  constituting  the  most  important  part  of 
the  gray  matter  of  the  nervous  system,  are  usually  rounded  bodies, 
though  often  of  very  irregular  outline,  and  consist  of  a  soft,  nearly 
transparent,  granular  albuminous  matter,  with  a  distinct  nucleus  and 
nucleolus,  and  contain  often,  in  addition,  pigment  of  a  yellowish 
brownish  hue,  The  nerve  cells  vary  very  considerably  in  size.  Thus, 
in  the  posterior  horn  of  the  gray  matter  of  the  cord,  they  are  often  as 

small  as  the  ^ ^Vo^1  °f  an  mcn  to  tne  tfo^1  °f  an  ^ncn  m  diameter ; 
whereas,  in  the  anterior  horn  of  the  cord,  they  may  be  as  large  as  the 
2-^y-th  of  an  inch.  The  nerve  cells  are  especially  characterized  by  the 
manner  in  which  the  body  of  the  cell  is  prolonged  into  one  or  more 
processes,  giving  rise  to  the  name  of  unipolar,  bipolar,  multipolar,  and 
apolar  cells,  where  such  processes  are  absent  altogether. 

As  examples  of  unipolar  cells  may  be  mentioned  those  in  the  Gasse- 
rian  and  spinal  ganglion,  and  of  multipolar  cells,  those  of  the  gray  matter 


Filnes  of  Keinak ; 
magnified  300  diam- 
eters.  With  the  gela- 
tinous fibres,  are  seen 
two  of  the  ordinary, 
dark  bordered  nerve  fi- 
bres.     (  Robin.) 


5-40 


STRUCTURE    OF    THE    NERVOl'S    SYSTEM. 


of  the  brain  and  spinal  cord.  Inasmuch,  however,  as  the  axis-cylinder, 
in  many  instances  at  least  (Fig.  279),  has  been  shown  to  be  continuous 
with  such  processes,  it  is  very  questionable  as  to  whether  any  such  abso- 
lute distinction  exists  in  the  body  as  indicated  by  the  terms  unipolar, 


Fig.  1278. 


Fro.  279. 


Nerve  cells,  from  the  anterior  horn  of  gray 
substance  of  the  spinal  cord.     (Dalton.) 


Ramified  nerve  cell  from  anterior  cornu  of 
spinal  cord  (man),  a.  Axis-cylinder  process. 
b.  Clump  of  pigment  granules.  Above  the 
cell  is  seen  part  of  the  network  of  fibrils  men- 
tioned iu  the  text.     (Gerlach.) 


apolar,  etc.,  the  distinction  observed  in  this  respect  between  nerve  cells 
being  very  possibly  due  to  the  fact  that,  usually,  in  histological  investi- 
gations, one  or  more  of  the  axis-cylinders  becomes  separated  from  the 
body  of  the  cell  in  which  they  are  the  prolongations.  In  other  words, 
that  the  axis-cylinder  of  the  nerve  fibre  is  essentially  a  portion  of  the 
body  of  the  nerve  cell  (Fig.  275),  finely  drawn  out  like  a  wire,  the  latter 
portion,  as  we  have  seen,  being  protected  by  a  neurilemma,  and  insu- 
lated by  the  white  substance  of  Schwann.  In  addition  to  the  cells,  the 
gray  matter  of  the  nervous  system  consists  of  scattered  nuclei,  usually 
smaller  than  those  of  the  cells,  and  of  a  fine  granular  matter,  which 
constitutes  a  kind  of  supporting  matrix  for  the  cells  and  their  prolonga- 
tions, or  the  axis-cylinders.  While  it  cannot  be  said  that  the  minute 
structure  of  the  gray  matter,  and  its  relation  to  the  axis-cylinders 
passing  out  of  it,  has  been  exactly  made  out  as  just  described,  never- 
theless, it  is  highly  probable  that  such  is  essentially  the  disposition  of 
the  same.  In  addition  to  the  nerve  cells  just  mentioned,  there  are 
other  cells  found  in  the  gray  matter  of  the  ganglia,  and  which  differ  in 
being  enclosed  by  a  distinct  sheath,  or  capsule  (Fig.  280).  The  latter 
consists  of  a  transparent  membrane  with  nuclei,  and  appears  to  be  con- 
tinuous with  the  primitive  sheath  of  the  nerve  fibre.  The  ganglia  them- 
selves, like  the  nerve  cells,  of  which  they  are  made  up,  are  invested  by  a 
thin,  but  firm,  envelope,  continuous  with  the  fibrous  sheath  of  the  nerves 
passing  into  them,  and  consist  of  connective  tissue  supporting  the  cells 
and  nerve  fibres.  While  many  of  the  nerve  fibres  simply  pass  through 
the  ganglia  (Fig.  281),  others  originate  in  the  cells  of  the  latter,  each 


PERIPHERAL    DISTRIBUTION    OF    NERVES, 


541 


cell,  according  to  Beale  and  Arnold,  giving  oft'  two  fibres,  one  of  which 
passes  out  of  tlie  cell  like  a  stalk,  so  to  speak,  while  the  other  arises  at 
some  distance  from  the  first,  and  after  making  several  turns  around  the 


Fig.  280. 


Fig.  281. 


Nerve  cells,  intermingled  with  fibres  ;  from  semilunar 
ganglion  of  cat.     (Dalton.) 


Multipolar  ganglion  cells  from  sympathetic 
of  man.  Magnified,  a.  Freed  from  capsule. 
6.  Enclosed  within  capsule.  The  processes 
of  both  are  broken  off  a  short  distance  from 
the  cell.     (Max  Schiltze.) 


latter,  passes  off  in  an  opposite  direc- 
tion. Such  cells  are  readily  ob- 
served in  the  ganglia  of  frogs,  but 
while  difficult  of  demonstration  in 
the  ganglia  of  mammals,  nevertheless  appear  to  exist  in  the  latter.  If 
the  nerve  fibres  be  traced  from  their  origin  in  the  gray  matter  of  the 

Fig.  282. 


Nerve-ending  in  muscular  fibre  of  a  lizard.  (Lacerta  viridis.)  a.  End-plate  seen  edgeways.  b.  From 
-the  surface,  s,  s.  Sarcolemma.  p,  p.  Expansion  of  axis-cylinder.  In  b  the  expansion  of  the  axis- 
cylinder  appears  as  a  clear  network  branching  from  the  divisions  of  the  medullated  fibre.  Highly  magni- 
fied.     (KUHNE.) 

central   nervous   system  to   their  peripheral    distribution    in    muscles, 
glands,  sensory  organs,  etc.,  it  will  be  observed,  so  far  as  the  manner  in 


542 


STRUCTURE    OF    THE    NERVOUS    SYSTEM, 


which  the  nerve  terminates  has  been  made  out,  that  the  only  pari  of  the 
primitive  nerve  left  at  its  termination  is  the  axis-cylinder.  Thus,  in 
the  termination  of  nerve  fibres  in  muscles  where  the  axis-cylinder  passes 
into  the  hitler,  expanding  into  the  motor  plate  (Fig.  282),  the  neuri- 
lemma of  the  nerve  fibres  becomes  continuous  with  the  sarcolemma  of 
the  muscle,  while  the  white  substance  of  Schwann,  though  continuing 
to  the  muscle,  does  not,  however,  penetrate  into  it,  and  while  there  may 
be  still  doubt  prevailing  as  to  whether  the  axis-cylinder  passes  into  the 
nuclei  of  the  cells  of  a  gland  in  the  manner  supposed  to  be  the  case  by 
Pfluger  and  others,  in  the  salivary  gland,  for  example,  there  is  no  doubt 
that,  however  exactly  the  axis-cylinder  does  terminate  in  glands,  it  is 
the  only  part  of  the  nerve  fibre  that  actually  reaches  the  cells,  of  which 
such  organs  consist.  Such  is  essentially,  also,  the  disposition  that 
obtains  in  the  case  of  sensory  organs,  so  far  as  has  been  established. 
Thus,  whether  it  be  a  Pacinian  corpuscle  attached  to  sensory  nerves 
(Fig.  283,  A,  B),  or  a  tactile  corpuscle  (Fig.  284),  as  we  shall  see,  are 

A  Fig.  283.  15 


A  nerve  of  the  middle  finger,  with   Pacinian  bodies 
attached.    Naturalsize.    (Henle and Kolliker  ) 

present  in  the  skin,  or  a  terminal  bulb 
(Fig.  285),  such  as  are  found  in  the 
conjunctiva  Or  tongue  ;  in  each  instance 
will  the  neurilemma  of  the  nerve  fibre 
become  continuous  with  the  capsule 
enclosing  such  bodies,  the  white  sub- 
stance of  Schwann  remains  without 
the  latter,  the  axis-cylinder  alone  pene- 
trating within.  It  is  evident,  there- 
fore, that  since  the  nerve  fibre  begins 
as  the  axis-cylinder,  a  prolongation  of 
the  gray  matter  of  the  cells  of  the  cen- 
tral nervous  system,  and  terminates  as  axis-cylinder  in  muscle,  gland, 
sensory  organ,  etc.,  and  as  it  is  only  the  portion  of  the  axis-cylinder 
intermediate  between  the  origin  and  termination  of  the  nerve  fibre  that 


Vater'sor  Pacini's  corpuscle.  «.  Stalk,  b. 
Nerve  fibre  entering  it.  «,  '1.  Connective 
tissue  envelope.  e.  Axis-cylinder,  with  its 
end  provided  at/.     (Quain.) 


COMPOSITION    OF    NERVOUS    SYSTEM. 


543 


is  inclosed  within  the  Avhite  substance  of  Schwann  and  the  neurilemma, 
that  the  axis-cylinder  or  the  gray  matter  is  the  essential  portion  of  the 
nerve  fibre,  as  it  is  of  the  cell  in  which  the  former  originates.    In  speaking 


Fig.  284. 


Fig.  285, 


Tactile  corpuscle,     b.  Nerve.     (Quain.) 


Three  nerve-end  bulbs  from  the  human  con- 
junctiva, treated  with  acetic  acid.  Magnified  300 
diameters.     (Quain.) 


of  the  vesicular  gray,  or  cellular,  and  the  white  fibrous  portions  of  the 
nervous  system,  it  must  not  be  forgotten  that  there  is  but  one  kind  of 
functional  nervous  matter,  the  gray,  the  white  simply  acting  as  a  pro- 
tection. While,  from  the  fact  of  the  nerve  fibre  losing  its  vitality  if 
separated  from  the  central  cell,  of  which  it  is  a  prolongation,  it  follows 
that  the  nerve  force,  whatever  its  nature  may  be,  is  generated  in  the 
cells  of  the  axis-cylinder  serving  for  its  transmission  only. 

If  the  above  view  be  accepted,  it  also  follows  that  the  sympathetic  must 
be  regarded  as  an  appendage  of  the  cerebro-spinal  system,  and  for  which 
there  are  good  reasons,  as  we  shall  see,  for  supposing  this  to  be  the  case. 
This  view  of  the  nervous  system,  based  upon  the  study  of  its  structure, 
is  further  confirmed  by  the  following  considerations  offered  by  Spencer:1 
That  the  gray  matter  contains  more  water  and  is  more  vascular  than  the 
white,  and  that  while  the  cells  are  unprotected  practically  by  an  envelope, 
the  axis-cylinder  is  inclosed  by  two  such  as  we  have  seen,  conditions 
favoring  in  the  unstable  gray  matter  destructive  molecular  changes  and 
disengagement  of  motion,  while  the  more  stable  nerve-threads  are  seats 
of  molecular  changes  not  so  much  destructive  as  isomeric  in  character. 
The  matter  of  which  the  nervous  system  is  composed  consists  chemically, 
like  the  remaining  tissues,  generally  of  from  three-fourths  to  four-fifths 
water,  the  white  matter  containing  about  seventy-five  per  cent.,  the  gray 
eighty-five  per  cent ;  the  residue  consists  chiefly  of  a  phosphoretted 
principle  known  as  protogen,  a  crystalline  body  containing  nitrogen  as 
well  as  phosphorus  and  carbon,  and  which,  according  to  some  chemists, 
is  composed  of  two  principles,  lecithin  and  neurin  (cholin),  C5H15N02, 
or  lecithin  and  cerebrin.  The  gray  matter  contains  about  five  per  cent, 
the  white  fifteen  per  cent,  of  such  phosphoretted  principles.  It  is  an 
interesting  fact  as  regards  lecithin,  C44H9()NP09,  that  it  is  the  only 
organic  principle  of  the  body  containing  phosphorus.     There  are  found 


1  Pi  inciples  of  Psychology,  p.  25.     Lond.  1S70. 


544  STRUCTURE    OF    THE    NERVOUS    SYSTEM. 

in  the  nervous  system  also  cerebrin,  <\-II.s:iXO.,,  cholesterin,  which  1ms 
already  been  referred  to,  various  extractives,  and  inorganic  sails.  Among 
the  extractives  may  be  mentioned  lactic  formic,  acetic  acids,  inosit, 
kreatin,  and  hypoxanthin.  The  inorganic  principles  consist  principally 
of  alkaline  and  earthy  phosphates,  sodium  sulphate  and  chloride,  iron 
phosphate,  and  traces  of  silica.  Of  the  latter  phosphoric  acid  (thirty- 
nine  per  cent.),  potash  (thirty-two  per  cent.),  and  soda  (ten  per  cent.), 
are  the  most  important.  Beyond  the  mere  statement  of  the  facts,  as 
just  given,  little  more  is  positively  known  of  the  chemical  composition 
of  the  nervous  system,  either  with  reference  to  the  manner  in  which  the 
ultimate  chemical  elements  are  combined  or  the  significance  of  the  latter. 
In  concluding  this  sketch  of  the  nervous  system,  it  may  be  mentioned 
here,  as  appropriately  as  elsewhere,  that  since  there  are  no  appreciable 
differences  physically  or  chemically  observed  between  the  ultimate  nerve 
fibres,  the  fact  of  there  being,  as  we  shall  see,  motor,  sensory,  and  secretory 
nerves  appears  to  depend,  not  upon  any  difference  between  the  nerves, 
but  upon  their  terminating  in  motor,  sensory,  or  glandular  organs  respect- 
ively. That  a  nerve  fibre  will  transmit  an  impression  made  upon  the 
periphery  to  the  centre,  or  from  the  centre  to  the  periphery,  is  shown  by 
such  an  experiment  as  that  performed  by  Bert.1  Thus  the  end  of  the 
tail  in  a  young  rat  being  denuded  of  integument  for  a  length  of  about 
two  inches  was  grafted  to  the  back  of  the  animal.  At  the  end  of  about 
a  week,  when  the  ingrafted  portion  had  become  adherent,  the  tail  was 
amputated  at  the  base,  the  tail  remaining  adherent  by  what  had  been  its 
tip.  Nevertheless,  at  the  end  of  six  months  sensibility  bad  been  unmis- 
takably reestablished,  the  caudal  nerves,  after  the  operation,  transmitting 
impressions  from  the  base  of  the  tail  to  its  tip  instead  of,  as  usually, 
from  the  tip  to  the  base. 

1  La  Vitalite  propre  des  Tissues  Vuimaux,  p.  13.    Paris,  1866. 


CHAPTER    XXXYII. 

BATTERIES.  OHM'S  LAW.  INDUCTION  APPARATUS.  PEN- 
DULUM. MYOGRAPH.  SPRING  MYOGRAPH.  WHIPPE. 
LATENT  PERIOD.     VELOCITY  OF  NERVE  FORCE,  ETC. 

From  daily  observation  we  learn  that  all  our  actions  are  the  result  of 
motives  or  stimuli.  Impressions  made  upon  the  surface  of  the  body 
and  transmitted  by  nerves  to  the  central  nervous  system  and  there  giving 
rise  to  sensations,  are  immediately  or  mediately  followed  by  actions. 
The  impressions  made  may  be  so  strong  and  the  corresponding  sensa- 
tion arising  so  acute  that  action  instantly  follows,  as  in  the  sudden, 
involuntary  shrinking  from  a  source  of  pain  or  the  sensation  giving 
rise  to  an  idea  a  longer  or  shorter  time  may  intervene,  during  which 
period  the  mind  has  time  to  reflect  as  to  the  course  of  action,  the  in- 
dividual being  swayed  by  this  or  that  idea  or  motive,  the  mind  is,  so  to 
speak,  in  abeyance,  like  the  ass  of  the  schoolmen  starving  between  the 
two  bundles  of  hay,  because  he  could  not  make  up  his  mind  which  to 
eat  first.  Sooner  or  later,  however,  one  motive  becoming  the  strongest, 
voluntary  action  follows,  or,  to  speak  in  ordinary  language,  the  will  asserts 
itself,  the  term  will  being  simply  a  convenient  one  for  expressing 
the  fact  that  action  is  the  result  of  the  strongest  motive,  the  result  of 
the  preceding  stimulus.  The  sole  difference  between  these  two  actions, 
the  involuntary  and  voluntary,  is  in  the  interval  of  time  elapsing 
between  the  application  of  the  stimulus  and  the  resulting  action,  and  in 
the  stimulus  being  that  of  the  will  or  some  other  exciting  cause,  as,  for 
example,  when  a  cough  is  voluntary  or  due  to  a  crumb  of  bread  in  the 
larynx.  In  addition,  however,  to  the  sensations,  or  ideas,  arising  within 
us  due  to  the  stimulation  of  nerves  from  without  inward  and  of  the 
involuntary  or  voluntary  actions  following  due  to  the  reflection  of  the 
impulses  from  such  stimulation  from  within  outward  of  which  we  are 
all  conscious,  there  are  similar  actions  following  the  stimulation  of  nerves, 
of  which  as  long  as  we  are  in  a  state  of  health  we  are  entirely  uncon- 
scious. As  illustrations  of  such  actions  may  be  mentioned  the  flow  of 
the  gastic  juice  in  response  to  the  stimulus  exerted  by  food  upon  the 
nerves  distributed  to  the  stomach,  of  the  dilatation  or  contraction  of  the 
bloodvessels  brought  about  through  the  influence  of  nervous  emotion, 
or  the  action  of  the  iris  under  the  influence  of  light.  The  phenomena 
of  secretion  like  those  of  sensation,  involuntary  and  voluntary  move- 
ments, result  from  the  application  of  a  stimulus  to  peripheral  nerves, 
which,  being  transmitted  to  the  nervous  centres,  is  thence  reflected  to 
the  parts  manifesting  the  phenomena.  That  it  is  by  means  of  the 
nerves  connecting  the  periphery  with  the  nervous  centre  and  the  centre 
with  the  organs  manifesting  the  phenomena  that  the  latter  are  pro- 
duced becomes  at  once  evident  if  the  nerves  involved  be  destroyed, 

35 


546 


BATTERIES, 


whether  by  disease,  injury,  or  experiment;  sensation,  voluntary  move- 
ment, secretion,  etc.,  at  once  disappearing  as  we  shall  see  presently. 
The  involuntary  muscular  contraction  the  result  of  pain,  the  voluntary 
one  made  in  the  carrying  out  of  some  of  some  matured  plan,  and  the  flow 
of  a  secretion,  are  equally  illustrations  of  the  truth  of  all  nervous  action 
being  of  this  reflex  character.  In  every  instance  if  the  phenomenon  be 
traced  to  its  source  it  will  become  evident  that  an  action  apparently 
due  to  an  impulse  generated  from  within  and  transmitted  outward  is  in 
reality  due  to  an  impression  first  made  from  without  and  transmitted 
inward,  and  then  finally  reflected  outward.  That  nervous  action  or 
force,  whatever  it  may  be,  is  never  generated  spontaneously,  but  must 
be  of  this  reflex  cluu-acter,  some  modified  preexistent  mode  of  motion, 
is  self-evident,  otherwise  nerve  force  would  arise  out  of  nothing.  What- 
ever view  may  be  taken,  however,  of  the  origin  of  ideas,  the  nature  of 
the  will,  etc.,  it  will  not  affect  the  fact  that  the  irritability  of  nerves,  like 
that  of  other  tissues,  may  be  called  into  excitement  by  appropriate 
stimuli.  While  tli3  irritability  of  a  muscle,  however,  shows  itself  by 
its  contraction,  and  that  of  a  gland  by  its  secretion,  that  of  the  nerve 
is  not  manifested  by  any  ordinary  visible  change  in  itself,  but  as  a 
sensation  or  a  motion  in  the  organ  to  which  it  is  distributed.  Of  the  dif- 
ferent stimuli,  mechanical,  chemical,  and  electrical,  available  in  calling 
into  excitement  the  property  of  irritability  possessed  by  nerves,  the 
electrical  is  by  far  the  most  convenient,  and  since  the  contraction  of  a 
muscle  brought  about  indirectly  by  the  stimulation  of  the  nerve  supply- 
ing it,  is  a  very  striking  phenomenon,  the  muscular  contraction  may  be 
taken  as  an  evidence  and  measure  of  nervous  irritability  causing  it. 
While  a  sensation  or  a  secretion  might  be  in  the  same  way  taken  as  a 
measure  of  nervous  irritability,  as  might  be  expected  from  the  nature  of 
the  case  it  would  be  less  convenient  and  less  reliable. 

As  in  the  stimulation  of  nerves  we  shall  usually  make  use  of  the 
electricity  supplied  by  a  Daniell  or  Bunsen  battery,  a  brief  description 
of  the  same  does  not  appear  superfluous.     A  single  Daniell's  element 

consists  (Fig.  286)  of  a  glass  vessel  S, 
containing  a  saturated  solution  of  copper 
sulphate,  in  which  is  immersed  a  copper- 
cylinder  (A),  open  at  both  ends  and  per- 
forated with  holes,  and  provided  with  an 
annular  shelf  supporting  crystals  of  copper 
sulphate  to  replace  the  solution  of  the 
same  decomposed  during  the  action  of 
the  battery.  Within  the  copper  cylinder 
is  a  thin  porous  vessel  of  unglazed  earth- 
enware, containing  diluted  sulphuric  acid, 
in  which  is  placed  a  cylinder  of  amalga- 
mated zinc  Z.  The  positive  electricity 
generated  by  the  action  of  the  acid  upon 
the  zinc  passing  through  the  liquid  of  the 
battery  to  the  copper  cylinder,  accumu- 
lates at  the  end  of  the  wire  attached  by  the  binding  screw  to  the  latter 
(C),  the  wire  becomes,  therefore,  the  positive  pole  or  electrode,  though 


Fig.  28fi. 


^- 


Daniell's  element.     (Oanot.) 


POLARIZATION 


547 


the  copper,  to  which  it  is  attached  from  being  relatively  little  acted 
upon,  is  called  the  negative  or  collecting  plate;  on  the  other  hand, 
through  the  disturbance  of  the  electrical  equilibrium  the  negative 
electricity  developed  passing  in  the  reverse  direction  from  the  copper 
to  the  zinc,  accumulates  at  the  end  of  the  wire  attached  to  the  latter  (Z), 
the  wire  becomes,  therefore,  the  negative  pole  or  electrode ;  the  zinc, 
however,  from  being  most  acted  upon,  is  called  the  positive  or  genera- 
ting plate.  As,  however,  the  effect  of  the  battery  is  due  to  the  dif- 
ference between  the  two  currents,  it  is  more  convenient  to  speak  as  if 
there  was  but  one  current  passing  from  the  zinc  or  positive  plate 
through  the  liquid  of  the  battery  to  the  copper  or  negative  one,  thence 
by  the  positive  pole  through  the  connecting  wire  back  to  the  negative 
pole  and  so  to  the  zinc  again.  Such  being  the  disposition  and  action 
of  the  parts  of  a  Daniell's  element  when  closed ;  the  hydrogen  resulting 
from  the  action  of  the  dilute  acid  upon  the  zinc  being  liberated  upon  the 
surface  of  the  copper  plate  would  be  deposited  upon  the  latter,  causing 
its  polarization  and  the  action  of  the  battery  would  be  interfered  with, 
were  it  not  for  the  presence  of  the  copper  sulphate,  which  reduces  it 
into  copper  and  sulphuric  acid,  the  former  being  deposited  upon  the 
copper  plate,  and  the  latter  replacing  that  in  the  porous  cup  used  up  in 
acting  upon  the  zinc  ;  the  constancy  of  the  battery  is  thus  insured  for 
several  hours  at  least,  upon  which  its  usefulness  for  our  purpose  depends. 
Did  the  hydrogen  gas  generated  settle  in  minute  bubbles  upon  the  copper 
plate,  which  it  otherwise  would  do  in  the  absence  of  the  solution  of 
copper  sulphate,  the  action  of  the  battery  would  be  at  once  interfered 
with,  as  just  mentioned,  by  the  polarization  of  the  plate,  by  which  is 
meant  that  the  hydrogen  when  so  deposited  not  only  offers  a  resistance 
to  the  current  passing  from  the  zinc  to  the  copper,  but  in  generating  a 

Fig.  1^7 


counter-current  in  opposition  to  the  latter,  proportionally  weakens  it. 
Further,  through  some  of  the  zinc  sulphate  produced  being  attacked  by 
the  hydrogen  and  deposited  upon  the  copper  plate,  the  latter  approach- 
ing the  condition  of  the  zinc  plate,  the  difference  in  electrical  potential 
would  be  correspondingly  reduced.  It  need  scarcely  be  added  that  if 
two  or  more  elements  are  used  in  coupling,  the  zinc  plate  of  one  must 


548 


BATTERIES. 


Fig.  288. 


be  connected  with  the  copper  plate  of  the  other  by  means  of  a  copper 
wire  or  strip,  as  in  Fig.  290. 

The  Bunsen  element,  or  the  zinc  carbon  element,  differing  from  a 
Grove  element  only  in  the  platinum  of  the  latter  being  replaced  by 
carbon,  consists  (Fig.  287)  of  a  glass  or  stoneware  vessel  (F)  containing 
dilute  sulphuric  acid,  in  which  is  immersed  a  hollow  cylinder  of  amal- 
gamated zinc,  within  which  is  placed  a  porous  vessel  (V)  containing 
ordinary  nitric  acid,  the  cylinder  of  carbon  being  placed  within  the 
latter.  As  in  the  Daniell  element,  the  zinc  constitutes  the  positive  plate, 
the  carbon,  however,  the  negative  one,  the  hydrogen  developed  decom- 
posing the  nitric  acid,  the  hyponitrous  acid  produced  passing  off  in 
fumes.  A  Grenet's  cell,  though  not  very  constant  in  its  action,  is  a 
convenient  form  of  element  to  work  with,  owing  to  the  absence  of 
fumes.  It  consists  (Fig.  288)  of  a  wide-mouthed  globe-shaped  bottle 
(^4),  containing  a  mixture  of  dilute  sulphuric  acid 
and  a  saturated  solution  of  potassium  bichromate 
and  two  plates  of  compressed  carbon  (KK),  which 
reach  from  the  cap  to  nearly  the  bottom  of  the 
vessel,  both  of  which  are  in  communication  with 
one  of  the  binding  screws  in  the  vulcanite  stopper. 
Through  the  latter  passes  a  movable  rod  by 
which  the  zinc  plate  (Z)  attached  to  the  latter, 
and  situated  between  the  carbon  plates  and  in 
communication  with  the  other  binding  screw,  can 
be  lowered  into  the  fluid  by  the  rod  B.  Since 
the  potassium  bichromate  is  reduced  to  the  sesqui- 
oxide  by  the  hydrogen  liberated  through  the 
action  of  the  dilute  acid  upon  the  zinc,  and  the 
salt  so  formed  deposited  upon  the  latter,  it  is 
desirable  that  the  bottle  should  be  shaken  up,  in 
order  to  separate  this  deposit,  otherwise  the  inten- 
sity of  the  current  will  be  much  diminished. 

In  describing  the  different  batteries  ordinarily 
made  use  of  for  physiologieal  purposes,  the  elec- 
tricity generated  was  spoken  of  as  if  flowing 
through  the  battery  to  the  poles,  as  one  might 
speak  of  the  flow  of  water  through  pipes,  just  as 
if  there  was  an  actual  electrical  current  present. 
As  a  matter  of  fact,  it  is  needless  to  say  with 
reference  to  the  development  of  electricity,  there 
is  no  evidence  of  a  transference  of  particles  from  place  to  place  as  is  the 
case  of  the  flow  of  water.  It  will  be  found,  nevertheless,  since  the 
molecular  changes  incidental  to  the  production  of  electricity  are  yet 
unknown,  that  such  a  comparison  offers  an  extremely  convenient  way 
of  presenting  the  essential  facts,  of  representing  to  the  mind  in  a  con- 
nected way  results  brought  about  by  changes,  the  intimate  nature  of 
which  we  know  nothing.  It  might  be  supposed,  however,  at  first  sight, 
that  the  consideration  of  this  subject  belongs  rather  to  the  domain  of 
physics  than  to  physiology  ;  but  as  we  shall  soon  learn  that  the  physiolo- 
gist not  only  continually  uses  electricity  as  a  nerve  stimulus,  but  that 


Grenet's  element.  A.  The 
glass  vessel.  K  K.  Carbon. 
Z.  Zinc.  D,  E.  Binding  screw 
for  the  wires.  15.  Bod  to  raise 
or  depress  the  zinc  in  the 
fluid.  0.  Screw  to  fix  B. 
(Landois.) 


POTENTIAL  ELECTROMOTIVE  FORCE,  ETC.      549 

both  nerve  and  muscle  exhibit  electrical  currents,  and  offer  a  resistance 
to  the  passage  of  electricity,  etc.,  it  becomes  indispensable  that  a  brief 
account  of  the  principal  facts  of  electricity  be  offered,  sufficient  at  least 
to  enable  the  student  to  understand  the  terms  constantly  used  in  the 
description  of  the  phenomena  of  general  nerve  physiology. 

It  is  a  well-established  fact  that  when  two  metals  are  placed  in  con- 
tact, as,  for  example,  zinc  with  copper  or  platinum,  a  disturbance  in  their 
electrical  condition,  or,  as  it  is  called  by  electricians,  a  difference  in 
potential,  ensues,  the  word  potential  being  used  in  electrical  science  in 
the  same  sense  as  level  or  head  of  water  in  hydrodynamics.  Now  just  as 
water  at  a  higher  level,  if  it  finds  a  channel,  tends  to  fall  to  a  lower  one 
until  equilibrium  is  established  ;  similarly  if  two  bodies,  or  two  parts  of 
the  same  body,  have  a  different  potential — that  is,  are  at  different  electri- 
cal levels,  so  to  speak — there  will  be  a  tendency  to  movement  from  the 
body  having  a  higher  potential  to  the  one  with  the  lower  until  electri- 
cal equilibrium  is  established.  The  force  to  which  this  change,  move- 
ment, so-called  electrical  current,  is  due,  is  called  the  electromotive 
force,  and  while  its  nature  is  unknown,  it  can,  like  any  other  force,  be 
measured  by  the  amount  of  work  performed  in  the  passage  of  a  unit  of 
electricity  from  one  position  to  another,  just  as  the  force  of  water  can 
be  measured  by  the  amount  of  work  performed,  as  in  the  turning  of  a 
water-wheel,  etc.  Just  as  the  force  exerted  in  a  definite  time  in  raising 
a  weight  against  gravity  may  be  stored  up  indefinitely,  to  be  set  free 
again  by  the  falling  of  the  weight,  and  applied  to  the  performance  of 
mechanical  work,  so  the  force  exerted  in  bringing  up  a  body  against 
another  similarly  electrified,  and  therefore  offering  a  resistance  like  that 
of  gravity,  maybe  temporarily  stored  up,  and  with  the  setting  free  of  the 
electricity  perform  work.  While,  therefore,  the  principle  of  electrical 
measurement  must  be  the  same  as  that  of  other  force  measurements,  the 
particular  standards  used  will  not  only  differ  according  as  statical  or 
dynamical  electricity  is  being  considered,  but  as  to  what  shall  be  accepted 
as  constituting  the  unit  of  time,  weight,  distance,  etc.  As  a  matter  of 
fact,  with  reference  to  statical  or  fractional  electricity,  each  of  two 
equally  charged  bodies  is  said  to  have  a  unit  of  electricity,  if  when 
separated  by  a  distance  of  one  centimetre  the  one  will  repel  the  other 
with  a  force  which  will  impart  in  one  second  a  velocity  of  one  centi- 
metre per  second  to  one  gramme  of  matter.  As  regards  the  galvanic 
or  current  electricity  with  which  we  have,  however,  more  particularly 
at  this  moment  to  do,  the  unit  of  electricity  is  usually  accepted  as  being 
that  quantity  of  electricity  carried  in  one  second  by  a  current  of  unit 
strength.  The  latter,  however,  is,  of  course  arbitrary,  but  in  the  sense 
just  used  is  one  such  that  if  a  conductor  one  centimetre  long  be  bent 
into  an  arc  of  one  centimetre  radius  it  will  exert  a  force  of  one  dyne, 
that  is,  ^ly  of  a  gramme  (a  gramme  acquiring  through  gravity  in  one 
second  a  velocity  of  981  cm.  a  second)  on  a  unit  magnet  pole  placed 
at  the  centre.  But  the  force  exerted  in  raising  one  dyne,  or  the  g^-T 
of  a  gramme,  through  one  centimetre — that  is,  that  performs  technically 
one  erg  of  work — will  raise  one  such  electro-magnetic  unit  as  just  de- 
scribed through  one  electro-magnetic  unit  of  potential,  or,  what  is  the 
same  thing,  the  fall  of  one   electro-magnetic  unit  through  one  unit  of 


550  VOLT,    OHM. 

electro-magnetic  potential  will  perform  one  erg  of  work.  The  latter  is, 
therefore,  in  terms  of  a  gramme  or  fraction  of  the  same,  metres  or  centi- 
metres,  and  seconds,  taken  as  the  measure  of  the  electromotive  force. 
For  convenience'  sake,  however,  in  practice  a  hundred  millions  of  such 
absolute  electro-magnetic  units  are  taken  as  a  unit  constituting  the  so- 
called  volt,  and  we  speak,  therefore,  of  the  electromotive  force  of  a 
Daniell's  cell  being  equal  to  1.079  volt.  Resuming  what  has  been  just 
said,  it  may  be  briefly  stated  that  the  unit  of  electromotive  force  is  that 
amount  of  force  which  sends  a  current  of  unit  strength  through  a  unit 
resistance,  and,  therefore,  a  unit  quantity  in  a  unit  time,  and  this  defi- 
nition brings  us  now  to  a  consideration  of  the  resistance  offered  by  the 
conductors  in  the  passage  of  the  electricity  and  the  fixing  of  some 
standard  for  the  same. 

As  the  latter  must  be,  of  course,  an  entirely  arbitrary  one,  the 
standard  of  resistance  ultimately  accepted  will  depend  upon  what  is 
considered  most  convenient  by  electricians.  As  a  matter  of  fact,  at  the 
present  time,  the  resistance  offered  by  a  column  of  mercury,  104.81  cm. 
long,  and  1  square  mm.  in  section  at  0°  C,  is  accepted  as  the  unit  of 
resistance  commonly  known  as  the  British  Association  unit,  or  one  ohm  ; 
or,  what  is  the  same  thing,  the  resistance  offered  by  a  wire  made  of  an 
alloy  of  silver  and  platinum  of  definite  length  and  thickness,  offering 
the  same  resistance  as  the  column  of  mercury  just  referred  to,  is  accepted 
as  the  unit  of  resistance,  or  one  ohm.  The  resistance  offered  by  dif- 
ferent bodies  to  the  passage  of  an  electrical  current  varies  very  consider- 
ably, according  to  the  nature  of  the  body.  Metals,  being  the  best  con- 
ductors, offer  the  least  resistance ;  liquids,  especially  those  of  a  saline 
character,  conduct,  but  not  so  readily  as  metals.  Apart,  however,  from 
the  conductibility  of  a  particular  substance,  which  is  constant  for  that 
substance,  the  resistance  offered  by  a  conductor  is  directly  proportional 
to  its  length,  and  inversely  proportional  to  its  cross-section — that  is,  the 
longer  the  conductor  the  greater  the  resistance,  the  thicker  the  con- 
ductor the  less  the  resistance.  In  the  case  of  a  galvanic  element,  how- 
ever, like  that  of  a  Daniell's  cell,  not  only  must  the  resistance  offered 
by  the  conducting  wires,  which  may  be  called  the  external  resistance, 
be  taken  into  consideration,  but  also  the  resistance  offered  by  the  plates 
and  liquid  within  the  cell,  and  which  may  be  called  the  internal  resist- 
ance. The  latter  is  directly  proportional  to  the  distance  of  the  plates 
from  each  other,  and  inversely  proportional  to  the  size  of  the  plates — 
that  is,  the  larger  the  plates  the  less  the  resistance,  the  conducting 
power  of  the  liquid,  of  course,  being  assumed  to  be  constant.  In  the 
determination  of  the  electromotive  force,  resistance,  etc.,  of  nerves  it 
will  be  found,  as  we  shall  see  presently,  that  it  is  of  great  advantage  to 
vary  by  known  amounts  the  resistance  offered  to  the  passage  of  an 
electrical  current.  For  this  purpose  we  make  use  of  a  resistance  box, 
which  consists,  essentially  (Fig.  289),  of  a  series  of  bobbins  (C  C)  on 
which  are  coiled  various  lengths  of  standard  insulated  wire,  the  latter 
being  so  disposed  in  the  box  that  two  ends  of  the  wire  of  each  bobbin 
(C  C)  are  connected  with  two  brass  plates  (B  B)  fitted  into  the  lid  of 
the  box,  the  resistance  offered  by  each  coil  of  wire  being  indicated  in 
ohms  on  the  lid  of  the  box.     Suppose,  by  means  of  the  two  binding 


RESISTANCE    BOX.  551 

screws  attached  to  the  lid  of  the  box,  a  current  of  electricity  be  sent 
through  the  coils  C  C,  the  resistance  encountered  will  be  equal  to  the 
total  resistance  offered  by  the  coils.     If,  however,  the  space  intervening 

Fig.  289. 


li.si-taiH'.'  box.     (McGrehor-Roisertsox.) 

between  the  brass  plates  be  plugged  up  by  tight-fitting  brass  plugs 
(Fig.  289),  so  that  the  brass  plates  are  then  connected,  the  current 
will  take  the  route  of  least  resistance,  passing  simply  through  the  brass 
portion  of  the  lid  of  the  box,  from  binding  screw  to  binding  screw, 
without  traversing  the  coils  at  all.  It  is  obvious,  therefore,  that, 
according  to  the  number  of  brass  plugs  that  are  out,  will  be  the  amount 
of  resistance  offered  to  the  current.  We  have  just  seen  that  the  passage 
of  an  electrical  current  through  a  galvanic  circuit  is  due  to  the  electro- 
motive  force  developed  by  the  element ;  and  further,  that,  according  to 
the  nature  of  the  circuit,  the  current  meets  with  more  or  less  resistance. 
It  follows,  therefore,  as  shown  by  Ohm,1  first  from  theoretical  consid- 
erations, and  subsequently  by  experiment,  that  the  intensity  of  the 
current — that  is,  the  quantity  of  electricity  which,  in  a  unit  of  time, 
flows  through  a  given  section  of  the  current — must  be  equal  to  the  ratio 
of  the  resistance  to  the  electromotive  force.  This  important  result, 
usually  known  now  as  Ohm's  law,  may  be  conveniently  expressed  by 

E 

the  equation  (1)  1=        in  which  I  represents  the  intensity,  JE  the 

electromotive  force,  and  R  the  resistance.  Ohm's  law  is  not  only  a 
most  important  one  from  a  theoretical,  but  also  from  a  practical  point 
of  view,  since,  by  means  of  it,  galvanic  batteries  are  so  arranged  as  to 
give  the  greatest  amount  of  electricity  possible.  From  this  point  of 
view,  however,  it  will  be  sufficient,  for  our  present  purpose,  to  illustrate 
Ohm's  law  only  by  such  examples  as  will  facilitate  the  comprehension 
of  the  methods  of  determining  the  electromotive  force  and  resistance  of 
nerves,  etc.,  to  be  presently  described. 

It  will  be  remembered  that  the  resistance  of  a  conductor  is  directly 
proportional  to  its  length,  and  inversely  proportional  to  its  conduc- 
tivity and  section,  if  now  the  length,  conductivity,  and  section  be  rep- 
resented respectively  by  I,  e,  and  s,  then  the  resistance  S,  will  be  equal 

to This  value  of  H  being  substituted  in  equation  (1)  we  shall 

C  X  8 

-      csE 
obtain   I =  i  =  - (2) — that  is  to  say,  the  intensity  of  a  current  is 

cs 

1  Die  galvanischo  Kette  mathsmatiscn  bsarbeitet,  Berlin,  Isjt.      Also  translated  in  Taylor's  Scientifi 

Memoirs. 


552 


OHM  S    L A  W . 


directly  porportional  to  the  section  and  conductivity  of  the  conductor, 
but  inversely  proportional  to  its  length.  In  the  case  of  a  galvanic 
element,  as  we  have  seen,  the  resistance  to  be  considered  is  not  only 
that  of  the  conducting  wires,  but  also  that  of  the  liquid  and  plates  of 
the  element  itself.  Calling  the  external  resistance,  that  of  the  wires, 
r,  and  the  internal  resistance,  that  of  the  element,  R,  Ave  obtain  from 

V 

equation  (1)  1= (3).     Now  it  is  obvious  that  if  any  number  of 

similar  elements  are  joined  together,  say  three,  as  in  Fig.  200,  there  is  n 

Fig.  290. 


Galvanic  elements. 


times  the  electromotive  force,  but,  at  the  same  time,  n  times  the  internal 

resistance,  and  equation  (1)  becomes  7= — — -  -    (4).    If,  however,  the 

nKXr 

conducting  wires  be  of  copper,  and  short  and  thick,  then  the  external 

resistance  r,  in  comparison  with   R,  may   be  neglected,  and  equation 

(4)  becomes  J=  — =—  (5) — that  is  to  say,  when  the  internal   resist- 

nR  R 
ance  is  great  and  the  external  is  small,  a  battery  consisting  of  several 
elements — three,  in  this  instance — produces  no  greater  effect  than  one 
element.  Suppose,  on  the  other  hand,  that  the  conducting  wires  be 
very  long  and  thin,  or  the  conductor  be  a  bad  one,  as  a  liquid,  the 
external  resistance  r  offered  is,  under  these  circumstances,  very  great ; 
but  if  now,  at  the  same  time,  the  internal  resistance  R  is  small,  as  in 
the  thermo-electric  pile,  for  example,  the  latter,  or  R,  can  be  neglected 

YbJij 

in  comparison  with  r,  and   equation  (1)  becomes  J——  -  (6),    but  as 

J—  _,  we  will  obtain  from  (6)  I  =  nl  (7)— that  is  to  say,  when  the 

R 
external  resistance  is  large,  and  internal  resistance  small,  the  intensity 
within  certain  limits  is  very  nearly  proportional  to  the  number  of 
elements — that  is,  a  battery  consisting  of  three  elements  produces 
nearly  three  times  the  effect  of  one  element.  Instead  of  increasing 
the  number  of  elements,  let  us  now  enlarge  the  plates,  say  n,  or  three 
times  of  a  single  element  (Fig.  291),  and  see  what  effect  will  be 
obtained  according  to  Ohm's  law.  The  electromotive  force  under 
these  circumstances  will,  of  course,  remain  unchanged — that  is,  not  in- 
creased, since  it  depends  upon  the  nature  of  the  plates  and  the  liquid, 
and  not  upon  the  size  of  the  element,  just  as  the  head  or  force  of  the 


INFUENCE    OF     RESISTANCE. 


553 


Fro.  "291. 


water  comparable  to  the  electromotive  force  is  not  increased  as  long  as 
the  level  remains  unchanged,  however  much  the  amount  of  water  may 
be  increased,  for  though  there  are  n  times  as  many 
regions,  in  this  case — three,  where  the  electromotive 
force  acts  side  by  side — they  do  not  assist  one  another 
any  more  than  the  neighboring  vertical  columns  of 
water  in  a  reservoir  affect  the  pressure  on  the  exit 
pipe.  Nevertheless,  just  as  in  the  previous  instance, 
in  which  the  battery  was  supposed  to  consist  of 
three  elements,  there  will  be  a  difference  in  the 
effect  produced  according  to  whether  the  external 
or  internal  resistance  is  neglected,  since  although 
the  electromotive  force  does  remain  unchanged, 
the  increase  in  the  size  of  the  plates  must  be  fol- 
lowed by  a  proportional  diminution  in  their  resist- 
ance which  permits  a  proportional  quantity  of  elec- 
tricity to  pass  through  them.  Let  us  first  suppose  that  the  external 
resistance,  or  r,  be  so  much  smaller  than  the  internal  or  i?,  that  it 
can  be  neglected,  and  that  the  plates  have  been  enlarged  three  n  times, 
then  we  have  obtained  from  equation  (1) — 


Galvanic  element. 


/ 


E 

E 

nE 
~  R  +  nr  ~ 

nE 

n 

~~  R  +  nR- 
n 

'    R 

nl    (8) 


that  is  to  say,  by  enlarging  the  plates  of  the  element  n,  or  three  times, 
(Fig.  291)  when  the  external  resistance  is  small,  the  intensity  is  in- 
creased correspondingly.  On  the  other  hand,  suppose  the  internal 
resistance,  or  R,  is  so  small  that   it  can  be   neglected,  then  equation 

— —  -  of  the  above  series  becomes  — -  —  — ,  and  since,  as  before, 
JxXnr  nr         it 

E 
J  —  -j),  we  finally  obtain  from  equation  (1)  7= I (9) — that  is  to  say. 
Jx 

by  enlarging  the  plates  of  the  element  n,  or  three  times,  when  the  in- 
ternal resistance  is  small  the  intensity  is  scarcely  increased.  Resum- 
ing what  has  just  been  said,  we  learn  by  Ohm's  law  that  if  the 
internal  resistance  be  small,  it  is  of  advantage  to  increase  the  number 
of  cells ;  on  the  other  hand,  if  the  internal  resistance  be  large,  while 
it  is  of  no  advantage  to  increase  the  number  of  cells,  it  is  of  advantage 
to  enlarge  the  cell,  nothing,  however,  being  gained  by  enlarging  the 
cell  if  the  internal  resistance  be  small.  It  need  hardly  be  added  that 
while  the  intensity  or  quantity  of  electricity  flowing  through  the  circuit 
in  a  given  time  remains  the  same,  the  density  of  the  current  may, 
however,  vary,  the  latter  being  inversely  as  the  cross  section  of 
the  conductor — that  is,  the  less  the  cross  section,  the  greater  the  in- 
tensity. 

As  in  the  stimulation  of  the  nerves  by  electricity  derived  from  the  bat- 
teries just  described,  we  ordinarily  make  use  of  the  induction  apparatus 
of  Du  Bois-Reymond1  (made  for  the  author  by  Elliott,  of  London),  a 


1  Untersuchungen  ttber  thierische  Electricitat,  Zweiter  Bend,  s.  393.     Berlin,  1849. 


554: 


INDUCTION    APPARATUS. 


brief  description  of  that  most  useful  instrument  in  this  connection 
appears  appropriate.  As  its  name  implies,  it  is  an  apparatus  (Fig. 
292)  by  means  of  which  an  induced  current  can  he  applied  to  a  nerve, 


Fig.  292. 


Du  BoiB-Beymond's  induction  apparatus.     (Landois.) 

and  in  order  that  the  strength  of  the  current  may  be  varied  at  pleasure, 
the  secondary  coil  8,  to  which  the  electrodes  LL  are  attached,  is  placed 
upon  a  graduated  slide  (Q),  so  that  it  can  he  made  to  approach  or 
recede  from   the   primary   coil    P,   as   near   or   far   as    desired.       The 

Fig.  293. 


Schema  of  Du  Bois-Reymond's  induction  apparatus.     (Landois.) 

current  from  the  battery  (B,  Figs.  293  and  294),  a  Daniell  or  Bunsen, 
entering  the  apparatus  at  the  binding  screw  a,  passes  up  the  pillar  b 
and  through  the  German  silver  spring  d,  then  through  the  primary  coil 
P,  and  the  coil  F,  returning  to  the  battery  by  the  binding  screw 
h.  As  the  current  enters  the  primary  coil  P,  an  induced  closing 
or  making  current  is  for  the  moment  developed  in  the  secondary  coil 
8,  and  in  an  opposite  direction  to  the  primary  current.  During  the 
passage  of  the  current,  however,  through  the  coil  F,  the  iron  core 
within  the  latter  becoming  magnetized,  the  spring  d  is  pulled  down 
from  the  screw  /,  the  result  of  which  is  that  the  current  is  short-cir- 
cuited, and  returns  directly  back  to  the  battery  through  the  pillar  m 
and  binding  screw  h  without,  therefore,  passing  through  the  primary 
coil,  the  result  of  such  short-circuiting  being  that  at  the  moment  of 
the  diverting  of  the  current  from  the  primary  coil  P  there  is  devel- 


INDUCTION    APPARATUS. 


555 


oped  for  a  moment  in  the  secondary  coil  8  an  induced  breaking  or 
opening  current  in  the  same  direction  as  that  of  the  primary  current. 
As  the  iron  cores  within  -the  coil  F  under  these  circumstances  become 
demagnetized  through  the  absence   of  the  current,  the   spring  d  flies 


Fig.  294. 


Fig.  295. 


HeImholtz"s  modification  of  NeeFs  ham- 
mer. As  long  as  /  is  not  in  contact  with  d, 
g  h  remains  magnetic  ;  thus  /  is  attracted  to 
d,  and  a  secondary  circuit,  «,  b,  d,  m,  is 
formed;  Cthen  springs  back  again,  and  thus 
the  process  goes  on.  A  new  wire  is  intro- 
duced to  connect  <<  with  /.  B.  Battery. 
(Landois.) 


Du  Bois-Keymond's  key.     (SANDERSON,  i 


up  again ;  contact  being  again  made  with  the  screw  /,  the  current 
passes  as  before  through  the  primary  coil,  to  be  again  broken  with  the 
magnetization  of  the  core  within  the  coil  F,  and  to  be  again  made 
with  the  demagnetization  of  the  same,  and  so  on  indefinitely.  The 
effect  produced  by  the  iron  core  within  the  primary  spiral  is  the  same 
as  that  of  the  primary  spiral  itself,  since  in  being  magnetized  and 
demagnetized  through  induction  by  the  making  and  breaking  of  the 
primary  circuit,  the  core  induces  closing  and  opening  currents  in  the 
secondary  spiral  similar  to  those  due  to  the  making  and  breaking  of 
the  current  in  the  primary  one.  By  applying  the  electrodes  LL 
attached  to  the  secondary  coil,  the  nerve  can  therefore  be  stimulated 
by  the  making  and  breaking  induced  currents,  which  so  rapidly 
succeed  each  other  that  the  muscle  is  soon  brought  into  a  tetanic  condi- 
tion. If,  however,  it  is  desired  to  stimulate  the  nerve  by  a  single  induc- 
tion shock — that  is,  by  one  closing  and  one  opening  induced  current, 
then  the  wire  of  the  battery  must  be  attached  to  the  binding  screw  S' 
instead  of  a,  a  Du  Bois-Reymond  key  (Fig.  295)  having  also  been 
inserted  within  the  circuit  of  the  primary  coil,  between  B  and  A. 
The  key  being  down,  the  current  will  then  be  short-circuited — that  is, 
will  pass  directly  back  to  the  battery  B,  since  the  resistance  offered  by 
the  key  is  less  than  that  offered  by  the  nerve. 


556 


DU    BOIS-REYMOND   S    KEY. 


With  the  elevation  of  the  key,  however,  the  current  will  pass  through 
the  primary  coil  P,  developing  the  closing,  or  making  induced  current 
in  the  secondary  coil  S  as  before;  but,  as-  the  current  through  the 
primary  coil  is  not  broken  through  the  fall  of  the  spring,  the  wire 
being  attached  in  this  experiment  to  S',  there  will  be  no  opening  or 
breaking  current  induced  in  the  secondary  coil.  The  latter  is,  however, 
at  once  developed  in  the  secondary  coil  (Fig-  296)  by  simply  depressing 
the  key,  the  current  being  then  short-circuited  again,  it  returns  back 
to  the  battery  without  passing  through  the  primary  coil.  It  will  be 
observed  that  when  the  induction  apparatus  is  so  arranged  and  used, 
that  the  nerve  is  stimulated  once  by  the  current  induced  by  the 
closing  of  the  primary  circuit,  and  once  by  the  opening  of  the  same. 
Suppose,  however,  it  be  desired  to  stimulate  the  nerve  by  only  the 
closing  or  the  opening  current  ?  To  accomplish  this,  a  second  Du  Bois- 
Reymond  key  (a)  must  be  also  inserted  within  the  circuit  of  the 
secondary  coil  S,  and  the  two  keys  worked  in  the  following  manner : 
We  will  suppose,  at  the  beginning   of  the  experiment,  that  the  key  b7 

Fig.  296. 


within  the  circuit  of  the  primary  coil  P,  is  down,  and  the  key  a,  within 
that  of  the  secondary  coil  S,  is  up,  then  the  elevation  of  the  key  b, 
and  the  passage  of  the  current  from  the  battery  through  the  primary 
coil,  there  will  be  developed  for  an  instant  in  the  secondary  coil  an 
induced  current,  and  the  nerve  will  be  stimulated  by  a  closing  or 
making  single  induction  shock.  The  key  a  should  now  be  depressed 
so  that  the  nerve  will  not  be  stimulated  by  the  opening  or  breaking  of 
the  current  in  the  primary  coil,  due  to  the  depressing  of  the  key  b,  and 
the  consequent  short-circuiting  of  the  current.  The  nerve  has  then 
been  stimulated  by  the  closing  of  the  current  only.  Supposing  the  two 
keys  to  be  both  down,  let  us  now  elevate  the  key  b ;  the  secondary 
current  developed  in  consequence  will  not  influence  the  nerve  as  in  the 
preceding  experiment,  since  the  key  a  being  down,  the  secondary  cur- 
rent is  short-circuited.  If,  however,  now  the  key  a  be  elevated,  and 
the  key  b  depressed,  the  secondary  current  developed  through  the 
breaking  of  the  primary  current  will  be  transmitted  to  the  nerve,  and 
the  latter  will  be  stimulated  by  the  opening  or  breaking  current  only. 
Whether  it  be  desired  to  stimulate  the  nerve  by  a  single  induction 
shock,  or  many  successive  ones,  or  by  the  secondary  current  induced 
through  the  making  or  breaking  of  the  primary  one,  it  is  of  advantage 


UNIPOLAR    INDUCTION. 


557 


always  to  use  the  key  (a,  Fig.  296)  just  described,  not  only  on  account 
of  convenience,  but  to  avoid  muscular  contraction  due  to  unipolar  in- 
duction, so-called,  on  account  of  the  current  being  transmitted  to  the 
nerve  by  one  electrode  only,  as  is  the  case  when  the  key  is  used,  as  in 
Fig.  297,  and  the  key   is  open.     While  no  secondary  current  is  then 


Fig.  297. 


Du  Bois-Reymond's  key. 

induced  in  S  by  that  in  the  primary,  the  second  circuit  (S)  being 
broken,  free  static  electricity,  however,  is  given  off  at  the  end  of  the 
single  electrode  (L),  and  transmitted  through  the  nerve  to  the  muscle, 
the  electricity  previously  accumulated  at  the  end  of  the  electrode  being- 
due  to  the  decomposition  of  the  neutral  electricity  in  the  secondary 
coil,  induced  by  that  in  the  primary,  as  takes  place  in  the  prime  con- 
ductor in  working  the  ordinary  electrical  machine.  If,  however,  the 
secondary  coil  be  short-circuited  by  a  Du  Bois-Reymond  key,  as  in  Fig. 
295,  the  key  being  down,  then  the  secondary  circuit  being  perfectly 
closed,  a  secondary  current  will  be  developed,  and  unipolar  induction 
prevented,  the  current  passing  directly  back  through  the  coil,  and  none 
passing  into  the  nerve,  which,  as  we  have  just  seen,  is  not  the  case,  the 
key  being  used,  as  in  Fig.  297,  and  open.  When,  however,  the  short- 
circuiting  key  is  opened,  and  the  secondary  circuit  is  completed  by  the 
nerve  intervening  between  the  electrodes,  the  circuit  being  but  imper- 
fectly closed,  unipolar  induction  may  occur  even  then,  as  when  the  key 
is  used  as  in  Fig.  297.  If,  however,  there  be  any  doubt  as  to  whether 
the  muscular  contraction  be  due  to  the  stimulus  exerted  by  the  nerve 
excited  by  the  secondary  current,  or  to  the  unipolar  induction  shock — 
that  is,  the  direct  transmission  of   the  static   electricity  through   the 


558 


EXTRA    CURRENTS    FKOil     INDUCTION 


nerve  to  the  muscle — it  can  be  at  once  decided  by  simply  dividing  the 
nerve  between  the  lower  electrode  and  the  muscle,  since,  if  contraction 
then  ensues,  the  ends  of  the  nerves  being  approximated,  it  must  be  due 
to  unipolar  induction,  and  not  to  the  nerve,  as  the  division  of  the  nerve 
does  not  interfere  with  the  transmission  of  the  electricity,  but  makes 
impossible  that  of  the  nerve  force.  It  may  be  mentioned,  in  this  con- 
nection, that  the  surest  way  to  avoid  unipolar  induction  is  to  put  the 
upper  electrode  in  communication  with  the  earth  through  the  gas  or 
water  pipe  of  the  laboratory  by  a  good  conductor,  and  in  so  leading  the 
free  electricity  off,  prevent  it  influencing  the  muscle,  and  so  effecting 
the  contraction  due  to  nerve  excitement,  as  brought  into  activity  by  the 
secondary  current  alone.  It  will  be  seen,  presently,  that  if  a  nerve  be 
stimulated  first  by  a  closing  and  then  by  an  induced  current,  that  the 
physiological  effect  due  to  the  latter,  as  shown  by  the  extent  of  the 
muscular  contraction,  is  greater  than  that  due  to  the  former.  Now,  it 
is  desirable,  under  certain  circumstances,  that  the  two  currents  should 
be  equalized  as  far  as  possible.  To  appreciate  the  manner  in  which  this 
is  accomplished,  it  will  be  first  necessary,  however,  to  explain  briefly 
why  the  induced  opening  current  is  more  powerful  than  the  closing  one. 
Inasmuch,  as  with  the  closing  of  the  current  in  the  primary  coil,  there 
is  developed,  momentarily,  a  current  in  the  secondary  one,  opposite  in 
direction  to  that  of  the  primary,  it  might  be  suspected  that,  in  a  similar 
manner,  the  individual  coils  of  the  primary  current  would  act  inductively 
on  each  other.  Such  is  found  to  be  experimentally  the  case,  the  current 
so  produced,  and  opposite  in  direction  to  that  of  the  inducing  current, 
being  known  as  the  inverse  extra  current.  The  latter,  being  opposite 
in  direction  to  that  of  the  inducing  current,  must  weaken  it,  and  it  is 
on  account  of  this  retarding  influence  of  the  inverse  extra  current  that 
the  closing  primary  current  only  gradually  attains  its  maximum  in- 
tensity, as  may  be  represented  graphically  (Fig.  298)1  by  the  curve 
line   Gr  U,    in    which    the   horizontal  line   T  represents    the    duration 


Fig   298. 


of  the  current.     The  corresponding    closing   current,   induced   in  the 
secondary  coil,  may  in  the  same  manner  be  represented  by  the  curve 

1  Du  Bois-Reymond  :  Ge*ammelte  Abhandlungen,  Erster  Band,  S.  J36.     Leipzig,  1875. 


HELMOLTZ'S    INDUCTION    APPARATUS  559 

I)  G-,  only  the  ordinate  o  s  must  be  drawn  below  the  line  D  -/, 
since  the  current  is  in  the  opposite  direction  to  that  inducing  it.  In 
a  similar  manner,  at  the  moment  of  the  opening  of  the  primary  current, 
there  is  developed  within  the  primary  coil  a  direct  extra  current,  so 
called  on  account  of  it  being  in  the  same  direction  as  the  current  in- 
ducing it,  and  therefore  intensifying  it.  But,  as  there  is  no  arrange- 
ment in  the  ordinary  inducting  apparatus  by  which  the  primary  current 
is  maintained,  the  direct  extra  current  is  suppressed  at  the  opening  of 
the  primary  current,  the  latter  is  therefore  suddenly  interrupted  when 
at  its  full  strength,  and  may  be  represented  graphically  by  the  perpen- 
dicular line  E  _T,  and  the  opening  current  in  the  secondary  coil  by  the 
perpendicular  J  L,  it  being  in  the  same  direction  as  that  in  the 
primary,  and  which,  having  attained  its  maximum,  suddenly  falls  off 
more  gradually,  as  shown  by  the  curve  line -TjfiT.  From  the  sudden 
manner  in  which  the  opening  current  developed  in  the  secondary  coil 
attains  its  maximum  intensity  J  L,  as  compared  with  the  gradual 
increase  of  the  closing  one  D  Gr,  it  becomes  evident  why  the 'effect  of 
the  stimulation  by  the  former  current  is  greater  than  that  by  the  latter. 
Such  being  the  case,  the  induction  apparatus  being  used  as  just 
described,  let  us  modify  the  instrument  a  little,  as  done  by  Helmholtz,1 
by  connecting  the  binding  screw  a  (Fig.  294),  by  means  of  a  wire  (tc). 
with  the  binding  screw  S',  and  lowering  the  silver  spring  (d)  away  from 
the  point  of  the  binding  screw,  the  current  will  then  pass  by  the  con- 
necting wire  directly  into  the  primary  coil  P  without  passing  first 
along  the  spring,  and  from  the  primary  coil  back  to  the  battery  by  the 
coils  g  h  ;  but  with  the  magnetization  of  the  core  within  the  latter  the 
spring  will  be  lowered,  and  the  greater  part  of  the  current  being  short- 
circuited  will  then  pass  directly  back  to  the  battery  by  the  spring  d  and 
pillar  m,  the  primary  current  being  then  weakened,  as  represented 
graphically  to  the  extent  of  the  lines  A  B,  the  magnetization  of  the 
core  within  the  coils  g  h  (Fig.  294)  will  not  be  sufficient  to  keep  the 
spring  down,  the  short  current  will  be  reopened,  and  all  the  current 
will  pass  through  the  primary  coil  again.  The  Helmholtz  modification 
being  used,  as  just  described,  it  will  be  observed  that,  as  the  current  in 
the  primary  coil  is  never  entirely  interrupted,  the  direct  extra  current 
developed  at  the  moment  of  the  opening  of  the  primary  current  wTithin 
the  latter  will  reinforce  the  primary  current,  the  two  currents  having 
the  same  direction.  The  partial  interruption  of  the  primary  current, 
and  the  development  of  the  opening  secondary  current  will,  therefore, 
be  both  gradual,  as  shown  by  the  curves  EM  and  J L,  respectively, 
which  is  not  the  case,  as  we  have  seen,  when  the  ordinary  inducting 
apparatus  is  used,  since  the  primary  current,  being  entirely  interrupted, 
the  direct  extra  current  cannot  make  this  reinforcing  effect  felt,  the 
opening  secondary  current  ./  L,  with  Helmholtz's  modification, 
attaining  then  its  maximum  intensity,  gradually,  like  that  of  the 
closing  secondary  one  D  H  G-.  D  R  Gr,  being  diminished  propor- 
tionately with  A  Cr,  differs  but  little  in  its  physiological  effect  from 
the  latter  when  used  as  a  stimulus.     Finally,  it  will  be  observed  that 

1  Uii  Bois-Beymond,  op.  cit.,  s.  231. 


560 


ELECTRIC    STIMULATION    OF    NERVES, 


the  primary  current  never  being  entirely  interrupted,  Ilelinholtz's 
modification  being  used,  the  closing  (D  H  G)  and  the  opening  (./  L) 
currents  are  produced  through  the  alternate  strengthening  and  weak- 
ening of  the  primary  current,  represented  by  C  B  to  A  and  back  to  B, 
due  to  the  opening  and  closing  of  the  short  circuit. 

That  part  of  the  sciatic  nerve  supplying  the  gastrocnemius  muscle  in 
the  frog  being  the  one  that  we  shall  make  use  of  in  our  experiments,  on 
account  of  its  length  and  the  readiness  with  which  it  is  exposed,  it  may 
be  mentioned  that  in  preparing  the  nerve  it  should  be  touched  as  little 
as  possible,  and  never  seized  with  a  pair  of  forceps,  though  it  must  be 
completely  separated  from  the  adjacent  nerves.  The  gastrocnemius 
muscle,  the  contraction  of  which  we  take  as  a  measure  of  the  stimulation 
of  the  nerve,  having  been  cut  through  at  its  insertion,  the  tendo  Achillis 
must  be  completely  freed  up  to  its  origin  at  the  end  of  the  femur  ;  of  the 
latter  enough  should  be  left  so  that  it  can  be  firmly  clamped  to  the  bar 
A  (Fig.  299),  of  the  upright  B,  the  tibia  and  fibula  being,  however,  entirely 

Fie.  299. 


The  moist  chamber,  with  the   nerve-muscle  preparation,   non-polarizable   electrodes,  electrobearer,  and 
lever  in  position  ready  for  an  observation.     The  glass  cover  is  not  shown.     (Foster.) 


removed.  If  the  nerve  and  muscle  preparations  so  prepared  and 
clamped  be  covered  with  a  glass  bell  fitting  into  the  rim  of  the  disk  D, 
of  ebony  or  other  hard  wood  through  which  the  upright  B  passes  and 
supports  a  few  pieces  of  wet  blotting  paper,  having  been  also  previously 
placed  upon  the  disk,  the  nerve  and  muscle  will  be  prevented  from  get- 
ting dry.  The  disk  is  also  provided  with  binding  screws  (S)  for  receiving 
the  wires  from  the  secondary  coil  of  the  induction  apparatus,  and  from 
the  electrodes  E  supporting  the  nerve  N.  The  electrodes  should  be 
non-polarizable — that  is,  electrodes  which,  while  transmitting  the  current 
from  the  secondary  coil  of  the  induction  apparatus,  will  not  generate  a 
current  by  contact  with  the  nerve.     Of  the   different  forms  of  non- 


TRACES    OF    MUSCULAR    CONTRACTION. 


561 


polarizable  electrodes  a  convenient  one  is  that  consisting  of  a  glass  tube 
(Fig.  299,  E),  bent  and  plugged  up  at  one  end  by  a  putty  made  of  china 
clay  and  0.75  per  cent,  solution  of  sodium  chloride,  and  containing  a 
saturated  solution  of  zinc  sulphate,  into  which  is  immersed  to  a  depth 
of  about  3  mm.  a  slip  of  thoroughly  amalgamated  zinc.  The  wire  W 
leading  to  the  binding  screw  is  attached  to  the  latter,  and  is  usually 
sufficiently  strong  to  hold  up  the  electrodes  ;  if  not,  the  latter  can  be 
movably  clamped  to  the  upright,  or  supported  as  in  Fig.  299,  by  an 
electrode  bearer.  The  glass  tube  is  often  closed  at  its  extreme  point, 
the  plug  of  clay  being  exposed  only  where  the  small  orifice  has  been 
drilled.  Through  an  opening  in  the  disk  of  the  moist  chamber  the 
muscle  can  be  attached  to  a  lever  (Fig.  299,  L),  and  its  contractions 
made  very  evident  by  the  elevation  of  the  latter.  If  the  point  of  the 
lever  be  terminated  by  a  brush  or  pen,  by  means  of  the  blackened  cylin- 
der already  described,  a  graphic  representation  of  the  muscular  contrac- 
tion can  be  obtained  and  preserved  for  future  reference.  The  lever 
consists  of  a  thin  slip  of  wood,  the  portion  near  the  fulcrum  being  of 
metal  and  perforated  or  notched  to  receive  the  hook  attached  to  the 
tendon  of  the  muscle,  and  has  usually  suspended  from  it  a  scale  pan 
containing  counterpoising  weights  varying  from  between  10  to  200 
grammes.  The  moist  chamber  being  so  attached  to  the  recording 
apparatus  by  means  of  its  upright  that  the  point  of  the  lever  is  brought 
in  contact  with  the  blackened  surface  of  the  cylinder,  the  latter  is  made 
to  rotate  for  a  moment  so  as  to  obtain  first  a  base  line.  The  nerve  being 
now  stimulated  first  by  a  closing  and  then  by  an  opening  shock  ;  with- 
out Helmholtz's  modification  being  used  it  will  be  observed  from  the 
traces  obtained  (Fig.  300),  that  the  lever  is  elevated  higher  in  the  latter 


Fig.  300. 


O 


case  O,  than  in  the  former  (7,  the  effect  of  the  opening  shock  being 
greater  than  that  of  the  closing  for  the  reasons  already  given.  The 
cylinder  being  now  made  to  rotate  rapidly,  and  the  nerve  stimulated  as 
before,  the  traces  obtained  (Figs.  301  and  302),  instead  of  being  vertical 
lines  will  be  curved  ones.  If  now  the  nerve  be  stimulated  by  a  series  of 
closin"1  and  opening  shocks  the  magnetic  interrupter  being  used,  the 
muscle  will  be  brought   into  a  tetanic  condition,  and   the  lever  will  be 

36 


562 


OHM    S    LAW,    ETC, 
Fig.  301. 


Opening  shock. 


Fig.  302. 


Fig.  303. 


Closing  shock. 


Curve  of  tetanus. 


observed  to  remain  elevated  (Fig.  303),  the  interval  between  each 
shock  being  of  short  duration,  that  the  lever  descends  but  a  little  dis- 
tance when  it  is  elevated  again.  The  elevations  and  depressions  of  the 
lever  due  to  the  individual  contractions  of  the  muscle  when  so  rapidly  pro- 
duced, are,  however,  soon  lost  to  view,  becoming  so  fused  together  that  they 
are  not,  therefore,  apparent  in  the  trace  of  the  muscle  curve  of  tetanus. 
The  slight  fall  and  rise  of  the  lever  become,  however,  quite  evident  if 
the  primary  current  be  interrupted,  not  by  the  magnetic  arrangement, 
but  by  a  reed  like  that  already  described,  vibrating  at  the  rate  of 
sixteen  times  a  second,  placed  between  the  primary  coil  and  a  key, 
as  shown  by  the  trace  (Fig-   304),  obtained  in  this  manner.     If,  in 

stimulating  a  nerve  by  the  induction 
apparatus,  for  example,  the  electrodes 
be  applied  to  the  nerve  as  near  as  pos- 
sible to  the  muscle,  a  chronographic  ap- 
paratus being  at  the  same  time  used, 
and  a  marking  lever  such  as  represented 
in  Fig.  305,  be  substituted  in  the  pri- 
mary circuit  for  the  key  b,  the  mo- 
ment at  which  the  nerve  is  stimulated 
will  be  recorded  upon  the  cylinder  by 
„    .  „ .  the  depression  of  the  point  of  the  lever 

Muscle  curve.     Primary  current  inter-  1  .  tr  _  _ 

rupted  sixteen  times  a  second.  (1 ),  the  velocity  ot  the  electricity  being 


Fig.  304. 


MARKING    LEVER. 


563 


so  great  that  the  nerve  may  be  regarded  as  being  stimulated  at  the 
same  instant  that  the  point  of  the  lever  is  depressed,  due  to  the  eleva- 
tion of  the   handle  H,  the  current  previously  short-circuited  through 


Fig.  305. 


The  marking  lever.     (Sanderson,) 

C  a  b  e,  the  lever  being  down  being  then  thrown  into  the  primary  coil 
and  inducing  a  current  in  the  secondary  coil.  The  marking  lever  A, 
being  placed  in  contact  with  the  cylinder  above  the  pen  of  the  chrono- 
graph b,  and  below  that  of  the  muscle  lever  c  (Fig.  306),  it  will  be 

Fig.  306. 


'//oo  efi  of  «  sec. 


Diagram  of  a  muscle  curve  as  drawn  on  a  travelling  surface,  c.  The  line  described  by  the  point  of  the 
lever  connected  with  the  muscle.  «.  The  line  described  by  marking  lever,  b.  The  line  described  by  the 
tuning-fork.  The  vertical  line  in  marks  the  moment  of  stimulation.  m>,  the  beginning ;  m2  the 
maximum  ;  and  m3,  the  end  of  the  contraction  of  the  muscle.     (Foster.) 

observed  that  usually  the  yo¥^  °f  a  second  elapses,  as  determined  by 
the  chronograph,  between  the  stimulation  of  the  nerve  and  the  contrac- 
tion of  the  muscle,  the  latent  period  so-called  on  account  of  the  irritation 
being  latent,  not  as  yet  actively  efficient  in  the  muscle.  If  the  electrical 
currents,  however,  be  thrown  not  into  that  part  of  the  nerve  (Fig.  307, 
b)  in  immediate  contact  with  the  muscle  M,  as  in  the  preceding  experi- 
ment, but  at  some  distance  from  the  latter,  say  an  inch,  as  at  A,  for 


564 


OHM'S    LAW,    ETC. 


example,  and  which  can  be  readily  done  by  means  of  the  whippe  (Fig. 
307,  W),  by  simply  connecting  the  ends  of  the  curved  wires  c  D,  with  the 
mercury   cups  at  5  and  6,  instead  of  with  the  cups  at  3  and  4,  the  cur- 


Whippe. 

rent  being  then  diverted  without  involving  any  other  change  in  the  dis- 
position of  the  apparatus.  .  It  will  be  observed,  as  in  Fig.  309,  that  not 
only  the  yw^1  °^  a  second  (a  b)  elapses  between  the  stimulation  of  the 
nerve  and  the  contraction  of  the  muscle,  as  in  the  preceding  experi- 
ment, but  an  additional  small  period  of  time,  about  the  ytVo^  °^  a  sec" 
ond  (b  b),  intervenes,  preceding  that  of  the  latent  period,  and  evidently 
due  to  the  current  having  been  thrown  into  the  nerve  at  a  distance  of 
an  inch  from  the  muscle,  the  nerve  force  having  then  to  traverse  that 
distance  before  it  reached  the  muscle,  which  is  at  the  rate  of  91.8  feet 
(28  metres)  per  second.  The  nerve  force  is  probably,  however,  trans- 
mitted at  even  a  slower  rate  in  the  nerves  of  the  frog  than  that  just 
given,  since,  if  a  long  nerve  be  stimulated  in  three  different  places,  near 
the  muscle,  midway  and  above,  the  curves  show  that  more  than  double 
the  time  elapses  during  the  passage  of  the  nerve  force  through  the  whole 
nerve  than  from  the  middle  point  to  where  the  nerve  passes  into  muscle.1 
While  the  latent  period  and  the  velocity  with  which  nerve  force  is 
transmitted,  can  be  determined  in  the  manner  just  described,  a  more 
convenient  and  graphic  method  is  by  means  of  the  pendulum  myograph2 
of  Fick,  as  modified  by  Helmholtz,  or  the  spring  myograph  of  Du 
Bois-Reymond.3  The  pendulum  myograph,  as  its  name  implies,  and  as 
constructed  for  the  author  by  Hawksley,  of  London  (Fig.  308),  consists 
of  a  pendulum  35  in.  (90  cm.)  in  length,  suspended  by  a  knife  edge 
working  upon  a  support  firmly  fixed  by  the  frame  imbedded  in  the  brick 
walls  of  the  laboratory.  The  pendulum  carries  two  glass  (only  one 
represented  in  figure)  plates  15  in.  (39  cm.)  long,  and  6  in.  (15.5  cm.) 
wide,  the  outer  smoked  one  a  serving  as  a  recording  surface,  the  inner 


i  Munk :  Archiv  fiir  Anat.  and  Phys.,  S.  798.     Leipzig,  1864. 
-  Wurzburger  Verhand.,  Neue  Folge,  ii.  S.  147,  1872. 


*  Op.  cit.,  S.  273,  Fig.  20. 


PENDULUM     MYOGRAPH, 


565 


one  as  a  counterpoise.      The  plates,  as  the  pendulum  vibrates  push  to  one 
side  the  two  bars  dd'  (the  latter  not  represented),  thereby  ^interrupting 


Fig.  808. 


Pendulum  myograpkion.     (Foster.) 

respectively  the  primary  current  of  the  induction  apparatus  and 
also  a  current  passing  through  the  small  electro-magnet,  to  which  is 
attached  a  pen   serving  as  a  marking  lever.      The   pendulum  bavin* 


566  ohm's  law,  etc. 

readied  b'  is  held  there  by  a  catch  similar  to  that  which  held  it  at  a 
before  its  vibration  began. 

With  the  interruption  of  the  primary  current,  the  nerve  is  stimu- 
lated by  the  opening  shock  of  the  secondary  current,  transmitted  to 
the  electrodes,  the  moment  of  stimulation  being  determined  by  the 
moving  of  the  pen  acting  as  a  marking  lever,  due  to  the  simulta- 
neous interrupting  of  the  current  passing  through  the  small  electro- 
magnet. The  time  elapsing  is  determined,  as  in  the  preceding  experi- 
ment, by  the  electro-magnetic  chronograph  /.  In  using  the  pen- 
dulum myograph  the  muscle  is  attached,  as  in  the  preceding  experi- 
ment, to  a  lever  (b) ;  the  latter  is,  however,  in  this  case  much  heavier, 
and  is  provided  with  a  projecting  steel  point,  which,  in  being  pressed 
against  the  smoked  plate  makes  the  curved  line  <?,  as  the  plate  is 
carried  past  by  the  vibration  of  the  pendulum  ;  after  the  latent  period, 
however,  with  the  contraction  of  the  muscle,  the  nerve  assumes  the  form 
b.  To  demonstrate  the  rapidity  with  which  the  nerve  force  is  trans- 
mitted, we  make  use  of  the  whippe,  as  in  the  preceding  experiment, 
throwing  the  current,  by  means  of  the  latter,  into  the  nerve  at  a  defi- 
nite distance  from  the  point  first  stimulated.  The  result,  as  shown  by 
a  tracing  (Fig.  309)  taken  with  the  pendulum  myograph,  is  the  same  as 

Fig.  309. 
a   66' 


Curves  illustrating  the  measurement  of  the  velocity  of  a  nervous  impulse.     (Diagrammatic.)     To  be 
read  from  left  to  right.     (Foster.) 

when  obtainable  by  the  cylinder.  If  it  be  desired  to  take  more  than 
one  tracing,  the  plate  g  is  lowered  or  raised  by  the  screw  s,  so  as  to 
avoid  confusing  the  tracings;  the  centre  of  gravity  of  the  apparatus  is 
not,  however,  thereby  affected,  the  inner  plate  being  elevated  as  the 
outer  one  is  depressed,  and  vice  versa,  by  the  same  movement  of  the 
screw.  In  order  to  preserve  the  tracing  on  the  smoked  glass,  the  latter 
is  placed  upon  sensitive  paper,  and  exposed  to  sunlight.  The  object  of 
having  the  two  bars  d  d',  referred  to  above,  is  to  enable  us  to  throw  a 
second  single  induction  shock  into  the  nerve  a  very  short  interval  after 
the  first,  the  position  of  the  bar  d'  being  changed  with  reference  to 
the  bar  d  by  the  movement  of  a  graduated  wheel.  In  this  manner 
we  obtain  two  tracings  superimposed  upon  one  another,  the  muscle 
having  contracted  twice  (Fig.  309),  and  from  which  it  may  be  seen  that 
the  second  contraction  took  place  just  after  the  first  contraction  attained 
its  maximum,  the  dotted  line  representing  the  course  of  the  first  con- 
traction if  the  second  had  not  occurred. 

The  latent  period,  and  the  velocity  with  which  nerve  force  is  trans- 
mitted, can  also  very  conveniently  be  determined  by  the  spring  myo- 


SPRING    MYOGRAPH. 


567 


graph.     In  this  apparatus,   as   constructed  for  the  author  by   Plath, 
of  Berlin  (Fig.  310),  a  smoked  glass  plate  (p),  160   mm.  (6.4  in.)  in 


Fig.  310. 


Spring  myograph,  as  used  by  Du  Bois-Reymond. 


length,  and  50  mm.  (2  in.)  in  breadth,  serves  as  the  recording  surface, 
being  moved,  however,  in  this  instance,  by  the  extension  of  the  steel 
spring  S  surrounding  the  rod  r,  which  moves  with  but  little  friction 
through    the    firm    uprights  A  and    B.       The    spring   S   being  com- 


Fig.  311. 


Tracing  of  a  double  muscle  curve.     To  be  read  from  left  to  right.     (Foster.) 

pressed  by  pushing  it  against  the  upright  B  by  the  button  b,  the  rod 
r  is  thereby  moved  from  B  through  A  until  it  is  caught  and  held  by 
the  trigger  t  attached  to  the  latter.  With  the  raisins;  of  the  trigger 
(t)  the  spring  extends  itself,  pulling  the  rod  r  quickly  through  A  and 
B,  the  latter  carrying  with  it  the  smoked  glass  p.  As  the  latter  flies 
along  from  A  to  B,  it  knocks  away  through  its  projection  (d)  the  lever 
h,  interrupting,  therefore,  the  primary  circuit  P  of  the  induction  appa- 
ratus, and  developing  the  secondary  current  S,  by  which  the  nerve  is 
stimulated,  If  the  glass  plate  be  previously  moved  slowly  from  A  to 
B  until  the  projection  d  just  touches  the  lever  /*,  and  the  muscle  be 


568  ohm's  law,  etc. 

made  to  contract  the  vertical  trace  then  obtained  on  the  smoked  glass 
plate  will  indicate  the  moment  of  the  stimulation  of  the  nerve,  the  use 
of  a  marking  lever  being  thereby  avoided.  The  same  method  may  be 
used  in  the  case  of  the  pendulum  myograph.  It  may  be  mentioned, 
though  not  shown  in  the  figure,  that  the  chronographic  apparatus  used 
in  the  present  form  of  spring  myograph  is  a  tuning-fork  set  in  vibration 
by  a  rod,  which  is  moved  simultaneously  with  that  of  the  plate,  and, 
like  the  latter,  by  the  loosening  of  the  trigger,  the  pen  being  a  needle 
attached  to  one  prong  of  the  fork,  and  placed  in  contact  with  the 
smoked  plate,  just  below  the  needle  to  which  the  muscle  is  attached. 
The  manner  in  which  the  nerve  muscle  is  clamped  not  differing  essen- 
tially from  that  which  obtains  in  the  other  apparatus,  though  somewhat 
modified,  does  not  need  detailed  description. 

The  results  obtained  by  the  spring  myograph,  as  may  be  seen  from 
the  tracing  (Fig.  312),  are  essentially  the  same  as  in   the  preceding 

Pig.  312. 


Tracing  taken  with  a  spring  myograph. 


experiments,  o  d  in  Fig.  312  corresponding  to  a  in  Fig.  309.  The 
rate  at  which  nerve  force  is  transmitted  has  been  determined  by  Helm- 
holtz  and  Baxt,1  in  man  as  well  as  in  the  lower  animals.  In  the  case 
of  the  motor  nerves  this  was  accomplished  by  applying  electrodes  to  the 
skin  over  the  median  nerve  at  the  wrist,  elbow,  and  upper  arm,  the  arm 
being  firmly  surrounded  by  gypsum,  except  at  the  points  stimulated. 
The  time  elapsing  between  the  application  of  the  electrodes  and  the 
muscular  contraction,  the  latter  being  evinced  by  the  swelling  of  the 
muscles  of  the  ball  of  the  thumb  against  a  delicate  lever,  was  greater 
when  the  stimulus  was  applied  to  the  upper  arm  than  at  the  wrist.  The 
average  rate  of  transmission  was  determined  to  be  about  33.9  metres 
(121  feet)  per  second,  varying,  however,  according  to  the  temperature ; 
being  more  rapid  at  a  high  than  at  a  low  one.  The  rate  of  transmission 
of  the  nerve  force  in  sensory  nerves  was  also  determined  by  Helmholtz2 
in  essentially  a  similar  manner.  A  tactile  impression  being  made  suc- 
cessively upon  the  foot,  thigh,  and  loins,  the  moment  at  which  the  sen- 
sation is  felt  is  indicated  in  each  instant  by  a  movement  of  the  finger. 
Now,  since  the  time  elapsing  during  which  the  impression  becomes 
conscious  perception  in  the  brain,  as  well  as  that  during  which  the 
nerve  force  is  transmitted  by  the  motor  nerve  to  the  finger,  is  the  same 
in  all  three  cases,  the  differences  observed  in   the  successive  observa- 

i  Monatsber.  d.  Berliner  Acad.,  1867,  S   228  ;  1870,  S.  184. 
2  Physo-Ocon  Ges.  zu  Konigsberg,  1850,  I»ec.  13. 


RAPIDITY    OF    TRANSMISSION    OF    NERVE    FORCE.      569 

tions  must  be  due  to  the  different  lengths  of  the  sensory  nerves  trans- 
mitting the  impression,  the  average  rate,  according  to  Helmholtz,  being 
about  60  metres  (196  feet)  per  second,  modified  by  the  temperature,  as 
in  the  case  of  motor  nerves. 

Knowing  the  rapidity  with  which  nerve  force  is  transmitted  through 
the  peripheral  nerves,  its  rate  of  transmission  through  the  spinal  cord  in 
man  can  be  inferred  from  the  difference  in  time  elapsing  during  the 
passage  of  a  voluntary  impulse  from  the  brain  through  the  cord  to  the 
upper  and  to  the  lower  extremity,  or  in  the  reverse  direction,  of  an 
impression  made  upon  the  periphery,  giving  rise  in  the  brain  to  a  sen- 
sation. Thus,  in  the  case  of  the  motor  fibres  of  the  cord,  if  the  hand 
be  moved  first  in  obedience  to  the  will,  and  then  the  foot,  it  is  evident 
that  a  longer  period  will  elapse  between  the  application  of  the  stimulus, 
the  will,  and  the  muscular  contraction,  in  the  latter  case  than  in  the 
former,  since,  in  the  transmission  of  the  nerve  force  through  the  spinal 
cord  to  the  sciatic  nerve,  three  times  the  distance  has  been  traversed  as 
in  its  transmission  to  the  median  nerve.  In  this  way  it  has  been  shown 
by  Burckhardt'  that  the  average  rate  of  transmission  of  the  nerve  force 
through  the  motor  fibres  of  the  cord,  is  about  10  metres  (33  feet)  per 
second,  or  about  one-third  of  that  of  the  motor  fibres  of  the  peripheral 
nerves.  On  the  supposition  that  0.08  of  a  second  elapses  during  the 
passage  of  the  nerve  force  from  the  brain  to  the  foot,  one-half  of  that 
time  is  consumed  in  its  transmission  through  the  cord,  and  one-half 
through  the  nerves.  The  rate  of  transmission  through  the  sensory 
fibres  of  the  cord  does  not  differ  very  much,  however,  from  that  of  the 
sensory  fibres  of  the  peripheral  nerves.  Supposing  that  the  distance 
traversed  through  the  sciatic  nerve  and  cord  from  the  periphery  to  the 
sensorium  by  a  sensory  impulse  be  the  same  as  that  of  the  motor  impulse 
just  referred  to,  the  time  elapsing  between  the  application  of  the  stimulus 
and  the  resulting  sensation  would  be  about  0.025  of  a  second. 

As  an  illustration  of  the  relative  slowness  with  which  nerve  force  is 
transmitted,  it  may  be  mentioned  that  a  whale  one  hundred  feet  long 
would  not  feel  the  wound  of  a  harpoon  until  half  a  second  after  the 
weapon  was  thrust  into  its  tail,  and  that  in  response  to  a  voluntary 
impulse,  about  two  seconds  would  elapse  before  the  tail  would  be  moved, 
supposing  that  the  nerve  force  is  transmitted  in  the  huge  cetacean  at 
the  same  rate  as  in  man.  It  should  be  mentioned,  however,  in  this 
connection  according  to  Burchhardt,  that  tactile  impressions  appear  to 
be  transmitted  much  more  rapidly  through  the  spinal  cord  than  painful 
ones,  the  former  at  the  rate  of  42  metres  (137  feet),  the  latter  13  metres 
(42  feet)  per  second.  The  latent  period  and  the  velocity  with  which 
the  nerve  force  is  transmitted  through  the  spinal  cord  being  known,  it 
becomes  possible  to  determine  approximately  at  least  the  time  required 
for  the  apprehension  or  perception  by  the  brain  of  an  impression  and 
volition.  Thus,  supposing  the  interval  elapsing  between  the  production 
of  a  sound  and  the  hearing  of  the  same  be  determined  to  amount  to 
about  0.198  of  a  second.  An  apparatus  being  used,  as  represented  in 
Fig.   3132    in   which  the   clockwork   of  the  Hipp's   chronoscope  (H), 

1  Die  Physiologische  Diagnostik,  S.  32.     Leipzig,  1S75. 

2  Wuudt  :  Physiologische  Psychologie   Zweiter  Band,  S.  231.     Leipzig,  1880. 


570 


ohm's  law,  etc, 


held  by  an  electro-magnetic  anchor,  is  set  going  through  the  weakcning  of 
the  current  Kl  m  n  2  IIS  Z4by  the  short-circuiting  current  iT/?  a  6  JZ4, 
due  to  the  tilting  up  of  the  board  through  the  electrodes,  by  the  falling 
of  the    ball,    the  cause  of  the  sound,  and  which  is   stopped  by  the 


Fia.  313. 


Apparatus  for  determining  the  interval  elapsing  between  the  production  and  hearing  of  a  sound. 


voluntary  elevation  of  the  lever  h  at  the  instant  that  the  sound  is 
heard.  It  follows  that  if  we  deduct  from  the  whole  interval  0.198 
second  elapsing  between  the  production  and  hearing  of  the  sound,  the 
time  required  in  the  mechanism  of  the  hearing  and  during  which  the 
nerve  force  is  transmitted  through  the  cord,  the  motor  nerves  and  the 
latent  period,  the  remainder,  or  0.112  second,  will  be  the  time  required 
by  the  brain  for  perception  and  volition  as  follows  : 

Mechanism  of  hearing 0.010  sec. 

Perception  and  volition 0.112" 

Transmission  through  spinal  cord         ....  0.022     " 

motor  nerve       ....  0.044     " 

Latent  period 0.010     " 

0.198     " 

The  determination  of  the  interval  between  the  production  of  a  light 
and  the  seeing  of  the  same  can  be  determined  in  a  similar  manner  by 
suitable  apparatus.1  Such  determinations,  apart  from  their  physiological 
interest,  are  also  of  practical  importance  to  astronomers,  it  being  well 
known  to  the  latter  that  considerable  difference  exists,  amounting  in 
some  instances  to  as  much  as  one  second,  between  observations  made 
upon  the  transit  of  a  star  for  example,  the  object  being  seen  by  one 
observer  sooner  than  the  other.  Indeed,  it  was  such  discrepancies  that 
lead  Hirsch2  to  determine,  as  far  as  possible,  the  rapidity  with  which 

1  Wundt,  op.  cit.,  S.  233.  2  Bull,  de  la  Soc.  des  Sciences  nat.  de  Neufchatel,  1862. 


MUSCULAR  AND  NERVOUS  FORCE.  571 

impressions  are  transmitted  through  the  optic  and  acoustic  nerves  and 
perceived  by  the  brain,  and  of  so  ascertaining  the  personal  error  due  to 
individual  peculiarities,  and  by  means  of  which  the  observation  could 
be  corrected  by  the  personal  equation,  as  it  is  called. 

The  determination  of  the  rapidity  with  which  nerve  force  is  trans- 
mitted is  a  striking  illustration  of  the  advances  made  in  physiology,  due 
to  the  introduction  in  its  study  of  physical  methods.  In  the  year  1844 
Johannes  Muller  expressed  the  view  that  "we  shall  never  have  the 
means  to  determine  the  rapidity  of  nerve  action,  as  the  comparison  of 
immense  distances  is  wanting,  by  which  the  rapidity  in  the  nerves  can 
be  calculated  in  the  same  respect  as  in  the  case  of  light,"1  and  yet  within 
six  years  of  this  period  what  was  considered  impossible  by  one  of  the 
greatest  biologists  was  actually  accomplished,  as  we  have  seen,  by  Helm- 
holtz.2  It  is  to  be  observed  that  in  the  preceding  experiments  in  which 
electricity  was  made  use  of  as  the  stimulant  to  call  into  activity  the 
nervous  irritability,  and  muscular  activity  as  the  measure  of  the  latter, 
that  three  distinct  forces  are  involved,  electricity,  nervous  and  muscular 
force.  That  the  electricity  acts  simply  as  a  stimulant  is  evident,  since 
it  is  only  transmitted  across  the  nerve  transversely  from  electrode  to 
electrode,  and  that  the  nerve  force  is  gradually  transmitted  from  the 
point  where  the  nerve  is  first  excited  by  the  electricity  to  the  muscle, 
is  equally  well  shown  by  the  length  of  time  that  is  required  by  the 
nerve  force  to  traverse  the  nerve  to  the  latter,  and  from  the  death  of 
the  nerve  progressing  gradually  from  its  cut  end  to  the  muscle.  Further, 
just  as  electricity  is  a  distinct  force  from  nerve  force,  so  is  the  latter 
to  be  distinguished  from  muscular  force.  Indeed,  the  effect  of  nerve 
force  can  be  prevented  by  curara,  the  latter  substance  probably  acting 
by  destroying  the  nerve  endings,  the  muscular  force,  however,  remain- 
ing unaffected,  whereas  the  latter  force  is  destroyed  by  sulphocyanide 
of  potassium,  the  nerve  force  being  unaffected.3 

It  has  already  been  mentioned  that  nervous  action  is  accompanied 
with  the  development  of  heat.  Little  or  nothing  more  has  as  yet, 
however,  been  positively  established  as  to  the  relation  existing  between 
the  two  forces,  and  the  same  may  be  said  as  to  the  nature  of  the 
chemical  changes  going  on. 

i  Physiologie,  i.  4  Aufl   S.  5S1.     Coblenz,  1844. 
*  Monatsber.  d.  Berliner  Acad.,  1850,  8.  14 

8  Bernard :  Systeme  Nerveux,  t.  i.  p.  19S.    Paris,  185S.     Vulpian  :  Physiologie  et  comparSe  du  Systeme 
Nerveux,  p.  1S6.     Paris,  1866. 


CHAPTER    XXXVIII. 

GALVANOMETERS.  NON-POLARIZABLE  ELECTRODES.  ELEC- 
TRICAL CURRENT.  RESISTANCE.  ELECTROMOTIVE  FORCE 
OF  NERVE.     CAUSE  OF  ELECTRICAL  CURRENT  OF  NERVE. 

It  will  be  observed,  in  the  preceding  experiments,  performed  with 
the  view  of  demonstrating  nervous  irritability,  that  the  muscular  con- 
traction following  the  stimulation  of  the  nerves  is  the  only  visible 
positive  evidence  that  we  have  obtained  so  far  of  the  nerve  having  been 
modified  in  any  way  by  the  application  of  the  stimulus.  That  some 
change,  however,  must  be  set  up  at  the  point  of  irritation  and  trans- 
mitted thence  through  the  nerve,  is  evident  from  the  fact  of  the  muscle 
contacting  in  response  to  the  stimulus,  though  the  latter  be  applied 
to  the  nerve  at  a  distance  from  the  muscle,  while  from  the  slowness 
with  which  the  irritation  is  transmitted  through  the  nerve,  it  is  to  be 
also  inferred  that  the  change  in  its  condition  during  a  state  of  activity, 
whatever  the  nature  of  the  change  may  be,  is  of  a  gradual  character. 
If,  however,  the  electrical  condition  of  the  nerve  be  examined  in  a  state 
of  rest,  and  in  one  of  activity,  it  will  be  learned  that  the  change  induced 
in  a  nerve  through  its  stimulation,  is  a  change  partly  at  least  in  its 
electrical  condition,  since  the  natural  electrical  current  that  is  present  in 
a  nerve  during  a  state  of  rest,  disappears  during  one  of  activity.  Indeed, 
it  can  be  shown  that  as  rapidly  as  the  electrical  current  disappears  in  the 
nerve,  the  nerve  current  or  irritability  of  the  nerve  appears,  and  it  may 
be  incidently  mentioned  here,  as  confirmatory  of  what  has  just  been  said 
with  reference  to  the  disappearance  of  the  electrical  and  the  appear- 
ance of  the  nerve  force,  that  the  fact  of  the  velocity  of  electricity 
being  at  the  rate  of  2,888,000  miles  a  second  and  of  neurility  of  100 
to  200  feet  a  second,  also  proves  the  non-identity  of  the  two.  To 
appreciate,  however,  the  change  in  the  electricial  condition  of  a  nerve 
brought  about  during  its  state  of  excitement  through  the  effect  of  a 
stimulus,  it  will  be  first  necessary  to  explain  the  construction  of  the 
galvanometer,  by  means  of  which  the  existence  of  an  electrical  current 
in  a  cut  nerve  during  a  state  of  rest  can  not  only  be  demonstrated,  but 
also  the  amount  and  direction  of  the  same  determined. 

The  construction  of  a  galvanometer  is  based  upon  the  fundamental 
fact  discovered  by  Oersted,  in  1819,  of  a  magnetic  needle  being  deflected 
out  of  the  magnetic  meridian  by  a  current  of  electricity  passed  along  a 
wire  parallel  to  it.  Thus,  for  example,  if  an  electrical  current  be 
passed  above  the  magnetic  needle  from  south  to  north  as  indicated  by 
the  direction  of  the  arrows  (Fig.  814,  a  b),  the  north  pole  N  of  the 
needle  will  be  deflected  toward  the  west,  while  if  in  the  reverse  direction, 
from  north  to  south  (Fig.  315,  a  5),  the  north  pole  N  of  the  needle 


MULTIPLIER. 


573 


will  be  deflected  toward  the  east.  On  the  other  hand,  if  the  current 
be  transmitted  from  north  to  south  but  below  the  needle,  then  the  north 
pole  of  the  needle  will  be  deflected  toward  the  west,  as  in  Fig.  314,  but 
if  in  the  reverse  direction  toward  the  east,  as  in  Fig.  315.  The  direc- 
tion according  to  which  the  needle  is  deflected  in  either  of  the  above 
cases  may  be  easily  remembered  by  the  memoria  technica  of  Ampere, 
according  to  which  the  north  pole  of  the  needle  is  always  deflected 
toward  the  left  of  an  individual  supposed  to  be  swimming  in  the 
electrical  stream,  and  always  facing  the  needle,  the  current  entering 
the  feet  and  leaving  the  head  of  the  individual  so  disposed.  That  is  to 
say,  the  north  pole  of  the  needle  is  always  deflected  toward  the  left  of 
the  current.  It  is  evident,  therefore,  if  the  current  be  transmitted 
through  a  wire  passed  around  the  needle  as  arranged  (Fig.  314,  a  <?), 


Fig.  315. 


Deflection  of  magnet  by  currents. 


Deflection  of  magnet  by  currents. 


Fig 


that  not  only  will  the  north  pole  of  the  needle  be  deflected  toward  the 
west  as  the  current  passes  above  the  needle  from  south  to  north,  but  still 
also  to  the  west,  as  the  current  is  transmitted  below  the  needle  from 
north  to  south,  and  that  if  the  wire  be  coiled  again  and  again  around  the 
needle  and  properly  insulated,  the  deflection  of  the  needle  will  be 
proportionally  intensified,  the  needle  being  de- 
flected to  the  east  if  the  current  passes  in  the  reverse 
direction,  as  in  Fig.  315,  b  c.  Hence,  the  name  of 
multiplier  given  to  such  an  instrument  (Fig.  316), 
as  invented  in  1829,  by  Schweigger. 

Further,  since  the  magnetic  needle  is  kept  in  the 
magnetic  meridian  by  the  magnetic  current  of  the 
earth,  the  latter,  in  circulating  around  the  globe  from 
east  to  west,  bringing  parallel  to  itself  and  in  the  same 
direction  the  magnetic  currents  of  the  under  surface  of  the  needle, 
the  latter  finally  coming  to  rest  with  the  currents  of  its  north  pole 
opposite  in  direction  to  that  of  the  hands  of  a  watch,  and  those  of  its 
south  pole  in  the  same  direction,  the  needle,  therefore,  pointing  north 
and  south,  with  its  currents  at  right  angles  to  its  long  axis,  it  is 
obviously  of  advantage  in  the  construction  of  a  galvanometer  that  if 
the  directive  influence  of  the  earth's  currents,  exercised  upon  those  of 


Multiplier. 


574 


GALVANOMETERS,  ETC. 


the  needle  can  be  eliminated,  the  deflect  on  of  the  needle  by  the 
directive  influence  of  an  electrical  current  passed  through  the  surround- 
ing wire  will  be  still  more  intensified.  This  was  accomplished  by 
Nobile,  in  1827,  by  rendering  the  needle,  or,  rather,  the  needles, 
astatic,  as  it  is  called — that  is  to  say,  two  needles  (Fig.  317)  iV/S'and 
8  iV,  connected  together,   are  suspended  by  a  fine   silk  filament,  the 


Fig.  317. 


Fio.  318. 


Astatic  needles. 


Thomson's  galvanometer. 


lower  one  within  the  electrical  circuit,  the 
upper  one  above  it,  so  that  the  north  pole 
N  of  the  lower  needle  is  opposite  the 
south  pole  8  of  the  upper  one,  and  the 
south  pole  8  of  the  lower  needle  is 
opposite  the  north  pole  iV  of  the  upper 
one.  Such  being  the  disposition  of  the 
needles,  the  influence  of  the  earth's  magnetism  exerted  upon  the  north 
pole  of  the  (iV)  lower  needle  is  more  or  less  neutralized  through  the 
same  being  exerted  upon  the  south  pole  (8)  of  the  upper  one.  In 
sensitive  galvanometers  this  latter  effect  is  still  more  thoroughly  accom- 
plished by  placing  a  magnet  above  the  upper  needle. 

It  hardly  need  be  mentioned  that,  according  to  the  Amperian  rule, 
the  north  end  N  of  the  lower  needle,  and  the  south  end  S  of  the  upper 
one  will  move  together,  and  toward  the  west,  if  the  electrified  current 
directing  them  be  transmitted  in  the  direction  indicated  by  the  direction 
of  the  arrows,  for,  though  the  upper  needle  S  N  is  subjected  to  the 
action  of  the  two  contrary  currents  below  it,  the  action  of  the  upper 
current  being  the  nearest  will  influence  it  to  the  greatest  extent.  Upon 
the  principles  just  enunciated  are  constructed  the  Thomson  and 
Wiedemann  galvanometers,  both  of  which  we  make  use  of  in  deter- 
mining the  presence,  intensity,  and  direction  of  the  electrical  currents  of 
nerves.  In  Thomson's  galvanometer  (Fig.  318),  as  made  for  the  author 
by  Elliott,  of  London,  the  magnetic  needles  are  very  small  and  light,  but 


SCALE     AND    LAMP     FOR    GALVANOMETER, 


575 


highly  magnetized,  and  are  disposed  in  an  upper  and  lower  set,  con- 
nected by  an  aluminium  rod,  and  arranged  astatically.  Each  needle  is 
separately  surrounded  by  numerous  coils  of  very  fine  wire,  ending  in 
the  binding  screws,  the  course  of  the  lower  coil  being  opposite  in 
direction  to  that  of  the  upper  one.  To  the  upper  set  of  needles  is 
fixed  a  slightly  concave  mirror  about  6  mm.,  or  one-fourth  of  an  inch  in 
diameter,  serving  to  reflect  the  beam  of  light  back  to  the  scale  B 
(Fig.  319),  the  light  being  transmitted  from  the  lamp  through  the 
narrow  slit  F  under  the  scale,  and  the  lamp  placed  back  of  the  scale 
(Fig.  320).  The  astatic  system  of  needles  is  suspended  by  a  single 
fibre  of  silk  from  a  brass  pin  fixed  to  the  top  of  the  vulcanite  frame  of 


Fig.  319. 


Fig.  320. 


Scale  and  lamp.     (Sanderson.) 


Lamp  and  scale  for  Thomson's  ; 
vanometer.     (Landois.) 


the  coils.  The  latter  are  supported  upon  brass  uprights,  and  are 
covered  by  a  glass  shade  fitting  into  the  rim  of  a  vulcanite  disk,  brass 
bound,  which  is  levelled  by  three  screws  (C  C).  The  brass-bound 
glass  shade  covering  the  uprights,  supports  a  brass  rod,  upon  which 
slides  a  curved  and  weak  magnet  (d),  serving  to  neutralize  the  earth's 
magnetism.  When  used,  the  galvanometer  should  be  so  placed  that  its 
mirror  faces  west,  the  light  and  scale  being  opposite  the  latter,  and 
between  two  and  three  feet  distant.  The  electrodes  being  attached  to 
the  outer  two  (b  b)  of  the  four  binding  screws,  and  the  two  intermediate 
ones  being  connected  together,  the  current  to  be  investigated  will  pass 
through  the  coils,  the  light  moving  from  the  zero  along  the  scale  to  the 
left  or  right,  according  to  the  direction  of  the  current. 

If  it  be  desired  to  compare  the  intensities  of  two  electrical  currents, 
then  the  connection  between  the  two  intermediate  binding  screws  a  a 
being  unmade,  the  two  electrodes  conveying  one  of  the  currents  must  be 
attached  to  one  of  the  outer  binding  screws,  and  the  adjacent  inner  one, 
the  other  two  electrodes  similarly  to  the  other  outer  binding  screw  and 
the  adjacent  inner  one.  If  the  currents  be  equal  in  intensity,  and 
opposite  in  direction,  the  mirror  will  be  unaffected,  and  the  light  will 
remain  at  zero,  only  moving  to  the  right  or  left,  according  as  one  or  the 


576 


GALVANOMETERS. 


Fig.  321 


Shunt.     (Sanderson.) 


other  of  the  currents  preponderates.  It  scarcely  need  be  added  that  if 
a  Thomson  galvanometer  be  used  in  determining  the  presence,  etc.,  of 
nerve  currents,  the  room  must  be  darkened. 
Inasmuch  as  this  galvanometer  is  an  exceedingly 
sensitive  instrument,  it  is  often  desirable  to  allow 
only  a  fractional  part  of  the  current  of  elec- 
tricity studied  to  pass  into  it,  more  or  less  of 
the  electricity  being  shunted  off.  In  accom- 
plishing this  object  we  make  use  of  the  electrical 
shunt.  This  instrument  (Fig-  321)  consists  of  a 
series  of  brass  plates,  separated  from  one  another, 
but  connected  by  wires  of  different  lengths, 
which  offer,  therefore,  more  or  less  resistance  to 
a  current  traversing  them.  The  plates  are, 
however,  also  capable  of  being  more  directly 
connected  by  means  of  a  brass  plug.  The  shunt 
is  provided  with  two  binding  screws,  to  which 
are  attached  the  two  wires  from  the  outer  bind- 
ing screws  of  the  galvanometer  and  the  two  electrodes  conveying  the 
current,  a  part  of  Avhich  is  to  be  diverted  from  the  galvanometer. 

The  two  binding  screws  of  the  shunt  can  be  brought  into  direct  con- 
nection  by  turning  down  a  brass  bar ;  if  this  be  done,  the  current  from 
the  nerve,  for  example,  will  be  short-circuited,  it  passing  from  one 
binding  screw  to  the  other,  back  to  where  it  came  from,  none  of  the 
current  going  to  the  galvanometer,  owing  to  the  resistance  offered.  If, 
however,  the  connection  between  the  binding  screws  be  unmade  through 
the  raising  of  the  bar,  and  the  plug  not  placed  in  any  of  the  holes  of 
the  shunt,  then  the  current,  not  being  able  to  pass  directly  across  from 
one  binding  screw  to  the  other,  will  traverse  the  galvanometer.  The 
coils  of  the  shunt  being  graduated,  however,  according  to  the  resistance 
of  the  galvanometer,  by  means  of  the  plug,  we  can  vary  at  will  the  pro- 
portional amount  of  the  current  going  to  the  galvanometer  to  that  short- 
circuited,  the  amount  depending  upon  the  ratio  of  the  resistance  of  the 
galvanometer  to  that  of  the  shunt.  Thus,  for  example,  suppose  the 
plug  be  inserted  into  the  hole  marked  1.9,  then  such  resistance  is 
offered  in  the  short  circuit  that  only  yg-th  of  the  total  current  goes  to 
the  galvanometer,  the  remaining  y^th  being  short-circuited  ;  if  in  the 
hole  marked  1.99,  or  1.999,  then  only  y^Q-th,  or  ^^^th,  respectively, 
of  the  current  traverses  the  galvanometer,  the  remaining,  y^th,  or 
rcrVo'  Demg  short-circuited. 

Weidemann's  galvanometer,  made  for  the  author  by  Plath,  of  Berlin, 
consists  of  a  thick  cylinder  of  copper  (Fig.  322),  through  which  a 
tunnel  is  bored,  the  latter  capable  of  being  closed  at  each  end  by  either  a 
cover  with  glass  front,  or  by  a  solid  plug  of  copper.  Within  the  copper 
tunnel  hangs  a  magnetized  ring  (Fig.  322,  A),  of  such  size  that  it  can 
just  swing  clear  of  the  sides.  The  object  in  making  the  magnet  ring- 
shaped  is  to  make  it  stronger  in  proportion  to  its  size,  the  centre,  or 
inactive  portion  of  the  magnet,  in  that  form  being  absent.  Connected 
with,  and  passing  upward  from  the  magnetized  ring  through  a  copper 
tube,    is  an  aluminium  rod,  terminating   in   a   light  frame   holding   a 


WIEDEMANN   S    GALVANOMETER, 


577 


circular  plane  mirror,  facing  east  and  west  (B).  In  order  to  prevent 
currents  of  air  moving  the  mirror,  the  latter  is  inclosed  within  a  circular 
brass  cover  (C)  having  a  circular  window  (W),  through  which  the  mirror 
can  be  viewed.  Above  the  mirror  is  screAved  a  long  glass  tube  (T),  at 
the  top  of  which  there  is  a  little  windlass,  supported  by  a  small  piece  of 
ebonite,  whose  centring  on  the  glass  tube  is  effected  by  three  screws. 
On  the  windlass  a  single  fibre  of  silk  is  wound,  passing  through  the 
ebonite  and  down  through  the  glass  tube,  by  means  of  which  the  magnet 
and  mirror  are  suspended,  the  frame  of  the  latter  being  pierced  with  an 
eye  for  the  attachment  of  the  platinum  hook,  to  which  the  end  of  the 
silk  fibre  is  looped.     The  magnetized  ring  can,  by  this  means,  be  raised 

Fig.  32-j!. 


Wiedemann's  galvanometer.     (McGregor-Robinson.) 


or  lowered  or  centred  in  the  copper  chamber,  the  latter  and  its  attach- 
ments being  supported  by  brass  columns  on  a  mahogany  plate,  levelled 
by  three  screws.  The  coils  C,  the  turns  of  which  in  sensitive  instruments, 
as  in  that  of  the  author,  may  amount  to  as  many  as  30,000,  and  through 
which  is  transmitted  the  electricity  exerting  a  directive  influence  upon 
the  magnetized  ring,  are  placed  upon  a  sledge,  that  they  can  be  so 
approximated  as  to  meet  right  over  the  copper  chamber,  and  when  so 
disposed  completely  conceal  the  latter,  as  in  Fig.  322.  Since  with  the 
movement  of  the  magnetized  ring  induced  currents  are  set  up  in  the 
surrounding  copper  chamber,  opposite  in  direction  to  those  of  the  needle, 
the  oscillations  of  the  latter  are  so  diminished  that  after  deflection  it 
comes  quickly  to  rest.  The  copper  chamber  is,  therefore,  called  the 
damper,  the  close  fitting  of  the  ring  within  the  latter  and  the  proximity 
of  the  coils  materially  assisting  in  the  dampening  by  it  of  the  oscilla- 
tions of  the  ring.  Further,  in  order  to  render  the  magnetized  ring  within 
the  copper  damper  astatic,  we  make  use  of  the  arrangement  of  Du  Bois- 

37 


578  GALVANOMETERS. 

Reymond1 — that  is,  an  accessory  magnet  (M),  a  ITauy  bar,  is  placed  in 
the  magnetic  meridian  horizontal  to  the  needle,  with  its  north  pole 
pointing  north,  like  that  of  the  magnetized  ring,  and  supported  upon  a 
bar  (D)  directed  perpendicularly  to  the  coils,  and  in  a  line  with  their 
axis.  The  accessory  magnet  can  slide  up  and  down  the  bar  within  its 
support,  the  bar  being  divided  into  centimetres,  for  measuring  the 
extent  of  the  movement.  One  end  of  the  magnet  being  caught  between 
a  spring  and  a  screw,  and  the  latter  being  turned  by  the  pulley  P1,  the 
magnet  can  be  moved  from  its  spring  end  on  the  other  end,  forming  an 
angle  with  the  plane  of  the  coils,  the  angular  movement  being  effected 
by  an  experimenter  seated  at  a  distance  by  means  of  the  pulley  P2. 
The  galvanometer,  being  properly  located,  the  accessory  magnet,  just 
described,  is  fixed  upon  its  bar  (B)  by  a  clamp  to  the  shelf.  The  magnet, 
being  first  placed  at  the  end  of  the  bar,  is  then  slowly  moved  down  it, 
the  effect  being  gradually  to  neutralize  the  magnetic  action  of  the 
earth.  The  moment,  however,  that  the  position  of  neutralization  is 
passed  the  magnetic  ring  swings  round,  carrying  the  mirror,  of  course, 
with  it,  now  facing  north  and  south,  so  that  its  opposite  poles  are 
placed  against  the  poles  of  the  magnet,  the  movement  involving  a  full 
half  twist  on  its  fibre.  To  prevent  this,  one  of  the  copper  plugs  should 
be  put  in  one  of  the  openings  of  the  chamber,  by  which  the  movement 
of  the  magnetic  ring  is  blocked,  the  other  opening  being  filled  with  a 
glass  plug,  the  movement  of  the  ring  can  be  seen.  This  twisting  tend- 
ency being  observed,  the  accessory  magnet  should  be  moved  back  again 
till  the  tendency  disappears,  and  the  magnetic  ring  is  just  sufficiently 
influenced  by  the  directive  action  of  the  earth  to  be  kept  in  the  meridian. 
The  instrument  will  then  be  found  to  be  very  sensitive.  When  both 
coils  are  to  be  used,  they  must  be  connected  by  carrying  a  wire  from 
a  binding  screw  of  the  one  to  a  binding  screw  of  the  other,  according 
to  the  coils  used,  the  remaining  free  binding  screws  receiving  the  wires 
conveying  the  current.  When  both  coils  enclose  the  copper  chamber 
the  most  intense  effect  is  obtained,  the  recession  of  coils  from  the 
chamber  diminishing  it. 

The  great  advantage  of  Wiedemann's  galvanometer  is  that  by  the 
copper  damper  the  disposition  of  the  coils  C,  and  the  accessory  magnet 
M,  the  magnetized  ring  is  made  aperiodic  or  dead  beat — that  is  to  say, 
the  magnetic  ring,  when  affected  by  the  current,  swings  around  com- 
paratively slowly,  until  the  maximum  deflection  is  reached,  and  arriving 
at  this  point  it  rests  there  without  oscillation ;  the  current  being  with- 
draAvn  it  swings  back  again  to  zero,  stopping  there  without  further  oscil- 
lation, a  current  in  the  opposite  direction  being  indicated  should  it  pass 
the  zero.  It  is  highly  important  in  locating  the  galvanometer  that  no 
iron  structures  whatever  should  be  present  in  its  neighborhood.  The 
instrument  may  be  placed  upon  a  strong  wooden  shelf  fixed  to  a  solid 
dry  wall,  or,  if  the  laboratory  or  lecture-room  be  upon  the  ground  floor, 
upon  a  pillar  of  concrete  capped  with  oak  built  upon  a  solid  stone  foun- 
dation. In  using  Wiedemann's  galvanometer  in  the  laboratory  the 
extent  of  the  deflection  of  the  magnetized  ring  is  observed  by  means  of 

i  Abhandlungen,  S.  870. 


TELESCOPE    AND    SCALE    FOR    GALVANOMETER. 


579 


Fig.  323. 


Telescope  and  scale. 


an  astronomical  telescope,  and  of  a  scale  (Fig.  323),  supported  by  uprights 
above  and  at  right  angles  to  the  long  axis  of  an  astronomical  telescope,  the 
scale  and  telescope  being  placed  upon 
the  same  table  to  which  the  pulley  P', 
already  referred  to,  is  attached,  and 
which  ought  to  be  from  6  to  9  feet 
distant  from  the  galvanometer.  The 
scale  being  directly  opposite  the  mir- 
ror, the  reversed  numbers  of  the  former 
will  be  seen  in  the  latter  in  their 
natural  position,  and  with  the  deflec- 
tion of  the  needle  the  numbers  will 
appear  as  if  drawn  across  the  mirror, 
the  amount  of  the  deflection  being 
indicated  by  the  number  seen  in  the 
mirror  when  the  needle  comes  to 
rest.  For  lecture  purposes,  however,  the  telescope,  etc.,  is  not  used,  a 
beam  from  a  lime  or  electric  light  being  received  upon  a  small  plane 
mirror,  is  thence  reflected  to  the  mirror  of  the  galvanometer,  and  from 
the  latter  to  a  white  scale  placed  at  a  distance  of  from  6  to  15  feet, 
according  to  the  magnification  desired.  In  this  way  the  deflection  of 
the  magnetic  ring  can  be  made  evident  to  a  large  audience.  Inasmuch 
as  in  demonstrating  the  presence  of  an  electrical  current  in  a  nerve  by 
means  of  the  galvanometer,  the  current  is  conveyed  by  the  wires  passing 
from  the  binding  screw  to  the  nerve,  it  is  obvious  that  these  wires  must 
terminate  in  non-polarizable  electrodes — that  is  to  say,  as  already  has 
been  incidentally  mentioned,  in  electrodes  that  will  convey  an  electrical 
current  already  existing  in  the  nerve  examined,  but  will  not  generate  a 
new  one  when  placed  in  contact  with  the  latter,  since  the  latter  current 
so  generated,  extremely  weak  though  it  may  be  in  deflecting  at  once 
the  needle,  the  galvanometer  being  so  sensitive,  might  readily  be  mis- 
taken for  the  preexisting  current  whose  presence  we  wish  to  demon- 
strate. 

In  order,  however,  to  understand  the  manner  in  which  the  generation 
of  the  current  is  prevented  by  the  contact  of  the  electrodes  with  the 
nerve  tissue,  it  will  be  first  necessary  to  explain  what  is  meant  by  the 
polarization  of  the  electrodes,  to  which  the  above  effect  is  due.  Let 
us  suppose  that  two  platinum  electrodes  have  been  immersed  in  acidu- 
lated water,  and  that  the  electricity  transmitted  from  the  battery  has 
decomposed  the  water,  the  positive  pole  being  covered  with  bubbles  of 
oxygen,  and  the  negative  with  bubbles  of  hydrogen.  If  suddenly,  now, 
the  electrodes  be  disconnected  with  the  battery,  and  connected  with  a 
galvanometer,  the  direction  in  which  the  needle  of  the  latter  is  deflected 
wrill  indicate  the  presence  of  a  current,  opposite  in  direction  to  that  of 
the  battery  and  weakening  the  latter,  developed  through  the  fact  of  the 
negative  pole  coated  with  hydrogen  becoming  positive  to  the  positive 
pole  covered  with  oxygen,  just  as  in  the  case  of  non-constant  batteries 
already  referred  to.  It  is  the  change  in  the  condition  of  the  electrodes 
which  is  known  as  their  polarization,  and  which  occurs  in  a  similar  man- 
ner if  a  nerve  be  placed  upon  two  copper  wires.     We  shall  see  hereafter 


580 


GALVANOMETERS. 


that  when  a  fresh  muscle  is  connected  with  the  galvanometer  by  copper 
wires,  the  deflection  of  the  needle  ensuing  indicates  the  presence  of  a 
current,  but  which,  on  account  of  the  polarization  of  the  electrodes, 
may  be  as  much  due  to  the  generation  of  a  current  as  to  the  presence  of 
a  preexisting  one.  Even  perfectly  clean  platinum  electrodes  soon 
become  differentially  affected  by  contact  with  organic  tissues,  and  so 
give  rise  to  difference  in  electrical  tension  or  electromotive  force. 
Regnault,  however,  showed  in  1854,  that  a  strip  of  chemically  pure 
zinc  immersed  in  a  solution  of  neutral  zinc  sulphate,  and  Matteuci, 
two  years  later,  that  ordinary  zinc  amalgamated  and  immersed  in  a 
saturated  solution  of  the  same,  exhibited  no  polarization.  Du  Bois- 
Reymond3  availing  himself  of  these  discoveries,  devised  non-polarizable 
electrodes,  convenient  forms  of  which,  known  as  diverting  vessels  and 
diverting  cylinders,  are  represented  in  Figs.  324  and  325,  and  by  which 
no  currents  are  generated  when  nerve  or  muscle  is  placed  in  contact 
with  the  same.     A  diverting  vessel  (Fig.  324),  as  made  by  Plath,  of 

Fig.  324. 


Homogeneous  diverting  vessel,  as  used  by  E.  Du  Bois-Keymond. 


Berlin,  consists  of  a  zinc  trough  (T),  containing  a  saturated  solution  of 
zinc  sulphate,  the  inner  surface  of  the  trough  being  carefully  amalga- 
mated, and  the  outer  surface  coated  with  a  layer  of  black  varnish,  the 
object  of  the  latter  being  to  prevent  the  sulphate  solution  coming  in 
contact  with  any  unamalgamated  zinc. 

It  may  be  mentioned  incidentally  in  this  connection  that  the 
amalgamating  fluid  used  is  that  known  as  Bergot's,  prepared  by 
dissolving  at  a  gentle  heat  200  grammes  of  metallic  mercury  in  a  1000 
gramme  mixture  consisting  by  weight  of  one  part  of  nitric  acid  to 
three  parts  of  hydrochloric  acid,  and  adding  then  1000  grammes  of 
the  latter  acid.  The  fluid  should  be  kept  in  a  cool,  dark  place,  to 
avoid  decomposition.  The  trough,  insulated  by  a  base  of  vulcanite  ( V), 
and  provided  with  a  binding  screw  (K),  can  be  lifted  by  a  handle  (R). 


DISPOSITION    OF    DIVERTING    VESSELS. 


581 


The  insulated  cushions  (C),  called  deriving  cushions,  are  made  up  of 
a  series  of  layers  of  white  Swedish  filtering  paper,  which  are 
stitched  together  at  one  end  to  secure  them,  and  their  sides  cut 
perpendicularly  with  a  sharp  razor,  and  soaked  in  the  zinc  solution 
and  squeezed  so  as  to  get  rid  of  the  buhbles  of  air  which  would  offer 
resistance  to  the  current.  These  cushions  fill  up  the  cavity  of  the 
trough,  and  project  over  the  lip  of  the  latter,  a  plate  of  ebonite  (E), 
and  an  India-rubber  band  (B)  retaining  the  cushion  in  this  position. 
Inasmuch,  however,  as  the  nerve  to  be  examined,  if  placed  directly 
upon  the  deriving  cushion  would  be  corroded  by  the  zinc  sulphate 
solution  in  which  the  cushion  has  been  soaked,  a  guard  (G)  is  made, 
consisting,  as  already  mentioned,  of  china  clay  worked  up  into  a 
soft  mass  with  h  or  1  per  cent,  solution  of  common  salt,  which 
when  freed  of  bubbles  of  air  and  flattened  into  a  sheet  (s)  is  folded 
over  the  cushion.  A  small  piece  of  mica  may  also  be  placed  upon 
the  clay  guard  to  limit  the  part  to  be  touched  by  the  tissue.     The  clay 

Fig.  325. 


Diverting  cylinders.     (E.  Du  Bois-Retmond. 


guard  not  only  prevents  the  corrosion  and  destruction  of  the  nerve,  but 
through  the  presence  of  the  salt,  the  secondary  resistance,  which  would 
otherwise  arise  between  the  liquid  conductor  and  the  tissue,  and 
diminish  the  intensity  of  the  current  to  be  examined  is  avoided,  the 
salt  at  the  same  time  being  a  good  conductor.  Two  diverting  vessels 
being  so  prepared,  a  fine  silk-covered  copper  wire  is  carried  from  the 
binding  screw  (K)  of  one  of  the  troughs  (T)  to  one  side  of  the  Du  Bois- 
Keymond  key,  and  another  wire  from  the  other  trough  (T'),  not  repre- 
sented, to  the  other  side  of  the  key,  wires  being  also  carried  from  the 
key  K  to  the  binding  screws  of  the  galvanometer  g,  as  in  Fig.  325. 
Such  being  the  disposition  of  the  diverting  vessel,  the  key  and  galva- 


>82 


GALVANOMETERS. 


nometer,  if  the  key  be  down,  the  diverting  vessels  are  short-circuited, 
but  if  up,  are  in  communication  with  the  galvanometer.  Finally  the 
troughs  can  be  directly  connected  together  by  approximating  them  or 
indirectly  by  a  closing  cushion  made  out  of  blotting  paper  saturated  in 
the  zinc  solution,  etc.,  like  the  deriving  ones.  The  diverting  vessels,  key, 
and  galvanometer  being  so  disposed  before  performing  any  experiment, 
it  ought  to  be  first  shown  that  the  diverting  vessels-  are  homogeneous  or 
non-polarizable.  To  do  this,  the  key  being  down,  the  needle  of  the 
galvanometer  is  brought  to  zero,  and  the  two  diverting  vessels  are  con- 
nected together,  the  key  being  then  opened,  if  the  needle  still  remains 
at  zero  we  may  be  assured  that  there  is  no  electrical  current,  that  the 
diverting  vessels  are  homogeneous  or  non-polarizable. 

Apart  from  the  fact  that  the  nerve  whose  electricity  is  to  be  exam- 
ined cannot  always  be  placed  between  the  cushions  in  the  position 
desired,  it  is  also  often  impossible  to  bring  particular  points  of  the 
nerve  in  contact  with  the  latter.  We  frequently,  therefore,  make  use 
of  the  non-polarizable  electrodes  represented  in  Fig.  325,  known  as 
diverting  cylinders,  Avhich,  as  constructed  by  Plath  of  Berlin,  con- 
sist of  a  flattened  tube  of  glass  (a)  mounted  on  a  universal  joint 
(m  l),  and  supported  on  a  brass  upright  (A)  closed  at  one  end  by 
moistened  china  clay  and  filled  with  the  saturated  zinc  sulphate  solution 
in  which  is  immersed  the  slip  of  amalgamated  zinc  Z.  The  clay 
(c)  projecting  from  the  end  of  the  tube  can  be  sharpened  into  a  point 
so  that  any  two  parts  of  the  nerve  can  be  touched  that  is  desired. 
That  no  polarization  occurs  when  the  points  of  such  electrodes  are 
placed  in  contact  with  the  nerve  is  shown  by  the  absence  of  the  pro- 
ducts of  electrolytic  action  which  would  have  otherwise  accumulated 

Fig.  326. 


Electrical  current  of  nerve. 


at  the  electrodes.  Such  electrodes  are  not  only  serviceable  in  divert- 
ing an  electrical  current  from  the  nerve  to  the  galvanometer,  but  can 
be  also  used  for  the  purpose  of  stimulating  a  nerve  by  electricity  in  the 
same  manner  as  already  described.  The  deriving  cushions  (Fig.  324), 
or  the  diverting  cylinders  (a),  and  the  key  (K)  and  galvanometer  (</) 


PHYSIOLOGICAL    RHEOSCOPE. 


583 


having  been  connected  as  represented  in  Fig.  325,  and  a  freshly  pre- 
pared nerve  (n)  having  been  placed  upon  the  cushions  or  in  contact 
with  the  points  of  the  cylinders  so  that  its  transverse  section  or  cut 
end  is  in  contact  with  one  of  the  cushions  or  cylinders,  and  its  longi- 
tudinal uninjured  surface  at  the  equator  with  the  other,  with  the  open- 
ing of  the  key  the  needle  of  the  galvanometer  will  at  once  be  deflected, 
and  in  a  direction  which  shows  that  the  electrical  current  in  the  nerve 
passes,  as  indicated  by  the  arrows  (Fig.  326),  from  the  longitudinal 
surface  of  the  nerve  (a)  through  the  galvanometer  to  the  transverse  cut 
surface  {xy),  the  remainder  of  the  circuit  being  completed  by  the  nerve 
itself  {Z).  In  this  connection  it  may  be  mentioned  that  the  galva- 
nometer is  not  indispensable,  if  we  wish  simply  to  demonstrate  the  elec- 
trical nerve  current,  as  it  may  be  accomplished  by  what  is  known  as  the 
physiological  rheoscope,  which  is  prepared  in  the  following  manner: 

Upon  an  insulated  glass  plate  A  (Fig.  327)  are  placed  two  pieces  of 
blotting  paper  (B  C)  soaked  in  salt  solution,  which  support  two  albu- 

Fig.  327. 


Physiological  rheoscope. 


minous  guards  (D  E),  upon  which  rests  the  nerve  (N)  of  a  nerve  muscle 
preparation,  the  cut  end  of  which  is  in  contact  witli  the  pad  D,  the 
longitudinal  surface  with  the  pad  E,  the  muscle  (M)  being  supported  by 
the  glass  plate  F,  also  insulated. 

The  nerve  being  so  disposed,  with  the  alternate  connection  and  dis- 
connection of  the  two  pieces  of  blotting  paper  (B  C)  by  a  third  piece  (G), 
the  muscular  contraction  that  follows  in  both  instances  indicates  the 
presence  of  an  electrical  current  in  the  nerve  passing  in  the  direction 
of  the  arrows. 

Returning  now  to  the  case  of  the  nerve  when  in  connection  with  the 
galvanometer  (Fig.  326),  and  experimenting  a  little  further  by  changing 
the  position  of  one  or  both  of  the  electrodes,  it  will  soon  be  learned  that 
while  the  current  always  passes  from  the  longitudinal  to  the  transverse 


584:  GALVANOMETERS. 

cut  surface,  the  amount  of  the  deflection  of  the  galvanometer  needle 
varies  very  much  according  to  the  position  of  the  electrodes.  In  certain 
positions,  indeed,  as  where  the  electrodes  are  placed  on  different  sides 
of  the  nerves  exactly  opposite  to  each  other  (a  b),  or  on  points  equidistant 
from  the  equator  (ef,xy),  the  needle  is  not  deflected  ;it  all,  there 
being  no  difference  of  electrical  potential  at  such  places.  Such  was 
also  supposed  to  be  the  case  with  reference  to  the  contents  of  the  nerve ; 
Recently  it  has  been  shown,  however,  by  Du  Bois-Reymond  and  Men- 
delssohn1 that  a  current  passes  through  the  nerve  from  transverse  sec- 
tion to  transverse  section,  to  which  the  name  of  "axial  stream"  has 
been  given  by  these  observers.  On  the  other  hand,  if  one  electrode 
remaining  at  the  cut  surface,  we  move  the  other  along  the  longitudinal 
surface  toward  the  equator  the  deflection  of  the  needle  will  be  increased, 
the  maximum  being  reached  when  the  electrodes  are  at  the  equator  of 
the  longitudinal  and  transverse  surfaces,  as  in  the  experiment  repre- 
sented in  Fig.  326,  a  b.  Experimentally,  in  this  way,  with  the  gal- 
vanometer, it  may  be  learned  that  all  parts  of  the  longitudinal  surface 
of  any  nerve  are  positively  electrified  with  reference  to  the  transverse 
cut  surface,  and  that  if  any  two  points  (ef)  of  the  longitudinal  surface, 
that  nearest  the  equator  of  the  nerve  (e)  is  positively  electrified  with 
reference  to  that  more  distant  (/). 

That  a  similar  relation  exists  between  the  equator  of  the  transverse 
cut  surface  and  its  periphery,  though  not  experimentally  demonstrated, 
is  rendered  highly  probable  from  the  fact  of  such  a  relation  having  been 
demonstrated  in  the  case  of  muscles,  as  we  shall  see  hereafter.  Further, 
by  experimenting  with  different  nerves  it  will  be  found  that  the  length 
and  thickness  of  the  nerve  influence  the  amount  of  the  electrical  cur- 
rent, it  beino;  greater  in  Ions;  thick  nerves  than  in  short  slender  ones. 
That  an  electrical  current  exists  in  the  nerve  during  a  state  of  rest  there 
can  be,  after  what  has  been  said,  no  doubt,  whatever  the  subsequent 
explanation  of  the  phenomena  may  be ;  but  it  must  be  admitted,  and 
the  admission  is  an  important  one  as  regards  any  inference  to  be  hereafter 
drawn  as  to  the  relation  between  nerve  electricity  and  nerve  force,  that 
in  an  uninjured  nerve,  in  which  no  transverse  cut  section  has  been  made, 
there  is  no  evidence  of  an  electrical  current.  As  might  be  supposed, 
the  nerve  offers  a  resistance  to  the  passage  through  it  of  an  electrical 
current,  and  the  manner  in  which  this  is  determined  may  be  considered 
as  appropriately  here  as  elsewhere.  This  is  accomplished  by  essentially 
the  same  method  as  ordinarily  made  use  of  in  determining  the  amount 
of  resistance  offered  by  bodies  in  general  to  the  passage  of  electricity, 
and  is  briefly  known  as  that  by  the  Wheatstone's  bridge.  This  method 
is  based  upon  the  principle  of  so  disposing  the  body  whose  resistance 
is  to  be  determined,  that  the  current  of  electricity  traversing  it  passes 
through  a  galvanometer  in  an  opposite  direction  to  that  traversing  a 
body  whose  resistance  can  be  varied,  until  the  current  traversing  the 
body  exactly  neutralizes  the  former  current,  as  shown  by  the  galva- 
nometer's needle  remaining  at  zero. 

Such  being  the  case,  the  unknown  resistance  is  then  equal  to  the 

1  Reichert  and  Du  Bois-Reymond  :  Anhiv,  1885,  separat-abdruek. 


RESISTANCE    OF    NERVE, 


585 


known  one,  otherwise  there  would  be  a  deflection  of  the  magnetic 
needle  according  as  the  one  body  would  offer  a  greater  or  less  resistance 
to  the  current  than  the  other.  Thus,  supposing  that  the  apparatus  be 
arranged  as  in  Fig.  328,  then  the  current  from  a  Darnell's  element 
D,  onarriving  at  A,  the  end  of  the  long  wire  A  B,  or  rheocord,  splits 

Fig.  328. 


Schema  for  determining  the  resistance  of  nerve. 

into  two  branch  currents,  one  of  which  will  traverse  the  body  JV,  a 
nerve  for  example,  whose  resistance  is  to  be  determined,  and  the  other 
the  wire  A  B.  Further,  the  first  branch  current,  on  arriving  at  0, 
will  divide  into  two,  one  of  which  will  pass  into  the  resistance  box  R, 
the  other  into  the  galvanometer  Gr  ;  the  latter  current  being  opposite 
in  direction  to  that  coming  from  S,  one  of  the  two  branch  currents 
into  which  the  current  A  8  divides,  the  remaining  one  passing  from 
8  to  B,  and  thence  back  to  the  Daniell's  element.  But,  as  the 
resistance  offered  to  the  current  passing  from  A  toward  B  can,  as  we 
know,  be  increased  or  diminished  by  the  sliding  of  8  from  or  toward 
A,  all  the  current  returning  to  the  battery  when  the  slider  is  at  A,  by 
varying  the  position  of  the  slider  a  point  will  be  reached  on  the  wire, 
as  at  8,  when  the  galvanometer  needle  will  remain  at  zero,  showing 
that  the  current  passing  down  from  the  nerve  from  0  to  the  galva- 
nometer is  equal  and  opposite  in  direction  to  that  passing  up  from  the 
wire  at  8.  Such  being  the  case,  then  the  resistance  offered  by  the 
nerve,  or  x,  is  to  that  of  the  resistance  box  R,  as  the  part  of  the  wire 
„  1  8  is  to  the  part  S  B — that  is,  x  :  R  : :  A  8  :  8  B.  Now,  as  the 
resistance  R  is  learned  by  observing  the  number  of  plugs  out,  and 
that  of  A  S  and  8  B  being  also  known,  the  rheocord  wire  having  been 
previously  graduated,  the  unknown  resistance  of  the  nerve,  or  x,  is 
given  in  terms  of  R,  AS,  and  SB,  as  shown  by  the  equation 

„_  R  X  A3X 
SB      ' 

1  Or  if  AS  and  SB  be  constant  and  equal,  then  the  resistance  of  2V equals  that  of  R,  and  ran  be  inferred 
from  that  of  the  latter  as  determined  by  the  number  of  plugs  out,  as  in  the  form  of  resistance  box  made 
for  the  author  by  Hartmanu,  of  Marburg. 


000  GALVANOMETERS. 

The  method  just  described  of  determining  the  resistance  offered  by  a 
nerve,  for  example,  to  the  passage  of  a  current  of  electricity  is  at  times 
inconvenient,  even  quite  awkward,  on  account  of  the  length  of  the 
rheocord  wire  involved.  This  is  readily  obviated,  however,  as  sug- 
gested by  Du  Bois-Reymond,  by  disposing  the  wire  in  the  form  of  an 
arc,  the  latter,  with  the  accessory  binding  screw  0,  Christiani's  modi- 
fication, being  then  known  as  the  modified  round  compensator  of 
Du  Bois-Reymond,  and  as  made  for  the  author  by  Pfeil,  of  Berlin,  is 
represented,  schematically,  in  Fig  329.  The  principle  of  determining 
the  resistance,  it  is  needless  to  add,  however,  is  not  at  all  affected  by 

Fig.  329. 


Ne  :  It  :  :  AS  :  SB 
Schema  of  round  compensator,  with  Christiani's  modification. 

this  modification  of  Du  Bois-Reymond  and  Christiani,  the  difference 
between  the  long  and  round  rheocord  or  compensator  being  simply  in 
the  disposition  of  detail.  Thus,  if  Fig.  329,  a  schematic  repre- 
sentation of  the  round  compensator,  be  compared  with  Fig.  328,  the  long 
one,  it  will  be  observed  that  in  both  instruments  the  current  from  the 
Daniell's  element  D,  on  arriving  at  A  splits  into  two  currents,  one  of 
which  passes  to  the  wheel  or  slider  S,  the  other  to  the  nerve ;  that  the 
current  at  S  divides  into  two,  one  of  which  passes  to  the  galvanometer 
Gr,  the  other  back  to  the  Daniell's  element ;  that  the  current  after 
traversing  the  nerve  divides  into  two,  one  of  which  passes  to  the  gal- 


ELECTROMOTIVE    FORCE 


587 


vanometer  Gr,  the  other  to  the  resistance  box  B,  and  thence  back  to 
the  DanielPs  element ;  that  the  two  currents,  passing  in  opposite  direc- 
tions through  the  galvanometer  neutralize  each  other.  It  follows, 
therefore,  that  in  using  the  modified  round  compensator  we  obtain  the 
same  proportion  as  in  using  the  long  one,  viz.: 

R  x  AS 


R 


A  S  :   SB,  or  z  = 


SB 


The  value  of  z,  or  the  resistance  of  the  nerve,  as  obtained  by  this 
method,  has  been  ascertained  to  be,  when  exerted  longitudinally,  two 
and  a  half  million  times  greater  than  mercury,  and,  when  exerted 
transversely,  twelve  million  times. 

For  the  measurement  of  electromotive  force,  as  in  that  of  electrical 
resistance,  we  make  use  of  the  same  principle  of  compensation,  or  that 
of  Poggendorf ' — that  is,  we  determine  experimentally  the  amount  of 
a  branch  stream  switched  off  from  a  rheocord  wire  sufficing  exactly  for 
the  neutralization,  or  compensation,  of  the  current  due  to  the  electro- 
motive force  of  the  nerve  to  be  determined.  Suppose  E  to  be  the 
electromotive  force — that  is,  1.079  volts  of  the  Daniell's  element 
D  (Fig.  330),  in  the  principal  circuit  a,  2),  b,  c,  a;  W -\-  w,  the 
resistance  of  the  latter,  w  being  that  of  the  portion  a  c  of  the  rheocord 
wire  a  b  forming  the  short  circuit,  and  e  the  electromotive  force  of  the 


Fig.  330. 


Fig.  331. 


1st  /tosct 


Diagrams  to  illustrate  the  determination  of  electromotive  force. 


nerve  n  to  be  compensated,  then,  according  to  Kirchoff's  theorem  of 
branched  currents,  as  the  conditions  of  compensation,  we  obtain  the 
equation 

e   :    w   :  :    E  :    TF+  w, 
and  as   e  (  W -\-  w)  =  wE 

e=^—XE.  (1) 

1  Pu  Bois-Eeymond  :  Gesammelte  Abhandlungen,  Erster  Baud,  S.  176,  S.  257. 


588  GALVANOMETERS. 

If  now  W-\-tv  be  constant — that  is,  if  the  rheocord  wire,  with  its 
now  short-circuiting  part  belongs  to  the  principal  circuit — then 

W     w     TP 

G 

that  is  to  say,  the  electromotive  force  e  of  the  nerve  to  be  determined 
is  directly  proportional  to  the  resistance  a  c  of  the  short  circuit.  In 
order,  however,  to  measure  this  force  e — that  is,  to  determine  the 
ratio  of  e  to  E,  as  the  ratio  of  w  to  W-\-w  is  not  directly  obtainable,  we 
proceed  in  the  following  manner  : l  E  being  the  electromotive  of  the 
Daniell's  element  D  (Fig.  331),  e  the  electromotive  force  of  the  nerve 
to  be  determined,  Gr  the  galvanometer,  a  b  the  rheocord  wire,  and  c 
the  slider,  let  us  determine  the  position  of  the  latter  when  e  is  com- 
pensated— that  is,  when  no  current  passes  through  Gr.  Suppose,  now, 
that  compensation  be  effected  when  the  slider  is  at  c,  and  that  W  be 
the  resistance  of  the  conductor  a  C  B,  I)  b  (Fig.  331,  first  position), 
iVthe  length  of  the  wire  a  b  in  millimetres,  n  the  length  of  the  part 
a  c,  and  w  the  resistance  of  a  millimetre  of  wire,  we  will  then  obtain 
from  equation  1  the  equation  2  : 

(2) 
(3) 


W+  Nw 
e  (  W  +  Nw)  =  nwE 
W+  Nw  =_    E 
niv  e 


but  which  we  will  write 


^  +   ^  =  A  (4) 

nw  7i  e 


For  the  accomplishment  of  our  object — that  is,  the  obtaining  of  the 
ratio  of  e  to  E,  there  only  now  remains  the  obtaining  that  of  nw  to  W, 
and  which  can  be  accomplished  in  the  following  manner :  Let  us 
suppose  that  ^equals  the  intensity  of  the  force  E  with  the  resistance 
W  and  J\  the  intensity  of  the  same  force,  but  with  the  resistance 
W-\-  niv.  With  the  object  of  comparing  these  intensities  by  the  galva- 
nometer, let  the  coil  of  wire  0  B  be  so  intercalated  in  the  principal 
current  during  the  first  or  compensating  part  of  the  experiment  (first 
position)  as  not  to  affect  the  galvanometer  ((7),  but  in  the  second  part 
of  the  experiment  is  brought  so  near  the  latter  (the  circuit  a  Gr  c  being 
open)  as  to  bring  about  a  deviation  of  the  magnetic  needle  (second 
position).  The  coil  OB  being  so  shifted  from  the  first  to  the  second 
position,  we  obtain  the  intensity  Jf,  corresponding  to  the  resistance 
W-\-nw,  while  the  coil  O  B  remaining  in  the  second  position,  if  the 
wire  ab  be  taken  out  of  the  circuit,  then  we  will  obtain  the  intensity 
J,  corresponding  to  the  resistance  W,  and  since  the  intensities  are 
inversely  as  the  resistance,  we  get  the  equation  : 

J   __   W+Nw 


J'  W 


(5) 


1  Du  Bois-Reymond,  op.  cit.,  S.  176. 

2  Hermann  :  Handuuch,  Brster  Band,  Erster  Theil,  S.  188.     Leipzig,  1879. 


GRADUATION    CONSTANT.  589 

but  which  we  will  write  in  the  form  of 

-  1  +  *■  =  1  +  -^   X  *Z  (6) 


J'  W  n     ~     W 

J_ 
J' 


or  calling  the  ratio  —  =  M 


M=l  +  Nx"w  (7) 

n  II 

or  since  (M —  1)  nW=  Nnw 

(M  —  l)  -^  X    W=nw  (8) 

Substituting  this  value  of  nw  =  (M —  1)  —   in  equation  (4)  —  =  _  -|-  -zl_ 
we  obtain 

J^   -=  W  A-   —  =  WN  A-    N_ 

_    WNn  +  (M  —  l)  WnN  __    W Nn  +  M  Wn  N  —  Wn  N 
(M—l)   WnX  n  n  (31  Wn  —  Wn) 

M  WN  M  WN  M  N 

X  — 


M  Wn  —  Wn  (M  —  1)  Wn        M—  1 

and  which  last  value  enables  us  to  determine  the  electromotive  force  of 
the  nerve,  since  from 

A  -*x*-  (8) 

e  M  —  1  n 

we  obtain  the  equation 

eMN=E(M—l)n    or     e  =  E  (J/~  1)         JL       (9) 
v  '  M  N        y  ' 

that  is  to  say,  the  electromotive  force  of  the  nerve  (e)  is  equal  to  that  of 
the  Daniell's  element  (E),  multiplied  by  the  ratio  of  the  two  intensities 

— -  or  M  less  unity  divided  by  that  ratio  M,  and  the  result  multiplied 
J 

by  the  ratio  of  the  number  of  millimetres  of  the  compensator  portion 
of    the  rheocord    wire    (w)    to    the   whole  number    of    millimetres  in 

Jf 1 

the  wire  (iV ),  the  expression  giving  the  fraction  of  the  force 

of  the  Daniell's  element  each  millimetre  of  the  rheocord  wire  is  worth, 
and  is  called,  therefore,  the  graduation  constant.1  It  suffices  to  measure 
once  in  the  manner  described  a  constantly  easily  reproducible  force  (e), 
for  example,  that  of  a  thermopile,  of  a  difference  of  100,  and  by  means 
of  this  force  to  learn  the  graduation  constant  of  the  apparatus  by 
determining  the  length  of  the  rheocord  wire — that  is,  n  or  the  number 
of  millimetres  necessary  for  compensation.  Suppose,  for  example,  that 
we  have  determined  (e)  to  be  equal  to  the  ^  of  a  Daniell,  and  560 
millimetres  equal  n  to  be  necessary  for  compensation,  then  each  milli- 
metre equals  the  -^  of  jfa  or  -g^Vo  of  D.      Finally,  by  means  of  a 

1  Du  Bois-Keyniond,  op.  cit.,  S.  2C1  ;  Idem,  Zweiter  Band,  S.  235. 


590 


GALVANOMETERS. 


resistance  box  introduced  into  the  circuit,  the  fraction  -^nr  _can  be 
made  a  more  convenient  one,  10ooo  for  example,  by  which  the 
calculation  will  be  facilitated. 

In  endeavoring  to  explain  the  manner  in  which  the  electro-motive 
force  of  a  nerve  is  determined  and  the  rheocord  wire  graduated,  we  have 
supposed,  for  the  sake  of  simplicity,  that  the  rheocord  used  is  the  long 
straight  one,  such  as  represented  in  Figs.  330  and  331.  As  in  the  case  of 

Fig.  332. 


Du  Bois-Reymond's  round  compensator. 


the  measurement  of  electrical  resistance,  so  in  that  of  the  electromotive 
force,  it  will  be  found,  however,  that  the  round  compensator  of  Du 
Bois-Reymond  is  a  much  more   convenient  instrument.     When   used, 


Fig.  333. 


Scheme  for  determining  electromotive  force  of  round  compensator. 

however,  for  the  latter    purpose  the  attachment  0  (Fig.  329)  is  left 
out  of  the  circuit.     That  is,  the  instrument  is  used  in  its  original   form 


ROUND    COMPENSATOR.  591 

(Figs.  332,  333),  without  Christiani's  modification.     As  an  illustration 
of  the  manner  of  using  the  compensator  in  this  form  let  us  suppose  : 

E  =  the  electromotive  force  of  a  Darnell's  element. 

e     =  the  unknown  electromotive  force. 

W=  the  resistance  of  the  circuit  without  the  short-circuiting  wire  of  the 
compensator. 

J   —  the  intensity  of  the  current  excluding  the  short-circuiting  wire  of  the 

compensator. 
J'  =  the  intensity  including  the  latter. 

n    =  the  number  of  divisions  on  the  graduated  scale  necessary  for  com- 
pensation. 
iV  =  1000  the  length  of  the  short-circuit  wire  of  compensator. 

Then  by  substituting  in  equation  (9),  p.  589,  for  31  its  value  —  we  shall 

obtain  the  equation  (10) 


Since 


"        N  '          J        /x  ~ 

J  - 

-  1  J—  J'  =  JJ'  —  Jn  =  J—  J' 

J' 

J'                 J  J'                 J 

J 

=       J 

J' 

J' 

(10) 


from  which  equation  e  can  be  obtained  after  n,  J"' and  J'  have  been  deter- 
mined experimentally.  With  the  view  of  accomplishing  this  object  the 
compensator,  etc.,  are  disposed  as  in  Fig.  333. 1  We  will  suppose  that 
the  current  from  the  Daniell's  element  D  enters  the  compensator  at 
I,  and  after  traversing  the  wire  on  arriving  at  III  divides  into  two  cur- 
rents, one  of  which  (III  IV  II  F  P)  returns  directly  to  the  battery,  the 
other  (III  P2  K2  N  G  P2  IV  II)  indirectly,  first  passing  through  the 
galvanometer  in  the  opposite  direction  to  that  of  the  nerve  current,  and 
exactly  neutralizing  the  latter,  the  needle  being  brought  to  zero,  the 
wheel  of  the  compensator  being  at  III.  Such  being  the  case,  it  is  only 
necessary  in  order  to  obtain  the  value  n  to  read  oft*  the  divisions  of  the 
scale  between  zero  and  III.  It  remains  now  to  obtain  the  values  of  J 
and  J'.  To  do  this  we  open  K2  and  turn  down  the  whippe  P  in  such 
a  way  that  B  is  included  in  the  circuit,  F,  however,  being  left  out. 
That  being  done  according  further  as  the  Daniell's  element  is  connected 
with  IV  or  I,  by  the  shifting  of  the  brass  piece  S,  the  current  will  pass 
respectively  through  D  S  IV  II B  P  D,  with  the  intensity  J,  or  through 
D  S  I  III  IV  II  B  P  D,  with  the  intensity  J'.  It  may  be  mentioned 
incidentally  here  that  the  coil  B  having  the  same  resistance  as  that  of 
F,  consists  of  only  two  coils,  but  of  thick  wire,  and  that  it  should  be 
placed  at  such  a  distance  from  the  magnet,  and  at  such  an  angle  to  the 
plane  of  the  magnetic  meridian,  that  the  deviations  of  the  needle  will 
not  exceed  300  seconds.  The  electromotive  force  of  the  sciatic  nerve 
of  the  frog  as  determined  by  the  compensator  amounts,  according  to 
Du  Bois-Reymond,2  to  0.022  of  a  Daniell  cell,  that  of  the  rabbit  not 
exceeding  0.026  D.     According  to  the  recent  elaborate   researches  of 

1  Du  Bois-Reymond,  op.  cit.,  S.  257.  •■*  Idem,  Zweiter  Band,  S.  232. 


592 


GALVANOMETERS, 


Mendelsohn,1  made  at  the  suggestion  of  Du  Bois-lieymond,  the  electro- 
motive force  of  the  axial  current  of  the  posterior  roots  of  the  spinal 
nerves  of  frogs — that  is,  of  the  current  from  equator  to  central  or  peri- 
pheral transverse  section  amounts  respectively  to  0.00893,  and  0.00767 
of  a  Raoul,  that  element  (copper  in  copper  sulphate  solution,  and  zinc  in 
zinc  sulphate)  being  used  instead  of  a  Daniell. 

Having  considered  the  electromotive  force  of  the  nerve,  the  nerve  cur- 
rent, and  the  resistance  offered  by  the  nerve  to  the  passage  of  electricity, 
it  remains  for  us  now  to  offer,  if  possible,  some  explanation  of  the  natural 
nerve  current  based  upon  its  physical  structure.  It  is  well  known  that  if  a 
solid  copper  cylinder  (6'w,  Fig.  334),  covered  except  at  its  ends  by  a  layer 

Fig.  334. 


of  zinc  Zn,  be  immersed  in  a  conducting  fluid  like  water,  that  electrical 
currents  are  developed,  which,  as  may  be  shown  by  the  galvanometer, 
pass  from  the  longitudinal  or  zinc  surface  to  the  transverse  copper  one, 
and  that,  according  as  the  electrodes  are  shifted  from  point  to  point  of 
its  copper  and  zinc  surfaces  these  currents  become  stronger,  weaker,  or 
disappear  altogether,  and  that  while  if  the  copper  be  entirely  covered  by 
its  zinc  mantel  there  is  no  appreciable  electrical  current,  however  the 
electrodes  may  be  placed.  In  a  word,  the  physical  apparatus  just 
described,  as  regards  its  electrical  conditions  exactly  resembles  a  nerve. 
When  it  is  remembered  that  the  ultimate  nerve  fibre  consists  histologi- 
cally of  the  axis-cylinder  surrounded  by  the  white  substance  of  Schwann 
and  neurilemma,  it  might  appear  at  first  sight  that  one  or  the  other  of 
these  two  membranes  bears  to  each  other,  or  to  the  axis-cylinder,  the 
same  relation  electrically  that  we  have  seen  the  outer  zinc  mantel  does 
to  the  copper  axis  of  the  simple  physical  apparatus  just  described. 

That  such,  however,  is  not  the  case,  is  proved  by  the  fact  that  even 
at  the  nodes  of  Ranvier  in  the  spinal  nerves,  and  in  the  sympathetic 
fibres  also,  where  the  white   substance  of  Schwann  is  absent,  neverthe- 


1  Uelerdcn  axialtn  Nervenslrom,  Maurice  Mendelsohn,  1885,  Archiv  f.  Anat.  und  Phys. 


DOUBLE    DIPOLAR    MOLECULES.  593 

less,  electrical  currents  can  be  shown  to  exist,  evidently  then  it  cannot 
be  the  contact  of  the  substance  of  Schwann  with  either  the  neurilemma 
or  the  axis-cylinder  that  is  the  cause  of  the  difference  in  the  electrical 
potential,  while  the  presence  of  electrical  currents  in  the  cord  in  the 
absence  of  the  neurilemma  equally  shows  that  the  contact  of  that 
membrane  with  the  axis-cylinder  has  nothing  to  do,  any  more  than 
the  white  substance  of  Schwann,  with  the  development  of  such  cur- 
rents. The  only  conclusion  to  be  drawn  from  such  facts  is  that  of  the 
three  parts  of  which  the  nerve  consists,  it  is  the  axis-cylinder  only 
which  is  concerned  in  the  development  of  the  electrical  current,  and 
which  confirms  the  conclusion  that  we  have  come  to  upon  other  grounds 
that  it  is  functionally  the  most  essential  part  of  the  ultimate  nerve  fibre, 
and  that  the  electrical  current  developed  in  a  nerve  in  which  a  transverse 
section  has  been  made,  is  due  to  the  fact  of  the  negatively  electrified 
axis-cylinder  being  then  exposed  to  the  positively  electrified  nutritive 
fluid  surrounding  it,  since,  as  we  have  just  seen,  the  difference  between 
the  longitudinal  and  cut  surfaces  electrically  cannot  be  attributed  to 
the  contact  of  either  neurilemma  or  substance  of  Schwann  with  the 
axis-cylinder.  If  such  be  the  case,  it  becomes  intelligible  why,  as  we 
have  already  mentioned,  there  is  no  appreciable  electrical  current  in  the 
uninjured  nerve — that  is,  in  one  without  a  transverse  cut  section,  since 
under  such  circumstances  the  negative  axis-cylinder  is  not  exposed  to 
the  positive  nutritive  fluid  surrounding  the  nerve,  just  as  in  the  case 
of  the  physical  apparatus  (Fig.  334).  There  is  no  electrical  current 
developed  as  long  as  the  negative  copper  axis  or  core  is  completely 
enveloped  by  the  positive  zinc  mantel  or  hull.  As  an  illustration  of 
the  influence  of  the  contact  of  a  surrounding  fluid  upon  a  tissue  in 
the  development  of  an  electrical  current,  it  may  be  here  mentioned 
that  if  the  transverse  cut  surface  of  a  dried  muscle  be  placed  upon  the 
surface  of  distilled  water,  that  an  electrical  current  will  be  developed, 
passing  from  the  longitudinal  to  the  cut  surface  as  soon  as  the  muscle 
begins  to  swell  through  imbibition  of  the  fluid  with  which  its  trans- 
verse section  is  in  contact.  While  the  explanation  just  offered,  that  of 
Gruenhagen,1  is  considered  by  that  physiologist  as  satisfactorily  ex- 
plaining the  electrical  condition  of  the  cut  nerve,  however  plausible  it 
may  appear,  it  must  be  mentioned  that  it  is  not  accepted  by  all  physi- 
ologists. Thus,  Du  Bois-Reymond,2  the  highest  living  authority  on 
electro-nerve  physiology,  has  for  many  years  held  that  the  nerve  con- 
sists not  of  a  homogeneous  axis,  surrounded  by  a  hull  like  that  of  the 
physical  apparatus  just  described  (Fig.  334),  but  of  a  series  of  electro- 
motive double  dipolar  molecules,  imbedded  in  an  indifferent  and 
imperfectly  conducted  medium.  Each  double  molecule  consists  of  a 
positive  and  negative  part,  being  so  disposed,  as  may  be  seen  from 
(Fig.  335),  that  the  two  positive  parts  of  the  two  halves  are  placed 
together  within,  the  two  negative  parts  without,  as  it  were,  the  double 
molecule  presenting  then  a  negative  surface  at  the  transverse  section  or 
cut  end,  and  a  positive  surface  at   the  longitudinal  surface  or  section  of 

i  Funke  :  Physiologie,  Erster  Band,  1876,  S.  487. 

8  Untersuchuugen  iiber  Thierische  Electrioitat,  Zweiter  Band,  S.  323.     Berlin,  1849. 

38 


594 


G  A  L VANOME T  E  I :  S  . 


the  nerve.  Regarding  the  double  molecule  as  a  minute  battery  whose 
positive  and  negative  poles  are  at  the  longitudinal  and  transverse  sur- 
faces, respectively,  currents  will  be  developed  which  through  the  im- 
perfect conductility  of  the  medium  will  circulate  in  more  or  less  eccentric 


Fig.  335. 


Electromotor  double  dipolar  molecules. 

lines  not  only  in  the  immediate  neighborhood  of  each  molecule,  but  at 
some  distance  from  the  latter,  from  the  positive  middle  surface  to  the 
negative  ends  of  the  nerve  as  indicated  by  the  arrows,  and  giving  rise 
to  the  deflection  of  the  galvanometer  needle,  as  we  have  seen  is  the 
case  when  the  electrodes  are  applied  to  the  nerve.  Suppose  that  the 
nerve  does  consist  according  to  this  hypothesis  of  molecules,  such  as 
just  described,  it  is  evident  that  the  electrical  current  within  it  is  a 
closed  one,  the  nerve  differing  in  this  respect  from  the  zinc-copper 
apparatus  as  regards  any  current  diverted  into  the  galvanometer.  In 
either  case  the  current  can  only  be  a  partial  one,  the  deflection  of  the 
needle  indicating  the  presence  of  a  current,  but  in  no  wise  the  total 
strength  of  the  current  due  to  the  electromotive  force  of  all  the  mole- 
cules. 

That  the  strength  of  the  latter  must  be  much  greater  than  the  partial 
current  deflecting  the  needle  is  shown  by  the  necessity  of  using  such 
sensitive  galvanometers,  and  is  implied  in  the  overcoming  of  the  resist- 
ance both  of  the  nerve  and  the  galvanometer  circuit,  which  is  consider- 
able. Indeed,  were  not  the  total  electric  strength  of  the  molecules 
much  greater  than  that  of  the  partial  current,  the  latter  would  not  be 
appreciated  by  the  galvanometer  at  all.  It  is  for  such  reasons  that  Du 
Bois-Reymond  holds  that  the  electromotive  force  of  the  nerve  mole- 
cules exceeds  that  producing  all  other  known  currents,  and  is  capable, 
in  the  highest  degree,  of  producing  all  the  known  effects  of  currents. 
While  there  is  much  to  be  said  in  favor  of  Du  Bois-Reymond's  view  of 
the  nerve  consisting  of  electromotive  molecules,  it  must  be  admitted  that 
it  is  difficult  to  explain  on  such  a  theory  the  weak  currents  that  are 
developed  by  placing  the  electrodes  upon  different  points  of  the  longi- 
tudinal surface,  and  why  currents  of  any  kind  are  only  present  in  the 
injured  nerve,  or  one  presenting  a  transverse  section.  Indeed,  this 
latter  fact,  equally  an  objection  to  the  view  offered  by  Gruenhagen,  has 
led  some  physiologists,   like   Hermann,1   to   deny  altogether    the  pre- 


i  Handbuch,  Zweiter  Band,  Erster  Tbeil,  S.  169.     Leipzig,  1879. 


STATIC     AND    DYNAMIC    ELECTRICITY. 


595 


Fig.  336. 


existence  of  any  electrical  current  in  the  nerve,  attributing  the  latter  to 
the  death  of  the  transverse  cut  surface,  which,  at  that 
moment,  becomes  negative  to  the  longitudinal  surface. 
On  the  other  hand,  according  to  Radcliffe,1  the  elec- 
trical character  of  the  nerve  current  is  rather  static 
in  its  nature  than  voltaic,  the  nerve  being  compared 
on  this  view  to  a  charged  Leyden  jar  (Fig.  336),  the 
current  being  simply  accidental,  and  due  to  the  apply- 
ing of  the  electrodes  of  the  galvanometer  to  points 
having  different  electrical  tensions.  After  all,  how- 
ever, the  difference  between  static  and  voltaic  or  cur- 
rent electricity  is  not  a  profound  one,  being  rather 
one  of  degree  than  of  kind,  since  the  former  is  one  of 
high  tension,  but  small  in  quantity,  the  latter  of  low 
tension,  but  large  in  quantity ;  by  tension  being  meant  the  tendency 
of  the  electricity  accumulated  at  the  extremities  of  the  electrodes  to  free 
itself. 

1  Dynamics  of  Xerve  and  Muscle,  p.  24.     London,  1871. 


Leyden  jar. 


CHAPTER    XXXIX. 

NEGATIVE  VARIATION.     RAPIDITY  OF  ITS  PROGRESSION. 
ELECTROTONIC  CURRENTS.     ELECTROTONUS. 

However  prevailing  views  may  differ  as  to  the  nature  and  cause  of 
the  electrical  current  present  in  a  cut  nerve  during  a  state  of  rest,  there 
is  no  difference  of  opinion  as  to  the  importance  of  the  fact  already 
alluded  to,  of  the  diminution  or  disappearance  of  the  electrical  current 
of  the  nerve  during  its  momentary  period  of  activity,  or,  as  it  is  usually 
called,  of  the  negative  variation  or  current  of  action,  according  as  the 
diminution  in  the  deflection  of  the  needle  is  regarded  as  being  due  to 
the  diminution  of  a  preexisting  natural  current,  or  of  a  current  of  rest, 
developed  through  the  nervous  tissue  when  injured  becoming  negative 
toward  that  part  of  it  uninjured.  Whether  the  electrical  current  present 
in  a  cut  nerve  during  a  state  of  rest  be  a  natural  or  an  artificial  one, 
preexisting  or  developed  by  injury,  the  fact  remains  the  same,  that 
during  the  activity  of  the  nerve  its  electrical  current  undergoes  a  nega- 
tive variation.     That  the  latter  phenomenon  is  not  simply  an  accidental 

Fig.  387. 


^^ 


Negative  variation. 


one,  but  constitutes  an  essential  feature  of  nervous  action,  is  still  further 
shown  from  the  intensity  of  the  one  varying  with  the  other,  and,  as 
already  mentioned,  from  the  rate  at  which  the  negative  variation  travels 
along  the  nerve  being  the  same  as  that  at  which  the  nerve  force  itself 
is  propagated.  While  the  negative  variation  can  be  shown  by  stimu- 
lating the  nerve  with  a  single  induction  shock  the  phenomenon  becomes 


NEGATIVE    VARIATION, 


597 


much  more  evident  when  the  induction  apparatus  is  used  with  the  auto- 
matic interrupter,  since  the  shocks  thrown  into  the  nerve  succeed  each 
other  then  so  rapidly  that  before  the  galvanometer  needle  can  return  to 
its  first  position,  that  due  to  the  electric  nerve  current  from  which  it 
was  deflected  by  the  negative  variation,  it  is  again  deflected  by  the 
latter,  and  consequently  remains  there  in  one  position,  that  due  to  the 
negative  variation.  Thus,  for  example,  suppose  that  the  transverse 
section  of  the  nerve  iV^be  in  contact  with  one  of  the  diverting  electrodes 
E'  (Fig.  337).  and  the  longitudinal  surface  with  the  other,  and  that 
the  deflection  of  the  magnetic  needle  at  G-,  due  to  the  electrical  current 
of  the  nerve  during  a  state  of  rest  is  perfectly  evident,  amounting  to, 
say  c.  Such  being  the  case,  if  now  the  nerve  iV  be  stimulated  by  the 
induction  apparatus  P  8  (at  such  a  distance  (d)  as  not  to  permit  of  the 
escape  of  the  current  into  the  electrodes  of  the  galvanometer)  the  deflec- 
tion of  the  needle  in  the  reverse  direction  back  toward  zero  0  at  once 
indicates  that  the  electrical  current  of  the  nerve  has  been  diminished, 
has  undergone  a  negative  variation.  If  now  the  experiment  be  so  modi- 
fied (Fig.  338)  that,  while  the  nerve  is  stimulated  in  the  middle  JV,  its 
two  ends  (c  d)  are  in  contact  with  the  electrodes  of  two  galvanometers 


Fic 

;.  338. 

L^  ~J    J> 

S 

Kt 

ar/^~ 

c 

^^ 

— s> 

—  h^ 

f               ^ 

r^    A 

o 

\ 

1 

o 

ipv 

Imi 

G 

\ — y 

Ne 

gatn 

e  variati 

on. 

(6r  G-'),  it  will  be  observed  that  there  is  a  diminution  in  the  electrical 
current  (a — o,  b — o)  of  the  nerve  at  both  ends,  showing  that  the  disturb- 
ance in  the  electrical  condition  of  the  nerve,  whatever  its  nature  may 
be,  is  propagated  in  both  directions,  from  the  centre  or  the  point  of  the 
application  of  the  stimulus :  a  very  important  fact,  since,  if  the  phe- 
nomenon of  the  negative  variation  is  intimately  associated  with  that  of 
the  development  and  propagation  of  nerve  force,  it  proves  that  the  latter 
is  transmitted  from  the  point  of  stimulus,  both  to  the  central  and  periph- 
eral ends  of  the  nerve,  confirming  the  view  already  advanced,  that  the 
nerve  force  is  transmitted  in  both  directions,  which  could  not  be  learned 
obviously  from  the  muscular  contraction,  and  that  the  function  of  a 
nerve  depends,  not  upon  its  intrinsic  structure,  but  whether  it  termi- 
nates in  a  motor,  sensory,  or  glandular  organ. 

By  extending  our  experiments  it  will  be  further  found  that  all  kinds 


598 


NEGATIVE    VARIATION. 


Fig. 339 


Curves  of  nerve  current  and  negative  variation. 


of  nerves  exhibit  the  phenomena  of  negative  variation,  and  that  from 
every  part  of  a  nerve,  during  a  period  of  rest,  an  electrical  current  can 
be  diverted,  and  that  it  is  indifferent  whether  the  central  or  the  periph- 
eral end  of  the  nerve  be  the  excited  or  the  diverting  portion.  Finally, 
that  the  amount  of  the  negative  variation  Y  B,  I  C,  at  the  different  points 
of  the  nerve  N  will  be  always  proportional  to  the  amount  of  the  preex- 
isting nerve  current  Y  A,  I  D,  of  which  it  is  nothing  but  the  diminution 
(Fig.  339),  hence  if  the  former  current  be  absent  there  will  be  naturally, 

therefore,  no  negative  variation. 
Such  is  the  case,  for  example,  if 
the  diverting  electrodes  be  placed 
upon  two  points  of  the  longi- 
tudinal surface  symmetrically 
disposed  with  reference  to  the 
equator,  the  magnetic  needle  not 
being  then  deflected  by  the  nerve 
current,  there  can  be  no  diminu- 
tion of  the  latter  or  negative  va- 
riation. An  interesting  fact  as 
regards  the  phenomenon  of  nega- 
tive variation  is,  that  it  can  not 
only  be  produced  by  artificial 
stimuli,  electrical,  chemical,  ther- 
mal, and  mechanical,  but  by 
natural  ones  inherent  in  the  ner- 
vous system  itself  by  influences  emanating,  for  example,  from  the  spinal 
cord.  Thus,  Du  Bois-Reymond  has  shown  that  if  the  sciatic  nerve  of 
a  living  frog  be  well  exposed,  avoiding,  however,  the  injuring  of  the 
bloodvessels  and  the  origin  of  the  nerve,  the  nerve  cut  through  at 
the  popliteal  space,  the  electrodes  so  disposed  that  the  point  of  one 
is  in  contact  with  the  equator,  and  the  point  of  the  other  with  the  cut 
surface  of  the  nerve,  that  with  the  appearance  of  the  muscular  cramps 
due  to  the  subcutaneous  injection  of  strychnia,  the  electrical  current  of 
the  nerve  will  undergo  a  negative  variation.  The  significance  of  this 
experiment  will  be  better  appreciated,  however,  when  the  subject  of 
reflex  action  has  been  considered ;  since  the  muscular  contraction,  with 
the  accompanying  variation  in  strychnia  poisoning  is  due  to  an  impres- 
sion made  upon  the  skin  and  thence  transmitted  to  the  spinal  cord,  and 
from  that  nervous  centre  reflected  to  the  muscles.  Further,  according 
to  the  same  high  authority  negative  variation  occurs  during  the  tetanus 
brought  about  by  the  mechanical  crushing  of  a  nerve,  or  the  destruction 
of  the  same  by  heat  and  during  tetanus  of  the  sciatic  nerve,  more 
especially  when  induced  by  the  stimulation  of  its  cutaneous  branches. 
It  has  already  been  mentioned  that  the  rapidity  at  which  the  negative 
variation  is  transmitted  is  the  same  as  that  of  the  nerve  force  itself.  This 
was  first  determined  by  Bernstein1  by  means  of  his  differential  rheotome. 
The  principle  of  this  instrument  consists  in  closing  the  circuit  stimulat- 
ing the  nerve  as  well  as  that  diverting  its  natural  current,  by  a  wheel 

1  Untersuchungen  iiber  den  Erreguns  vorgang  im  Nerven— und  Muskel  systeme.     Heidelberg,  1871. 


DIFFERENTIAL    RHEOTOME. 


599 


rotating  at  a  known  rate  and  of  so  disposing  the  two  pairs  of  electrodes 
that  the  stimulating-  circuit  is  closed  before  the  diverting:  one.  The 
interval  of  time  between  the  two  being  determined  from  the  rate  at 
which  the  wheel  is  rotating;,   and  the  negative  variation  being;  trans- 

Fig.  340. 


Bernstein's  differential  rheotome.     Horizontal  view. 


mitted  along  the  nerve  from  the  point  of  the  application  of  the  stimulus 
to  that  of  the  diverting  electrodes,  if  the  deflection  of  the  needle  in  the 
reverse  direction  appears  at  the  moment  that  the  diverting  circuit  is 
closed,  the  rate  at  which  the  negative  variation  has  been  transmitted 
from  the  point  of  stimulation  to  that  of  the  diverting  electrodes  becomes 
at  once  known  :  and  experimentally  it  was  so  found  by  Bernstein  to  be 
the  same  as  that  of  the  rate  of  the  nerve  force  itself,  viz.,  in  the  frog 
twenty -eight  metres  a  second. 

The  differential  rheotome,  somewhat  more  in  detail,  as  made  for  the 
author  by  Zimmerman,  of  Heidelberg,  consists  of  a  wheel  (Fig.  3-40,  W) 
having  a  diameter  of  12.5  cm.  (5  inches)  horizontally  disposed,  whose 
hub  or  axis  (a)  is  elongated  vertically  upward  and  downward,  the 
lower  end  (Fig.  341,  e)  working  in  a  mercury  cup  (m),  the  upper  end  (r) 
in  the  frame,  the  axis  passing  through  a  groved  disk  (d),  serving  for 
the  attachment  of  the  cord  of  the  electro-magnetic  rotation  apparatus  to 
be  described  presently,  by  means  of  which  the  axis  and  the  wheel  are 
uniformly  rotated.  To  the  periphery  of  the  wheel  (Fig.  310)  is  at- 
tached a  brass  piece  (k),  insulated  by  ebonite,  which  carries  the  steel 
pointer  (//),  the  latter  being  elevated  or  depressed  by   the   screw  and 


600 


NEGATIVE    VARIATION*. 
Fig.  341. 


H 


HJ 


Bernstein's  differential  rheutouie      Profile  view. 


Fig.  342. 


Scheme  fur  determining  negative  variation. 


obliquely  disposed,  so  that  the 
upper  part  is  inclined  toward 
the  direction  of  the  motion  of 
the  wheel.  With  each  rota- 
tion of  the  wheel,  contact  is 
made  between  the  pointer  p 
and  the  wire  10  stretched 
across  the  brass  cup  resting 
upon  the  ebonite,  or  instead 
with  a  mercury  cup  not  rep- 
resented in  the  figure,  the 
brass  or  mercury  cup,  which- 
ever is  used,  being  raised  or 
lowered  by  means  of  the 
screw  working  in  the  cylinder 
y.  With  each  contact  of  jo  and 
w  (Figs.  341,  342)  the  stimu- 
lating circuit  is  closed,  the 
current  passing  then  from  the 
battery  B  (Fig"  342)  through 
p  and  iv  to  the  wire  in  the 
spoke  (sp)  at  the  wheel,  and 
alongside  of  the  axis  a  e  back 
to  the  primary  current  and  to 
the  battery,  a  key  (if)  being 
interposed  in  the  secondary 
circuit  (S).  The  opening  and 
closing-  shocks  transmitted  to 
the  nerve  follow  each  other  so 


DIFFERENTIAL    RHEOTOME.  601 

rapidly  that  they  may  be  regarded  as  one  momentary  stimulus.  The 
periphery  of  the  wheel  W  (Fig.  340),  opposite  to  the  brass  box  and  wire 
just  described,  carries  also  an  insulated  bar,  through  which  pass  two 
sharp-pointed  steel  pointers  (pl p2,  Figs.  340,  341)  obliquely  disposed, 
capable  of  being  elevated  and  depressed  by  screws,  which,  as  the  wheel 
rotates,  glide  smoothly  over  the  surface  of  the  mercury  in  the  two  steel 
insulated  cups  c1  c2,  supported  by  the  brass  arms  (q1  <f).  In  order  to 
insure  perfect  contact  with  the  mercury,  the  latter  should  be  pure 
and  renewed  daily,  the  steel  pointers  should  be  also  dipped  every  day 
in  copper  sulphate  solution.  As  the  steel  pointers  glide  over  the  mer- 
cury, the  current  diverted  from  the  nerve  is  then  closed,  the  current 
passing  (Fig.  342)  from  the  non-polarizable  electrode  on  the  longitudinal 
surface  (6),  the  two  binding  screws,  through  the  mercury  cups  (cl  <r)  to 
the  galvanometer  Gr,  Daniell  element,  rheocord  Rh,  back  to  the  other 
electrode  £,  on  the  transverse  surface.  A  key  or  shunt  is  introduced 
in  the  circuit,  and  the  time  of  closing  can  be  varied  by  moving  the 
arms  supporting  the  cups. 

As  the  rapidity  of  the  transmission  of  the  negative  variation  in  the 
nerve  is  determined  from  that  of  the  rotation  of  the  wheel,  it  becomes 
necessary  to  determine  the  latter.  This  is  readily  accomplished  by 
counting  the  number  of  turns  made  by  the  marked  thread  connecting 
the  wheel  and  the  rotation  apparatus  and  the  number  of  rotations  of  the 
wheel  corresponding  to  each  turn  of  the  thread,  the  latter  being  best 
done  by  so  placing  the  point  p  that  a  sound  is  made  each  time  it  comes 
in  contact  with  the  wire  w.  The  wheel  being  slowly  rotated,  the 
number  of  contacts  between  p  and  w  are  determined,  corresponding  to, 
say.  five  turns  of  the  thread  ;  this  number  being  divided  by  five  will  then 
give  the  number  corresponding  to  one  turn,  and  so  of  the  rapidity  of 
rotation  of  the  wheel,  amounting  in  our  experiments  to  five  rotations  in 
one  second. 

It  will  be  seen  in  a  moment  that  it  is  not  only  essential  that  the 
number  of  rotations  made  by  the  wheel  in  a  given  time  should  be 
known,  but  that  it  is  also  necessary  to  determine  the  time  during  which 
the  needle  is  deflected  by  the  natural  nerve  current,  and  the  interval  of 
time  intervening  between  the  contact  of  p  and  w,  and  the  closing  and 
opening  of  the  diverting  circuit.  In  order  to  accomplish  this,  the 
position  of  the  box  across  which  the  wire  w  is  stretched  must  be  varied 
by  sliding  the  brass  piece  supporting  it  along  the  periphery  of  the  disk 
situated  under  the  wheel,  the  distance  through  which  it  is  moved  by 
the  screw  being  determined  by  means  of  the  scale  and  vernier  on  the 
periphery  of  the  disk,  the  scale  being  divided  into  hundredths,  the 
vernier  into  thousandths.  In  order  to  determine  the  short  interval  of 
time  during  which  the  diverting  circuit  is  closed,  the  pointer  jt?  is  firmly 
clamped  against  the  wire  w,  so  that  the  wheel  follows  the  motion  of  the 
screw.  As  soon  as  a  deflection  of  the  galvanometer  needle,  due  to  the 
diverting  current,  becomes  apparent,  the  position  of  the  slider  is  read 
off  bv  the  vernier,  which  we  will  call  S' ;  continuing  to  turn  the  wheel 
slowly  onward,  the  needle  will  return  to  rest,  and  the  position  of  the 
slider  then,  or  S;/,  is  read  off,  the  rate  of  rotation  of  the  wheel  R  being 
also  known,  the  time  required  will  be  given  by  the  equation  t=(S' — Srf)R. 


602 


NEGATIVE    VARIATION. 


Thus,  suppose  that  S'  =  0.9370,  S"  =  0.9254,  and  R  =  £th  sec, 
then  t,  or  the  time  during  which  the  diverting  circuit  is  closed,  will 
amount  to  0.00232  sec,  t  =  0.0116  X  1-th  sec.  =  0.00232  sec  In 
reading  oft'  Sr  and  S"  it  must  be  remembered  that  each  division  of  the 
scale  corresponds  to  the  yfni^1  °f  tne  distance  traversed  by  the  wheel 
during  a  single  rotation,  each  division  of  the  vernier  to  the  yoVotli  part, 
and  that  the  numbers  on  the  scale  run  in  the  opposite  direction  to  that  of 
the  motion  of  the  wheel.  Further,  that  the  time  during  which  the  divert- 
ing circuit  is  closed  will  vary  according  to  the  position  of  the  mercury 
cups  toward  each  other.  The  interval  of  time  T  elapsing  between  the  con- 
tact of  p  and  w  and  the  contact  of  the  pointers  with  the  mercury  cups, 
or  the  breaking  of  the  contact  with  the  same,  is  determined  in  the  fol- 
lowing manner.  Let  us  suppose  that  the  position  of  the  slider  be  as  in 
the  preceding  experiment  at  0.9254  of  the  scale — that  is,  that  the 
pointers  at  this  instant  leave  the  mercury  cups.  No  modification  of 
the  natural  electrical  current  by  the  stimulus  can  then  be  expected, 
since  the  diverting  circuit  remains  open  during  an  interval  of  time 
almost  equal  to  that  of  a  complete  rotation  of  the  wheel.  Pushing, 
however,  the  slider  along,  and  observing  a  deflection  of  the  magnetic 
needle,  the  slider  being  at  0.9500,  then  0.9254—0.9500  =  0.0246  X 
•Jth  sec.  =  0.0492  sec.  will  be  the  time  required.  In  the  same  manner 
the  time  elapsing  between  the  contact  of  p  and  w,  and  the  contact  of 
the  pointers  with  the  mercury  cups,  can  be  determined.  It  will  be 
observed  from  Fig.  342  that  the  natural  nerve  current  is  compensated 
by  means   of  the  Daniell's  element  and  rheocord,  the  magnetic  needles 


Fig.  843. 


The  rheocord.     (Sanderson.) 


remaining  at  zero,  except  during  the  moment  that  the  negative  varia- 
tion takes  place,  the  nerve  current  being  then  diminished  the  magnetic 
needle  will  move  in  a,  direction  due  to  the  current  from  the  Daniell's 
cell — that  is,  in  a  direction  opposite  to  that  which  would  be  due  to 
the  nerve  current  acting  alone.  The  object  of  so  compensating  the 
nerve  current  in  the  study  of  its  negative  variation  by  means  of  the 
differential  rheotome  is  that  the  movement  of  the  needle  should  always 
begin  at  the  same  point,  viz.,  zero.  It  will  be  noticed,  however,  that 
the  rheocord  used — that  of  Du  Bois-Reymond — differs  in  its  form  from 
that  previously  described,  though  the  latter,  for  the  present  purpose, 


RHEOCORD.  603 

might  have  been  just  as  well  used.  The  rheocord  as  made  for  the 
author  by  Elliot,  of  London  (Fig.  343),  consists  of  a  long  box,  at  the 
edge  of  which  are  stretched  two  platinum  wires  w  >c\  passing  through 
the  connected  mercury  cups  m  m,  which  can  be  pushed  to  the  other  end 
of  the  box  along  the  scale  graduated  in  millimetres  at  the  side.  When 
the  mercury  cups  are  directly  in  contact  with  the  brass  a,  the  resistance 
offered  by  the  rheocord  to  the  Daniell's  circuit  is  practically  nothing  as 
compared  with  that  offered  by  the  nervous  circuit,  consequently  the  cur- 
rent from  the  Daniell's  element  simply  passes  through  the  rheocord  back 
to  the  cell,  none  being  diverted  into  the  nervous  circuit.  If,  however,  the 
mercury  cups  be  pushed  away  from  the  brass  along  the  platinum  wires, 
the  wires  offering  a  resistance,  the  amount  indicated  by  the  scale, 
358  mm.  =  1  ohm,  and  there  being  no  passage  for  the  current  from  one 
side  of  the  rheocord  to  the  other,  except  through  the  parts  of  the  wires 
lying  between  the  mercury  cups  and  the  brass,  it  follows  that  a  pro- 
portional part  of  the  total  current  from  the  Daniell's  element  is  thrown 
into  the  nervous  circuit. 

If  a  greater  amount  of  resistance  is  needed  than  that  obtained  by 
pushing  the  mercury  cups  through  the  whole  length  of  the  platinum 
wires,  then  the  plugs  lettered  b,  c,  d,  e,  /,  g,  or  numbered,  can  be  drawn 
out,  these  being  multiples  of  the  resistance  offered  by  the  total  length 
of  the  platinum  wires  traversed  by  the  mercury  cups,  the  amount  of 
current  thrown  into  the  nervous  circuit  will  be  then  proportionally 
increased.  Thus,  for  example,  if  the  plug  5,  letter  </,  be  withdrawn, 
then  the  amount  of  current  thrown  into  the  nerve  will  be  five  times 
as  great  as  when  the  mercury  cups  were  at  the  end  of  the  wire,  and  so 
proportionally  for  the  remaining  plugs.  In  fact,  the  rheocord  is  a  form 
of  resistance  box,  such  as  already  described.  The  stimulus  made  use 
of  to  excite  the  nerve  in  the  study  of  the  negative  variation  is  the 
induction  apparatus  supplied  by  six  to  eight  small  Grove  or  Bunsen 
cells  (B,  Fig.  342),  but  it  is  better,  according  to  Bernstein,1  that  the 
magnetic  core  of  the  primary  spiral  be  withdrawn  so  that  the  mag- 
netization and  demagnetization  of  the  same  do  not  retard  the  course 
of  the  secondary  induced  current.  Under  these  circumstances,  the 
opening  shock  being  more  intense,  but  not  lasting  as  long  as  the  closing 
one,  if  the  current  used  be  strong,  electrotonic  currents  appear,  which 
modify  the  negative  variation.  Such  currents,  however,  can  be 
avoided  by  making  the  course  of  the  two  induced  currents  approxi- 
mately equal,  which  Bernstein  accomplished  by  intercalating  in  the 
primary  circuit  a  short  circuit  consisting  of  twro  copper  plates  dipping  in 
copper  sulphate  solution  (not  represented  in  Fig.  344).  The  significance 
of  what  has  just  been  said  with  reference  to  the  production  of  electro- 
tonic  currents,  and  of  the  modification  of  the  negative  variation  by  the 
same,  will  be  appreciated  when  the  subject  of  electrotonus  has  been 
considered. 

The  wheel  of  the  differential  rheotome,  as  has  already  been  men- 
tioned, is  uniformly  rotated  by  the  electromagnetic  rotation  apparatus 
of  Helmholtz  (Fig.    344,    E).      The    latter    consists  of  four    electro- 

1  Op.  cit.,  S.  16. 


604 


NEGATIVE    VARIATION. 


magnets,  the  two  external  ones  (X  Y)  immovable,  the  two  internal 
ones  (UK)  movable  ;  the  latter  are  fixed  to  the  axis  by  their  dissimilar 
poles,  and  are  supplied  by  three  Daniell's  elements,  the  external  ones  by 
one.  As  the  two  internal  magnets  are  repelled  by  the  external  ones,  the 
axis  is  rotated,  and  with  it  the  wheel  (  /'),  through  which  it  passes,  and 


RATE     OF    PROPAGATION    OF    NEGATIVE    VARIATION.    605 

around  which  passes  the  thread  from  the  disk  of  the  rheotome.  Having 
described  now  the  rheotome  of  Bernstein,  with  the  accessories,  and  the 
manner  in  which  it  is  used,  let  us  consider  how  by  means  of  it  the  rapidity, 
duration,  etc.,  of  the  negative  variation  are  determined.  '  In  order  to 
determine  the  rapidity  of  the  transmission  of  the  negative  variation. 
let  us  begin  the  experiment  by  so  arranging  the  slider  that  contact 
is  made  between  P  and  TF,  at  division  1  of  the  scale  at  the  moment 
that  the  diverting  circuit  is  opened — that  is.  at  the  instant  the  pointers 
pxp2  leave  the  mercury  cups  c1  <■'-.  As  the  time  elapsing  before  the 
diverting  current  is  again  closed  is  then  almost  equal  to  one  entire 
rotation  of  the  wheel,  no  deviation  of  the  magnetic  needle  occurs,  since, 
though  the  nerve  current  be  diminished,  the  needle  will  give  no  evidence 
of  it,  the  diverting;  current  not  having  been  closed  in  time.  Let  us 
now  push  the  slider  along  the  scale  to  the  division  2 — that  is,  over  the 
yJj-jjth  of  the  circumference,  and  suppose  that  the  needle  begins  to  be 
deflected  through  the  commencing  diminution  of  the  nerve  current, 
then,  as  the  interval  of  time  elapsing  between  the  application  of  the 
stimulus  to  the  nerve  at  a  (Fig.  342),  through  the  contact  of  P  and 
IT.  and  the  beginning  of  the  negative  variation  at  b — that  is,  the  time 
during  which  the  negative  variation  is  transmitted  through  the  nerve 
from  a  to  b — is  the  same  interval  of  time  during  which  the  wheel  moves 
from  division  2  to  1,  carrying  the  pointer  from  A  to  B,  equal  to  0.01  X 
\  sec.  or  x^otn  sec-  Co  sec-  being  the  rate  of  rotation  of  the  wheel),  it 
follows  that  the  negative  variation  must  have  travelled  along  the 
nerve  from  the  point  stimulated  (a),  to  the  point  from  which  the  current 
was  diverted  (b),  a  distance  of  5  cm.,  or  2  inches,  at  the  same  rate,  viz., 
-g-J-g-  sec.  or  on  an  average,  according  to  Bernstein,1  of  about  25.8, 
2?. 7  metres  a  second,  the  rate  of  propagation  of  the  nerve  force  itself. 
At  first  sight,  as  an  objection  to  the  conclusion  just  reached,  it  might 
be  urged  that  an  interval  of  time  may  elapse  between  the  application  of 
the  stimulus  and  the  beginning  of  the  negative  variation  at  the  point 
stimulated.  That  no  such  latent  period,  so  to  speak,  however  exists, 
at  least  as  determined  by  present  means  of  investigation,  can  be  shown 
by  first  stimulating  the  nerve  at  some  distance  from  the  diverting  elec- 
trodes, and  then  near  the  latter,  the  difference  in  the  time  of  the  trans- 
mission of  the  negative  variation  depending  upon  the  length  of  the 
nerve  traversed.  Although  the  phenomenon  of  the  negative  variation  is 
a  momentary  one,  it  occupies  a  sufficiently  large  interval  of  time  to  be 
measurable  by  the  rheotome.  Thus,  for  example,  suppose  that  when 
the  negative  variation  begins  the  slider  is  at  a  position  that  we  will 
call  Se,  and  when  it  ends  that  the  latter  is  at  Sa,  and  the  time  of 
closing  the  nerve  circuit  be  called  t,  and  the  rate  of  the  rotation  of  the 
wheel  P,  then  the  formula  (Se — Sa — t)  R  will  give  the  duration  of  the 
negative  variation,  which  Bernstein2  finds,  on  an  average,  amounts  to 
0.0006759  sec. ;  or,  let  us  suppose  that  the  slider  is  at  a  position  Se, 
when  the  negative  variation  ends,  and  that  S'  be  the  position  of  the 
slider  at  the  moment  of  contact  p  and  w,  then  (Se — S7)  P  will  be  the 
interval  of  time  elapsing  between  the  moment  of  stimulation  and  the 

1  Op.  cit.,  S.  22.  *  Idem.,  S.  2 


606 


NEGATIVE    VARIATION. 


end  of  tlie  negative  variation,  while  if  by  /  we  denote  the  time  during 
which  the  nerve  force  is  propagated  from  the  spot  stimulated  to  the 
first  diverting  electrode,  then  the  formula  Se — s'  R — t  will  give  the 
duration  of  'the  negative  variation,  which  obtained  by  this  method 
amounts,  according  to  Bernstein,2  to  0.0007026  sec.,  and  which  value 
does  not  differ  very  much  from  the  value  obtained  by  the  preceding 
method.  In  observing  the  phenomenon  of  the  negative  variation,  as 
just  described,  from  its  beginning  to  its  end  it  cannot  fail  to  be  observed, 
if  the  slider  be  pushed  very  gradually  along  that  it  attains  its  maximum 
and  minimum  limits  very  gradually.  Thus,  suppose  that  when  the 
slider  is  at  0.9555  the  negative  variation  begins,  it  is  not  until  the 
slider  passes  from  0.960  to  0.980  that  the  maximum  intensity  is 
attained,  and  until  it  has  reached  0.0994  that  it  entirely  disappears. 
In  other  words,  the  negative  variation  propagates  itself  in  the  form  of 
a  wave,  and  it  remains  for  us  now  to  explain  how  such  a  wave  can  be 
graphically  represented,  and  its  length  estimated. 

Let  the  abscissa,  t'  T'  (Fig.  345)  represent  the  time  of  one  entire  rota- 
tion of  the  wheel,  and  the  ordinate  t  T  the  deviation  of  the  magnetic 

Fig.  345. 


Graphic  representation  of  distance  and  length  of  the  negative  variation. 

needle  due  to  the  natural  nerve  current,  then  T  T'  will  represent  the 
condition  of  that  nerve  current  during  that  time,  supposing  its  inten- 
sity remains  unaltered.  Let  us  suppose,  also,  that  at  the  moment  {t) 
the  nerve  is  stimulated,  the  negative  variation  begins  at  a,  then  the 
period  intervening  between  the  application  of  the  stimulus  at  t  and 
the  beginning  of  the  negative  variation  at  a — that  is,  the  time  during 
which  the  negative  variation  has  travelled  through  the  part  of  the  nerve 
intervening  between  the  stimulating  and  diverting  electrodes — will  be 
represented  by  t  S2,  82  being  the  moment  of  the  closing  of  the  diverting 
circuit.  Further,  let  us  suppose  that  the  negative  variation  beginning 
at  a,  attains  a  maximum  at  6,  and  disappears  again  at  c,  the  slider 
having  been  pushed  along,  as  already  described  ;  if  the  deviation  of  the 
magnetic  needle  occurring  between  the  moments  a  and  c,  represented 
by  ordinates  drawn  downward  from  T  T',  then  we  will  obtain  a  curve 
a  d  c,  the  graphic  representation  of  the  negative  variation  as  it  passes 
over  a  given  portion  of  the  nerve,  and  which,  as  may  be  seen,  while 
falling  suddenly,  rises  rather  slowly  again  to  the  line  T  T' .  It  should 
be  mentioned,  with  reference  to  this  curve,  that  while,  according  to 


1  Op.  cit.,  S.  25. 


WAVE    OF    NEGATIVE    VARIATION.  607 

Bernstein,1  its  lowest  point  (d)  may  lie  either  above,  on,  or  even  below 
the  abscissa  line ;  according  to  Funke2  the  lowest  part  of  the  curve 
may  reach  the  abscissa,  hut  never  falls  below  it.  On  account  of  the 
wave  of  the  negative  variation  being  due  to  that  stimulus,  which,  in  a 
nerve,  gives  rise  to  sensation,  muscular  contraction,  etc.,  it  may  be 
called,  as  by  Bernstein,  the  stimulus  wave.  Finally,  if  it  be  admitted 
that  the  duration  of  the  negative  variation  represented  in  Fig.  367  by 
a  c,  be  equal  to  0.0006-0.0007  sec,  and  that  the  negative  variation 
travels  at  the  rate  of  28  metres  a  second,  evidently  then  the  length  of 
the  wave  a  c  will  be  equal  to  0.0006-0.0007  of  28  metres=16-18  mm. 
Further,  if  it  be  supposed  that  while  the  negative  variation  travels  at 
the  rate  of  28  metres  a  second,  that  during  the  same  period  of  time  the 
nerve  be  stimulated  28  times,  then  a  nerve  28  metres  long  would 
exhibit  at  the  end  of  the  second  28  waves  of  negative  variation,  each 
wave  being  separated  by  an  interval  of  1  metre  (Fig.  346).     The  exact 

Fro.  346. 


i-rn^U  7?yie6. 

Waves  of  negative  variation. 

limits  of  the  wave  are  readily  determined  by  the  rheotome,  since,  by 
employing  a  series  of  rotations,  we  get  the  effect  of  the  summation  of  a 
series  of  stimuli,  instead  of  that  due  to  a  single  one.  In  the  latter  case 
the  indications  are  not  sufficiently  delicate  to  define  the  beginning  and 
end  of  the  wave.  While  in  the  present  state  of  our  knowledge  of  the 
nervous  system  it  may  be  premature  to  draw  any  very  positive  conclu- 
sion as  to  the  nature  of  the  negative  variation,  nevertheless,  from  what 
has  just  been  learned  by  the  rheotome,  of  the  negative  variation  being 
produced  by  opening  and  closing  periodical  shocks  following  each  other 
not  too  rapidly,  of  being  propagated  in  the  form  of  a  wave,  of  having 
a  definite  duration,  there  can  be  but  little  doubt  that  the  change  under- 
gone by  the  nerve  during  the  negative  variation  is  vibratory  molecular 
in  character  similar  to  the  propagation  of  water  waves,  of  sound  waves 
in  air,  of  light  waves  in  ether. 

With  this  difference,  however,  that  in  the  case  of  the  negative  varia- 
tion wave  coincidently  with  the  vibratory  motion  of  the  nerve  mole- 
cules, chemical  modifications  of  the  substance  of  the  same  are  going  on 
which  are  wanting  during  the  propagation  of  sound  and  light  waves. 
Further,  the  electrical  condition  of  the  nerve  during  its  phase  of  nega- 
tive variation  becomes  intelligible  if  we  assume  that  every  part  of  the 
longitudinal  surface  of  the  nerve  becomes  successively  negative  with 
reference  to  the  preceding  point  that  has  just  undergone  the  negative 
variation,  and  to  the  succeeding  one  still  to  undergo  it.  Such  an  elec- 
trical condition    can  be   accounted  for  by  supposing  that  during  the 

i  Or.  fit.,  S.  33.  -  Thysiologie,  Band  i.  S.  509. 


608  NEGATIVE    VARIATION. 

negative  variation  the  electromotive  force  and  the  resistance  are  both 
diminished.  As  a  matter  of  fact,  the  latter  has  been  proved  to  be  ex- 
perimentally the  case1  and  as  a  more  perfect  closure  of  the  nerve  circuit 
is  then  effected  a  partial  current  correspondingly  weakened  will  pass 
through  the  diverting  electrodes,  while  from  the  chemical  changes  going 
on  in  the  active  nerve  it  is  a  reasonable  inference  to  suppose  that  its 
electromotive  force  is  also  modified.  Finally,  whatever  view  may  be 
be  taken  of  the  electrical  condition  of  the  nerve  during  the  negative 
variation,  or  its  cause,  the  conclusion  seems  unavoidable  that  the  dimi- 
nution of  the  natural  nerve  current  during  the'  activity  of  the  nerve, 
its  negative  variation  or  stimulus  wave  whether  produced  by  electrical, 
chemical,  thermal,  or  mechanical  stimuli,  is  that  which  excites  the 
muscle  to  contract,  the  gland  to  secrete,  the  organ  to  feel. 

Up  to  the  present  moment,  in  exciting  the  nerve  by  electrical  stimuli 
we  have  made  use  of  single  or  repeated  induction  shocks,  and  this  not  only 
for  convenience'  sake,  but  especially  on  account  of  the  short  duration  of 
induced  currents,  the  object  in  view  being  the  avoidance  of  the  considera- 
tion of  the  changes  undergone  by  the  nerve  during  the  passage  of  a  con- 
stant current,  and  which,  had  they  been  present,  would  have  rendered  the 
explanation  of  the  changes  due  to  the  induced  current  a  more  difficult 
one.  Such  changes  as  are  induced  in  the  condition  of  a  nerve  through 
the  passage  of  a  constant  current  passing  directly  to  the  nerve  without 
the  intervention  of  an  induction  apparatus  can  now,  however,  be  con- 
veniently considered.  Let  us  suppose,  then,  that  N  (Fig.  347)  repre- 
sents a  nerve,  and  that  through  the  deviation  of  the  magnets  of  the 
galvanometers  G-Gr'  we  learn  that  the  natural  electrical  nerve  currents 
are  present,  passing  from  the  longitudinal  surface  through  the  galva- 
nometers to  the  transverse  cut  surface  of  the  nerve,  through  the  nerve  to 
the  longitudinal  surface  again  in  the  direction  indicated  by  the  arrows. 
Let  now  the  nerve  N  be  stimulated  through  the  non-polarizable  elec- 
trodes f  jp'  at  a  point  intermediate  between  its  ends,  b,  by  means  of  a 
constant  current,  say,  from  a  Daniell's  element,  and  which  we  will  here- 
after designate  as  the  polarizing  current,  the  deflection  of  the  galva- 
nometer needles  in  the  reverse  direction  toward  zero  will  show  that  the 
natural  electrical  nerve  currents  have  both  been  diminished,  the  nega- 
tive variation  travelling  as  already  mentioned  in  both  directions  along 
the  nerve  from  the  point  stimulated,  and  giving  rise  to  a  contraction  of 
the  muscle  if  the  latter  were  still  attached  to  one  end  of  it.  The 
negative  variation  lasting,  however,  as  we  have  seen,  but  a  very  short 
time,  having  come  and  gone  in  the  interval  of  the  0.0007  of  a  second 
is  but  a  very  transitory  phenomenon  ;  the  magnetic  needles  should 
therefore  at  once  return  to  the  position  they  occupied  before  the  deflec- 
tion due  to  the  diminution  of  the  natural  electrical  nerve  current. 
Such,  however,  is  not  the  case,  since,  as  shown  by  the  deviation  of  the 
needles,  the  current  passing  through  the  galvanometer  Gr  is  diminished 
(c),  that  through  &'  increased  (d).  It  is  evident,  therefore,  that  the 
electrical  condition  of  the  nerve  is  not  only  modified  temporarily  by  the 
momentary  stimulus  of  the   constant  current,  the  negative  variation, 

1  Gruenhagen :  Zeits.  fur  Rat.  Med  ,  iii.  R.,  1869,  Band  xxxvi.  S.  132. 


EFFECT    OF    CONSTANT    CUEEENT. 


609 


but  permanently  also  during  the  passage  of  the  current  through  the 
nerve  in  the  modification  of  its  electrical  condition  in  the  manner  just 
mentioned.     It  will  be  observed  from  an  inspection  of  Fig.  347,  that 


Pig.  347. 


a-\-      J> 


rc^ 


JV 


Anelectrotonic  and  katelectrotonic  currents. 


the  polarizing  current  is  direct — that  is,  as  it  passes  through  the  nerve 
from  the  anode  a,  or  positive  pole,  to  the  kathode  k,  or  negative  pole, 
it  flows  in  the  same  direction  as  the  nerve  force  itself.  Now  if  it  be 
assumed  that  the  polarizing  current  develops  outside  of  the  electrodes 
p  p\  a  new  current,  the  electrotonic  current,  having  the  same  direc- 
tion as  itself,  it  is  evident  that  the  increasing  or  diminishing  of  the 
natural  nerve  current  by  the  electrotonic  current,  according  as  the  latter 
is  flowing  in  the  same  or  in  the  opposite  direction,  will  account  for 
the  difference  in  the  electrical  condition  of  the  nerve  outside  of  the 
anode  a,  and  kathode  Jc,  the  former  being  positively,  the  latter  nega- 
tively, electrified.  Such  being  the  case,  we  may  call  that  part  of  the 
electrotonic  current  increasing  the  natural  nerve  current  the  anelectro- 
tonic, that  diminishing  the  same  the  katelectrotonic  current,  indicating 
the  electrical  conditions  of  the  two  currents  respectively  bv  the  sio-ns 
plus  +  and  minus  — .  If  now  the  position  of  the  two  electrodes  p  p' 
be  reversed  so  that  the  polarizing  current  flows  through  the  nerve  in 
the  opposite  direction  to  that  of  the  nerve  force,  then  the  anelectrotonic 
current  will  be  developed  atj?,  the  katelectrotonic  atj!?,  and  the  current 
passing  through  the  galvanometer  G-  will  be  increased,  that  through 
the  galvanometer  Cr'  diminished.  It  will  be  observed,  therefore,  that 
the  anelectrotonic  and  katelectrotonic  condition  just  described  will  de- 
pend upon  the  fact  of  the  polarizing  current  passing  through  the  nerve 
in  the  direct  or  reverse  direction.    In  either  instance,  when  the  polarizino- 

39 


G10 


NEGATIVE    VARIATION. 


current  is  broken  the  natural  nerve  current  previously  diminished 
or  increased  is  for  a  brief  moment  increased  or  diminished.  While 
there  can  be  no  doubt  as  to  the  existence  of  the  anelectrotonic  or  kat- 
electrotonic  currents,  and  that  the  same  spread  along  the  extrapolar 
portions  of  the  nerve  from  the  anode  and  kathode,  respectively,  with  a 
gradual  diminution  in  intensity,  there  is  some  doubt  as  to  what  extent 
if  at  all,  the  intrapolar  current  is  similarly  affected.  By  varying  the 
strength  of  the  polarizing  current  it  will  be  found  that  the  strength  of 
the  electrotonic  currents  depends  upon  that  of  the  polarizing  current 
and  of  the  length  of  the  intrapolar  portion  of  the  nerve  exposed  to  the 
latter,  and  of  the  irritability  of  the  nerve,  a  dead  nerve  not  exhibiting 
the  electrotonic  current. 

Finally,  the  electrotonic  currents  undergo  a  negative  variation  dur- 
ing the  passage  of  the  nervous  impulse.  Of  the  electrotonic  currents 
developed,  the  anelectrotonic  portion  differs  from  the  katelectrotonic, 
not  only  in  being  positively  electrified,  but  in  being  greater  and  attain- 
ing its  maximum  and  minimum  more  slowly  (Fig.  348).     Further,  while 

Fig.  348. 


Graphic  representation  of  anelectrotonic  and  katelectrotonic  currents. 

according  to  Du  Bois-Reymond,1  the  electromotive  force  of  the  electro- 
tonic current  amounts  to  0.5  of  a  Daniell,  that  of  the  katelectrotonic 
current  0.05  D.  While  the  electrotonic  currents  just  described  are 
without  doubt  produced  by  the  polarizing  current,  there  is  still  some 
difference  of  opinion  among  physiologists  as  to  whether  these  currents 
are  due  to  some  especial  modification  of  the  electromotive  condition  of 
the  nerve,  which,  like  the  negative  variation,  is  transmitted  from  the 
point  stimulated  through  the  nerve,  from  molecule  to  molecule,  or  are 
due  to  the  direct  effect  of  the  polarizing  current  through  an  escape  of  the 
latter,  from  the  electrodes  along  the  extra-polar  portions  of  the  nerve. 
The  grounds  which  induced  Du  Bois-Reymond2  to  suggest  the  former  or 
molecular  view  are,  for  example,  the  alleged  absence  of  electrotonic 
currents,  if  the  nerve  be  ligated  at  a  point  intervening  between  the 
polarizing  and  diverting  electrodes,  or  if  it  be  divided  and  the  two  cut 
ends  subsequently  brought  in  close  contact,  or  if  a  moistened  thread  be 
substituted  for  the  nerve  in  the  experiment  described  at  p.  609,  and 
illustrated  by  Fig.  347,  which  ought  not  to  be  the  case  if  the  elec- 
trotonic current  is  simply  an  escape  of  the  polarizing  one.  Du  Bois- 
Reymond,  therefore,    considers,    according   to  his    view  of  the  nerve 

1  Gesammt.  Abhandl.,  ii.  S.  260. 

2  Uutersuchungeu  iiber  Tkierische  Electricitiit,  Berlin,  1848-C0. 


ELECTROMOTIVE    MOLECULES, 


611 


consisting  of  electromotive  molecules  (Fig.  349),  that  the  effect  of  the 
polarizing  current  is  so  to  modify  the  position  of  these  molecules  that 
their  opposite  poles  are  brought  to  face  each  other  as  in  Fig.  350,  the 


+ 


effect  being  then  that  all  the  currents  have  the  same  direction — that  is, 
an  electrotonic  current  is  developed.    The  modification  in  the  position  of 

Fig.  350. 
D 


+ 


Modification  of  molecular  conditions  of  nerve  by  passage  of  constant  current. 

the  molecules  a,  c,  e,  the  direction  of  whose  currents  is  opposed  to  that 
of  the  polarizing  current,  supposing  the  latter  to  be  direct,  as  in  Fig. 
349,  is  attributed  to  an  electrolysis,  similar  to  that  produced  by  trans- 
mitting an  electric  current  through  water,  with  this  difference,  however, 
that  the  electrifying  influence  extends  itself  beyond  the  electrodes,  with- 
out which  assumption  it  would  be  impossible  to  explain  the  existence  of 
the  anelectrotonic  and  katelectrotonic  currents.  Further,  in  order  to 
account  for  the  strength  of  the  electrotonic  current  depending  upon  that 
of  the  polarizing  one,  Du  Bois-Reymond  supposes  that  of  the  numerous 
molecules  of  which  the  nerve  consists  either  with  a  weak  current  only  a 
few  of  them  are  turned,  or  that  all  are  turned,  but  only  more  or  less 
imperfectly.  On  the  other  hand,  it  is  argued  by  Matteuci,1  Gruenhagen,2 
and  Hermann,3  that    the    electrotonic  currents  can  only  be  produced 


1  Oomptes  RenduS,  1863,  lvi.  p.  700  ;  1807,  lxv.  pp.  151,  191, 

2  Fuuke  :  Physiologie,  Zweiter  Baud  i.  S.  495. 


:;  18R8,  Ixvi.  p.  580. 
3  Physiologie,  Zweiter  Band,  S.  174. 


612  NEGATIVE     VARIATION. 

by  electrical  ones  and  not  by  other  nerve  stimulants,  such  as  heat, 
chemical  agents,  etc.,  which  oughl  not  to  be  the  case,  if  the  electro- 
tonic  currents  be  due  to  an  essential  modification  of  the  electrical  con- 
dition of  the  nerve  molecules;  further,  that  if  a  moistened  thread  so 
prepared  as  really  to  resemble  nerve  structure  be  substituted  for  the 
nerve  of  Fig.  847,  electrotonic  currents  will  be  developed,  and  the 
fact  that  the  ligation  or  division  of  a  nerve  interferes  with  the  pro- 
duction of  electrotonic  currents  does  not  necessarily  imply  that  the 
electrotonic  current  is  transmitted  from  molecule  to  molecule,  and 
is  inconsistent  with  the  view  that  its  production  is  due  to  the  polar- 
izing current,  since  the  ligation  or  dividing  the  nerve  may  destroy  a 
portion  of  it  essential  in  the  development  of  electrotonic  currents  through 
a  polarizing  one.  In  other  words,  the  vitality,  or,  better,  the  continuity 
of  the  nerve  may  be  as  an  indispensable  condition  in  the  production  of 
electrotonic  currents,  whatever  view  may  be  taken  of  their  origin. 

It  has  already  been  mentioned  that  one  of  the  objections  to  the  view 
of  the  electrotonic  current  being  the  direct  effect  of  the  polarizing  one, 
is  the  fact  of  a  moistened  silk  thread,  when  traversed  by  a  current, 
not  exhibiting,  like  a  nerve,  electrotonic  currents,  which  ought  to  be  the 
case  if  the  phenomenon  is  due  simply  to  the  escape  of  the  electrical 
current,  and  not  to  a  physiological  modification  generated  and  trans- 
mitted through  the  nerve.  Now  while  it  is  true  that  when  a  moistened 
silk  thread  of  small  transverse  section  is  substituted  for  the  nerve,  the 
galvanometer  gives  no  evidence  of  electrical  currents,  it  does  not,  how- 
ever, follow  that  such  currents  are  not  developed  in  the  thread  by  the 
polarizing  current ;  on  the  contrary,  from  the  presence  of  electrical 
currents  in  threads  of  large  transverse  section  we  infer  that  they  are 
also  developed  in  threads  of  small  transverse  section,  even  though  the 
galvanometer  gives  no  evidence  of  such.  The  reason  of  this  becomes 
clear  from  an  inspection  of  Fig.  351,  representing  a  moistened  silk 
thread  of  large  transverse  section  traversed  through  a  portion  of  its 
extent  by  a  polarizing  current.  The  latter,  on  arriving  at  the  positive 
pole  or  anode  (a)  divides  into  two  brandies,  one  of  which  returns  at 
once  through  the  intrapolar  portion  of  the  nerve  to  the  negative  pole 
or  kathode  (&),  and  so  back  to  the  Daniell's  element ;  the  other,  on 
the  contrary,  spreads  outwardly  from  the  anode  as  the  leaving  current 
(e),  and  after  traversing  the  diverting  circuit,  and  deflecting  the  gal- 
vanometer ((x),  returns  as  the  returning  current  (r)  to  the  kathode, 
and  so  to  the  Daniell's  element.  It  will  be  observed,  however,  from 
Fig.  351,  that  according  as  the  diverting  electrodes  Cr  Gf'  are  dis- 
posed with  reference  to  the  leaving  or  returning  currents,  they  change 
their  sign  as  at  c  b,  the  diverting  electrode  c  lying  nearest  to  the  stimu- 
lating electrode  a,  assuming  the  electrical  condition  corresponding  to 
that  electrode,  that  at  b  the  electrical  condition  corresponding  to  K. 
Now  it  is  obvious,  that  if  the  silk  thread  have  a  very  small  transverse 
section,  the  leaving  or  returning  currents  lie  then  so  closely  together, 
that  in  being  diverted  into  the  galvanometer,  they  neutralize  each  other, 
and  exercise  no  influence  upon  the  magnetic  needle.  It  becomes 
perfectly  clear,  therefore,  why  moist  conductors  of  small  transverse 
section  traversed  by  a  polarizing  current  exhibit  no  electrical  currents 


PASSAGE    OF    ELECTRICAL    CURRENT,    ETC. 


613 


in  the  extrapolar  portions  of  the  nerve.  Now  a  nerve  differs  essen- 
tially from  such  a  moist  conductor  not  only  in  exhibiting  electrotonic 
currents  when  traversed  by  a  polarizing  one,  even  though  presenting 
a  small  transverse  section,  but  also  that  these  currents  have  the  same 


Fig.  351. 


D 


Passage  of  electrical  current  in  moistened  silk  thread. 

sign  whether  the  diverting  electrodes  be  placed  upon  the  same  side  of 
the  nerve  as  the  stimulating  electrodes,  or  the  opposite  side,  as  at  c  b 
(Fig.  352).  No  such  difference  between  a  nerve  and  a  moist  con- 
ductor, however,  is  apparent  if  the  latter  is  so  made  as  to  resemble  a 
nerve  in  its  structure — that  is,  consists  of  a  central  axis,  which  is  a 
better  conductor  than  the  surrounding  envelope,  as,  for  example,  when 
a  thread  (t,  Fig.  352)  moistened  with  strong  salt  solution,  is  surrounded 
by  a  porous  clay  tube  (ct)  whose  walls  have  been  previously  soaked  in 
distilled  water,  or  when  a  stick  of  amalgamated  zinc  is  surrounded  by 
a  similar  tube  soaked  in  zinc  sulphate  solution.  The  leaving  currents 
will,  in  such  a  conductor,  have  the  same  direction,  owing  to  the  fact 
of  the  substance  coating  the  axis  being  a  better  conductor  than  the 
envelope,  while  the  return  currents  all  running  in  the  better  conduct- 
ing axis,  the  current  will  also  have  the  same  sign,  however  the  divert- 
ing electrodes  be  placed  upon  the  surface  of  the  nerve.  Further,  the 
electrotonic  currents  so  developed  resemble  those  of  a  nerve  in  being 
entirely  dependent  upon  the  polarizing  current,  of  the  length  of  the 
nerve  traversed  by  the  latter,  etc.  If,  now,  such  a  heterogeneous  con- 
ductor be  divided  in  the  middle,  and  the  cut  ends  be  joined  by  a 
homogeneous  moist  conductor  like  that  already  described,  no  electro- 
tonic currents  will  appear,  lor  the  reasons  already  given.  It  is  in 
this  way,   probably,   that  the  ligation  or  the   crushing  of  the    nerve 


614 


NEGATIVE    VARIATION. 


interferes  with  the  development  of  such  currents,  the  nerve,  after 
death,  being  changed  from  a  heterogeneous  to  a  homogeneous  con- 
ductor. Further,  as  the  escape  of  the  polarizing  current,  either  in  the 
nerve  or  the  heterogeneous  conductor,  appears  to  be  due  to  the  resist- 
ance developed  through  the  inner  polarization  set  up  between  the  core 


Fig.  352. 


Fig.  353. 


Passage  of  current  through  moistened  thread, 
enclosed  in  clay  tube  ct. 


Passage  of  current  through  platinum,  surrounded  by 
zinc  sulphate. 


and  the  sheath,  it  is  to  be  expected  that  the  amount  of  the  polarizing 
current  escaping  along  the  extrapolar  portions  of  the  nerve  will  be 
proportional  to  such  resistance,  and  such  a  fact  is  found  to  be  the  case. 
Thus,  for  example,  if  a  platinum  thread  be  passed  through  a  zinc 
sulphate  solution  in  a  clay  tube  (Fig.  353),  the  electrotonic  currents 
developed  will  be  much  greater  than  if  the  axis  consisted  of  amalga- 
mated zinc.  Indeed,  as  we  have  already  seen,  amalgamated  zinc  and 
zinc  sulphate  solution  are  so  homogeneous,  that  we  use  them  to  make 
non-polarizable  electrodes.  An  interesting  illustration  of  the  difference 
in  effect  as  regards  the  development  of  electrotonic  currents  due  to  the 

Fig.  354. 


Passage  of  current  through  heterogeneous  conductor. 

conductor  being  homogeneous  or  heretogeneous  can  be  readily  shown 
by  the  following  simple  apparatus  (Fig.  354),  which  consists  of  a  glass 
tube  through  which  passes  an  axis  of  amalgamated  zinc. 

If  the  tube  be  filled  with  zinc  sulphate  solution,  the  galvanometer 
gives  no   evidence  of  electrotonic  currents  ;   but  if  a  number  of  little 


ELECTROTONIC    CURRENTS. 


615 


glass  beads  be  run  along  the  axis,  the  spaces  between  the  beads  cor- 
responding, let  us  say,  to  the  nodes  of  Ranvier  in  the  nerve,  the 
galvanometer  will  be  at  once  deflected,  the  conductor  having  been  con- 
verted  from  a  homogeneous  into  a  heterogeneous  one.  The  different 
facts  just  referred  to,  established  by  Funke,  Gruenhagen,  Hermann, 
etc.,  all  go  to  show  that  the  living  nerve  is  a  heterogeneous  conductor, 
consisting  (Fig.  355)  of  a  central  axis,  which  is  a  better  conductor  than 
its   surrounding  envelopes,  the  white  substance  of  Schwann,   and  the 

Fig.  355. 


rVl^ 

siiwfivtrvmSr  f'ur-r^TiC 

A'atelf c front c  Current 

-*'-'""""""    +a 

PotaruJtti? 

K 

<<ti 

wJ>7X> 

Passage  of  current  through  nerve. 

neurilemma,  and  that,  owing  to  the  inner  polarization  set  up  between 
the  axis  and  its  sheath,  a  resistance  is  offered  to  the  polarizing  current, 
hence  its  escape  along  the  extrapolar  portions  of  the  nerve;  the  latter, 
owing  to  the  resistance  being  gradually  diminished,  at  last  passes  into 
the  axis,  and  thence  by  the  kathode  back  to  the  Daniell's  element. 
Finally,  the  electrotonic  current  so  developed,  in  increasing  or  diminish- 
ing the  neutral  nerve  current,  gives  rise  to  the  anelectrotonic  and 
katelectrotonic  currents  respectively.  While  in  the  present  state  of 
physiological  knowledge  it  may  appear  premature  to  accept,  without 
reserve,  the  view  that  attributes  the  electrotonic  current  to  the  escape 
of  the  polarizing  one,  nevertheless,  it  must  be  admitted  that  the  facts, 
so  far  as  they  have  been  established,  are  better  explained  by  this  view 
than  by  any  other  yet  advanced.  Finally,  if  a  nerve  (iV,  Fig.  356) 
be  placed  upon   another  {N  2),  the  latter  exhibiting   an   electrotonic 

Fig.  356. 


JV< 


J^ 


Secondary  electrotonic  current. 


current,  a  secondary  electrotonic  current  will  be  developed  in  the  former 
opposite  in  direction  to  that  of  the  current  producing  it  as  represented 
in  Fig.  356,  the  current  being  closed  by  the  ends  of  the  nerve  lying  in 


616  NEGATIVE    VARIATION. 

contact  with  each  other.  It  is  an  interesting  fact,  in  this  connection, 
that  when  a  nerve  is  traversed  by  a  polarizing  current  not  only  do  the 
anodal  and  kathodal  portions  of  the  nerve  differ  in  the  presence  of 
anelectrotonic  and  katelectronic  currents,  but  also  in  exhibiting  the 
conditions  of  anelectrotonus  and  katelectrotonus  (Fig.  355),  the  former 
being  one  of  diminished,  the  latter  of  increased,  excitability  and  con- 
ductivity respectively.  The  anelectrotonic  and  katelectrotonic  conditions 
are  not  only  interesting  from  being  intimately  connected  in  so  many 
respects  with  the  anelectrotonic  and  katelectrotonic  currents,  the  latter, 
indeed,  being  so  named  for  this  reason  by  Du  Bois-lleymond,  the 
phenomena  of  anelectrotonus  and  katelectrotonus  having  been  dis- 
covered first,  but  also  on  account  of  such  conditions  offering  an  expla- 
nation of  certain  well-established  facts  as  regards  the  excitability  of 
nerves  by  electrical  stimuli.  It  might  naturally  be  supposed  in  using 
the  constant  current  as  a  nervous  stimulant  that  the  current  would 
excite  the  nerve  during  the  whole  time  that  it  was  applied,  that  so  long 
as  the  current  passed  through  the  nerve  successive  impulses  would  be 
generated,  with  the  effect  of  throwing  the  muscle  into  a  kind  of 
tetanus.  While  under  certain  circumstances  the  above  does  take 
place,  in  the  great  majority  of  cases,  however,  the  muscle  remains 
entirely  quiet  during  the  passage  of  the  current  through  the  nerve, 
provided  the  current  remains  constant,  contractions  taking  place  at  the 
making,  or  at  the  making  and  breaking,  according  as  we  shall  see 
presently,  to  the  strength  and  direction  of  the  current.  It  may  be  said, 
therefore,  as  a  general  rule,  that,  during  the  passage  of  a  constant 
current  the  muscle  remains  at  rest.  Nevertheless,  as  Ave  have  just  seen, 
in  the  absence  of  any  muscular  contraction,  the  nerve  is  profoundly 
modified  during  the  passage  of  a  constant  current  by  the  development 
at  the  anode  and  kathode  of  the  anelectrotonic  current  and  anelectro- 
tonic condition  of  the  katelectrotonic  current  and  katelectrotonic 
condition,  respectively,  conditions  intimately  connected  with  the  pecu- 
liarities just  referred  to  as  regards  the  muscular  contraction  brought 
about  by  the  opening  and  closing  of  the  electrical  circuit. 

Before  considering,  however,  these  relations,  let  us  first  show  how 
the  difference  already  mentioned  in  the  excitability  of  the  nerve  at  the 
anode  and  kathode,  respectively,  can  be  demonstrated.  With  this 
object,  we  will  dispose  the  necessary  apparatus,  as  represented  in  Fig. 
357,  and  let  us  suppose,  first,  that  the  polarizing  current  thrown  into 
the  nerve  by  the  opening  of  the  key,  and  whose  strength  is  regulated 
by  the  rheocord,  is  direct,  descending — that  is,  traverses  the  nerve  in 
the  same  direction  as  that  of  the  nerve  force — a  being,  therefore,  the 
anode,  and  K  the  kathode.  It  will  then  be  found  that  if  the  nerve  be 
stimulated  at  a  point  x  the  irritability  of  the  nerve  will  be  increased 
during  the  passage  of  the  polarizing  current  as  shown  by  the  greater 
elevation  of  the  lever  due  to  the  muscular  contraction,  as  compared  with 
the  average  elevation  previously  determined  with  the  same  stimulus, 
but  in  the  absence  of  the  polarizing  current.  On  the  other  hand,  if  the 
nerve  be  stimulated  at  a  point  y  the  irritability  of  the  nerve  will  be 
found  to  be  diminished.  That  it  is  not  the  distance  of  the  point  y  from 
the  muscle,  as  compared  with  that  of  x,  to  which  the  diminution  in 


ELECTROTONUS. 


617 


irritability  at  y  is  due  is  shown,  apart  from  -what  has  already  been  said 
with  reference  to  the  stimulation  of  a  nerve  at  different  distances  from 
the  muscle,  by  reversing  the  polarizing  current  by  means  of  the  whippe, 
so  that  it  becomes  an  inverse  ascending  one,  the  anode  being  then, 
therefore,  nearer  the  muscle  than  the  kathode  ;  even  then  the  irritability 


Fig.  357. 


Disposal  of  apparatus  to  demonstrate  electrotonus. 

of  the  nerve  at  x  is  diminished,  and,  with  certain  qualifications,  to  be 
mentioned  presently,  that  at  y  is  increased.  In  this  way,  then,'  it  is 
shown  that  during  the  passage  of  a  constant  current  the  irritability  of 
the  nerve  at  the  kathode  is  increased  and  at  the  anode  diminished,' the 
change  in  the  condition  of  the  nerve  being  described  as  that  of  kat- 
electrotonus  and  aneleetrotonus.  or  as  the  katelectrotonic  increase,  and 
anelectrotonic  decrease  of  irritability.  The  condition  of  katelectrotonus 
and  aneleetrotonus  not  only  modifies  the  irritability  of  the  nerve  as 
regards  the  originating  of  nervous  impulses,  but  appears  also  to  influ- 
ence their  propagation — at  least  it  may  be  said  that  the  condition  of 
aneleetrotonus  offers  an  obstacle  to  the  passage  of  a  nervous  impulse. 
The  condition  of  katelectrotonus  and  aneleetrotonus  not  only  spreads 
out  along  the  extrapolar  portions  of  the  nerve,  but,  unlike*  the  kat- 
electrotonic and  anelectrotonic  currents,  extends  also  into  the  intrapolar 


618  NEGATIVE    VARIATION. 

portion,  the  point  where  they  merge  into  each  other — that  is,  where  the 
irritability  is  unchanged — being  known  as  the  neutral  or  indifferent 
point.  The  position  of  the  latter  varies  somewhat,  according  to  the 
strength  of  the  current,  with  a  strong  current  approaching  the  kathode, 
with  a  weak  one  the  anode.  While  the  katelectrotonic  increase  and 
anelectrotonic  decrease  of  irritability  reach  a  maximum  shortly  after 
the  making  of  the  polarizing  current,  and  then  gradually  diminish,  the 
katelectrotonic  increase,  attains  its  maximum  and  minimum  limits 
sooner  than  the  anelectrotonic  decrease.  The  strength  of  the  katelec- 
trotonic and  anelectrotonic  conditions  depends,  up  to  a  certain  limit, 
upon  the  strength  of  the  polarizing  current,  and  the  general  irritability 
of  the  nerve.  With  the  opening  of  the  polarizing  current  the  phenomena 
of  katelectrotonus  and  anelectrotonus  disappear  momentarily,  how- 
ever, there  is  an  increase  of  irritability  at  the  anode,  a  decrease  at  the 
kathode.  In  bringing  about  this  condition  of  katelectrotonus  and 
anelectrotonus,  while  usually  the  constant  current  is  made  use  of  as  the 
stimulus,  as  in  the  preceding  instance,  this  is  not  indispensable,  an 
induced  current  producing  the  same  effect ;  this  is  as  might  be  expected, 
since  a  single  induction  shock  may  be  regarded  as  a  constant  current, 
but  of  very  short  duration,  developing  very  suddenly,  and  disappearing 
more  gradually.  Whether,  therefore,  the  constant  or  induced  current 
be  used  as  a  stimulus  th%  nerve  is  thrown  into  the  condition  of  kat- 
electrotonus and  anelectrotonus,  and  with  the  disappearance  of  the  cur- 
rent, as  just  mentioned,  there  is  a  rebound  at  the  poles,  their  condition 
being  then  momentarily  reversed.  It  will  be  also  particularly  observed 
that  during  the  passage  of  the  current  through  the  nerve  the  muscle 
remains  quiescent,  contraction  only  taking  place  if  the  strength  of  the 
current  varies,  or  at  the  entrance  or  exit  of  the  current  into  or  from  the 
nerve.  The  stimulus  causing  the  nervous  impulse  is  due  to  a  change 
from  one  condition  to  another,  not  to  the  condition  itself,  the  effect  not 
depending  so  much  upon  the  intensity  of  the  condition  as  on  variation 
of  the  same.  Further,  it  will  be  observed  by  extending  our  experi- 
ments, that  a  nervous  impulse  is  only  generated  when  the  nerve  passes 
from  its  normal  condition  into  that  of  katelectrotonus,  or  that  of  in- 
creased irritability,  and  diminished  electrical  potential,  or  passes  from 
the  condition  of  anelectrotonus,  that  of  diminished  irritability  and 
increased  electrical  potential,  back  to  the  normal  condition,  the  latter 
normal  condition  being  then,  relatively  at  least,  one  of  katelectrotonus, 
as  compared  with  the  immediately  preceding  anelectrotonic  condition. 
As  might  be  expected,  however,  the  passage  of  the  nerve  from  the 
anelectrotonic  to  the  normal  condition  is  far  less  effective  as  a  generator 
of  nervous  impulses  than  that  from  the  normal  to  the  katelectrotonic 
condition,  since  the  return  from  the  anelectrotonic  to  the  normal  con- 
dition is  a  gradual,  not  a  sudden  one,  and  the  change  acts  as  a  stimulus, 
at  best  only  relatively.  Hence,  with  induced  currents  at  least,  usually 
the  muscular  contraction  takes  place  only  at  the  closing,  not  at  the 
opening  of  the  current. 

Let  us  now  modify  the  arrangement  of  the  apparatus  just  used  so 
that  (Fig.  358)  by  means  of  the  rheocord  Ave  can  modify  the  strength  of 
the  constant  current,  and,  by  the  whippe,  reverse  the  direction  through 


EFFECT  OF  STRENGTH  OF  CONSTANT  CURRENT.   619 

■which  it  traverses  the  nerve,  and  let  us  suppose  first  that  the  current  is 
a  weak  one,  descending  direct  at  the  moment  of  stimulation — that  is,  at 
the  making  of  the  circuit,  the  muscle  will  contract,  remaining  quiet, 
however,  during  the  passage  of  the  current  and  also  at  the  breaking  of 
the  same.  Let  us  now  reverse  the  direction  of  the  current,  so  that  it 
becomes  an  inverse  ascending  one  (Fig.  359),  then,  as  before,  the  muscle 
will  contract  only  at  the  making  of  the  circuit.  The  effect  in  both 
instances  being  the  same,  can  be  accounted  for  by  supposing  the  kat- 

Fig.  3")8. 


electrotonic  condition  acts  as  a  stimulus,  the  impulse  generated  at  the 
kathode  in  the  case  of  the  inverse  current  being  still  effective,  even 
though  the  distance  of  the  kathode  from  the  muscle  is  increased.     Since, 

Fig.  ?,.">9. 


3C  I  — 


hoAvever,  the  latter  impulse  generated  at  the  kathode  has  to  traverse 
the  anelectrotonic  portion  of  the  nerve  (a),  which,  as  it  will  be  re- 
membered, offers  an  obstacle  to  the  propagation  of  the  impulse,  the 


620  NEGATIVE    VARIATION. 

muscular  contraction  due  to  the  making  of  the  inverse  cm-rent  will  be 
less  than  thai  due  to  the  making  of  the  direct  one.  That  no  contraction 
takes  place  at  the  breaking  of  the  circuit  with  either  the  direct  or 
inverse  currents  is  to  be  expected,  since,  with  the  breaking  of  the  direct 
current,  the  kathode  offers  an  obstacle,  having  become  momentarily  the 
anode,  to  the  propagation  of  the  impulse  due  to  the  weak  katelec- 
trotonic  condition  momentarily  developed  at  the  anode,  and.  with  the 
breaking  of  the  inverse  current,  the  fall  at  the  anode  from  anelectro- 
tonus  to  the  normal  is  too  slight  to  generate  an  impulse.  Let  us  now 
intensify  the  current  and  reverse  its  direction  by  i,he  whippe,  so  that  it 
is  again  a  direct  one  (Fig.  358)  :  muscular  contraction  will  take  place 
both  at  the  making  and  breaking  of  the  circuit,  in  the  latter  case  the 
effect  being  due  to  the  passage  of  the  anelectrotonic  condition  back  to 
the  normal — that  is,  relatively  to  a  condition  of  katelectrotonus.  Reverse 
the  current  so  as  to  make  it  an  ascending  one  (Fig.  359),  and,  as  before, 
we  will  have  muscular  contraction  taking  place  both  at  the  making  and 
breaking  of  the  circuit :  the  katelectrotonic  condition  generating  the 
impulse  at  the  making  and  the  return  of  the  anelectrotonic  condition  to 
the  normal  at  the  breaking  of  the  circuit.  Finally,  with  a  very  strong 
current,  if  the  latter  be  direct  (Fig.  358),  contraction  takes  place  only 
at  the  making  of  the  circuit,  and  with  the  inverse  current  only  at  the 
breaking.  The  fact  of  there  being  no  contraction  at  the  breaking  of 
the  circuit  with  the  direct  current  may  be  accounted  for  by  partly  sup- 
posing that  the  general  irritability  and  conductivity  of  the  intrapolar 
portion  of  the  nerve  has  been  depressed  by  the  strong  current  and  partly 
by  the  fall  of  anelectrotonus  not  being  effective  on  account  of  the  relative 
anelectrotonic  condition  developed  through  the  fall  of  the  katelectrotonic 
offering  an  obstacle  to  the  transmission  of  the  impulse.  On  the  other 
hand,  with  the  ascending  current  (Fig.  359)  there  will  be  no  contraction 
at  the  making  of  the  circuit,  since  the  anelectrotonic  condition,  an 
obstacle  to  the  propogation  of  the  impulse  generated  at  the  kathode, 
intervenes  between  the  latter  and  the  muscle ;  but,  at  the  breaking 
of  the  circuit,  the  fall  of  the  anelectrotonus  to  the  normal  relatively 
katelectrotonus  will  generate  an  impulse,  since  no  obstacle  intervenes 
then  between  the  point  of  stimulation  and  the  muscle,  and  the  latter 
will  contract.  The  above  facts,  established  among  others  by  Pfaff,  Ritter, 
and  Pfluger,  may  be  summarized  as  a  law  of  muscular  contraction,  under 
the  following  formula,  in  which  the  direct  and  inverse  currents  are 
indicated  by  the  letters  D  and  _Z"  and  the  arrows,  and  the  making  and 
breaking  of  the  circuits  by  the  letters  M  and  B,  and  the  contraction 
and  rest  of  the  muscle  by  0  and  It  respectively. 

Law  of  Muscular  Contraction. 

Weak  current.  Medium  current.  Strong  current. 

D  |  M  C,  B  R,  M  C,  B  C  M  C,  B  R, 

M  C,  B  R,  M  C,  B  C,  M  R,  B  C, 


The  above  law  can  be  readily  remembered,  and  the  facts  explained, 
if  it  be  admitted,  that  muscular  contraction  only  takes  place  when  there 


hitter's  law.  621 

is  a  rise  of  katelectrotonus  or  a  fall  of  anelectrotonus  (relative  kat- 
electrotonus) ;  but  not  by  the  rise  of  anelectrotonus  or  fall  of  katelec- 
trotonus (relative  anelectrotonus). 

In  concluding  the  subject  of  electroton us  one  cannot  but  be  impressed 
with  the  significance  of  the  fact  of  the  katelectrotonic  condition,  that 
generating  the  nervous  impulse,  being  situated  at  that  electrode  whose 
electrical  condition  is  diminished,  when  it  is  remembered  that  the  propa- 
gation of  the  nervous  impulse  or  the  negative  variation  is  also  charac- 
terized by  a  diminution  in  electrical  condition.  These  facts  taken 
together  at  once  suggest  the  idea  of  nerve  force  not  being  identical 
with  electricity  as  once  thought,1  but  of  being  correlated  with  the  latter 
in  some  manner,  the  appearance  of  the  one  depending  upon  the  disap- 
pearance of  the  other,  or  the  absence  of  the  one  favoring  the  develop- 
ment of  the  other,  and  while  this  view  cannot  at  present  be  accepted 
without  reserve,  to  say  the  least  it  is  certainly  a  plausible  one  and  de- 
serves consideration,  being  in  harmony  with  the  general  doctrine  of  the 
conservation  of  force. 

In  concluding  our  account  of  nerve  physiology  it  remains  for  us  now 
to  say  a  few  words  with  reference  to  the  conditions  influencing  the 
general  irritability  of  nerves,  which  for  convenience'  sake  have  been 
reserved  for  the  present  moment,  such  as  the  influence'  exerted  by  the 
distance  from  the  muscle  of  the  point  of  the  nerve  stimulated,  the  dura- 
tion of  and  number  of  the  stimuli,  the  temperature  and  blood  supply, 
the  functional  activity,  severance  from  the  central  nervous  system,  etc. 
Thus,  if  two  pairs  of  electrodes  are  placed  upon  the  nerve  of  a  freshly 
prepared  nerve  muscle  preparation,  one  pair  near  the  muscle,  the  other 
pair  near  the  cut  end  of  the  nerve,  it  will  be  found  that  the  muscular 
contraction  is  greater  when  the  stimulus  is  applied  through  the  latter 
pair  than  when  through  the  former.  This  result  can  be  accounted  for 
either  on  the  supposition  that  the  nervous  impulse  gathers  strength, 
avalanche-like,  as  it  travels  from  the  cut  end  of  the  nerve  toward  the 
muscle,  or  that  the  central  end  of  the  nerve  is  more  irritable  than  the 
distal  end— v-tliat  is,  that  that  portion  of  the  nerve  generates  a  longer 
nervous  impulse  when  stimulated.  The  latter  view  is  the  most  probable 
one.  since  the  negative  variation  following  in  the  stens  of  the  nervous 
impulse  exhibits  no  such  avalanche-like  increase  as  it  progresses  wave- 
like from  the  point  stimulated  to  the  muscle.  It  has  been  shown  by 
Konig2  thai  the  constant  current  if  used  as  a  stimulus  must  last  at  least 
the  0.0015  second  to  produce  a  nervous  impulse,  and  by  Kroniker  and 
Stirling.3  that  inductive  shocks  even  if  repeated  as  rapidly  as  2200 
times  ;i  second  will  throw  a  muscle  into  tetanus.  In  this  connection  it 
is  an  interesting  fact  according  to  Helmholtz,4  that  if  maximum  induc- 
tion shocks  he  thrown  into  a  nerve  following  each  other  at  a  rate  of  less 
than  the  ,;,1l0th  of  a  second,  half  the  shocks  will  produce  no  effect, 
the  muscle  being  devoid  of  irritability  for  the  -g^th  of  a  second  subse- 
quent to  each  shock.      A  rise  in   temperature,  say  to  45°  C.  (113°  F.), 

1  According  to  nailer.  Elements  Physiologiae,  t.  iv.  pp.  3.">7,  373,  the  mathematician  Hansen  was  the 
first  t.>  suggest  tint  nerve  force  and  electricity  are  iilentie.il.  llis  views  were  not,  however,  published 
until  alt'  r  Ins  death,  appearing  first  in  his  "  Nbvi  profectus  in  historia  electricitates,"  according  to  Du 
Bois-Reymond,  Dntersuchnngen,  ii.  1,  S.  211. 

•■i  Wien  Sitz.  Bericht,  lxii.  (1870).  s  Archiv  Aflat,  u.  rhys.,  1S78,  S.  1. 

*  Berlin  Moiiats.  Bericht,  1854. 


622  NEGATIVE    VARIATION. 

in  the  case  of  the  frog's  nerve  favors  the  development  of  nerve  irritability ; 
the  activity  of  the  molecular  processes  being  increased,  nervous  impulses 
are  generated  more  readily  by  stimuli,  and  the  muscular  contractions 
are  proportionately  greater.  On  the  other  hand,  the  application  of 
cold  benumbs  the  nervous  system,  diminishes  nervous  irritability,  the 
latter  disappearing  altogether  if  the  temperature  be  reduced  to  0°  C. 
(32°  F.).  Judging  from  what  we  shall  learn  hereafter  from  the  analo- 
gous case  of  muscle  there  can  be  little  doubt  that  the  irritability  of 
a  nerve  depends  upon  a  full  supply  of  oxygenated  blood  and  that 
through  prolonged  use  the  nerve  becomes  exhausted.  Finally,  if  a 
nerve  be  divided  in  the  living  body  or  even  out  of  it,  it  will  be  observed 
that  at  the  peripheral  end  of  the  cut  nerve  the  irritability  at  first 
slightly  increases,  then  diminishes,  and  finally  disappears,  the  changes 
in  the  irritability  advancing  from  the  cut  end  of  the  nerve  toward  the 
muscle.  Coincidently  with  the  changes  in  the  irritability  of  the  nerve 
just  mentioned,  a  degeneration  is  set  up  in  the  substance  of  Schwann 
and  the  axis-cylinder  extending  to  the  terminal  filaments,  involving 
even  their  endings  in  the  motor  plates.  A  similar  degeneration  may 
extend  also  centripetally  from  the  cut  end,  but  not  beyond  the  first  node 
of  Ranvier.     Beyond  this  point  the  nerve  is  usually  found  normal. 


CHAPTER    XL. 


THE   SPINAL   CORD,   ITS   STRUCTURE   AND     FUNCTION'S    AS    A 
CONDUCTOR  OF  MOTOR  AND  SENSORY  IMPULSES. 

The  spinal  cord  lying  in  the  vertebral  canal,  enveloped  within  its 
membranes,  extends  as  a  cylindrical  cord  of  from  fifteen  to  eighteen 
inches  in  length  from  the  medulla  oblongata,  with  which  it  is  continuous, 
at  the  level  of  the  occipital  foramen  to  the  lower  part  of  the  first  lumbar 
vertebra.  It  weighs  about  one  and  one-half  ounces.  If  a  transverse 
section  of  the  cord  be  made,  it  will  be  observed  (Fig.  360)  that  ir  consists  of 
white  matter  externally,  and 
of  gray  matter  internally,  the 
latter  being  found  in  the 
greatest  amount  opposite  the 
cervical  and  lumbar  enlarge- 
ments, the  origin  of  the  large 
nerves.  The  gray  matter  is 
disposed  as  two  crescents, 
placed  back  to  back,  some- 
what in  the  form  of  the  letter 
II,  the  anterior  portion,  the 
widest,  being  known  as  the 
anterior  cornu.  the  posterior 
portion,  the  largest,  as  the 
posterior  cornu,  the  middle 
connecting  portion  the  gray 
commissure*  The  latter  is  often  subdivided  into  the  interior  and  pos- 
terior gray  commissures  by  its  central  canal,  which,  as  we  shall  see 
hereafter,  is  the  remnant  of  the  primitive  neural  canal.  This  peculiar 
arrangement  of  the  gray  matter  within  the  spinal  cord  serves  conveni- 
ently to  subdivide  the  white  portions  of  the  cord  into  the  anterior,  lateral, 
and  posterior  columns.  The  anterior  columns  are  made  up  by  that 
pari  nf  the  white  matter  of  the  cord  lying  between  the  anterior  median 
fissure  and  the  anterior  cornu.  It  will  be  observed,  however,  that,  as 
the  anterior  median  fissure  does  not  extend  into  the  anterior  gray  com- 
missure, a  band  of  white  matter,  the  white  commissure,  intervening,  the 
anterior  columns  run  into  each  other,  and  that,  as  the  anterior  cornu  do 
not  extend  to  the  outer  edge  of  the  cord,  the  anterior  columns  pass  into 
the  lateral  ones,  lying  between  the  two  crescents.  On  the  other 
hand,  the  posterior  median  fissure  extending  down  to  the  posterior 
gray  commissure,  and  the  posterior  cornu  of  the  gray  matter  to  the 
inner  edge  of  the  cord,  the  posterior  columns  lying  between  them  are 
completely  separated  from  the  lateral  columns,  and  from  each  other. 
In  certain  regions  of  the  cord  each  posterior  column  is  further  sub- 


liansverse  section  of  the   spinal  curd.     ",   b.  Spinal 
f   right    and    left    sides.      <?.    Origin     of    an- 
terior root.     e.  Origin  of  posterior  root.     c.  Ganglion  of 
posterior  root.    (Dalton. 


624 


TJIE    SPINAL    COIH). 


divided  by  a  rather  obscure  fissure  into  two  sub-columns,  the  one,  the 
posterior  median  column,  lying  immediately  next  to  the  posterior 
median  fissure,  often  called  the  column  of  Groll,  also  the  inner  root  zone 
of  Charcot,  the  other  the  posterior  external  column,  or  the  column  of 
Burdach,  or  the  outer  root   zone  of  Charcot.     The  white    matter   of 

the    spinal   cord    constituting   its 
Fig.  361.  columns,   as  just  described,  con- 

sists principally  of  medullated 
nerve  fibres,  in  Avhich,  however, 
a  neurilemma  and  nodes  of  Ran- 
vier  are  absent. 

The  course  of  these  fibres 
through  the  columns  is  generally 
in  a  longitudinal  direction,  with 
the  exception  of  such  of  them  as 
pass  transversely  and  decussating 
through  the  white  commissure,  or 
from  the  roots  of  the  spinal 
nerves,  and  from  the  gray  matter 
of  the  cord  into  the  columns,  the 
latter  having  a  transverse  or 
oblique  direction.  If  the  white 
matter  of  the  cord  be  viewed  in 
transverse  sections  with  the  micro- 
scope, the  nerve  fibres  will  then 
appear  like  small  circles  of  different 
sizes  (Fig.  361),  with  a  rounded 
dot  in  the  centre,  the  latter,  or 
the  axis-cylinder,  being  very  dis- 
tinct if  the  preparation  be  stained 
with  carmine,  while  between 
groups  of  these  nerve  fibres  fine 
septa  of  connective  tissue  may 
also  be  observed  supporting  delicate  bloodvessels.  The  gray  matter  of 
the  cord  consists  of  a  supporting  connective  tissue,  the  neuroglia  of 
Virchow,  composed  of  a  fine  network  of  round  and  large  branched  cells, 
imbedded  in  a  homogeneous  matrix,  which,  from  being  particularly 
abundant  at  the  sides  of  the  posterior  cornu,  is  there  known  as  the 
gelatinous  substance  of  Rolando,  of  bloodvessels  derived  from  the 
anterior  median  posterior  root,  and  central  vessels,  of  nerve  cells,  and 
nerve  fibres. 

The  cells  in  the  gray  matter  of  the  cord  are  of  two  kinds,  large 
multipolar  cells  (Fig.  361,  d),  such  as  are  found  in  the  anterior 
cornu,  and  small  spindle-shaped  cells  (e)  in  the  posterior  cornu.  Large 
multipolar  cells  are  also  found  principally  in  the  lower  part  of  the 
dorsal  region  of  the  cord,  behind  the  gray  commissure,  and  on  the  inner 
surface  of  the  posterior  cornu,  constituting  the  posterior  vesicular 
column  of  Clarke.  The  gray  matter  of  the  cord  consists  also,  or, 
rather,  is  traversed  by  innumerable  delicate,  non-medullated  nerve 
fibres,  which,  in  some  instances,  are  undoubtedly  continuations  of  the 


•8 


Transverse  section  through  the  under  half  of 
the  human  cord.  «.  Central  canal,  b.  Anterior, 
c.  Posterior  fissure.  (I.  Anterior  cornu,  with  large 
ganglion  cells,  e.  Posterior  cornu  with  smaller. 
/.  Anterior  white  commissure,  g.  Sustentacula!1 
substance  around  the  central  canal,  h.  Posterior 
gray  commissure.  »'.  Bundles  of  the  anterior,  and 
it  of  the  posterior  spinal  nerve  roots.  ?.  Anterior. 
m.  Lateral.    ».   Posterior  column.    (After  Deiters.) 


COURSE    OF    NERVE    FIBRES. 


625 


Fig.  362. 


poles  or  tails  of  the  cells  just  mentioned,  and  which  pass  either  into  the 
roots  of  the  spinal  nerves  or  into  the  columns.  On  account,  however, 
of  the  manner  in  which  the  sections  are  made  necessarily,  in  many 
cases  it  is  impossible  to  say  anything  positively  as  to  either  the  origin 
or  termination  of  such  nerve  fibres.  Comparison  of  sections  made, 
however,  both  in  a  longitudinal  and  in  a  transverse  direction,  leads  to  the 
supposition  that  all  such  non-medullated  nerve  fibres,  or  axis-cylinders, 
found  in  the  gray  matter  of  the  cord,  originate  in  either  encephalic  or 
spinal  cells,  and  directly  or  indirectly,  through  spinal  nerves,  terminate 
in  muscle,  gland,  or  sensory  organ.  What  lias  been  positively  learned 
by  such  methods  of  investigation  as  to  the  origin  and  course  of  these 
fibres  may  be  briefly  summed  up  as  follows.  The  ultimate  nerve  fibres 
of  the  anterior  roots  of  the  spinal  nerves  pass 
directly  into  the  axis-cylinder  like  prolonga- 
tions of  the  cells  of  the  anterior  cornu  of  the 
gray  matter.  The  gray  network  produced 
through  the  repeated  branching  of  these  cellu- 
lar prolongations  gives  rise  to  broad  fibres, 
some  of  which,  passing  through  the  white 
commissure,  ascend  in  the  anterior  column  of 
the  opposite  side  of  the  cord,  while  others 
(Fig.  362)  passing  into  the  antero-lateral 
columns  of  the  same  side,  ascend  to  the  medulla 
oblongata,  where  a  greater  proportion  decus- 
sating with  corresponding  fibres  from  the 
antero-lateral  column  of  the  opposite  side,  pass 
thence  through  the  pons  Varolii  and  lower 
portion  of  the  crus  cerebri  to  the  corpus  striatum 
at  the  base  of  the  brain.  It  appears,  therefore 
(Fig.  303),  that  there  are  continuous  tracts 
from  the  corpus  striatum  of  one  side  of  the 
brain  through  the  crus.  pons,  medulla,  through 
the  antero-lateral  column  to  the  anterior  roots 
of  the  spinal  nerves  emanating  from  the 
opposite  side  of  the  cord.  The  fibres  from  the 
posterior  roots  of  the  spinal  nerves,  after  enter- 
ing the  cord,  apparently  separate  (Fig.  362). 

some  ascending,  other-  descending  in  the  posterior  columns,  while 
others  pass  into  the  posterior  cornu,  and,  after  there  dividing,  terminate 
in  a  network  of  gray  matter,  by  which  they  are  indirectly  connected 
with  the  cells  of  the  posterior  cornu.  It  will  be  observed  that,  while 
the  fibres  of  the  anterior  root  pass  directly  into  the  cells  of  the  anterior 
cornu,  those  of  the  posterior  root  pass  only  indirectly  into  the  cells  of 
the  posterior  cornu,  being  connected  with  the  latter  by  the  intermediate 
network  just  mentioned.  As  fibres  have  also  been  satisfactorily  demon- 
strated connecting  the  gray  matter  of  the  anterior  and  posterior  cornu 
of  the  same  side  of  the  cord,  and  the  cells  of  the  anterior  and  pos- 
terior cornu  of  one  side  of  the  cord  with  those  of  the  other,  the  latter 
fibres  passing  in  front  of  and  behind  the  central  canal,  it  is  evident 
that  the  fibres  of  the  posterior  roots  of  the  spinal  nerves  entering  the 

40 


a.  Posterior  column.  B.  Pos- 
terior horn  of  gray  matter,  c. 
Anterior  horn  of  gray  matter, 
n  Anterior  lateral  column.  E. 
Loop-fibres  of  the  posterior 
column  proper.  F.  A  posterior 
nerve-root.  G.  Ascending  fas- 
ciculus of  this  root  H.  Direct 
fasciculis.  I.  Descending  fas- 
ciculus, j.  Reflex  motor  root. 
K.  Chain  of  sensory  cells.  L. 
Chain  of  motor  cells,  m.  En- 
cephalic fibres  of  the  anterior 
columns,  n.  Anterior  nerve- 
roots  D.  Loop-fibres  of  the  an- 
terior roots.     (Carpextkr.  i 


626 


THE    SPINAL    CORD. 


posterior  cornu  on  one  side  of  the  cord  are  indirectly  connected  with 
the  posterior  cornu  of  the  opposite  side  ;  and,  as  fibres  have  also  been 
demonstrated   passing  upward  in  the   gray   matter   of   the  cord,   and 

Fig.  36  !. 
.1 


Diagram  of  the  structure  of  the  brain.  C  C.  Cortical  substance  of  the  cerebral  hemispheres.  C.  s. 
Corpus  striatum.  N.  1.  Nucleus  lenticularis.  T  o.  Thalamus  opticus.  V.  Corpora  quadrigemina.  P. 
Pedunculus  cerebri.  P.  Basis  or  crusta,  and  II,  tegmentum.  1,1  Fibres  of  the  corona  radiata  of 
the  corpus  striatum  ;  2,  2,  those  of  the  lenticular  nucleus  ;  3,  those  of  the  optic  thalamus  ;  4,  4,  those 
of  the  corpora  quadrigemina  ;  5,  5,  direct  strands  to  the  cortex  cerebri  (Flechsig);  6,  fibres  from  the 
corpora  quadrigemina  to  the  tegmentum  ;  7,  fibres  from  the  optic  thalamus  to  the  tegmentum  ;  m, 
further  course  of  these  fibres.  8.  Fibres  from  the  corpus  striatum  and  lenticular  nucleus  to  the  pes 
of  the  pedunculus  cerebri  ;  M,  further  course  of  these  fibres.  S,  S.  Course  of  the  sensory  fibres.  R 
Transverse  section  of  the  spinal  cord  ;  v  W,  anterior  roots  ;  h  W,  posterior  roots  of  the  spinal  nerves  ; 
a,  a,  association  fibres;  c,  c,  commissural  fibres.    (Carpenter  ) 


thence  by  the  lateral  columns  through  the  medulla,  pons,  and  upper 
portions  of  the  cms  cerebri  to  the  thalamus  opticus  at  the  base  of  the 
brain,  it  would  appear  that  there  are  also  continuous  tracts  (Figs.  363, 


MEDULLA    OBLONGATA. 


627 


364)  passing  from  the  thalamus  opticus  on  one  side  of  the  brain  through 
the  eras,  pons,  medulla,  and  gray  matter  of  the  same  side  to  the  posterior 
roots  of  the  spinal  nerves  emanating  from  the  opposite  side  of  the 
cord.  From  what  has  just  been  said,  it  is  obvious  that,  while  for  con- 
venience' sake,  the  spinal  cord  may  be  described  as  beginning  at  the 
great  foramen,  as  a  matter  of  fact,  it  passes  so  continuously  into  the 
medulla  that  the  latter  may  be  regarded  as  its  upper  expanded  portion, 
and,  since  the  medulla  is  largely  made  up  of  fibres  from  the  cords 
passing  through  it  to  the  basal  ganglia,  corpora  striata,  tlialami  optici, 
etc.,  the  cord,  physiologically,  may  be  regarded  as  beginning  in  these 
ganglia  at  the  base  of  the  brain,  rather  than  at  the  great  foramen. 

The  medulla  oblongata  (Fig.  364)  is  of  a  pyramidal  form,  having  its 
broad  extremity  upward  and  expanded  laterally  at  its  upper  part.      Its 

Fio.  364. 


Inferior  surface  of  the  cerebellum  with  the  pons  Varolii  and  medulla  oblongata.  1.  Placed  in  the 
notch  between  the  cerebellar  hemispheres,  is  below  the  inferior  vermiform  process.  2,  2.  Median  depres- 
sion, or  vallecula.  3,  3,  3.  The  biventral,  slender,  and  posterior  inferior  lobules  of  the  hemisphere.  4. 
The  amygdala.  5V  Flocculus,  or  subpeduncular  lobule.  6.  Pons  Varolii.  7.  Its  median  groove.  8. 
Middle  peduncle  of  the  cerebellum.  9.  Medulla  oblongata.  10,11.  Anterior  part  of  the  great  horizontal 
fissure.  12,  13.  Smaller  and  greater  roots  of  the  fifth  pair  of  nerves.  14.  Sixth  pair.  15.  Facial  nerve. 
16.  Pars  intermedia.  17.  Auditory  nerve,  18.  Glosso-pharyngeal.  19.  Pneuinogastric.  20.  Spinal 
accessory.     21.  Hypoglossal  nerve.     (From  Sappey,  after  Hirschfeld  and  Leveij.l£.) 

length  is  about  an  inch  and  a  quarter,  its  breadth  nearly  an  inch,  and 
its  thickness  about  three-quarters  of  an  inch.  Like  the  spinal  cord,  the 
medulla  presents  two  median  fissures.  The  anterior  median  fissure 
terminates  just  below  the  pons  in  a  recess,  the  foramen  caecum  of  Vicq 
d'Azyr;  the  posterior  is,  however,  continued  up  into  the  floor  of  the 
fourth  ventricle,  where,  after  expanding  into  a  superficial  furrow,  it  is 
gradually  lost.  In  other  respects,  however,  the  medulla  differs  entirely 
in  the  arrangement  of  its  parts  from  the  spinal  cord,  each  of  its  halves 
being  characterized  by  four  eminences,  or  columns,  which  are  known 
in  the  order  in  which  they  present  themselves  from  before  backward  as 
the  anterior  pyramids,  the  olivary  bodies,  the  restiform  bodies,  and  the 
posterior  pyramids.  The  anterior  pyramids  are  situated  on  either 
side  of  the  anterior  fissure,  and  are  separated  from  the  olivary  bodies 


628 


THE    SPINAL    CORD. 


by  a  slight  depression.  Each  anterior  pyramid  consists  of  two  sets  of 
fibres,  inner  and  outer :  the  outer  fibres  are  continuations  of  those  of 
the  anterior  columns  of  the  cords  of  the  same  side,  and,  together 
with  the  decussating  fibres  from  the  opposite  side  of  the  cord  pass 
upward  through  the  pons  into  the  cerebral  peduncles ;  the  inner  or 
decussating  fibres,  so  called  because  they  interlace,  to  a  considerable 
extent,  with  those  of  the  opposite  pyramid,  are,  in  reality,  almost 
entirely  derived  from  the  fibres  of  the  lateral  column  of  the  opposite 
side  of  the  cord,  the  anterior  pyramids  being  pushed  aside,  as  it  were, 
by  the  lateral  columns  inserting  themselves  between  them  as  they  inter- 
lace with  each  other.  The  anterior  pyramid  proper  contains  no  gray 
matter,  its  so-called  nucleus  consisting  of  stellate  nerve  cells  lying 
behind  and  between  it  and  the  olivary  body.  The  olivary  bodies  are  two 
smooth  oval  eminences  sunk  deeply  into  the  medulla,  and  consist  of 
both  white  and  gray  matter ;  the  fibres  of  the  former  run  in  a  longitu- 
dinal direction.  The  gray  matter,  presenting  a  very  characteristic  zigzag 
contour  in  section,  is  known  as  the  corpus  dentatum,  or  ciliare,  or  oli- 

Fig.  365. 


View  of  the  floor  of  the  fourth  ventricle  with  the  posterior  surface  of  the  medulla  oblongata  and  neigh- 
boring parts.  On  the  left  side  the  three  cerebellar  peduncles  have  been  cut  short ;  on  the  right  side  the 
white  substance  of  the  cerebellum  has  been  preserved  in  connection  with  the  superior  and  inferior  pedun- 
cles, while  the  middle  one  has  been  cut  short.  1.  Median  groove  of  the  fourth  ventricle  with  the  fasciculi 
teretes,  one  on  each  side.  2.  The  same  groove  at  the  place  where  the  white  striaj  of  the  auditory  nerve 
emerge  from  it  to  cross  the  floor  of  the  ventricle.  3.  Inferior  peduncle  or  restiform  body.  4.  Posterior 
pyramid  ;  above  this  the  calamus  scriptorius.  5.  Superior  peduncle,  or  processus  a  cerebello  and  cere- 
brum ;  on  the  right  side  the  dissection  shows  the  superior  and  inferior  peduncles  crossing  each  other  as 
they  pass  into  the  white  centre  of  the  cerebellum.  6.  Fillet  to  the  side  of  the  crura  cerebri.  7.  Lateral 
grooves  of  the  crura  cerebri.   8.  Corpora  quadrigemina.    (From  Sappey  after  Hirschfeld  and  Leveille.) 


vary  nucleus ;  while  the  gray  lamina  above  the  latter  is  often  described 
as  the  accessory  olivary  nucleus.  The  fibres  of  the  anterior  columns  of 
the  cord,  which,  as  just  mentioned,  are  thrown  outward  as  they  are 
continued  up  as  the  outer  fibres  of  the  anterior  pyramids,  pass  partly  en 
the  outside  of,  and  partly  beneath  the  olivary  bodies,  and  being  joined 
by  fibres  from  the  olivary  nucleus  pass  upward  as  the  olivary  fasciculus 


MEDULLA     OBLONGATA.  629 

and  fillet  to  the  corpora  quadrigemina  and  cerebral  peduncles.  The 
restiform  bodies,  or  the  inferior  peduncles  of  the  cerebellum,  situated 
behind  and  to  the  outer  side  of  the  olivary  bodies  (Fig.  365),  while 
.  containing  a  considerable  quantity  of  gray  matter,  consist  principally  of 
white  fibres  continued  upward  partly  from  the  posterior  column  of  the 
cord,  and  partly  from  the  lateral  and  anterior  columns;  the  latter 
fibres,  a  small  band,  connect  the  anterior  column  with  the  cerebellum. 
The  posterior  pyramids  situated  on  either  side  of  the  posterior  median 
fissure,  containing  much  gray  matter,  consist  of  white  fibres,  continuous 
with  those  of  the  posterior  median  columns  of  the  cord ;  ascending, 
they  diverge  from  one  another,  forming  the  lower  boundary  of  the 
fourth  ventricle,  and  tapering  off  become  closely  applied  to  the  resti- 
form bodies. 

Resuming  what  has  iust  been  said  with  reference  to  the  structure  of 
the  medulla,  it  will  be  seen  that  the  fibres  of  the  anterior  columns  of 
the  cord  pass  through  it  by  three  routes :  1st,  as  the  fibres  of  the  ante- 
rior pyramids  to  the  cerebral  peduncles ;  2d,  as  the  inner  fibres  of  the 
anterior  pyramids  (together  with  the  decussating  fibres),  as  the  olivary 
fasciculus  and  fillet  to  the  corpora  quadrigemina  and  cerebral  peduncles  ; 
3d,  as  the  band  behind  the  olivary  body,  from  the  restiform  body  to  the 
cerebellum.  The  fibres  of  the  lateral  columns  pass  through  the  medulla 
also  by  three  routes :  1st,  as  the  decussating  fibres  (together  with  the 
inner  fibres  of  the  anterior  pyramids),  as  the  olivary  fasciculus  and  fillet  to 
the  corpora  quadrigemina,  and  cerebral  peduncles  ;  2d,  by  the  restiform 
body  to  the  cerebellum  ;  3d,  by  the  fibres  in  the  floor  of  the  fourth 
ventricle  (fasciculus  teres)  into  the  cerebrum.  The  fibres  of  the  poste- 
rior columns  pass  through  the  medulla  by  two  routes :  1st,  the  outer 
portions  of  the  columns  by  the  restiform  bodies  to  the  cerebellum  ;  2d, 
the  inner  portion  (fasciculus  gracilis),  by  the  posterior  pyramids  to  the 
cerebrum. 

The  fourth  ventricle  (Fig.  365),  just  alluded  to  incidentally,  is  the 
space  left  between  the  medulla  oblongata  in  front,  and  the  cerebellum 
behind.  It  is  bounded  laterally  by  the  superior  peduncles  above,  and 
by  the  diverging  posterior  pyramids  and  restiform  bodies  below,  and  is 
covered  in  behind  by  the  valve  of  Vieussens  and  inferior  vermiform 
process  of  the  cerebellum,  the  floor  being  constituted  by  the  back  of 
the  medulla  oblongata  and  pons  Varolii,  marked  by  the  median  furrow 
terminating  inferiorly  as  the  calamus  scriptorius;  above  the  fourth 
ventricle  communicates  through  the  sylvian  aqueduct  or  iter  with  the 
third  ventricle,  and  below  with  the  central  canal  of  the  spinal  cord  and 
the  subarachnoid  cavity  through  the  foramen  of  Magendie  in  the  pia 
mater.  The  gray  matter  of  the  floor  of  the  fourth  ventricle  disposed 
as  a  continuous  series  of  nuclei  extending  from  beneath  the  corpora 
quadrigemina  to  a  point  corresponding  to  the  decussation  of  the  pyra- 
mids, is  of  extreme  interest  physiologically  as  constituting,  as  we  shall 
see.  the  nuclei  of  origin  of  the  so-called  cranial  nerves  from  the  third 
to  the  twelfth  inclusive.  The  gray  matter  of  the  medulla,  like  that  of 
the  spinal  cord  proper,  differs  as  regards  its  form,  amount,  etc.,  accord- 
ing to  the  position  of  the  section.  Thus,  if  the  latter  be  made  just 
above  the  level  of  the  first  cervical  nerve  (Fig.  366),  the  central  gray 


630  THE    SPINAL    CORD. 

substance  is  encroached  upon,  pushed  back  by  the  decussating  fibres 
from  the  lateral  columns,  which,  in  coursing  inward,  separate  the 
anterior  cornu  from  the  rest  of  the  gray  substance,  while  if  the  section 
be  made  through  the  lowest  part  of  the  olivary  bodies  (Fig.  367),  the 

Fig.  366.  Fig.  367. 

PP 


Transverse  section   of   the  medulla  oblongata, 
showing  the  arrangement  of  the  gray  matter. 

gray  matter  will  be  seen  to  be  still  further  modified.  The  pons  Varolii 
entering;,  as  we  have  seen,  into  the  formation  of  the  floor  of  the  fourth 
ventricle,  consists  not  only  of  the  longitudinal  fibres  passing  upward 
through  it  from  the  cord  and  medulla  to  the  crura  cerebri,  but  also  of 
commissural  fibres  connecting  the  lateral  halves  of  the  cerebellum  and 
of  gray  matter.  The  functions  of  the  latter  will  be  considered  after 
those  of  the  spinal  cord  and  medulla  have  been  treated  of. 

From  the  fact  of  the  spinal  nerves  being  distributed  in  general  to 
the  muscles  of  the  trunk  and  extremities,  the  sphincters,  and  to  the 
integument  covering  these  parts,  of  the  posterior  part  of  the  head,  and 
a  portion  of  the  mucous  membrane,  it  is  evident  that  a  complete 
account  of  their  functions  would  necessitate  not  only  a  detailed  descrip- 
tion of  each  spinal  nerve,  but  of  the  parts  supplied  by  the  latter. 
Inasmuch,  however,  as  a  knowledge  of  the  properties  of  the  spinal 
nerves  in  general  will  enable  one  usually  to  perceive  from  the  ana- 
tomical relations  involved  in  the  functions  of  any  one  of  them,  a  brief 
description  of  these  nerves  only  will  be  given,  the  student  being 
referred  for  details  to  the  classical  treatises  on  anatomy.1 

There  are  thirty-one  pairs  of  spinal  nerves,  eight  cervical,  twelve 
dorsal,  five  lumbar,  five  sacral,  and  one  coccygeal.  Each  spinal  nerve 
(Fig.  368,  AB)  arises  from  the  cord  by  an  anterior  and  a  posterior 
root,  the  latter  being  the  largest,  and  having  a  ganglion.  Immediately 
beyond  the  ganglion  the  two  roots  unite  into  a  single  spinal  nerve, 
which,  after  passing  out  of  the  spinal  canal  by  the  invertebral  foramen 
(with  the  exception  of  the  sacral  and  coccygeal  nerves,  which  divide 
within  it),  divides  into  two  branches,  anterior  and  posterior,  distributed 
respectively  to  the  anterior  and  posterior  portions  of  the  body,  the 
anterior  branch  being  the  largest.     It  will  be  observed  that  a  distinc- 

1  It  may  be  mentioned  in  this  connection,  that  the  author  is  accustomed  to  illustrate  his  lectures  on 
the  spinal,  as  also  the  cerebral  and  sympathetic  nerves,  by  means  of  the  oxyhydrogen  lantern  and  colored 
photographs  of  Hirschfeld's  and  Leveille'e  plates.  The  latter,  furnished  for  the  author  by  Queen  &  Co., 
are  models  of  artistic  work,  and  give  the  student  an  excellent  idea  of  the  whole  nervous  system. 


FUNCTIONS    OF    ANTERIOR    AND    POSTERIOR    ROOTS, 


681 


tion  is  made  between  the  anterior  and  posterior  roots  of  a  spinal  nerve 
and  its  anterior  and  posterior  branches.  The  significance  of  this  dis- 
tinction will  become  at  once  apparent  after  it  has  been  shown  experi- 


Fio.  368. 


Different  views  of  a  portion  of  the  spinal  cord  from  the  cervical  region,  with  the  roots  of  the  nerves 
slightly  enlarged.  In  A,  the  anterior  surface  of  the  specimen  is  shown,  the  anterior  nerve-root  of  its 
right  side  being  divided  ;  in  E,  a  view  of  the  right  side  is  given  ;  in  C  the  upper  surface  is  shown  ;  in 
D,  the  nerve-roots  and  ganglion  are  shown  from  below;  1,  the  anterior  ruediau  fissure;  2,  posterior 
median  fssure;  3,  anterior  lateral  depression,  over  which  the  anterior  nerve-roots  are  seen  to  spread; 
4,  posterior  lateral  groove,  into  which  the  posterior  roots  are  seen  to  sink  ;  5,  anterior  roots  passing  the 
ganglion  ;  .V,  in  A,  the  anterior  root  divided  :  <i.  the  posterior  roots,  the  fibres  of  which  pass  into  the  gan- 
glion &  :  7,  the  united  or  compound  nerve  ;  "',  the  posterior  primary  branch,  seen  in  A  and  D  to  be 
derived  in  part  from  the  anterior  and  in  part  from  the  posterior  root.     (From  Quain.  - 

mentally  that  the  anterior  root  is  purely  motor  in  function,  and  the  pos- 
terior  root  purely  sensory,  whereas  the  anterior  branch,  consisting  of 
fibres  derived  from  both  the  anterior  ami  posterior  roots,  will  be  found  to 
be  both  motor  and  sensory  in  function,  and  the  posterior  branch  beino- 
made  up  also  of  fibres  derived  from  both  the  anterior  and  posterior  roots 
is  also  motor  and  sensory  in  function.  The  anterior  and  posterior 
branches  of  a  spinal  nerve  are  therefore  mixed  in  their  function,  whereas 
the  anterior  root  is  purely  motor,  and  the  posterior  root  wholly  sensory. 
The  discovery  that  the  anterior  root  of  a  spinal  nerve  is  motor,  the 
posterior  root  sensory  in  function,  is  an  excellent  illustration  of  the 
indispensability  of  vivisection  as  a  means  of  research  in  physiological 
investigation — indeed,  it  is  difficult  to  conceive  how  the  discovery  could 
have  been  made  in  any  other  manner,  comparative  anatomy,  from  the 
nature  of  the  case,  throwing  no  light  upon  the  question,  since  the 
spinal  nerves  arise  in  a  similar  manner  in  all  vertebrates,  while  patho- 
logical changes,  even  when  recorded  from  involving  both  roots  simul- 
taneously, rendered  such  data  of  little  or  no  use.     Such  being  the  case, 


632  THE    SPINAL    COKD. 

the  only  available  means  of  investigation  was  experimental,  and,  as  a 
matter  of  fact,  it  was  by  such  means,  a  vivisection,  that  Magendie1  first 
demonstrated  the  function  of  the  roots  of  the  spinal  nerves,  one  of  the 
most  important  discoveries  ever  made  in  the  whole  range  of  science, 
which,  on  account  of  its  importance,  will  now  be  repeated.  The 
vertebral  canal  being  laid  open  and  the  spinal  cord  and  nerves  exposed 
in  a  frog,  for  example,  or  a  rabbit  or  dog,  the  anterior  roots  of  the 
spinal  nerves  supplying  the  lower  extremity  are  divided.  Allowing 
sufficient  time  to  elapse  for  the  effect  of  shock,  hemorrhage,  etc.,  to  pass 
off,  it  will  be  observed  that  the  lower  extremity  on  the  same  side  as  that 
on  which  the  nerves  have  been  divided  is  paralyzed  so  far  as  regards 
motion,  sensation  remaining  intact.  If,  however,  the  distal  end  of 
the  divided  anterior  roots  (Fig.  369,  c)  be  now  stimulated,  the  lower 

Fig.  369. 


Diagram  of  spinal  cord  and  nerves.     The  posterior  root  is  seen  divided  at  a,  b,  the  anterior  at  c,  <i. 

extremity  will  be  at  once  thrown  into  muscular  contraction,  whereas 
no  effect  is  observed,  on  the  other  hand,  either  of  a  motor  or  sensory 
character,  if  the  central  end  d  of  the  divided  anterior  root  be  stimu- 
lated. These  facts  show  conclusively  that  the  functions  of  the  anterior 
roots  of  the  spinal  nerves  is  motor,  and  that  the  stimulus  emanating 
from  the  cord,  whatever  its  nature  may  be,  is  transmitted  through  the 
anterior  root  from  the  centre  to  the  periphery.  That  the  anterior  root 
possesses  in  itself  no  sensory  properties  is  shown  from  the  fact  that  even 
if  at  times  signs  of  sensibility  manifest  themselves  on  its  stimulation, 
such  sensibility  at  once  disappears  after  division  of  the  posterior  root, 
the  sensibility  occasionally  exhibited  on  stimulation  of  the  anterior  root 
being  due  either  to  muscular  cramp  produced,  as  suggested  by  Brown- 
Sequard,2  or  to  there  being  recurring  fibres  passing  backward  from  the 
anterior  root  through  the  posterior  root  to  the  cord,  hence  the  name  of 
recurrent  sensibility  given  to  the  phenomenon  by  Magendie3  and  Longet.4 

l  Journal  de  physiologie,  tome  ii.  pp.  276,  368.     Paris,  1822. 

*  Physiology  and  Pathology  of  the  Central  Nervous  System,  p.  8.     Philadelphia,  1860. 
8  Comptes  Rendus,  t.  xxiv.  p.  3.     Paris,  1847. 

*  Bernard  :  Systeme  Nerveux,  tome  i.  p.  35.   Paris,  1858.     Physiologie,  tome  iii.  p.  115.  Paris,  1869. 


DEGENERATION    OF    THE    NERVE    FIBRES. 


(333 


If,  now,  the  posterior  roots  of  the  spinal  nerves  in  the  same  animal,  but 
on  the  uninjured  side,  be  divided,  it  will  be  observed  that  while  the 
animal  retains  the  power  of  moving  the  lower  extremity  it  has  lost  sen- 
sation entirely  in  it.  and  that  while  no  effect  is  observable  if  the  distal 
end  (a,  Fig.  369)  of  the  divided  posterior  root  be  stimulated,  sensibility 
at  once  manifests  itself  if  the  'central  end  (b)  of  the  same  be  stimulated, 
showing  conclusively  that  the  function  of  the  posterior  root  of  the  spinal 
nerve  is  sensory,  and  that  the  impression  made  upon  the  periphery  is 
transmitted  through  the  posterior  root  to  the  cord.  That  the  posterior 
root  possesses  in  itself  no  motor  properties  is  shown  from  the  fact  that 
if  the  anterior  root  be  divided  no  motion  ever  ensues  on  stimulating  its 
central  end,  any  motion  ensuing  on  stimulation  of  the  central  end  of  the 
posterior  root  being  reflex  in  character,  a  kind  of  recurrent  motility,  so 
to  speak — that  is  to  say,  the  impression  made  upon  the  central  end  of 
the  divided  posterior  root  is  transmitted  to  the  gray  matter  of  the  cord, 
and  is  thence  reflected  out  through  the  anterior  root.  While  the  gan- 
glion already  mentioned,  so  characteristic  of  the  posterior  roots  of  the 
spinal  nerves,  does  not  appear  to  influence  in  any  way  the  transmission 
of  impressions  from  the  periphery  to  the  centres,  it  does  exercise  a  very 
great  influence  upon  the  nutrition  of  the  nerves  after  their  division. 
Thus  it  has  been  shown  by  Waller,1  if  the  roots  be  divided  between  the 
ganglion  and  the  cord  (Fig.  370),  that  while  the  central  end  of  the 

Fig.  370. 


Degeneration  of  Bpinal  nerves  and  nerve  routs  after  section.  A  Section  of  nerve  trunk  beyond  the 
ganglion.  B.  Section  of  anterior  root.  C.  Section  of  posterior  root.  D.  Excision  of  ganglion,  a.  An- 
terior root.    p.   Posterior  root.     g.  Ganglion. 

anterior  root  preserves  its  normal  structure,  the  distal  end  degenerates, 
exhibiting  the  usual  changes  undergone  by  a  nerve  when  separated  from 
its  centre ;  whereas,  in  the  case  of  the  posterior  root  it  is  the  distal  end, 
that  attached  to  the  ganglion,  which  remains  normal,  the  central  end 
degenerating.  It  would  appear,  therefore,  from  these  experiments,  that 
the  ganglion  of  the  posterior  roots  exerts  a  nutritive  influence  upon  the 
sensitive  nerves,  like  that  exerted  by  the  spinal  or  higher  centres  on 
motor  ones,  and  it  is  worthy  of  observation  that  the  degeneration  takes 
place  in  the  direction  in  which  the  nerve  force  is  transmitted.  In  this 
connection  it  may  be  mentioned  also,  as  confirmatory  of  the  explanation 
offered  of  recurrent  sensibility,  that   if  the  posterior  root  be  divided 


1  Comptes  Rendu?,  tome  xliv.  p.  168.     Paris,  1857 


634  THE    SPINAL    COU  I>. 

beyond  the  anterior  roots  will  then  be  found  to  contain  degenerated 
fibres,  showing  that  some  of  the  fibres  of  the  anterior  root  at  least  are 
really  derived  from  the  posterior  one.  While  there  can  be  no  doubt 
that  tlie  spinal  cord  is  the  exclusive  organ  of  communication  between 
the  brain  on  the  one  hand,  and  the  external  organs  of  sensation  and 
motion  on  the  other,  a  complete  loss  of  sensibility  and  voluntary 
motion  following  its  division,  compression,  or  disorganization  ;  there  still 
prevails  some  uncertainty  as  to  the  exact  routes  by  which  impressions 
made  upon  the  periphery  are  transmitted  from  the  posterior  roots  through 
the  cord  to  the  sensorium  and  voluntary  impulses  in  the  reverse  direc- 
tion through  the  anterior  roots  to  motor  organs. 

The  difference  of  opinion  held  in  this  respect  by  physiologists,  the 
diametrically  opposed  views  that  have  been  maintained,  are  no  doubt 
due  partly  to  the  fact  of  the  structure  of  the  spinal  cord  not  yet  being 
thoroughly  understood  either  in  man  or  animals,  pathological  facts, 
therefore,  being  of  little  use  as  a  means  of  discovering  its  func- 
tions,  but  also  in  a  great  measure  to  the  conclusion  based  upon  experi- 
ments performed  upon  animals  being  applied  to  man  without  it  being 
taken  into  consideration  that  not  only  does  the  spinal  cord  of 
animals  differ  in  certain  respects  from  that  of  man,  but  that  it  varies 
in  its  structure  in  different  parts  of  its  course  even  in  the  same  ani- 
mal. The  brief  expose  that  we  have  to  offer  of  the  functions  of  the 
spinal  cord  in  man  as  a  conductor  of  sensory  and  motor  impulses  to 
and  from  the  periphery,  as  derived  from  the  experiments  and  observa- 
tions of  Chauveau,1  Longet,2  Brown-Sequard,3  Vulpian,4  Schiff,5 
Ludwig6  and  Woroschiloff  Turck,7  Charcot,8  and  the  author,  must  be 
taken,  therefore,  with  qualification,  and  subject  to  the  further  advance 
of  our  knowledge  of  this  difficult  subject.  From  the  fact  of  the 
anterior  roots  being  motor  in  function,  and  the  fibres  of  which  they 
consist  passing  into  the  cells  of  the  anterior  horns  of  the  gray  matter, 
thence  into  the  antero-lateral  columns  of  the  same  side,  it  might  be 
expected  that  these  columns  are  motor  in  function.  That  such  is  the 
case  appears  to  be  shown  both  by  experimental  and  pathological 
evidence.  Thus,  if  a  section  be  made  in  an  animal,  a  rabbit,  guinea- 
pig,  or  dog,  for  example,9  involving  only  the  antero-lateral  columns  of 
one  side  of  the  cord  there  is  entire  loss  of  the  power  of  voluntary 
motion  on  that  side  below  the  level  of  the  section,  while  if  the  columns 
be  stimulated  at  their  distal  ends,  the  muscles  supplied  by  the  portion 
of  the  cord  below  the  section  will  be  thrown  into  contraction.  On  the 
other  hand,  if  the  posterior  columns  and  the  gray  matter  of  the  cord 
be  divided,  the  antero-lateral  columns,  however,  being  uninjured,  the 
power  of  voluntary  motion  is  preserved,  that  of  sensibility  and  muscular 

1  Journal  de  la  Physiologic,  tome  iv.  p.  369.     Paris,  18G1. 

2  Anatomic  et  physiologie  du  systenie  nerveux,  tome  i.  p.  272.  Paris,  1842.  And  Physiologie,  tome  iii. 
p.  338      Paris,  1869. 

3  Physiology  and  Pathology  of  the  Central  Nervous  System.     Philadelphia,  1860. 

4  Lecons  stir  la  physiologie  generale  et  comparee  du  systeme  nerveux.     Paris,  1866. 
6  Lehrbuch  der  Physiologie. 

6  VerhaadluDgen  der  Koniglich  Sachsischen  Gesellschaften  zu  Leipzig,  1875,  iii.  iv.  v.  S.  248. 

7  Wiener  Denkscriften,  1851. 

8  Lecons  Bur  les  Localisations  dans  les  maladies  du  cerveau  et  de  la  moelle  epeniere.     Paris,  1830. 

9  In  making  sections  of  the  cord  in  an  animal  it  is  indispensable  that  tin-  spinal  column  should  be 
firmly  fixed,  and  that  the  cord  be  denuded  within  certain  defined  measurable  areas.  These  conditions 
are  fulfilled  by  using  the  instrument  devised  by  Ludwig  and  Woroschiloff,  and  described  in  Ludwig's 
Arbeiteu,  1875 


DECUSSATION    OF    NERVE    FIBRES 


635 


coordination  is  lost.  The  available  pathological  evidence  confirms 
also  what  has  been  learned  from  histological  examination  of  the  cord 
of  man  and  experiment  upon  animals,  that  of  the  motor  fibres  in  the 
antero-lateral  columns,  and  more  especially  in  the  lateral  ones,  by  far 
the  most  of  them  pass  down  continuously  from  the  corpus  striatum  of 
one  side  of  the  base  of  the  brain  through  the  crus,  pons,  medulla, 
thence  to  the  opposite  side  of  the  cord,  and  down  the  lateral  columns, 
connecting  in  them  with  the  prolongations  of  the  cells  in  the  anterior 
horns  of  the  gray  matter,  which  in  turn  are  connected  with  the  fibres  of 
the  anterior  roots.  Thus,  disorganization  beginning  in  the  corpus 
striatum  or  thereabouts,  progresses  gradually  downward  through  the 
tract  just  mentioned,  involving  motor  paralysis. 

In  the  study  of  the  functions  of  the  corpus  striatum  more  especially, 
additional  facts  will  be  mentioned,  confirming  the  view  just  advanced 
that  the  antero-lateral  columns  of  the  cord,  more  particularly  the  lateral 
portions,  are  motor  in  function,  and  are  the  routes  by  which  motor 
impulses  are  transmitted  from  the  base  of  the  brain  to  the  periphery. 
That  the  gray  matter  of  the  cord  is  essentially  that  portion  of  it 
which  transmits  the  impressions  made  upon  the  periphery  to  the  senso- 
rium  is  shown  by  the  fact  of  sensibility  remaining  as  long  as  the  gray 
matter  preserves  its  normal  structure,  even  after  all  the  columns  have 
been  divided,  and  by  the  experiment  just  mentioned,  in  which  sensation 
is  lost  after  division  of  the  gray  matter,  and  the  posterior  columns,  the 
latter  owing  what  sensibility  they  possess  not  to  their  own  intrinsic 
fibres,  but  to  those  of  the  posterior  roots  which  pass  through  them  in  an 
upward,  downward,  and  horizontal  direction,  on  the  way  to  their  termi- 
nation in  the  posterior  horn  of  the  gray  matter.  Now  it  is  an  interesting 
and  important  fact  that  while  the  motor  fibres 
of  the  cord  decussate  in  the  medulla,  path- 
ological cases  show  that  in  man  at  least  the 
sensory  fibres  decussate  in  the  cord  itself,  at 
about  the  level  in  which  they  enter  through 
the  posterior  roots.  Thus,  if  the  gray  matter 
of  the  cord  and  lateral  column  be  divided 
in  man  on  one  side,  as  by  the  penetration  of 
some  sharp  instrument,  or  compresed  by  a 
tumor  or  disorganized  by  disease,  as  in  cases 
that  have  come  under  the  observation  of  the 
author  and  others,  sensibility  is  lost  on  the 
side  of  the  body  below,  but  opposite  to  the 
side  on  which  the  wound  has  been  inflicted. 
or  the  tumor  located,  the  power  of  voluntary 
motion,  however,  being  lost  on  the  same 
side  of  the  body  as  that  of  the  wound,  etc. 
(Fig.  371,  3).  If  the  section  be  made,  however,  at  a  higher  level  as 
at  -  or  1.  then  the  paralysis  of  both  motion  and  sensation  will  be  on 
the  same  side  of  the  body,  bur  on  the  opposite  side  to  that  of  the  section. 
It  follows,  also,  that  if  the  spinal  cord  be  divided  longitudinally  below 
the  medulla,  in  a  dog,  for  example,  that  while  the  animal  is  able  to 
stand   on  his  four  legs  and  make  voluntary  movements,  as  first  shown 


Fig. 


Diagram  showing  tin arse  of 

the  motor  and  Bensory  fibres  in  the 
spinal  cord  and  medulla  oblongata. 


636  THE    SPINAL    CORD. 

by  Galen,1  it  has  lost  all  sensibility  in  them,  all  the  sensory  fibres 
being  divided  at  their  decussation  in  the  middle  line,  the  motor  fibres 
remaining  uninjured  by  the  section. 

While  there  can  be  but  little  doubt  that  the  decussation  of  the  sensory 
fibres  in  the  spinal  cord  of  man  is  complete,  such  does  not  obtain,  to  the 
same  extent,  in  all  animals,  the  decussation  being  much  less  complete  in 
reptiles  and  birds  than  in  mammals,  and  less  in  the  lumbar  than  in  the 
dorsal  portions  of  the  cord  in  certain  animals.  In  connection  with  the 
anesthesia  of  the  opposite  side  of  the  body  following  a  hemisection  of 
the  cord  may  be  here  appropriately  mentioned  the  hyperesthesia  usually 
developed  in  the  same  side  as  that  of  the  section.  This  remarkable 
condition  of  excited  sensibility,  made  quite  evident  within  a  few  hours 
after  the  operation  by  the  movements  of  the  animal  made  in  response  to 
the  slightest  pinching,  etc.,  of  the  skin,  and  lasting  often  for  weeks,  is 
probably  due  to  the  increase  in  temperature  and  vascularity  brought 
about  by  the  division  of  the  vasomotor  nerves,  or  the  nerves  regulating 
the  calibre  of  the  bloodvessels,  which,  we  shall  see  hereafter,  descending 
from  the  vasomotor  centre  in  the  medulla  oblongata  through  the  antero- 
lateral columns,  but  is  also,  no  doubt,  to  be  attributed  to  the  division 
of  the  inhibitory  or  restricting  fibres,  whose  influence  being  lost,  there- 
fore, upon  the  parts  below  the  section,  the  latter  becomes  more  excitable, 
more  susceptible  to  external  stimulus. 

It  is  a  remarkable  fact  that,  while  the  gray  matter  of  the  cord  trans- 
mits sensory  impressions,  it  itself  appears  to  be  insensible  to  ordinary 
mechanical  or  electrical  stimuli,  since  it  may  be  pricked,  pinched,  or 
electrically  stimulated  without  the  animal  giving  any  signs  of  pain. 
The  gray  matter  can  be,  however,  excited  by  chemical  stimuli,  certain 
poisons,  and  venous  blood.  It  has  already  been  mentioned  that  if  the 
posterior  columns  and  the  gray  matter  of  the  cord  are  divided,  that  the 
power  of  muscular  coordination,  as  well  as  sensibility  is  lost,  and,  as  we 
have  just  seen,  that  sensibility  cannot  be  attributed  to  the  posterior 
columns,  it  would  appear  that  the  function  of  the  posterior  columns  is 
to  coordinate,  to  bring  together  in  harmonious  action,  different  portions 
of  the  cord.  This  view,  based  upon  experiments  made  upon  animals, 
is  confirmed  by  the  pathological  evidence  afforded  by  cases  of  locomotor 
ataxia,  in  which  loss  of  the  power  of  muscular  coordination  is  associated 
with  disease  of  that  portion  of  the  posterior  columns  of  the  cord  known 
as  the  columns  of  Burdach,  the  power  of  voluntary  motion  and  sensi- 
bility being,  however,  retained.  It  may  be  here  mentioned  that  it  is 
quite  possible  that  such  portions  of  the  anterior  columns  not  containing 
the  motor  fibres  of  the  anterior  roots,  like  the  posterior  columns,  may 
be  also  commissural,  coordinating  in  character.  It  must  be  mentioned 
in  this  connection,  with  what  has  been  said  as  to  the  result  of  division 
of  different  parts  of  the  spinal  cord,  that  from  the  fact  of  the  loss  of  the 
power  of  voluntary  motion  and  sensibility  being  frequently  restored, 
that  there  must  exist  potentially,  so  to  speak,  a  vicarious  power  of  inter- 
change of  function  between  different  parts  of  the  cord,  certain  fibres 

l  De  Anat.  Administrate  Lib.  viii.  Cap.  v.,  Opera  Omnia,  t.  ii.  p.  683.     Lips.,  1821. 
Galen  does  not  appear,  however,  to  have  observed  the  loss  of  sensibility  in  such  cases,  which  was  first 
observed  by  Fedora  in  1822,  Journal  de  Physiologic,  t.  iii   p.  199.     Paris,  1823. 


DISTRIBUTION     OF    SPINAL    NERVES.  637 

being  capable,  if  necessary,  of  assuming  the  power  of  transmitting  sen- 
sory and  motor  impulses,  in  addition  to  their  ordinary  characteristic 
functions. 

Resuming,  it  may  be  said,  in  all  probability,  that  in  man,  at  least, 
usually  the  fibres  conducting  motor  impulses  pass  from  the  corpus 
striatum  from  one  side  of  the  brain  down  through  the  lateral  column, 
principally  of  the  opposite  side  of  the  cord  through  to  the  gray  matter 
to  the  anterior  roots,  that  the  fibres  transmitting  sensory  impressions 
pass  from  the  posterior  roots  to  the  gray  matter  of  the  opposite  side  of 
the  cord  upward  in  the  gray  matter  to  probably  the  thalamus  opticus,  and 
that  the  function  of  the  anterior  and  posterior  columns  is  commissural, 
coordinating  in  character.  Finally,  if  it  be  admitted  that  there  is  no 
essential  difference  between  motor  and  sensory  nerves,  then  the  anterior 
root  of  the  spinal  nerves  is  motor,  because  the  fibres  of  which  it  consists 
terminate  in  muscle,  and  the  posterior  sensory,  because  its  fibres  begin 
in  sensory  organs.  Having  demonstrated  now  experimentally  this 
important  distinction  in  function  between  the  roots  and  the  branches  of 
the  spinal  nerves,  and  offered  an  explanation  of  the  cause  of  the  same, 
let  me  briefly  point  out  the  general  distribution  of  the  anterior  and  pos- 
terior branches,  it  being  always  borne  in  mind  that  the  branches,  whether 
anterior  or  posterior,  are  in  their  functions  mixed  nerves,  possessing 
both  motor  and  sensory  properties.  The  anterior  branches  of  the  four 
upper  cervical  nerves  form  the  cervical  plexus,  and  the  four  lower 
cervical,  together  with  the  first  dorsal  nerve,  the  brachial  plexus. 
From  the  cervical  plexus  are  derived  the  superficial  cervical,  great 
auricular,  small  occipital,  supraclavicular,  and  phrenic  nerves,  and  mus- 
cular branches;  the  brachial  plexus  supplying  mainly  the  upper  ex- 
tremity, but  giving  off,  also,  the  supra-  and  subscapular  and  thoracic 
nerves.  The  posterior  branches  of  the  cervical  nerves,  with  the  excep- 
tion of  the  first,  after  passing  backward  from  the  vertebral  canal  divide 
into  external  and  internal  branches,  and  supply  the  muscles  and  integu- 
ment behind  the  spinal  column,  the  posterior  branch  of  the  first  cervical 
issuing  between  the  arch  of  the  atlas  and  the  vertebral  artery,  being 
distributed  to  the  contiguous  straight,  oblique,  and  complex  muscles. 

The  anterior  branches  of  the  dorsal  or  thoracic  nerves,  with  the 
exception  of  the  last  one,  pass  outwardly  in  the  intercostal  spaces,  as 
the  intercostal  nerves,  the  anterior  branch  of  the  last  dorsal  being  situ- 
ated below  the  last  rib  crosses  the  quadrate  lumbar  muscle  as  it  ad- 
vances between  the  internal  oblique  and  transverse  muscle  in  a  similar 
manner  as  an  intercostal  nerve.  In  their  course  the  intercostal  nerves, 
as  they  supply  the  muscles,  give  off  lateral  cutaneous  branches,  that 
from  the  second  intercostal  or  the  intercosto-humeral  nerve  being  an 
important  one,  since  it  extends  across  the  axillary  space,  running  in 
juxtaposition  with  the  small  cutaneous  nerve  from  the  brachial  plexus, 
and  supplies  the  skin  on  the  inner  part  of  the  arm.  The  posterior 
branches  of  the  dorsal  nerves,  like  those  of  the  spinal  nerves,  generally, 
after  turning  backward  between  the  transverse  processes  of  the  vertebrae, 
divide  into  external  and  internal  branches,  the  former  supplying  the 
skin  contiguous  to  the  angle  of  the  ribs,  the  longissimus  and  sacro- 
lumbal- muscles,  the  latter  the  skin  over  the  spinous  processes  of  the 


638  THE    SPINAL    CORD 

vertebrae,  the  multifid  and  semispinal  muscles.  The  anterior  branches 
of  the  upper  four  lumbar  nerves,  together  with  a  filament  from  the  last 
dorsal  nerve,  constitute  the  lumbar  plexus,  and  which,  after  supplying 
the  psoas  and  quadrate  lumbar  muscles,  give  off  the  iliohypogastric, 
ilio-inguinal,  genito-crural,  external  cutaneous,  obturator  and  anterior 
crural  nerves.  The  posterior  branches  of  the  lumbar  nerves  pass  back- 
ward, like  those  of  the  dorsal,  to  supply  the  longissimus  and  sacrolumbar 
muscles,  and  the  adjacent  skin.  The  anterior  branches  of  the  upper 
four  sacral  nerves,  together  with  the  fifth  and  part  of  the  fourth  lumbar 
nerves,  form  the  sacral  plexus,  from  which  are  derived  the  filaments 
supplying  the  pyriform,  internal  obturator  muscles,  etc.,  the  levator  and 
sphincter  ani,  the  superior  gluteal,  pudic,  and  great  and  small  sciatic 
nerves.  The  sacral,  together  with  the  lumbar  plexus,  give  off  the 
nerves  supplying  the  lower  extremity.  The  anterior  branch  of  the  fifth 
sacral,  a  small  nerve,  emerges  from  the  end  of  the  vertebral  canal,  and 
divides  into  two  branches,  one  of  which  passes  with  a  filament  from  the 
fourth  sacral  to  end  in  the  sympathetic,  the  other  joining  the  coccy- 
geal nerve.  While  the  posterior  branches  of  the  upper  four  sacral 
nerves  pass  out  of  the  vertebral  canal  by  the  corresponding  sacral  fora- 
mina, the  posterior  branch  of  the  fifth  sacral  emerges  from  the  end  of 
the  vertebral  canal,  and,  together  with  the  posterior  branch  of  the  coccy- 
geal nerve,  supplies  the  skin  and  muscles  of  the  back.  The  anterior 
branch  of  the  coccygeal  nerve  also  passes  out  of  the  end  of  the  vertebral 
canal,  is  joined  by  a  branch  from  the  fifth  sacral  after  perforating  the 
coccygeal  muscle  and  great  sacro-sciatic  ligament,  and  terminates  in 
the  skin  of  the  buttock.  The  posterior  branch  of  the  coccygeal,  like 
the  anterior  branch,  emerges  from  the  end  of  the  vertebral  canal ;  its 
distribution  has  just  been  referred  to  in  connection  with  that  of  the 
posterior  branch  of  the  fifth  sacral. 


CHAPTER    XLI. 

THE  SPINAL  CORD  AS  A  NERVOUS  CENTRE.     REFLEX  ACTION. 


One  of  the  most  striking  differences  in  the  organization  of  animals  is 
the  extent  to  which  the  division  of  labor,  physiologically  speaking,  is 
carried.  Indeed,  the  lowest  forms  of  life,  such  as  the  monera  (con- 
sisting, as  we  have  seen,  of  mere  masses  of  protoplasm),  are  so  utterly 
unorganized  as  to  make  it  impossible  to  say  whether  such  things 
should  be  assigned  genealogically  to  the  vegetable  or  animal  kingdom. 
It  is  true,  that  among  such  primitive  forms  of  life  there  are  beings, 
like  the  common  amoeba,  in  which  there  is  a  slight  differentiation  of 
structure,  in  that  not  only  a  nucleus  and  nucleolus  are  present,  but 
that,  at  times,  even  an  enveloping  membrane  or  cell  wall  is  developed, 
and  that  among  the  infusoria  are  also  seen  forms,  like  paramcecium, 
apparently  cpute  organized ;  nevertheless,  even  these  protozoan  ani- 
malcuhe,  so  much  more  complex  in  their  structure  than  the  monera, 
cannot  be  said  to  be  organized  in  the  same  sense  that  the  remaining 
members  of  the  animal  kingdom,  or  metazoa  are.  Even  the  infusoria, 
apparently  complex  as  they  are  in  their  structure,  are  morphologically 
only  unicellular,  and  never  passing  beyond  this  primitive  one-celled 
stage  ;  tissues,  and  still  less  organs,  are  never  developed  in  them  similar 
to  those  of  which  the  body  of  one  of  the  higher  animals  is  made  up, 
since,  as  we  have  already  seen,  the  organs  in  the  latter  consist  of  tissues 
and  the  tissues  of  cells,  the  latter  resulting 
from  the  division  of  the  primitive  cell.  In- 
deed, it  is  not  until  we  reach  in  the  tree  of 
life  the  porifera,  actinozoa,  and  hydrozoa,  of 
which  the  sponge,  anemone,  and  jelly  fish, 
familiar  objects  at  the  sea-shore,  are  examples, 
that  we  meet  with  anything  like  organization. 
at  least  in  the  true  morphological  sense  of  the 
word — that  is  to  say,  of  an  animal  consisting 
of  organs  made  up  of  tissues  developed  out 
of  cells  resulting  from  the  segmentation  of  a 
primitive  cell,  or  ovum.  Suppose  that  the 
structure  of  one  of  the  hydrozoa  be  consid- 
ered as  that  of  the  common  <j;vvv\\  hydra  (Fig. 
372),  found  during  the  summer  in  almost 
every  fresh  water  pool,  and  therefore  an  object 
for  study  accessible  to  all,  it  will  be  found 
that  the  animal,  about  half  an  inch  in  length 
and  a  line  in  diameter,  is  essentially  a  double-layered  tube,  closed  at 
one  end  and  open  at  the  other,  the  latter  serving  as  a  mouth  and  sur- 
rounded with  slight  tentacles,  or  feelers,  by  means  of  which  it  seizes  its 


Fig.  372. 


Hydra.     (Milne  Edwards.) 


640 


THE    SPINAL    CORD. 


Fig.  373. 


prey,  the  outer  layer,  or  ectoderm,  of  the  tube,  functionating  as  skin, 
the  inner  layer,  or  endoderm,  as  a  mucous  digestive  surface. 

Leaving  out  of  consideration  an  imperfectly  developed  neuromuscular 
layer  or  mesoderm  intermediate  between  the  ectoderm  and  endoderm 
(absent  in  the  protohydra),  the  hydra  may  be  considered  functionally  as 
little  more  than  a  digestive  sac.  That  the  differentiation  of  ectoderm  and 
endoderm  is  very  incomplete,  is  shown  from  the  fact  that  if  the  animal  be 
turned  inside  out  the  skin  or  ectoderm  becomes  digestive  in  function, 
and  the  digestive  surface  or  endoderm  epidermal,  just  as  the  mucous 
membrane  of  the  mouth  or  anus  in  man  may  become  skin  if  everted,  or 
the  skin  of  the  same  parts  mucous  membrane  if  inverted.  This  is,  how- 
ever, as  might  have  been  expected,  since,  as  we  shall  see  hereafter,  there 
can  be  little  doubt  but  that  the  ectoderm  and  endoderm  of  the  hydra  are 
homologous  with  the  epiblast  and  hypoblast  of  the  embryo,  or  the  parts 
corresponding  to  the  skin  and  mucous  membrane  of  the  adult.  Further, 
that  no  one  part  of  the  hydra  differs  essentially  from  any  other  part,  is 
shown  by  the  well-established  fact  that  if  a  hydra  be  cut  up  into  several 
pieces  each  piece  will  live  and  lead  an  independent  existence  and  develop 
into  a  perfect  hydra.    While,  at  first  sight,  such  a  result  may  appear  as  a 

very  extraordinary  one,  it  becomes  a  perfectly 
natural  and  intelligible  one  when  it  is  remem- 
bered that  all  parts  of  the  body  of  the  hydra 
have  essentially  the  same  function,  and  that 
there  is  no  interdependence  between  the  parts 
of  which  it  consists.  Reproduction  by  fission, 
whether  produced  artificially  or  naturally,  is 
not  confined,  however,  by  any  means  to  such 
low  forms  of  life  as  the  hydra,  being  observed 
as  well  in  quite  highly  organized  animals  as 
among  the  annelida,  of  which  the  marine 
worms,  such  as  the  clam  worm  (nereispelagica) 
of  our  coasts  (Fig.  373),  etc.,  are  examples. 
The  body  of  a  nereid  worm,  consisting  of  nu- 
merous segments,  is  naturally  very  apt  to  break 
up  into  numerous  pieces  consisting  of  one  or 
more  of  the  segments,  as  the  animal  glides 
along  among  the  rocks,  sand,  or  sea-weed, 
each  piece  becoming,  under  favorable  circum- 
stances, a  perfect  animal.  Indeed,  at  certain 
seasons  of  the  year  there  may  be  seen  in  cer- 
tain kinds  of  these  worms  (protula)  at  different 
portions  of  the  body  constrictions  indicating 
the  parts  where  the  body  will  break  up,  by 
natural  fission,  into  a  progeny  of  worms. 
That  such  a  mode  of  reproduction  should 
take  place  in  an  animal  as  highly  organized 
as  those  just  mentioned,  having  a  distinct 
body  cavity  inclosing  a  nervous  system,  ali- 
mentary canal,  heart,  may  appear  even  more  extraordinary  than  the 
case  of  the  hydra  just  referred  to.     It  must  be  borne  in  mind,  however, 


THE    SPINAL    CORD     AS     A    NERVOUS    CENTRE.  641 

that  in  the  worm,  as  in  the  hydra,  there  is  but  little  interdepend- 
ence of  parts,  each  segment  having  its  own  nervous  ganglion  and 
fractional  part,  so  to  speak,  of  the  alimentary  canal  and  vascular  tubes 
running  from  end  to  end  of  the  animal.  In  fact,  an  annelid  may  be 
regarded,  morphologically,  as  consisting  of  a  chain  of  small  annelids 
(the  segments  depending  but  little  upon  each  other,  linked  together, 
as  it  were,  for  only  the  time  being).  A  glance  now  at  the  organiza- 
tion of  a  vertebrate  animal,  or  even  one  of  the  higher  invertebrates, 
will  at  once  show  how  profoundly  such  an  animal  differs  from  any 
of  those  hitherto  mentioned.  The  brain,  as  in  man,  for  example, 
situated  in  the  skull,  depending  for  its  activity  upon  the  blood  driven 
to  it  by  the  heart,  in  the  thoracic  cavity,  the  rhythmical  action  of  the 
heart  and  lungs  maintained  by  nervous  influences  emanating  from  the 
base  of  the  brain,  the  alimentary  canal  within  the  abdominal  cavity 
supplying  the  materials  for  the  nourishment  of  the  brain  and  other 
organs,  but  dependent  upon  the  blood  supplied  to  it  by  the  heart  for  the 
elaboration  of  the  alimentary  secretions,  illustrating  sufficiently  how 
intimate  is  the  connection  existing  between  the  cranial,  thoracic,  and 
abdominal  organs,  and  the  impossibility  of  any  one  segment  of  the  body 
containing  such,  living  a  life  entirely  independent  of  the  remaining  ones, 
as  we  have  just  seen  is  the  case  in  many  of  the  lower  animals.  This 
contrast  between  the  lower  and  higher  animals  with  reference  to  the 
extent  with  which  the  division  of  labor  is  carried  on,  is  well  illustrated 
by  the  difference  between  the  savage  and  civilized  state  of  society — and, 
indeed,  the  difference  is  something  more  than  a  mere  comparison,  being 
of  a  profound  meaning  to  those  who  believe  that  the  life  of  a  nation  is 
developed  according  to  law  as  certainly  as  that  of  the  individuals  of 
which  it  is  composed. 

In  the  uncivilized,  savage  state,  each  individual  is  independent  of  his 
neighbors  as  the  one  segment  of  the  worm  may  be  to  that  of  the  other ; 
his  interest  not  being  usually  their  interest — on  the  contrary,  often 
antagonistic — he  builds  his  simple  hut,  hunts  his  own  game,  clothes 
himself;  a  birth  among  his  tribe  adds  to,  a  death  takes  away  nothing 
from  his  daily  life.  Under  such  circumstances  there  can  be  no  accu- 
mulation of  wealth  and  the  development  incidental  to  it.  In  the 
civilized  state,  on  the  contrary,  the  interest  of  the  one  is  the  interest 
of  all,  as  that  of  the  one  organ  in  the  human  body  is  that  of  the 
others  ;  each  individual  confining  himself  to  one  avocation,  the  latter 
is  advanced  to  its  utmost  limits,  depending  upon  others  for  that  which 
he  does  not  produce  himself,  the  product  of  his  own  industry  reaches 
the  highest  perfection  ;  and  so  with  the  productions  of  others,  and  thus 
the  wealth  of  the  nation  increases  both  in  variety  and  amount.  Just 
as  with  the  uncivilized,  as  compared  with  the  civilized,  so  with  the  lower 
animals  as  compared  with  the  higher  ones;  just  as  the  development  of 
a  nation  depends,  not  only  upon  the  variety  of  the  interests,  but  upon 
the  mutual  interdependence  of  the  same;  so  the  life  of  an  animal  is 
high  in  proportion  to  the  variety  of  its  organs,  and  the  mutual  har- 
monious working  of  the  same.  The  famous  example  of  the  number  of 
persons  engaged  in  the  making  of  nails  or  pins,  and  the  great  number 

4\ 


642 


THE    SPINAL    C0U1). 


Fig.  374. 


that  can,  consequently,  be  so  produced,  as  mentioned  by  Adam  Smith,1  is 
as  applicable  as  illustrating  biological  as  well  as  politico-economical  laws. 
The  life  of  a  man  biologically  as  well  as  socially,  when  compared  with 
that  of  a  sponge,  may  be  summed  up  in  saying  that  in  the  former  the 
division  of  labor  is  carried,  so  far  as  we  yet  know,  to  its  utmost  limits  ; 
in  the  latter  but  little,  if  at  all.  This  division  of  labor,  so  characteristic 
of  the  higher  animals,  and  which  we  have  illustrated  on  account  of  its 
importance  somewhat  in  detail,  is  not  only  well  seen  in  the  general 
organization  of  the  higher  animals,  but  in  the  extreme  differentiation 
exhibited  in  their  alimentary,  vascular,  nervous  systems,  etc.,  and  as 
it  is  the  functions  of  the  latter  that  we  are  now  more  particularly  con- 
sidering, it  will  be  well  to  illustrate  the  general  structure  of  the  nervous 
system  in  animals  by  a  few  examples  before  taking  up  the  consideration 
of  the  subject  of  the  reflex  action  of  the  spinal  cord  of  man,  the  nature 
of  which  it  is  hoped  will  be  made  clearer  by  the  preceding  introductory 
than  it  would  have  been  without  it. 

Of  the  simplest  form  of  nervous  system  may  be  mentioned  that  of 
the  ascidiordia,  as  seen,  for  example,  in  a  phalusia,  in  which  the  entire 
nervous  system  consists  (Fig.  374)  of  a  single  ganglion,  receiving  or 
giving  off  filaments  from  or  to  the  periphery.  On 
touching  this  worm-like  animal,  and  seeing  it  con- 
tract its  body,  judging  from  one's  own  feelings  and 
actions,  we  would  infer  that  the  animal  felt  the 
touch,  and  voluntarily  retracted  its  body,  and  con- 
clude that  the  impression  made  upon  the  integu- 
ment was  transmitted  by  an  afferent  centripetal,  or 
sensory  nerve,  to  the  ganglion,  and  there  felt,  and 
that  the  impulse  emanating  from  the  latter  was 
transmitted  by  an  efferent,  or  centrifugal,  or  motor 
nerve  to  the  muscle,  and  there  resulted  in  volun- 
tary motion,  the  whole  action  being  called  a  reflex 
one  from  the  fact  of  the  impression  made  upon  the 
periphery  being  first  transmitted  to  the  ganglion 
and  thence  reflected  back  again.  If  the  ganglion 
be  not  endowed  with  sensation  and  volition,  then 
the  animal  must  be  without  either,  since  it  pos- 
sesses no  other  structure  of  which  such  qualities 
can  be  predicated.  Further,  if  muscular  action,  in 
response  to  stimuli  applied  to  the  periphery,  is  no  evidence  of  either 
sensation  or  volition,  then  it  is  impossible  to  say  whether  any  animal 
feels,  or  wills,  under  any  circumstances.  If  now  the  nervous  system  of 
a  starfish  be  compared  Avith  that  of  the  ascidian,  just  mentioned,  the 
only  essential  difference  presented  by  the  former  is  that,  instead  of  one 
ganglion  there  are  five  (Fig.  375),  which,  together  with  the  commis- 
sural filaments,  constitute  a  circum-oral  ring,  from  which  are  given  off 
the  nervous  filaments  supplying  the  rays. 

It  follows,  therefore,  that  if  the  ganglion  of  the  ascidian  be  endowed 
with  sensation  and  volition,  then   all  five  ganglia  of  the  starfish    are 


Nervous  system  of  an 
ascidian.  A.  the  mouth. 
B.  The  vent.  C.  The 
ganglion.  J).  The  muscu- 
lar sac. 


An  Inquiry  into  the  Nature  and  Causes  of  ihe  Wealth  of  Nations,  vol.  i.  p.  7.     Edinburgh,  1814. 


NERVOUS    SYSTEM    OF    SEA     HARE     AND    CENTIPEDE.       643 

endowed  with  the  same  functions,  the  only  difference  between  the  two 
being  that,  in  the  one,  whatever  sensation  and  volition  the  animal  may 


Fio.  375. 


Fig.   376. 


Nervous  system  of  starfish.     (Dalton.) 


Nervous  system  of  aplyeia.     (D-vlton.) 


be  possessed  of  is  concentrated  in  the  single  ganglion,  Fig.  3^ 
whereas,  in  the  other,  the  sensation  and  volition  are  dif- 
fused among  the  five  ganglia.  It  is  obvious,  also,  that, 
on  account  of  the  radial  symmetry  presented  by  the 
starfish,  it  is  impossible  to  assign  any  special  function  to 
any  one  of  the  ganglia  that  is  not  possessed  by  the 
others.  And,  while  even  in  the  mollusca,  of  which  the 
aplysia  (Fig.  376),  or  sea  hare,  is  an  example,  the 
supra -oesophageal  ganglion  (1)  is  regarded,  morpho- 
logically, as  a  brain,  there  is  little  reason  to  suppose 
that  it  possesses,  exclusively,  any  very  specialized  func- 
tion not  shared  by  the  infra-oesophageal  (2)  one,  or 
that  the  latter,  in  turn,  differs  very  much,  functionally, 
from  the  remaining  ganglia  (3,  4)  distributed  through  the 
body,  and  with  which  it  is  connected  by  commissural 
filaments  as  well  as  with  the  supra-oesophageal  one. 
It  is  true  also,  that  the  supra  -  oesophageal  ganglion 
(Fig.  377)  of  centipedes,  insects,  etc.,  is  usually  spoken 
of  as  the  brain  of  such  animals,  and  the  ventral  chain  of 
ganglia  compared  to  the  spinal  cord  of  vertebrates,  but,  as 
some  of  the  nerves  in  insects,  for  example,  supplying  the 
head,  are  derived  from  the  supra-oesophageal  ganglion, 
and  others  from  the  infra-oesophageal  ganglion  and,  as 
the  latter  ganglion  does  not  differ  essentially  from  the 
remaining  ones  of  which  the  ventral  chain  consists,  it 
is  difficult  to  see  why  any  one  ganglion  should  be  desig- 
nated as  cerebral  and  the  other  as  spinal.  That  there 
is  no  such  essential  difference  between  the  so-called  cerebral  and  spinal 
ganglion   is   shown  from  the  fact  that,  if  a  worm  breaks  up  into  two, 


Nervous     system 
o    centipede.  (Dal- 

TON.) 


644 


THE    SPINAL    CORD. 


through  fission,  the  ganglion  that  was  central  in  the  parent  animal  be- 
comes  anterior  in  the  new  individual,  and  goes  to  form  its  brain. 
Further,  in  the  ease  of  worms,  insects,  etc.,  it  is  questionable  whether 
such  animals  are  comparable  at  all  as  regards  their  nervous  systems 
with  vertebrated  ones,  since,  as  a  glance  at  Fig.  378  Avill  show,  while 
the  cerebro-spinal  nervous  centres  of  the  vertebrate  are  dorsal,  the 
ganglion  chain  of  the  articulate  is  ventral,  and,  while  the  heart  is  dorsal 
in  the  articulate,  it  is  intermediate  in  the  vertebrate  between  the  ali- 
mentary canal  and  the  nervous  centre.  In  other  words,  to  compare 
an  articulated  with  a  vertebrated  animal,  with  reference  to  homolo- 
gizing  their  nervous  systems,  one  or  the  other  must  be  placed  upside 
down,  and,  however  the  vertebrated  animal  be  placed,  it  is  obvious  that 
no  comparison  can  be  made  at  all  between  its  nervous  system  and  that 
of  the  echinodermatous  or  molluscus  type.  Such  being  the  case,  it 
would  be  illogical  to  apply  the  results  of  investigation  made  upon  the 
nervous  system   of   invertebrates   to  that   of    vertebrates,  the   nervous 


Fig.  878. 


N- 


Diagrammatic  sections  of  an  articulated  invertebrate  and  vertebrate.  1.  Longitudiual  section  of  in- 
vertebrate. 2.  Longitudinal  section  of  vertebrate.  3.  Transverse  section  of  invertebrate.  4.  Trans- 
verse section  of  vertebrate.     U.  Heart.    A.  Alimentary  canal.    N.  Nervous  system.    CM.  Cborda  dorsalis. 


system  not  being  comparable  in  the  two  great  divisions  of  the  animal  king- 
dom. For  this  reason,  any  conclusion  as  to  the  functions  of  the  different 
parts  of  the  nervous  system  in  man,  drawn  from  the  study  of  the  nervous 
system  in  animals,  must  be  based  upon  that  of  the  vertebrates  only, 
more  particularly  of  such  classes  in  which  the  parts  composing  the 
nervous  system  can,  without  doubt,  be  homologized.  The  amphioxus, 
the  lowest  of  vertebrates,  being  headless,  offers,  in  the  structure  of  its 
nervous  system,  absolutely  nothing  comparable  with  the  brain  of  the 
remaining  vertebrates.  Unless  it  be  denied  that  the  amphioxus  can  feel 
or  will,  of  which  there  is  not  the  slightest  evidence,  it  necessarily  follows 
that  the  spinal  cord  of  this  primitive  vertebrate,  at  least,  is  endowed 
with  sensation  and  volition.  If  such  be  admitted,  and  it  is  difficult  to 
see  how  the  conclusion  can  be  avoided,  analogy  would  lead  us  to  suppose 


RATIO    OF    BRAIN    TO    SPINAL    CORD.  6-i5 

that  the  spinal  cord  of  the  lamprey  and  myxine,  to  a  certain  extent,  at 
least,  would  possess,  also,  similar  qualities,  particularly  as  the  sensation 
and  volition  exhibited  by  such  animals  are  out  of  all  proportion  to  the 
•  amount  of  brain  present.  Inasmuch,  however,  as  these  marsipo- 
branchial  fishes  have  a  brain,  or,  at  least,  the  basal  ganglia  of  the 
brain  of  the  higher  vertebrates,  it  is  to  be  inferred  that,  with  these 
additional  important  structures,  even  if  little  developed,  there  would  be 
exhibited  corresponding  higher  faculties  than  shown  by  the  amphioxus, 
and  such  is  found  to  be  the  case,  and,  as  we  pass  from  these  lowly 
organized  vertebrates  through  the  higher  ones,  to  man,  it  will  be 
observed,  as  may  be  seen  from 

Table  LXXIII. — Ratio  of  Brain  to  Spinal  Cord. 

Man 33.0      to  1 

Mouse 4.0      to  1 

Pigeon 3.3      to  1 

Triton 0.550  to  1 

Lamprey 0.001  to  1 

Amphioxus.         .......  0.0      to  1 

that  the  brain  becomes  more  and  more  developed  both  relatively  and 
absolutely  with  reference  to  the  spinal  cord,  the  extremes  of  the  series 
being  represented  by  man  and  the  amphioxus  respectively. 

Now,  as  we  have  seen  in  general  that  the  higher  animals  differ  from 
the  lower  ones  in  the  extent  to  which  the  division  of  labor  is  carried, 
the  higher  grade  of  life  exhibited  by  the  former  depending  upon  the 
greater  differentiation  of  their  organization,  the  development  of  the  brain 
just  alluded  to  might  have  been  anticipated,  it  being  obviously  of  ad- 
vantage that  certain  functions  of  the  nervous  system  would  be  restricted 
to  the  brain,  others  to  the  spinal  cord,  and  hence,  as  we  shall  see  pres- 
ently, the  great  development  of  the  intellectual  powers  in  the  higher 
animals  as  compared  with  the  lower  ones.  Further,  it  will  be  found 
that  corresponding  with  this  idea  of  the  division  of  labor,  that  while  the 
spinal  cord^of  the  lower  vertebrates  may  possess  both  sensation  and 
volition,  that  of  the  higher  ones  in  becoming  to  a  considerable  extent  a 
conductor  of  sensory  and  motor  impulses  loses  such  qualities,  the  seat 
of  the  sensorium  and  will  being  transferred  to  a  higher  plane,  being 
gradually  elevated,  so  to  speak,  in  the  higher  animals.  Thus  while 
sensation  and  volition  are  diffused  through  the  spinal  nervous  axis  of 
the  lowest  vertebrates  it  gradually,  through  the  process  of  development, 
becomes  concentrated  in  the  cranial  expansion  of  that  of  the  higher  ones. 
The  theoretical  considerations  just  offered  are  fully  borne  out  by  experi- 
ment as  well  as  by  the  facts  of  comparative  anatomy.  Thus,  if  a  frog  be 
decapitated  and  a  drop  of  acetic  acid  be  placed  upon  the  skin  near  the 
anus1  the  animal  keeps  changing  its  position,  and  Avill  endeavor  to  wipe 
off  the  acid  by  means  of  the  foot  of  the  same  side  of  the  body  to  which 
the  acid  was  applied,  and,  if  the  latter  be  amputated,  by  means  of  the 
opposite  foot.  Not  infrequently,  also,  the  author  has  seen  the  animal 
trv  to  remove  the  acid  by  one  of  the  upper  extremities,  both  legs  having 

1  Pfliiget  :  Die  Sensorischen  Funktionen  lies  Ruckemnarks.  1853 


64()  THE    SPINAL    CORD. 

been  amputated.  Considerable  difference  of  opinion  still  exists  as  to 
whether  such  an  action  as  that  exhibited  by  a  decapitated  frog  involves 
sensation  and  volition,  or  is  to  be  regarded  as  a  simple  reflex  action — 
that  is,  of  an  action  such  that  an  impression  being  made  upon  the  skin 
of  an  animal  and  being  transmitted  by  an  afferent  nerve  to  the  gray 
matter  of  the  cord,  is  thence  reflected  by  an  efferent  nerve  to  a  muscle 
without  the  animal  necessarily  feeling  anything  or  making  any  volun- 
tary effort.  It  appears  to  us,  however,  that  a  frog  with  its  head  on 
when  stimulated  by  acetic  acid  gives  but  little  more  evidence  of  sensa- 
tion and  volition  than  with  its  head  oft'  when  so  stimulated,  the  difference 
exhibited  between  the  cases  being  rather  one  of  degree  than  of  kind. 
Of  course,  the  frog  with  its  head  on  feels  and  wills  more  than  with  its 
head  off,  but  it  does  not  follow,  in  the  latter  case,  that  the  animal 
does  not  feel  or  will  at  all.  Indeed,  if  it  be  denied  that  the  decapitated 
frog  feels  and  wills,  it  becomes  very  questionable  whether  there  is  any 
way  at  all  of  positively  proving  that  the  frog  with  its  head  on  feels  and 
Avills.  Further,  if  it  be  affirmed  that  sensation  and  volition  are  restricted 
to  the  brain,  then  the  amphioxus  must  be  without  either,  and  that  ex- 
hibited by  the  lower  vertebrates,  the  frog  included,  out  of  proportion  to 
the  amount  of  brain  present.  It  is  often  urged  that,  as  we  know  from 
cases  in  which  the  spinal  cord  has  been  injured  in  man,  that  muscular 
contractions  resulting  from  the  tickling  of  the  sole  of  the  foot  are  per- 
formed unconsciously,  that  the  muscular  action  just  described  as  taking 
place  in  the  decapitated  frog  is  no  evidence  that  the  animal  either  feels 
or  wills.  It  should  be  borne  in  mind,  however,  that  no  one  ever  saw  a 
man  with  a  fractured  spine,  still  less  with  his  head  cut  off,  apply  his 
hand  or  foot  to  his  anus  and  Avipe  away  acetic  acid  placed  thereupon,  as 
done  by  the  decapitated  frog,  and  until  this  has  been  observed  it  can 
hardly  be  said  that  the  cases  are  parallel,  or  that  conclusions  can 
be  drawn  as  to  the  sensation  or  volition  possessed  by  the  spinal  cord  of 
the  decapitated  frog  from  observations  made  upon  human  beings  suffer- 
ing from  injuries  of  the  spine  by  tickling  the  soles  of  the  feet.  Indeed, 
the  muscular  contractions  following  the  tickling  of  the  sole  of  the  foot 
in  cases  of  injuries  of  the  spine  in  human  beings  are  very  simple  in 
character,  similar  to  those  ensuing  when  the  nerve  of  an  amputated 
limb  is  stimulated,  whether  it  be  that  of  a  man  or  frog. 

Such  contractions  are  never  coordinated  with  reference  to  the  per- 
formance of  any  definite  object,  and  do  not  suggest  in  any  way  the 
idea  that  the  amputated  limb  either  feels  or  wills,  and  the  case  is  not 
substantially  altered,  by  the  limb  being  attached  to  the  body,  the  only 
difference  being  then  that  the  nerve  is  bent  into  an  afferent  and 
efferent  arc,  the  gray  matter  of  the  cord  connecting  the  axis-cylinder 
of  the  ascending  and  descending  parts  of  the  same.  The  question 
may  never  be  settled  as  to  whether  the  headless  frog  feels  and  wills  or 
not,  or  to  what  extent  sensation  and  volition  may  be  properties  of  the 
spinal  cord  in  the  lower  vertebrates,  or  as  to  the  true  nature  of  reflex 
action ;  on  the  supposition,  however,  that  man  has  gradually  developed, 
and  in  harmony  with  the  idea  that  as  we  pass  from  the  lower  to  the 
higher  vertebrates  through  the  division  of  labor,  the  properties  of  the 
spinal  cord  from  being  general,  become    more   and    more    special    in 


NATURE    OF    A    REFLEX    ACTION. 


647 


character,  it  is  quite  possible  that  many  actions  which  are  now  per- 
formed unconsciously  in  the  higher  animals  may  have  been  originally 
accompanied  with  both  sensation  and  volition  in  the  lower  ones,  and  to 
a  certain  extent  are  still.  As  a  matter  of  fact,  many  actions  like  that 
of  walking,  playing  upon  musical  instruments,  etc.,  involving  at  first 
both  sensation  and  volition,  through  constant  repetition  are  performed 
in  time  unconsciously.  Whether  this  view  of  all  reflex  action  being 
originally  accompanied  with  consciousness,  but  through  constant 
repetition  being  finally  performed  unconsciously,  becoming,  as  it  were, 
organized  within  us,  a  kind  of  second  nature,  be  accepted  or  not, 
there  is  no  doubt  that  in  man,  at  least,  that  the  seat  of  sensation  and 
volition  is  limited  to  the  brain,  and  that  there  are  many  and  varied 
actions  going  on  in  the  body  not  involving  consciousness  at  all,  and 
performed  entirely  by  the  spinal  cord  and  medulla,  and  to  the  considera- 
tion of  which  let  us  now  turn. 

A  reflex  action  (Fig.  379)  implies  the  presence   of  an  afferent  or 
centripetal  nerve  (A)  of  the  gray  matter  of  the   cord  (0),  and  of  an 


Fig.  879 


Fig.  380. 


Diagram  to  illustrate  reflex 
action. 


efferent  or  centrifugal  one  (E).  We  make  use  of  these  terms  in  prefer- 
ence to  those  of  sensory  and  voluntary  motor  nerves,  since  many  reflex 
actions  like  the  rhythmical  action  of  the  heart  and  lungs  are  performed 
entirely  unconsciously  without  our  feeling  or  willing  in  the  matter  at 
all,  while  others,  involving  sensation,  as  the  winking  of  the  eye- 
lids on  an  object  being  brought  suddenly  close  to  the  eyes  is  entirely 
involuntary,  as  we  all  know,  from  daily  experience.  In  many  instances 
of  reflex  action,  as  in  deglutition,  walking,  coughing,  sneezing,  tetanus, 
vomiting,  etc.,  both  the  afferent  and  efferent  nerves  involved  are  spinal 
nerves.  In  other  cases,  as  in  blushing,  etc.,  while  the  afferent  nerves 
are  spinal,  the  efferent  nerves  belong  to  the  sympathetic  system.  On 
the  other  hand,  the  afferent  nerves  may  be  derived  from  the  sympa- 
thetic, the  efferent  from  the  spinal  system,  as  in  convulsions  due  to 
the  presence  of  intestinal  worms,  not  uncommon  in  infants.  Finally, 
both  afferent  and  efferent  nerves  may  be  sympathetic  nerve  fibres,  as  in 
the  production  of  certain  of  the  intestinal  secretions.  Whether,  how- 
ever, the  afferent  and  efferent  nerves  be  spinal  or  sympathetic  in  origin, 


6-18  THE     SPINA  I,    CORD. 

or  the  phenomena  be  accompanied  with  sensation,  but  without  volition, 
or  without  either  in  each  of  the  instances  just  referred  to,  an  impression 
being  made  upon  the  periphery  and  transmitted  by  an  afferent  nerve 
to  the  gray  matter  of  the  cord  is  thence  reflected  outwardly  again  to 
the  periphery  by  an  efferent  one,  and  while  muscular,  glandular,  or 
vascular  action  may  in  response  to  an  afferent  irritation  respectively 
follow,  as  in  the  instance  given  above,  according  as  the  efferent  nerve 
is  distributed  to  a  muscle,  gland,  or  vessel,  it  is  not  impossible  that  all 
three  effects  may  be  produced  simultaneously  by  a  single  impression,  as 
in  Fig.  380.  Many  of  the  examples  just  given  being  rather  illustra- 
tions of  the  reflex  action  of  the  medulla  than  of  the  spinal  cord,  their 
further  consideration  will  be  deferred  until  the  afferent  and  efferent 
nerves  involved  have  been  described. 

If  the  impression  made  upon  the  periphery  be  not  a  very  strong  one, 
usually  the  reflex  action  resulting  is  unilateral — that  is  to  say,  is  con- 
fined to  the  same  side  of  the  body  irritated.  If,  however,  the  im- 
pression be  sufficiently  strong  to  pass  through  the  gray  matter  of  the 
cord  and  be  reflected  outwardly,  then  the  reflex  action  is  symmetrical — 
that  is,  the  general  effect  produced  on  the  opposite  side  of  the  body  is 
the  same  as  that  of  the  side  irritated.  As  might  be  expected,  if  the 
impression  be  sufficently  strong  to  produce  the  same  effect  on  both 
sides  of  the  body,  the  movements  upon  the  opposite  side  never  surpass 
in  extent  those  of  the  side  irritated ;  further,  while  the  efferent  nerve 
affected  is  usually  on  the  same  plane  as  that  of  the  afferent  one  irritated, 
if.  the  impression  be  sufficiently  strong  to  be  propagated  beyond  the 
point,  the  nerves  affected  are  always  situated  above  and  never  below 
that  point.  It  should  be  mentioned,  however,  in  this  connection  in  the 
case  of  the  reflex  action  of  the  encephalon  the  impression  passes  down- 
ward to  the  medulla  oblongata,  the  latter  having  the  power  of  gen- 
eralizing all  reflex  actions.  That  the  different  parts  of  the  body  are 
intimately  connected  has  been  well  known  from  time  immemorial  to 
the  physician,  but  it  is  only  within  comparatively  modern  times  that 
it  has  been  recognized  that  the  sympathy,  as  it  was  called,  undoubtedly 
existing  between  the  various  organs,  depends  upon  reflex  action.  As 
the  doctrine  of  sympathy  is  a  very  important  one  from  a  pathological 
as  well  as  from  a  physiological  standpoint,  it  may  not  appear  superfluous 
to  illustrate  it  a  little  by  a  few  examples.  Thus,  for  example,  the 
oesophagus  having  been  divided,  if  the  stomach  be  irritated,  the  salivary 
glands  will  secrete;  on  the  other  hand,  if  the  lingual  nerve  be  stimulated 
as  by  the  taking  of  tobacco,  the  stomach  will  secrete.  Evidently  the  im- 
pression made  upon  the  stomach  in  the  first  case  is  transmitted  to  the 
cord  and  thence  reflected  outwardly  to  the  salivary  glands,  whereas  in 
the  second  case  the  impression,  being  made  upon  the  tongue,  is  trans- 
mitted to  the  cord  and  thence  reflected  to  the  stomach.  Similarly  the 
irritation  due  to  hemorrhoids  modifies  the  character  of  the  gastric  juice 
to  such  an  extent  that  digestion  becomes  impossible,  and  the  ensuing 
dyspepsia  only  curable  by  removal  of  the  hemorrhoids  or  the  ex- 
citing cause.  The  flow  of  tears  due  to  some  external  irritation  disappears 
with  the  loss  of  sensibility,  while  photophobia,  often  attributed  to  irrita- 
tion of  the  optical   nerve,   is  in   reality   due   to  irritation  of  the  fifth 


SPINAL    NERVE    CENTRES.  649 

pair  of  nerves.  The  fact  of  disease  in  one  eye  often  involving  loss  of 
the  other  illustrates  the  nervous  sympathy  existing  between  the  two. 
Neuralgia  of  branches  of  the  frontal  nerve,  due  to  caries  of  the  teeth,  is 
of  frequent  occurrence.  The  irritation,  and  even  inflammation  of  the 
abdominal  viscera  following  severe  burns  is  well  known  to  the 
surgeon.  The  stoppage  of  the  heart  brought  about  by  blows  on  the 
epigastrium,  the  tetanus  due  to  injuries  of  the  thumb  and  big  toe,  the 
paraplegia  from  disease  of  the  urogenital  organs,  the  development  of 
the  mammary  glands  coincident  with  that  of  the  foetus,  are  illustrations 
among  many  offered  by  Brown  Sequard1  of  the  important  fact  never  to 
be  lost  sight  of,  that  the  exciting  causes  of  many  physiological  and 
pathological  phenomena  are  to  be  sought  for,  not  where  the  latter  are 
exhibited,  but  frequently  at  a  remote  portion  of  the  body,  the  impression 
made  upon  one  organ  being  transmitted  by  an  afferent  nerve  to  the 
spinal  cord,  and  thence  reflected  outwardly  by  an  efferent  one  to  where 
the  phenomena  are  exhibited.  If  the  various  spinal  nerves  involved  in 
the  production  of  reflex  actions  be  considered  specifically,  it  will  be  found 
that  just  as  the  osseous  spinal  column  is  subdivided  into  osseous  seg- 
ments, so  the  spinal  cord  may  be  subdivided  into  nervous  ones  physio- 
logically at  least,  the  gray  matter  of  which,  according  to  this  view, 
constituting  so  many  reflex  centres,  and  the  spinal  nerves  the  afferent 
and  efferent  nerves  to  and  from  the  same.  Up  to  the  present  time 
seven  such  centres  appear  to  have  been  satisfactorily  made  out. 

First.  The  cilio-spinal  centre,  by  which  the  dilatation  of  the  pupil  is 
effected,  situated  in  the  lower  part  of  the  cervical  and  upper  part  of 
the  dorsal  regions  of  the  cord;  it  will  be  considered  again  in  connection 
with  the  svmpathetic.  Second.  The  sweat  centre,  whose  influence 
upon  the  secretion  of  sweat  will  be  treated  of  under  the  skin.  Third. 
The  ano-spinal  centre,  governing  the  act  of  defecation,  situated  in  the 
lumbar  region,  the  afferent  fibres  being  constituted  by  the  hemorrhoidal 
and  inferior  mesenteric  nerves,  the  efferent  by  the  pudendal  plexus, 
distributed  to  the  sphincter  ani  muscle.  Fourth.  The  vesico-spinal 
centre,  both  that  governing  the  sphincter  vesicas  and  detrusor  urinoe, 
being  situated  in  the  lumbar  region  of  the  cord.  Fifth.  The  centre  for 
erection  of  the  penis,  lying  in  the  lumbar  region  of  the  cord,  the  afferent 
fibres  being  the  sensory  nerves  of  the  penis,  the  efferent  ones  the  nervi 
erigentes,  stimulation  of  which,  as  we  shall  see  hereafter,  dilates  the 
vessels  of  the  penis.  Sixth.  The  centre  for  the  emission  of  semen, 
also  situated  in  the  lumbar  region,  the  afferent  nerves  being  the  dorsal 
sensory  nerves  of  the  penis;  the  efferent  nerve  fibres,  which,  emerging 
with  the  fourth  and  fifth  lumbar  nerves,  pass  into  the  sympathetic,  and 
are  distributed  to  the  vesiculae  seminales  and  vasa  differentia,  and 
with  the  third  and  fourth  sacral  nerves  pass  into  the  perineal  nerves, 
and  are  distributed  to  the  accelerator  muscle:  Seventh.  The  centre  for 
parturition,  lying  in  the  lumbar  region,  the  afferent  and  efferent  fibres 
consisting  of  part  of  the  uterine  plexus.  From  the  fact  of  the  reflex 
actions  being  stronger,  and  of  less  time  elapsing  between  the  application 
of  the  stimulus,  and  the  resulting  reflex  when  the  spinal  curd  has  been 

1  Central  Nervous  System,  p.  15:3     Philadelphia,  I860. 


650  THE    SPINAL    CORD. 

divided,  it  has  been  inferred  that  the  encephalic  centres  exercise  a 
restraining  or  inhibitory  effect  upon  the  reflex  action  of  the  cord.  Thus, 
the  spinal  cord,  being  intact  in  a  frog,  and  the  average  length  of  time 
elapsing  between  the  application  of  the  stimulus  and  the  resulting  reflex 
effect  being  determined,  it  will  be  observed  that  if  the  optic  lobes,  for 
example,  be  stimulated,  a  greater  length  of  time  elapses  now  than  before 
between  the  stimulus  and  the  reflex.  On  the  other  hand,  the  spinal  cord 
being  divided,  less  time  elapses  between  the  application  of  the  stimulus 
and  the  reflex.  While  such  experiments  would  lead  one  to  conclude 
that  the  optic  lobes  contain  a  restraining  or  inhibitory  centre,  Setsche- 
now1  centre,  it  must  not  be  supposed  that  the  inhibitory  influence  of  the 
encephalon  is  limited  to  the  optic  lobes  ;  and  further,  it  must  be  borne 
in  mind  that  any  reflex  action  would  be  stronger,  and  would  take  place 
more  quickly,  the  cord  divided,  than  when  intact,  since,  under  such 
circumstances,  the  whole  effect  of  the  impression  made  upon  the 
periphery  would  appear  as  a  reflex  action,  none  becoming  cerebral  in 
character:  whereas,  the  cord,  being  intact,  part  of  the  impression  only 
is  reflected  from  the  cord,  the  remaining  part  being  transmitted  to  the 
encephalon  becoming  cerebral.  That  there  must  be  some  internal 
mechanism  in  ourselves,  by  which  the  reflex  action  of  the  cord  is  inhib- 
ited, is  shown  by  the  manner  in  which  we  are  able  to  restrain,  for  a 
time  at  least,  the  various  actions  performed  by  it. 

1  Ueber  die  Hemmungsmechanismus  fiir  die  Reflexthiitigkeit  des  Riickenmarks,  18G3. 


CHAPTER     XLII. 

THE  MEDULLARY  NERVES. 

The  medulla  oblongata,  regarded  as  a  centre  of  reflex  action,  is  even 
more  important  than  the  spinal  cord,  on  account  of  its  giving  origin  to 
ten  of  the  so-called  cranial  nerves — that  is,  of  the  nerves  involved  in  the 
performance  of  mastication,  insalivation,  deglutition,  of  gastric  and 
intestinal  digestion,  circulation,  and  respiration — in  a  word,  of  the  func- 
tions of  nutrition.  In  order,  however,  to  appreciate  the  manner  in 
which  these  nerves  conduct  afferent  and  efferent  impressions  to  and 
from  the  medulla,  the  latter  acting  as  a  reflex  centre,  it  will  be  first 
necessary  to  describe  their  origin,  distribution,  and  function.  From  the 
fact  of  the  medulla  being  simply  the  upper  expanded  portion  of  the 
spinal  cord  one  would  be  led  to  suppose  that  the  ten  nerves  originat- 
ing in  it  would  be  either  motor  or  sensory  in  function,  and  that  taken 
together  in  pairs  from  below  upward  each  pair  would  be  comparable  to 
the  anterior  or  motor  and  posterior  or  sensory  roots  of  one  of  the  true 
spinal  nerves.  As  a  matter  of  fact,  the  roots  of  the  two  nerves  of  any 
one  of  the  medullary  pairs,  supposing  such  to  exist,  do  not  unite 
together  into  a  single  nerve  as  in  the  case  of  a  spinal  nerve,  but  pass 
on  separately  to  their  ultimate  distribution  as  two  distinct  nerves ;  and 
further,  the  reflex  centres  of  the  medulla  oblongata,  of  which  these 
nerves  are  the  afferent  and  efferent  fibres,  are  so  fused  together  in  man 
and  the  higher  vertebrates  that  the  primitive  disposition  of  these  cen- 
tres and  the  relation  of  the  nerves  originating  in  them  are  no  longer 
apparent.  In  fact,  the  union  is  so  intimate  that  it  is  impossible  to  say 
now  how  many  such  nerves  or  roots  there  were  originally,  and  until 
that  is  determined  it  will  be  impossible  to  homologize  the  medullary  with 
the  true  spinal  nerves.  Indeed,  until  the  development  of  the  cranial 
nerves  in  the  mammalia  has  been  thoroughly  worked  out  by  the 
embryologist,  and  the  relations  between  the  cranial  and  spinal  nerves 
in  some  of  the  lower  vertebrates  been  established  by  the  comparative 
anatomist,  any  view  yet  offered  may  be  considered  as  based  upon  little 
more  than  mere  speculation.  The  most  plausible  theory  is  that  enter- 
tained by  Gegenbaur,1  based  upon  the  disposition  of  the  cephalic  nerves 
in  the  shark,  according  to  whom  the  third,  fourth,  sixth,  seventh,  and 
eighth  nerves  are  regarded  as  being  originally  parts  of  the  fifth  nerve 
or  trigeminal  group,  and  the  ninth,  eleventh,  and  twelfth  as  parts  of  the 
tenth  or  the  vagal  group,  both  groups  consisting  of  a  great  number  of 
small  nerves  corresponding  to  the  numerous  segments  of  which  the 
primitive  vertebrate  skull  consisted,  and  of  which  but  few  are  repre- 
sented even  in  the  skull  of  the  sharks  of  the  present  day. 

1  Elements  of  Comparative  Anatomy,  trans,  by  F.  .r.  Bell,  p.  r>li.     London,  1878. 


652 


THE     MEDULLARY     NERVES, 


Twelve  pairs  of  nerves  arc  given  off  from  the  base  of  the  brain. 
The  first  two  pairs,  the  olfactory  and  optic,  the  special  nerves  of  the 
sense  of  smell  and  sight,  are,  as  we  shall  see  hereafter,  morphologically 
outgrowths  of  the  anterior  cerebral  vesicle;  the  remaining  ten  pairs, 
however,  while  apparently  arising  like  the  first  two  pairs  from  the  base 

of  the  brain,  in  reality  originate,  as 
already  mentioned,  in  the  medulla, 
hence  our  reference  to  them  as  medul- 
lary nerves.  Taking  them  in  the  order 
in  which  they  succeed  the  olfactory 
and  optic  nerves,  they  are  as  follows  : 
The  third  pair,  or  motor  oculi  com- 
munis; fourth  pair,  or  patheticus ; 
fifth  pair,  or  trigeminal  or  trifacial  ; 
sixth  pair,  or  abducens  ;  seventh  pair, 
or  facial ;  eighth  pair,  or  auditory,  the 
special  nerve  of  the  sense  of  hearing  ; 
ninth  pair,  glosso-pharyngeal ;  tenth 
pair,  pneumogastric ;  eleventh  pair, 
spinal  accessory  ;  twelfth  pair,  hypo- 
glossal The  third  nerve  or  motor 
oculi  communis  (Fig.  381  and  382, 
III)  consisting  of  about  15,000  fibres,1 
arises  from  a  nucleus  of  multipolar 
cells  situate  beneath  the  gray  fibres  of 
the  aqueduct  of  Sylvius,  beneath  the 
corpora  cjuadrigemina,  and  extends 
beneath  the  upper  part  of  the  fourth 
ventricle,  the  fibres  of  the  nerves  de- 
cussating at  their  origin.  From  this 
nucleus  the  fibres  pass  forward  through 
the  crus,  emerging  at  the  base  of  the 
brain  from  the  inner  surface  of  the 
crura  cerebri  immediately  in  front  of 
the  pons.  As  the  nerve  passes  through 
the  sphenoidal  fissure  into  the  orbit 
(Fig.  383)  it  divides  into  two  branches, 
the  superior  and  smaller  branches  sup- 
plying the  superior  rectus  and  levator 
palpebrse  superioris  muscles,  the  in- 
ferior and  larger  branch  the  internal 
and  inferior  recti  and  the  superior  oblique  muscles.  The  latter  or 
inferior  branch  gives  off  also  a  short,  thick  filament,  which  passing 
into  the  ophthalmic  ganglion  of  the  sympathetic  is  supposed,  as 
we  shall  see,  to  pass  thence  as  the  short  ciliary  nerves  into  the  iris, 
innervating  the  circular  muscular  fibres  of  the  latter.  During  its 
course  the  fibres  of  the  third  pair  run  in  common  or  in  juxtaposition 
with   fibres  derived  from  the  ophthalmic  division  of  the  fifth  pair,  and 


d.  ca 

View  from  below  of  the  connection  of  the 

principal  nerves  with  the  brain.  I'.  The  right 
olfactory  tract.  II.  The  left  optic  nerve  ;  II'. 
The;  right  optic  tract ;  the  left  tract  is  seen 
passing  hack  into*  and  e,  the  internal  and  ex- 
ternal corpora  geniculata.  III.  The  left  ocu- 
lomotor nerve.  IV.  The  trochlear.  V.  V.  The 
large  roots  of  the  trifacial  nerves.  ++.  The 
lesser  roots,  the  +  of  the  right  side  is  placed 
on  the  Gasserian  ganglion.  1,  the  ophthal- 
mic ;  2,  the  superior  maxillary  ;  and  3,  the 
inferior  maxillary  nerves.  VI.  The  left  ab- 
ducent nerve.  VII.  a,  b.  The  facial  and  audi- 
tory nerves,  a,  VIII.  6.  The  glosso-pharyngeal, 
pneumogastric,  and  spinal  accessory  nerves. 
IX.  The  right  hypoglossal  nerve.  C  I.  Tin- 
left  suboccipital  or  first  cervical  nerve. 


1  Rosenthal  :  De  Numero  atque  Mensura  Microscop  Fibrillarum.     Breslau,  1845. 


THIRD    NERVE  ;    MOTOR    OCULI    COMMUNIS. 


653 


from  the  cavernous  plexus  of  the  sympathetic.       We  make  use  of  the 
expression    running    in   company    with,    or    in  juxtaposition  with,    in 


Fig.  382. 


VII 


wJf' 


r 


IX  \ 
X 
XIJ 


Kuots  of  the  cranial  nerves.  I.  First  pair  ;  olfactory.  II.  Second  pair  ;  optic.  III.  Third  pair  ;  motor 
oculi  communis.  IV.  Fourth  pair  ;  patheticus.  V.  Fifth  pair  ;  nerve  of  mastication  and  trifacial.  VI. 
Sixth  pair  ;  motor  oculi  externus.  VII.  Facial,  VIII.  Auditory — Seventh  pair.  IX  Glosso-pharyngeal, 
X.  Pneumogastric,  XI  Spinal  accessor}' — Eighth  pair.  XII.  Ninth  pair ;  sublingual.  The  numbers  1 
to  15  refer  to  branches  which  will  be  described  hereafter.  (Hirschfeld.  i 

V\<;.  383. 


Distribution  of  the  motor  oculi  communis.  1.  Trunk  of  the  motor  oculi  communis.  2.  Superior 
branch.  3.  Filaments  which  this  branch  sends  to  the  superior  rectus  and  the  levator  palpebrse  superioris. 
4.  Branch  to  the  internal  rectus.  5.  Branch  to  the  inferior  rectus.  6.  Branch  to  the  inferior  oblique 
muscle  ;  7.  Branch  to  the  lenticular  ganglion.  8.  Motor  oculi  externus.  9.  Filaments  of  the  motor 
oculi  externus  anastomising  with  the  sympathetic.     10.  Ciliary  nerves.      (Hiesciifeld.) 


654 


THE    MEDULLARY    NERVES. 


preference  to  that  of  anastomosis,  etc.,  since  the  various  medullary 
nerves  do  not  actually  receive  fibres  from  or  anastomose  with  each 
oilier  in  the  sense  that  arteries  and  veins  anastomose.  The  nerves,  in 
fact,  never  lose  their  individuality,  but  undoubtedly  preserve  through 
the  whole  extent  of  their  course  the  characteristic  functions  obtaining 
at  their  roots,  as  in  the  case  of  the  spinal  nerves. 

This  distinction  must  be  continually  borne  in  mind,  for,  as  we  shall 
see  presently,  while  each  of  these  nerves,  at  its  origin,  has  a  definite 
function — motor,  or  sensory — they  become,  sooner  or  later,  apparently 
mixed  nerves,  from  the  fact  of  being  accompanied  by  the  fibres  of  the 
adjacent  cranio-medullary  nerves.  It  is  in  this  sense  that  the  third 
nerve  is  to  be  understood  as  being  a  motor  nerve,  any  evidences  of 
sensibility  being  due,  not  to  its  intrinsic  fibres,  but  to  the  extrinsic 
ones  of  the  fifth  pair.  That  the  third  nerve  is  exclusively  a  motor  nerve 
is  shown  by  the  fact  of  irritation  of  the  root  causing  contractions  of  the 
muscles  to  which  it  is  distributed,  but  no  pain,  while  division  of  the 
nerve  is  followed  by  paralysis  of  the  same.1  Pathological  facts,  like 
the  falling  of  the  upper  eyelid,  or  blepharoptosis,  external  strabismus, 
immobility  of  the  eye,  except  outwardly  ;  inability  to  rotate  the  eye  on 
its  antero-posterior  axis  in  certain  directions  ;  slight  protrusion  of  the 
eyeball ;  dilatation  of  the  pupil,  with  some  interference  with  the  move- 

Fig.  38J. 


Distribution  of  the  patheticus.  /.  Olfactory  nerve.  II.  Optic  nerves.  III.  Motor  oculi  communis. 
IV.  Patheticus,  by  the  side  of  the  optbthalmic  branch  of  the  fifth,  and  passing]to  the  superior  oblique- 
muscle.  VI.  Motor  oculi  externus.  1.  Ganglion  of  Gasser.  2,  3,  4,  5,  6,  7,  8,  9,  10.  Ophthalmic  division 
of  the  fifth  nerve,  with  its  branches.     (Hirschfeld.) 

ments  of  the  iris,  following  disease  of  the  third  pair  in  man,  are  among 
the  proofs  that  may  be  offered  that  the  third  pair  of  nerves  is  in  man 
motor,  as  we  would  be  led  to  suppose  it  would  be,  both  from  its  ana- 
tomical distribution  as  well  as  from  the  results  obtained  by  vivisection. 


1  Mayo:  Anatomical  and  Physiological  Commentaries,  p.  5.  London,  1823.  Outlines  of  Human 
Physiology,  p.  204.  London,  1827.  Bernard  :  Systeme  nerveux,  tome  ii.  p.  204.  Paris,  18.58.  Ohauveau  t 
Journal  de  physiologic,  tome  v.  p.  274.    Paris,  1862.    Longet  :  Physiologie.  tome  iii.  p.  554.    Paris,  1809. 


fourth  nerve:  patheticus, 


655 


The  fourth  nerve,  or  patheticus,  consisting  of  about  1100  fibres, 
arises  in  the  valve  of  Vieussens.  The  fibres,  after  decussating  at  their 
origin,  emerge  at  the  base  of  the  brain  (Figs.  381,  382,  iv),  as  compara- 
tive slender  filaments  at  the  sides  of  the  pons,  and,  winding  around  the 
crura,  pass  through  the  sphenoidal  fissure  (Fig.  384)  into  the  orbit,  and 
supply  the  superior  oblique  muscle.  Irritation  of  the  nerve  in  a  living 
animal,  at  its  origin,  causes  contraction  of  the  superior  oblique  muscle, 
and  division  of  the  nerve  paralysis  of  the  same.1  In  cases  where  the 
nerve  is  diseased  in  man,  paralysis  of  the  superior  oblique  muscle  is 
observed  as  well    as  immobility  of  the  eveball,  so  far  as  rotation  is  con- 


View  of  tlic  posterior  surface  of  the  medulla,  the  roof  of  the  fourth  ventricle  being  removed  to  show 
the  rhomboid  sinus  clearly.  The  left  half  of  the  figure  represents  :  C».  Funiculus  cuneatus,  and  g,  funi- 
culus gracilis  0.  Obex.  cp.  Nucleus  of  the  spinal  accessory,  p.  Nucleus  of  pneumogastric.  p+sp. 
Ala  cinera.  i?.  Kestiform  body.  XII'.  Nucleus  of  the  hypoglossal,  t.  Funiculus  teres,  a.  nucleus 
of  tbe  acousticus.  m.  Stria;  medullares.  1,  2,  and  3  Middle,  superior,  and  inferior  cerebellar  peduncles 
respectively./.  Fovea  anterior.  4.  Eminentia  teres  (genu  nervi  facialis).  5.  Locus  cceruleus.  The  right 
half  of  the  figure  represents  the  nerve  nuclei  diagrammatical  ly :  V.  Motor  trigeminal  nucleus.  V.  Median 
and  V",  inferior  sensory  and  trigeminal  nuclei.  VI.  Nucleus  of  abducens.  VII.  Facial  nucleus.  VIII 
Posterior  median  acoustic  nucleus.  VIII'.  Anterior  median.  VIII".  Posterior  lateral.  VIII'".  Anterior 
lateral  acoustic  nuclei.  IX.  Glosso-pharyngi-al  nucleus.  X,  XI,  and  XII.  Nuclei  of  vagus,  spinal 
accessory,  and  hypoglossal  nerves  respectively.  The  Roman  numerals  at  the  side  of  the  figure,  from  V. 
to  XII.,  represent  the  corresponding  nerve  roots.     (Erb.) 

cerned,  and,  when  the  eye  is  moved  toward  the  shoulder,  we  have 
double  vision,  the  eye  not  rotating  to  maintain  the  globe  in  the  same 
relative  position.  The  pathological  facts  observed  in  man,  as  well  as 
the  anatomical  distribution,  confirm  the  view  based  upon  vivisections, 
that  the  fourth  nerve  is  exclusively  motor  at  its  origin,  any  sensibility 

1  Longet,  op.  cit.,  tome  iii.  p.  557.     Chauveau,  op.  cit.,  tome  v.  p.  275. 


656  THE     MEDULLARY    NERVES. 

it  may  possess  further  on  in  its  course  being   due  to  adjacent  filaments 
from  the  ophthalmic  branches  of  the  fifth  pair,  or  the  sympathetic. 

The  sixth  nerve,  the  abducens,  or  motor  oculi  externus,  being,  like 
the  fourth  nerve,  distributed  to  a  single  muscle,  the  external  rectus, 
and,  therefore,  exclusively  motor  in  function,  will  be  considered  now 
before  the  fifth  nerve,  which  would,  otherwise,  be  the  next  in  order. 
The  sixth,  consisting  of  from  2000  to  2500  fibres,  arises  from  a  nucleus 
of  large  multipolar  cells,  situated  beneath  the  eminentia  teres,  in  the 
middle  of  the  floor  of  the  fourth  ventricle  (Fig.  385,  vi).  Unlike  the 
fibres  of  the  third  and  fourth  pairs,  it  has  not  yet  been  shown  that  the 
fibres  of  the  sixth  nerve  decussate  at  their  origin  in  the  floor  of  the 
fourth  ventricle.  The  sixth  nerve  appears  at  the  base  of  the  brain  in 
the  groove  separating  the  anterior  pyramid  of  the  medulla  from  the 
pons  (Fig.  381),  and  passes  thence  through  the  sphenoidal  fissure  into 
the  orbit.  While  in  its  course  the  sixth  nerve  runs  in  juxtaposition 
with  the  filaments  derived  from  the  sensitive  opththalmic  branch  of  the 
fifth  pair,  and  from  the  sympathetic  through  the  carotid  plexus,  and 
Meckel's  ganglion.  It  is  undoubtedly  exclusively  a  motor  nerve,  supply- 
ing only  the  external  rectus  muscle.  Irritation  of  the  nerve  at  the 
root  in  a  living  animal  causes  the  latter  muscle  to  contract,  but  no  pain, 
while  division  of  the  nerve  is  followed  by  paralysis  of  the  external 
rectus  and  internal  strabismus,1  the  latter  being  also  observed  in  man 
in  cases  of  disease  of  the  sixth  nerve.  The  third,  fourth,  and  sixth 
pairs  of  nerves,  taken  together,  constitute  the  efferent  or  motor  nerves 
in  the  reflex  actions  involved  in  the  movements  of  the  pupil  and  the 
eyeball  in  vision,  and  which  will  be  considered  hereafter,  the  optic 
nerve  and  the  opththalmic  division  of  the  fifth  nerve  the  afferent  or 
sensory  nerves. 

The  fifth  nerve,  or  trigeminus,  in  arising  from  the  base  of  the  brain  by 
two  roots,  the  posterior,  large  and  sensory,  with  ganglion  attached,  and 
the  anterior,  small  and  motor,  is  usually  regarded  as  especially  comparable 
with  a  spinal  nerve.  For  the  reasons  already  given,  it  is  cpuite  as  pos- 
sible, however,  that  the  fibres  of  the  third,  fourth,  and  even  of  the  sixth 
nerves,  may  constitute  the  true  motor  fibres  corresponding  to  the  sensory 
fibres  of  the  fifth  (ophthalmic  and  superior  maxillary)  as  that  the  fibres 
of  its  small  motor  root  should  be  so  especially  regarded,  particularly  as 
the  latter,  as  we  shall  see  presently,  are  distributed  exclusively  in 
company  with  the  fibres  of  the  inferior  maxillary  branch  of  the  fifth. 

The  two  roots,  both  large  and  small,  of  which  the  fifth  nerve  actually 
consists  without  any  reference  to  their  morphological  significance,  arise 
by  decussating  fibres  in  the  cells  situated  in  the  outer  angle  of  the  floor 
of  the  fourth  ventricle  (Fig.  385,  v  v'  \") ;  passing  thence  separately  for- 
ward and  upward  through  the  substance  of  the  pons,  they  emerge  from 
the  upper  border  of  the  side  of  the  latter  (Fig.  381,  v).  The  posterior 
large  or  sensory  root,  consisting  of  about  30,000  fibres,  passes  thence  into 
the  Grusserian  or  semilunar  ganglion  (Fig.  381,  -)-),  situated  in  the  de- 
pression on  the  internal  portion  of  the  anterior  face  of  the  petrous  portion 
of  the  temporal   bone,  which  subdivides  into  the  ophthalmic  superior 

1  Longet,  op.  cit.,  tome  iii.  p  5G0.     Chauveau,  op.  cit.,  tome  v.  p.  275. 


FIFTH     NER'VE  ;    TRIGEMINAL. 


657 


maxillary  and  inferior  maxillary  nerves  (Fig.  386),  hence  its  name,  tri- 
facial. The  anterior  small  or  motor  root,  consisting  of  about  10,000 
fibres,  passes  underneath  the  ganglion  of  Gasser,  from  which  it  occa- 


Fig.  386. 


General  plan  of  the  branches  of  the  fifth  pair.  1.  Lesser  root  of  the  fifth  pair.  2.  Greater  root  passing 
forward  Into  the  Gasserian  ganglion  3.  Placed  on  the  bone  above  the  ophthalmic  nerve,  which  is  Been 
dividing  into  the  supraorbital,  lachrymal,  and  nasal  branches,  the  latter  connected  with  the  ophthalmic 
ganglion.  4.  Placed  on  the  bone  close  to  the  foramen  rotundum,  marks  the  superior  maxillary  division. 
5.  Placed  on  the  bone  over  the  foramen  ovale,  marks  the  submaxillary  nerve.  (After  a  sketch  by  Charles 
Bell.)    %. 


sionally  receives  a  few  filaments,  and  lying  behind  the  inferior  max- 
illary branch  of  the  large  root,  passes  through  the  foramen  ovale  in 
company  with  the  latter,  with  which  it  is  finally  distributed.  It  will  be 
observed  that  while  the  ophthalmic  and  superior  maxillary  branches  of 
the  fifth  are  purely  sensory,  being  derived  solely  from  the  large  root 
through  the  Gasserian  ganglion,  the  inferior  maxillary  branch  is  both 
motor  and  sensory,  being  derived  not  only  from  the  ganglion  but  from 
the  small  or  motor  root  as  well.  It  may  be  appropriately  mentioned 
here,  with  reference  to  certain  effects  following  division  of  the  fifth  nerve 
to  be  mentioned  presently,  that  the  ganglion  of  Gasser  receives  filaments 
from  the  sympathetic.  While  it  is  an  extremely  difficult  operation 
if  not  impossible,  to  stimulate  the  small  root  of  the  fifth  nerve  in  a 
living  animal,  nevertheless,  there  can  be  little  doubt  that  it  is  a  purely 
motor  nerve  in  function,  since  if  it  be  stimulated  in  an  animal  just  dead, 
in  which  the  cerebral  lobes  have  been  removed,  such  of  the  muscles  of 
mastication  as  are  supplied  by  the  fibres  of  the  small  root  (running  in 

42 


658  THE    MEIH'LLAKY    NERVES. 

the  inferior  maxillary  division  of  the  fifth)  at  once  contract,1  and  in  the 
case  of  old  horses,  for  example,  with  such  force  as  to  break  off'  pieces 
of  the  teeth2,  no  such  result  following  stimulation  of  the  large  root. 

In  division  of  the  nerve  in  a  living  animal  with  the  view  of  deter- 
mining its  function3  both  roots  are  necessarily  divided,  and  with  the 
complete  loss  of  sensibility  ensuing  under  such  circumstances,  there  is 
also  observed  paralysis  of  the  temporal,  masseter,  internal  and  ex- 
ternal pterygoid,  mylohyoid,  and  anterior  belly  of  the  digastric  muscles, 
or  the  muscles  of  mastication  supplied  by  the  fibres  of  the  small  root 
running  in  the  inferior  maxillary  division  of  the  fifth  nerve  and  of  the 
tensor  muscles  of  the  velum  palati.  The  effect  of  division  of  the  fifth 
nerve  is  very  striking  in  the  case  of  the  rabbit,  in  which,  through  the 
consequent  paralysis  of  the  muscles  of  mastication,  the  line  of  con- 
tact between  the  incisor  teeth  becomes  oblique  instead  of  horizontal, 
the  incisor  teeth  being  worn  away  unevenly  through  the  jaw  being 
drawn  to  on«  side  by  the  action  of  the  active  muscles.  The  cases  of 
paralysis  of  the  fifth  nerve  that  have  been  noted  in  man  confirm  in  the 
main  the  results  of  experiments  made  upon  animals.  In  all  instances 
where  both  the  large  and  small  roots  were  involved  by  the  disease,  entire 
loss  of  sensibility  and  paralysis  of  the  muscles  supplied  by  the  fifth  were 
observed,4  the  only  cases  in  which  there  was  no  paralysis  of  the  muscles 
of  mastication  being  those  in  which  the  small  root  was  unaffected,  loss 
of  sensibility  on  the  side  affected  being  then  only  noted.  In  order  to 
appreciate  the  results  following  division  of  the  large  root  of  the  fifth 
nerve  in  a  living  animal  or  disease  in  man,  it  will  be  first  necessary  to 
describe  briefly  the  distribution  of  its  principal  branches.  It  has  already 
been  mentioned  that  the  large  root  after  expanding  into  the  ganglion 
of  Gasser  subdivides  into  the  ophthalmic  superior  and  inferior  maxillary 
nerves.  The  ophthalmic,  the  smallest  of  the  three  branches  of  the  large 
root,  passes  through  the  sphenoidal  fissure  into  the  orbit,  subdividing  into 
the  lachrymal,  frontal,  and  nasal  nerves,  and  gives  off,  during  its  course 
to  the  orbit,  fibres  to  the  third,  fourth,  and  sixth  nerves,  to  the  tentorium 
and  to  the  sympathetic.  The  lachrymal  nerve  supplies  the  lachrymal 
gland,  conjunctiva,  integument  of  the  upper  eyelid,  and  gives  off  fibres 
to  the  orbital  branch  of  the  superior  maxillary.  The  frontal  branch 
divides  into  the  supratrochlear  and  supraorbital  nerves,  the  former  nerve 
supplies  the  integument  of  the  forehead  and  gives  off  a  long,  delicate 
filament  to  the  nasal  nerve;  the  latter,  or  supraorbital  nerve,  passing 
through  the  supraorbital  foramen  supplies,  to  a  certain  extent,  the  upper 
eyelid  and  forehead,  the  anterior  and  median  portions  of  the  scalp,  the 
mucous  membrane  of  the  frontal  sinus,  and  the  pericranium  covering  the 
frontal  and  parietal  bones. 

The  nasal  branch,  before  enterino-  the  orbit,  gives  off  a  long  filament 
to  the  ophthalmic  ganglion,  and  then  the  long  ciliary  nerves  supplying 
the  ciliary  muscle,  iris,  and  cornea ;  it  then  divides  into  the  external 
nasal,  or  infra-trochlearis,  and  the  internal  nasal,  or  ethmoidal  nerves. 

1  Longet :  Anatomie  et  physiologic  du  systeme  nerveux,  tome  ii.  p.  190.     Paris,  1842.     Physiologie, 
op.  cit.,  p.  502. 

2  Chauveau,  op.  cit.,  p.  276. 

3  Bornard  :  Systems  Nerveux,  tome  ii.  p.  100.     Paris,  1858. 

*  Longet:  Anat.  et  Phys.  du  systeme  nerveux,  tome  ii.  p.  191.     Paris,  1842. 


FIFTH     NERVE;    TRIGEMINAL. 


659 


The  infra-trochlearis  nerve  supplies  the  integument  of  the  forehead  and 
nose,  the  internal  surface  of  the  lower  eyelid,  the  lachrymal  sac,  and 
caruncula.  The  internal  nasal,  or  ethmoidal  nerve,  supplies  the  mucous 
membrane  of  the  nose,  and  partly  its  integument.  The  second  branch 
of  the  fifth  nerve,  the  superior  maxillary  nerve  (Fig.  387),  passes  out  of 
the  cranium  by  the  foramen  rotundum,  and  traversing  the  infraorbital 
canal  emerges  by  the  infraorbital  foramen  upon  the  face,  giving  off  pal- 
pebral branches  to  the  lower  eyelid,  nasal  branches  to  the  side  of  the 
nose,  the  latter  running  in  common  with  the  nasal  branch  of  the  oph- 
thalmic and  labial  branches  to  the  integument  and  mucous  membrane 
of  the  upper  lip.  During  its  course  through  the  spheno-maxillary  fossa 
the  superior  maxillary  nerve  gives  off  several  branches ;  the  orbital, 
which,  passing  into  the  orbit,  gives  off,  in  turn,  the  temporal  and  malar 
nerves,  which,  emerging  by  foramina  in  the  malar  bones,  are  distributed 
to  the  integument  of  the  temple  and  side  of  the  forehead,  and  the  integu- 
ment covering  the  malar  bone  respectively,  the  two  posterior  dental 
nerves  (Fig.  387),  the   latter   supplying  the  molar  and  bicuspid  teeth, 


Fig.  387. 


Dissection  of  the  superior  maxillary  nerve  and  Meckel's  ganglion.  1.  Superior  maxillary  nerve.  2. 
Posterior  dental  nerves.  3.  Inner  wall  of  orbit.  4.  Orbital  branch  (cut).  5.  Anterior  dental  nerve.  6 
Meckel's  ganglion.  7.  Vidian  nerve.  8.  Sixth  nerve.  9.  Carotid  branch  of  Vidian.  10.  Greater  super- 
ficial petrosal  nerve.  11.  Carotid  plexus  of  sympathetic.  12.  Lesser  superficial  petrosal  nerve.  13. 
Superior  cervical  ganglion  of  sympathetic.  14.  Facial  nerve.  15.  Internal  jugular  vein.  16.  Chorda 
tympani  nerve.  17.  Glosso-pharyngeal  nerve.  19.  Jacobson's  nerve.  (From  Hirschfeld  and  Le- 
veillk.) 

the  mucous  membrane  of  the  alveolar  processes  and  of  the  antrum.  In 
the  infraorbital  canal  the  anterior  dental  is  given  off,  constituting, 
together  with  the  posterior  dental,  the  dental  arcade,  the  anterior  dental 
supplying  the  canine  and  incisor  teeth,  and  the  mucous  membrane  of  the 
alveolar  processes.  The  third  branch  of  the  fifth  nerve,  or  the  inferior 
maxillary  (Fig.  386),  passes  out  of  the  cranial  cavity  by  the  foramen 
ovale,  and  after  uniting  with  the  small  or  motor  root  of  the  fifth,  divides 
into  anterior  and  posterior  branches,  the  former  containing  the  motor 
fibres  supplying  the  principal  muscles  of  mastication,  and  the  tensor 
muscles  of  the  velum  palati  through  the  otic  ganglion,  and  derived,  as 


660  THE    MEDULLARY    NERVES. 

already  mentioned,  from  the  small  or  motor  root,  the  latter  containing 
principally  sensory  fibres.  Among  the  most  important  of  these  may  be 
mentioned  the  auriculo-temporal,  the  lingual,  and  the  inferior  dental 
nerves.  The  auriculo-temporal  nerve  supplies  the  integument  of  the 
temporal  region,  of  the  ear,  the  auditory  meatus,  the  temporo-maxillary 
articulation,  and  the  parotid  gland  :  it  gives  oft",  also,  filaments  that  run 
in  common  with  those  of  the  seventh  nerve,  or  facial.  The  lingual  nerve, 
distributed,  to  the  mucous  membrane  of  the  point  of  the  tongue,  mouth, 
gums,  sublingual  gland,  submaxillry  ganglion,  consists,  as  we  shall  see, 
through  a  considerable  extent  of  its  course,  of  two  distinct  nerves,  the 
lingual  proper  and  the  chorda  tympani,and  whose  relations  will  be  con- 
sidered presently.  The  inferior  dental  nerve,  after  giving  off  the  mylo- 
hyoid nerve,  passes  through  the  dental  canal  in  the  inferior  maxillary 
bone,  and  supplying  the  lower  teeth,  emerges  upon  the  face  at  the 
mental  foramen,  and,  as  the  mental  nerve,  supplies  the  integument  of 
the  chin,  the  lower  part  of  the  face,  and  lower  lip,  and  partly  the 
mucous  membrane  of  the  mouth.  While,  as  already  mentioned,  it  is 
impossible  to  stimulate  directly  the  large  root  of  the  fifth  nerve  in  a 
living  animal,  yet,  since  all  of  its  accessible  branches,  both  in  man  and 
animals,  have  been  shown  to  be  very  sensitive,  it  might  reasonably  be 
inferred  that  the  large  root  from  which  all  these  branches  arise  is  sen- 
sory in  function,  especially  when  it  is  remembered  that  its  stimulation 
in  an  animal  just  dead  is  followed  by  no  contractions  of  the  muscles  to 
which  the  fifth  nerve  is  distributed.  Further,  as  well  known,1  if  the 
large  root  be  divided  in  a  living  animal,  or  be  injured  or  diseased  in 
man,  entire  loss  of  sensibility  on  the  side  of  the  head  affected  at  once 
follows,  any  muscular  paralysis  ensuing  being  limited  to  the  parts 
supplied  by  the  fibres  of  the  small  or  motor  root.  The  immediate  effect 
of  division  of  the  large  root  is  very  striking,  the  cornea,  integument, 
and  mucous  membrane  of  the  side  affected  are  at  once  deprived  of  sensi- 
bility, and  may  be  burned,  lacerated,  or  pricked  without  the  animal 
evincing  any  pain.  Loss  of  general  sensibility  in  the  tongue  is  also 
observed,  though  no  loss  of  taste,2  since,  as  we  shall  see  hereafter,  the 
gustatory  properties  of  the  anterior  part  of  the  tongue  are  due  to  the 
chorda  tympanic  fibres  of  the  lingual  nerve,  and  not  to  those  fibres  of 
the  lingual  proper  derived  from  the  inferior  maxillary  branch  of  the 
fifth  nerve.  Deglutition  becomes  impossible,  also,  on  the  side  of  the 
head  affected. 

The  loss  of  general  sensibility,  the  interference  with  deglutition,  etc., 
are  also  observed  in  paralysis  of  the  fifth  nerve  occurring  in  human 
beings.  In  one  of  these  cases,3  it  may  be  mentioned  as  a  proof  of  the 
sensory  properties  of  the  large  root  of  the  fifth  nerve,  that  an  operation 
was  performed  without  the  slightest  evidence  of  pain  on  the  part  of  the 
patient.  In  addition  to  the  loss  of  sensibility,  etc.,  following  division 
of  the  large  root  of  the  fifth  nerve,  in  certain  cases  of  inflammation  of 
the  eye,  ear,  and  nose  have  also  been  observed,  depending  apparently 

1  Magendie :  Journal  de  Physiologie,  tome  iv.  pp.  17(5,  302.     Paris,  1824.     Bernard  :  Lecons  :  Sur  la 
physiologie  et  la  pathologie  du  Syateme  nerveux,  tome  ii.  p.  53.     Paris,  1858. 

2  Schiff :  Lecons  sur  la  physiologie  de  la  digestion,  tome  i.  p.  103.  Floreuce,  1867.    Lusanna  :  Archives 
de  Phys.,  tome  ii.  p.  27.     Paris,  1869. 

3  Noyes  :  New  York  Med.  Journal,  1871,  vol.  xiv.  p.  163. 


SEVENTH     NERVE;    PORTIO    DURA,    FACIAL 


661 


Fig.  388. 


upon  division  of  those  fibres  of  the  sympathetic,  already  alluded  to,  as 
passing  into  the  ganglion  of  Gasser,  since  it  is  only  when  these  fibres 

ST  O  DC  J 

ai'e  involved  through  division  of  the  large  root  through  the  ganglion,  or 
anterior  to  it,  that  such  effects  are  noticed,  none  such  following  if  the 
large  root  be  divided  between  its  origin  and  the  ganglion.  In  the 
former — that  is,  where  the  sympathetic  fibres  have  been  divided  within 
from  about  one  to  two  days  after  the  operation — the  eye  on  the  side 
affected  becomes  the  seat  of  purulent  inflammation ;  the  cornea,  after 
becoming  opaque,  ulcerates,  the  humors  of  the  eye  are  discharged,  and 
the  organ  destroyed.  Ulcers  also  appear  upon  the  tongue  and  lips,  and 
there  is  a  discharge  from  the  mucous  membrane  of  the  nose  and  mouth, 
and  the  hearing  appears  to  be  affected.  The  impairment  in  the 
nutrition  of  the  eye,  mouth,  etc.,  following  division  of  the  fifth  nerve, 
and  of  the  fibres  of  the  sympathetic,  appears  to  be  due,  both  to  the 
hyperemia  induced  through  the  division  of  the  vasomotor  fibres  of  the 
sympathetic,  and  which,  we  shall  see  hereafter,  regulate  the  calibre  of 
the  bloodvessels,  and  to  the  paralysis  of  the  muscles  of  mastication,  and 
consequent  imperfect  digestion  of  food,  the  increased  vascularity  and 
consequent  exaggerated  nutrition  necessitating  a  greater  amount  of 
nutritive  matter;  in  the  diminution  of  the  latter,  the  parts  involved 
become  inflamed.  That  such  is  the  true  explanation,  to  a  considerable 
extent,  is  shown  from  the  fact  that  the 
inflammation  of  the  eye,  etc.,  can  be  pre- 
vented, for  some  weeks  at  least,  if  the 
animal  be  artificially  fed  with  good  nutri- 
tive food.  It  need  hardly  be  mentioned 
that  the  nervous  fibres  transmitting  gus- 
tatory, olfactory,  and  auditory  impressions 
are  not  in  any  way  derived  from  the  large 
root  of  the  fifth  nerve,  as  once  thought, 

the  large  root  being  only  a  nerve  of  gen- 
es o  J  o 

eral  sensibility,  the  small  root  of  motion. 

The  seventh  nerve,  the  nerve  of  expres- 
sion, the  facial,  or  the  portio  dura  of  the 
seventh  pair,  supposing  the  latter  to  in- 
clude, as  in  the  arrangement  of  Willis,  not 
only  the  fibres  of  the  facial  proper,  but  those 
of  the  auditory,  or  portio  mollis,  containing 
about  4500  fibres,  arises  in  a  fan-shaped 
manner  in  the  gray  matter  of  the  floor  of 
the  fourth  ventricle  (Fig.  385,  vii).  Pa- 
thological cases,  like  these  observed,  par- 
ticularly by  Gubler,1  lead  one  to  conclude 
that  the  fibres  of  the  facial  decussate,  not 
only  at  their  apparent  origin  in  the  floor 
of  the  fourth  ventricle,  but  that  many  of 
them,  passing  upward,  decussate  in  the 
pons  Varolii.  At  least,  it  is  only  on  such  a  supposition  that  cases  of 
so-called  alternate  paralysis  can    be  explained,  in  which  (Fig.   388), 

1  Gazette  hebdomadaire  tie  medecine  et  Chirurgie.     Paris,  1856,  58,  59. 


To  illustrate  alternate  paralysis.  G. 
Cerebrum.  P.  Pons.  M.  Medulla. 
F.   Facial.     L.  Lesion,  spinal  cord. 


662 


THE     MEDULLARY    NERVES. 


while  a  lesion  of  the  brain,  situated  anterior  to  the  pons,  is  associated 
■with  facial  paralysis  on  the  same  side  as  that  of  the  accompanying  hemi- 
plegia, a  lesion  situated  in  the  pons,  or  below  it,  is  accompanied  with  a 
facial  paralysis  on  the  opposite  side  to  that  of  the  hemiplegia.  It  must 
be  admitted,  however,  that,  as  yet,  no  such  decussating  fibres  as  those 
just  supposed  to  exist  as  accounting  for  the  pathological  phenomena, 
have  been  actually  demonstrated  by  the  anatomist.  The  fibres  of  the 
facial  nerve,  from  their  origin  in  the  fourth  ventricle,  passing  forward 
and  outward  through  tjie  medulla,  emerge  from  the  latter  at  the  lower 
border  of  the  pons  Varolii  in  the  outer  part  of  the  depression  between 
the  olivary  and  the  restiform  bodies  (Fig.  381,  vii),  the  auditory  nerve 
lying  to  the  outer  side  of  the  facial,  the  two  being  not  infrequently  con- 
nected by  a  separate  fasciculus  of  the  facial,  the  so-called  pars  inter- 
media, or  nerve  of  Wrisberg.  After  emerging  from  the  medulla,  the 
facial,  the  auditory,  and  the  intermediary  nerves,  if  the  latter  exists, 
pass  thence  together  into  the  internal  auditory  meatus.  The  further 
distribution  and  origin  of  the  auditory  nerve  will  be  considered  hereafter; 
leaving  the  latter  nerve,  then,  for  the  present,  at  the  bottom  of  the 
meatus,  the  facial  and  nerve  of  Wrisberg  will  be  found  to  enter  the 
aquseductus  Fallopii  (Fig.  389),  and  passing,  by  this  route,  through  the 

Fig.  389. 


Chorda  tympani  nerve.  1,  2,  3,  4.  Facial  nerve  passing  through  the  aquseductua  Fallopii.  5.  Gangli- 
form  enlargement.  G.  Great  petrosal  nerve.  7.  Spheno-palatine  ganglion.  8.  Small  petrosal  nerve. 
9.  Chorda  tympani.     10,11,1-2,13.  Various  branches  of  the  facial.     14,  14,  IS.  Glosso-pharyngeal  nerve 

(HlRSCHFELD.) 

petrous  portion  of  the  temporal  bone,  the  two  nerves  uniting,  emerge 
as  a  common  trunk  by  the  stylo-mastoid  foramen.  It  may  be  men- 
tioned here,  though  the  fact  has,  as  yet,  but  little  functional  significance, 
that  in  the  aqugeduct  the  nerve  of  Wrisberg  exhibits  a  little  reddish 
ganglion,  containing  nerve  cells.  The  most  important  branches  of 
the  facial  are  briefly  as  follows :  The  large  and  small  petrosal  nerves 
passing,  respectively,  to  Meckel's  and  the  otic  ganglia  (Fig.  389), 
the  external  petrosal  to  the  sympathetic  fibres  of  the  middle  menin- 
geal artery,  the  tympanic  branch  distributed  to  the  stapedius  muscle, 
the  chorda  tympani  nerve  (Fig.   389)  passing  through  the  tympanum 


SEVENTH    NERVE;    l'ORTIO    DURA,    FACIAL. 


663 


to  join  the  lingual  branch  of  the  inferior  maxillary,  the  branch  to  the 
pneurnogastric. 

The  six  branches  just  mentioned  are  given  off  by  the  facial  during  its 
course  through  the  aqueduct  of  Fallopius.  The  remaining  branches 
still  to  be  mentioned  are  given  off  after  the  nerve  has  emerged  from  the 
stylo-mastoid  foramen,  the  branch  to  the  glosso-pharyngeal  nerve,  the 
posterior  auricular  connected  with  the  cervical  plexus  by  the  auricularis 

Fro.  390. 


.  ■&.... 


2.  Posterior  auricular  nprve. 
5,  6.  Branches  to  the  muscles 
9.  Superior  terminal  branch. 


Superficial  branches  of  the  facial  and  the  fifth.  1.  Trunk  of  the  facial. 
3.  Branch  which  it  receives  from  the  cervical  plexus.  4.  Occipital  branch. 
of  the  ear.  7.  Digastric  branches.  8.  Branch  to  the  stylo-byoid  muscle. 
10.  Temporal  branches.  11.  Frontal  branches.  12.  Branches  to  the  orbicularis  palpebrarum  13  Nasal, 
or  suborbital  branches  14.  Buccal  branches.  15  Inferior  terminal  branch  16.  Mental  branches.  17. 
Cervical  branches.  18.  Superficial  temporal  nerve  (branch  of  the  fifth  |  10,  20.  Frontal  nerve  (branches 
of  the  fifth).  21,  22,  23,  24,  25,  26,  27.  Branches  of  the  fifth.  28,  29,  30,  31,  32.  Branches  of  the  cervical 
nerves.     (Hirschfeld.) 

magnus  and  distributed  to  the  retrahens  and  attolens  aurem,  the  occipital 
portion  of  the  occipito-frontalis  muscle,  and  the  integument,  the  digastric 
branch  receiving  filaments  from  the  glosso-pharyngeal  supplying  the 
posterior  belly  of  the  muscle  of  the  same  name  and  the  stylo-hyoid,  a 
distinct  branch  also  to  the  stylo-hyoid  muscle,  the  lingual  branch — that 
is,  the  branch  passing  behind  the  stylo-pharyngeus  muscle  and  receiv- 


664  THE     MEDULLARY    NERVES. 

ing  filaments  from  the  glosso-pharyngeal  nerve  to  be  distributed  to  the 
mucous  membrane,  tongue,  stylo-glossus,  and  palato-glossus  muscles,  and, 
finally  (Fig.  390),  the  temporo-facial  and  cervico-facial  branches  into 
which  the  main  trunk  divides  as  it  passes  through  the  parotid  gland. 
The  temporo-facial  branch  passing  upward  and  forward  is  distributed  to 
the  attrahens  aurem,  the  frontal  portion  of  the  occipito-frontalis,  the 
orbicularis  palpebrarum,  corrugator  supercilii,  pyramidalis  nasi,  levator 
labii  superioris,  levator  labii  superioris,  alaeque  nasi,  the  dilator  and 
compressor  nasi,  part  of  the  buccinator,  the  levator  anguli  oris,  and  the 
zygomatic  muscles.  During  its  course  the  temporo-facial  branch  receives 
filaments  from  the  auriculotemporal  branch  of  the  inferior  maxillary 
nerve  from  the  temporal  branch  of  the  superior  maxillary  and  from  the 
ophthalmic,  it  becomes,  therefore,  a  mixed  nerve  in  function.  The 
cervico-facial  nerve,  passing  downward,  supplies  the  buccinator,  orbicu- 
laris oris,  risorius,  levator  labii  inferioris,  depressor  labii  inferioris,  de- 
pressor anguli  oris,  and  platysma  myoides.  From  the  fact  that  division 
of  the  fifth  nerve  is  at  once  followed  by  entire  loss  of  sensibility  in  the 
parts  supplied  by  that  nerve,  it  is  evident  that  the  facial,  supplying  to  a 
considerable  extent  identical  regions,  cannot  be  a  sensory  nerve,  other- 
wise sensibility,  though  weakened,  should  nevertheless  persist  in  the 
face,  etc.,  even  after  division  of  the  fifth  nerve.  Direct  evidence,  how- 
ever, as  well  as  indirect,  proves  conclusively  that  the  seventh  nerve,  at  its 
origin  at  least,  is  a  purely  motor  nerve.  Thus,  division  of  the  nerve  in 
a  living  animal  or  disease  in  man  is  at  once  followed  by  paralysis  of  the 
facial  and  other  muscles  that  we  have  just  seen  are  supplied  by  the 
nerve,  while  stimulation  of  the  nerve  at  its  root  in  a  living  animal  or  in 
one  recently  dead,  causes  contraction  of  the  muscles,  but  in  the  case  of 
the  living  animal  no  pain.  Any  sensibility  then  exhibited  by  the  facial 
nerve  beyond  its  root  must  be  attributed  to  the  fibres  derived  from  the 
fifth  nerve,  glosso-pharyngeal,  and  pneumogastric,  that  we  have  seen 
run  in  juxtaposition  with  it.  In  order  to  appreciate  the  varied  and 
important  functions  of  the  facial  nerve,  it  will  be  best  to  consider  those 
of  its  branches  seriatim.  In  the  consideration  of  the  sympathetic,  to 
be  taken  up  hereafter,  it  will  be  then  shown  that  the  nerve  fibres  sup- 
plying the  levator  palati,  azygos  uvulse,  palato-pharyngeus,  and  palato- 
glossus are  derived  from  the  ganglion  of  Meckel,  and  those  supplying 
the  tensor  palati  and  tensor  tympani  from  the  otic  ganglion  ;  and  on 
the  supposition  that  the  great  and  small  petrosal  nerves  pass  respectively 
through  the  two  ganglia  to  the  muscles  just  mentioned,  supplied  by  the 
latter,  it  might  be  inferred  that  paralysis  of  the  facial  nerve  would  be 
accompanied  with  difficulty  in  deglutition  and  an  increased  sensitiveness 
to  sound,  the  tympanic  membrane  being  relaxed  through  the  paralysis 
of  the  tensor-tympani  muscle,  it  being  well  known  that  the  tympanic 
membrane1  vibrates  more  intensely  when  relaxed  than  when  tensed. 
Pathological  cases  of  facial  paralysis  occurring  in  man  fully  confirm  this 
view,  since  in  such  cases  both  difficulty  in  deglutition  and  increased 
susceptibility  to  sounds,  etc.,  are  observed.2    Further,  as  confirming  the 

1  Muller's  Elements  of  Physiology,  vol.  ii.  p.  1256.     London,  1S43. 

2  Bell :  The  Nervous  System,  p.  329.  Loudon,  1844.  Bernard  :  Lecons  sur  la  physiologie  et  la  path- 
ologie  du  systeme  nerveux,  tome  ii.  pp.  114,  133.  Paris,  1858.  Montanet :  Dessertation  sur  l'hemiplegie 
faciale.     These  No.  300.     Paris,  1831. 


SEVENTH    NERVE:    PORTIO    DURA,    FACIAL. 


665 


Fig.  391. 


view  that  the  muscles  of  deglutition  are  supplied  by  the  facial,  may  be 
mentioned  the  fact  of  the  facial  nerve  giving  off  the  branch  already 
alluded  to  supplying  the  stylo-glossus  and  palato-glossus  muscles,  and 
occasionally  of  the  branch  distributed  to  the  palato-glossus  and  palato- 
pharyngeus  muscles  passing  directly  to  the  latter  without  being  connected 
with  the  glosso-pharyngeal,  as  is  usually  the  case.1  The  chorda  tympani 
nerve,  one  of  the  most  remarkable  nerves  in  the  body,  both  on  account 
of  its  origin  and  distribution  as  well  as  of  its  properties,  is  usually  said 
to  arise  from  the  facial  in  the  aqueduct  of  Fallopius  and  passing  through 
the  canal  of  Huguier  into  the  tympanum,  to  cross  the  latter  between  the 
malleus  and  incus,  to  enter  the  Gasserian  fissure,  emerging  thence  to 
join  the  lingual  nerve  at  the  acute  angle  (Fig.  389).  In  the  horse  and 
calf,  however,  as  shown  by  Owen2,  the  chorda  tympani  nerve,  while 
apparently  arising  from  the  facial,  as  in  man,  in  reality  can  be  traced 
through  the  fibres  of  the  facial  as  a  continuation  of  the  large  petrosal, 
and  as  the  latter  nerve  is  connected  through  the  ganglion  of  Meckel 
with  the  superior  maxillary  nerve  a  pathway 
evidently  exists  in  these  animals  by  which  the 
impressions  made  upon  the  tongue  can  be  trans- 
mitted 'to  the  latter  nerve,  and  while  the  chorda 
tympani  nerve  has  not  been  actually  demonstrated 
in  man  to  be  a  continuation  of  the  large  petrosal, 
as  in  Fig.  391,  both  experiments  upon  animals 
and  pathological  cases  in  man  lead  one,  as  we 
shall  see,  to  suppose  that  such  is  substantially  the 
case.  On  the  other  hand,  apart  from  the  fact  of 
nerve  fibres   not    anastomosing,  there  is   direct 

o7 

experimental  evidence  to  show  that  the  chorda 
tympanic  fibres  do  not  lose  their  individuality 
after  mining  those  of  the  lingual  branch  of  the 
inferior  maxillary,  but  preserve  their  functional 
activity  entirely  independent  of  those  of  the  latter. 
Thus,  if  the  lingual  branch  of  the  inferior  max- 
illary be  divided  before  it  is  joined  by  the  chorda 

tympani,  its  fibres  alone  atrophy,  with  ensuing  loss  of  general  sensibility 
of  the  anterior  part  of  the  tongue,  whereas,  if  the  chorda  tympani  nerve 
be  divided  before  it  reaches  the  lingual  its  terminal  fibres  alone  atrophy, 
loss  of  taste  ensuing. 

Experiment  not  only  shows,  however,  that  the  terminal  portion  of  the 
lingual  nerve  consists  of  fibres  derived  from  both  the  lingual  branch  of 
the  inferior  maxillary,  and  from  the  chorda  tympani,  but  that  the  latter 
consists  of  three  distinct  sets  of  fibres  :  1st,  those  endowing  the  anterior 
two-thirds  of  the  tongue  with  the  sense  of  taste;  2d,  those  modifying 
the  bloodvessels  of  the  tongue,  vasa  dilator  nerves  ;  3d,  those  stimu- 
lating through  the  submaxillary  ganglion  the  submaxillary  and  sub- 
lingual glands.  The  chorda  tympani  nerve,  consisting,  as  it  undoubtedly 
does,  then,  of  sensory,  motor,  and  secretory  fibres,  it  is  to  be  expected 


Diagram  to  illustrate  sup- 
posed connection  of  chorda 
tympani  with  superior  maxil- 
lary through  facial,  great 
petrosal,  and  ganglion  of 
Meckel. 


1  Longet,  op.  cit.,  tome  iii.  p.  581. 

2  The  Anatomy  of  Vertebrates,  vol.  iii.  p.  156.     London,  1868. 


666  THE    MEDULLARY    NERVES. 

that  it  should  have  specifically  different  centres  of  origin,  which  is  in 
harmony  with  the  view  just  offered  of  its  motor  fihres  being  derived 
from  the  facial,  and  its  sensory  fibres  from  the  superior  maxillary  nerve 
through  the  large  petrosal  and  the  ganglion  of  Meckel.  That  the 
chorda  tympani  nerve  does  contain  at  least  some  fibres  derived  from  the 
superior  maxillary  appears  from  the  fact  of  paralysis  of  the  fifth  nerve 
in  man  being  often  accompanied  with  loss  of  the  sense  of  taste  in  the 
anterior  portion  of  the  tongue,1  and  that  these  gustatory  fibres  are  a 
continuation  of  those  of  the  large  petrosal  is  still  further  confirmed  by 
another  fact,  that  paralysis  of  the  seventh  neive  involves  equally 
as  well  as  that  of  the  fifth  nerve,  loss  of  the  sense  of  taste  in  the 
tongue.2  The  further  consideration  of  the  gustatory  and  vaso-dilator 
fibres  of  the  chorda  tympani  will  be  deferred  for  the  present.  Inas- 
much, however,  as  those  fibres  of  the  chorda  tympani  that  pass  to  the 
submaxillary  ganglion  and  sublingual  glands  constitute  the  efferent 
fibres  in  the  reflex  mechanism  of  insalivation  as  effected  by  those 
glands,  the  fibres  of  the  lingual  branch  of  the  inferior  maxillary, 
together  with  those  of  the  glosso-pharyngeal  and  pneumogastric,  the 
afferent  fibres,  and  the  medulla  the  centre ;  their  function,  in  this  con- 
nection, may  be  appropriately  here  considered,  and,  to  avoid  repetition, 
it  may  be  mentioned  that,  in  the  case  of  the  parotid  gland,  while  the 
afferent  fibres  are  the  same,  the  efferent  fibres  involved  in  the  reflex 
mechanism  are  contained  in  the  auriculo-temporal  branch  of  the  fifth, 
whose  motor  fibres  are  derived  from  the  small  or  motor  root,  and  in  the 
fibres  from  the  otic  ganglion  derived  from  the  facial,  through  the  small 
petrosal  nerve.  If  the  submaxillary  and  sublingual  glands  be  cleanly 
dissected  out,  as  in  a  living  dog,  for  example,  in  which  the  glands  are 
very  accessible,  they  will  be  seen  to  be  comparatively  at  rest,  secreting 
little  or  no  saliva,  and  their  venous  blood  of  a  dark  hue.  If  now  a 
drop  of  vinegar  be  placed  upon  the  tongue  of  the  animal,  at  once  the 
arterial  twigs  enlarge,  the  blood  flows  more  rapidly,  the  veins  pulsate, 
the  color  of  their  blood  becomes  scarlet,  and  the  pressure  increases, 
followed  by  an  abundant  discharge  of  limpid,  very  alkaline  saliva,  the 
so-called  chorda  tympani  saliva,  containing  small  quantities  of  albumen, 
globulin,  mucin.  That  the  phenomena  just  described  are  due  to  im- 
pressions transmitted  to  the  medulla  by  the  afferent  sensory  fibres  of 
the  lingual  branch  of  the  inferior  maxillary  and  glosso-pharyngeal 
nerves,  and  thence  reflected  back  to  the  submaxillary  and  sublingual 
glands  by  the  efferent  secreto-motor  fibres  of  the  chorda  tympani,  is 
shown  by  such  facts  as  that,  after  division  of  the  lingual  branch,  the 
secretion  of  saliva,  etc.,  ceases,  but  recommences  if  the  central  end  of 
the  divided  nerve  be  stimulated.  On  the  other  hand,  if  the  chorda 
tympani  be  divided,  the  vessels  supplying  the  submaxillary  and  sub- 
lingual glands  contract ;  owing  to  the  unopposed  action  of  the  sympa- 
thetic vaso-constricting  fibx-es,  the  blood  flows  slowly,  is  diminished  in 
quantity,  and  becomes  dark,  the  secretion  of  saliva  diminishes  ;  the 
application  of  vinegar  no  longer  excites  the  secretion.  That  the  secre- 
tion  does  not  altogether  cease  after  division  of  the  chorda  tympani 

1  Schiff :  Lecons  sur  la  Physiologie  de  Digestion,  tome  premier,  p.  100.     Florence  and  Turin. 

2  Bernard  :  Svsteme  Nerveux,  1858,  tome  ii.  p.  122.    Schiff.  op.  cit.,  tome  i.  p.  183.    Lusanua  :  Archives 
de  Physiologie, 'tome  ii.  p.  201.     Paris,  1869. 


SEVENTH     NERVE-,    P0ET10     DURA,    FACIAL.  667 

appears  to  be  due  to  the  independent  reflex  action  of  the  submaxillary 
ganglion.  If  now,  however,  the  divided  chorda  tympani  be  stimulated 
at  its  distal  end,  all  the  former  phenomena  recur.  It  may  be  mentioned, 
in  this  connection,  though  anticipated  somewhat,  that  if  the  sympathetic 
plexus  surrounding  the  facial  artery  be  stimulated,  the  bloodvessels  of 
the  glands  become  very  much  contracted,  the  blood  flowing  more  slowly, 
and  darker  in  color  in  the  veins,  and  that  the  saliva  then  secreted — the 
so-called  sympathetic  saliva — is  not  only  diminished  in  quantity,  but 
contains,  in  addition  to  albumen  and  mucin,  sarcode-like  bodies.  With 
division  of  the  sympathetic  fibres,  the  secretion  of  saliva  does  not 
altogether  cease,  a  small  quantity  of  the  so-called  paralytic  saliva  being 
secreted,  if  the  tongue  be  stimulated  with  induced  electricity. 

In   concluding;   our   account  of  the  functions   of  the  facial   nerve  it 

ill 

remains  for  us  now  briefly  to  call  attention  to  its  external  branches. 
Immediately  after  the  nerve  passes  out  of  the  stylo-mastoid  foramen, 
as  already  mentioned,  it  sends  a  branch  to  the  glosso-pharyngeal,  upon 
which,  as  Ave  shall  see,  the  motor  properties  of  the  latter  nerve  depend. 
The  posterior  auricular  branch  receiving  sensory  filaments  from  the 
cervical  plexus  supplies  the  attolens  and  retrahens  aurem  and  the 
posterior  portion  of  the  occipito-frontalis  muscle  and  the  adjacent 
integument.  The  branches  supplying  the  posterior  belly  of  the  digas- 
tric, stylo-hyoid  and  stylo-glossus  muscles  are  important,  as  these 
muscles  are  involved  in  mastication  and  deglutition.  The  temporo- 
facial  branch,  as  we  have  seen,  supplies  all  the  muscles  of  the  upper 
part  of  the  face.  If  this  branch  be  paralyzed,  the  eye  remains,  there- 
fore, constantly  open  through  paralysis  of  the  orbicularis  palpebrarum 
muscle,  and  may  become  inflamed  in  consequence  from  constant  ex- 
posure. The  frontal  portion  of  the  occipito-frontalis,  attrahens  aurem, 
and  the  corrugator  supercilii  are  also  paralyzed.  A  striking  symptom  of 
paralysis  of  the  facial  nerve  if  these  filaments  be  affected,  is  inability 
to  corrugate  the  brow  upon  one  side,  as  in  frowning.  Through  paral- 
ysis of  the  muscles  that  dilate  the  nostrils  olfaction  and  inspiration  are 
also  somewhat  interfered  with.  To  appreciate  the  influence  exerted  by 
the  facial  nerve  upon  inspiration  it  may  be  mentioned  that  in  the  horse, 
where  the  breathing  is  entirely  nasal,  death  from  suffocation  very  soon 
takes  place  if  both  facial  nerves  be  divided,  both  nostrils  then  collapsing 
and  becoming  closed  with  each  inspiratory  effort.1  The  effect  of  paralysis 
of  the  facial  nerve  is  well  seen  in  cases  of  facial  palsy  affecting  one  side, 
the  distortion  of  the  features  being  due  in  such  cases  to  the  unopposed 
action  of  the  muscles  upon  the  unaffected  side.  When  the  paralysis  is 
complete  the  angle  of  the  mouth  is  drawn  to  the  sound  side,  the  eye  on 
the  affected  side  is  widely  opened,  even  during  sleep,  the  lips  are  para- 
Ivzed  upon  one  side,  the  saliva  frequently  flowing  from  the  corner  of  the 
mouth  while  the  food  tends  to  accumulate  between  the  teeth  and  cheek 
through  paralysis  of  the  buccinator,  mastication  in  consequence  being 
materially  interfered  with.  If  both  facial  nerves  be  paralyzed,  masti- 
cation becomes  very  difficult,  and  the  face  exhibits  a  peculiarly  ex- 
pressionless appearance. 

1  Bernard :  Lerons  sur  la  physiologie  et  la  pathologie  du  Syateme  Nerveux,  tome  ii.  p.  308.    Paris,  1858. 


lillS 


THE     MEDULLARY    NERVES, 


The  next  nerve  in  order,  the  ninth  or  glossopharyngeal,  the  con- 
sideration of  Ihi'  eighth  nerve  or  auditor  being  deferred  for  the  present, 
.•irises  from  ;i  column  of  cells  deeply  situated  beneath  the  lower  and 
outer  part  of  the  floor  of  the  fourth  ventricle  (Fig.  :>><Sf),  ix),  between 
the   auditory  and   vagal  nuclei.     From  this  origin    the    fibres   proceed 


Pig.  392. 


Distribution  of  the  pneumogastric.  1.  Trunk  of  the  left  pneuinogastric  -l.  Ganglion  of  the  trunk. 
3.  Anastomosis  with  the  spinal  accessory.  4.  Anastomosis  with  the  sublingual.  5.  Pharyngeal  branch  (the 
auricular  branch  is  not  shown  in  the  figure).  (>.  Superior  laryngeal  branch.  7.  External  laryngeal  nerve. 
8.  Laryngeal  plexus.  9,9.  Inferior  laryngeal  branch.  10.  Cervical  cardiac  branch.  11.  Thoracic  cardiac 
branch.  12,13.  Pulmonary  branches.  14.  Lingual  branch  of  the  fifth.  15.  Lower  portion  of  the  sub- 
lingual. 16.  Glosso-pharyngeal.  17.  Spinal  accessory.  18,  19,  20.  Spinal  nerves.  21.  Phrenic  nerve.  22, 
23.  Spinal  nerves.     24,  25,  20,  27,  28,  29,  30.  Sympathetic  ganglia.     (HiRsciiFKLn.) 

forward  and  outward  through  the  medulla,  emerging  from  the  side  of 
the  latter  by  a  series  of  five  or  six  roots  containing  about  9000  fibres 
attached  to  the  surface  of  the  i*estiform  body  (Fig.  382,  viii),  the 
highest  being  close  to  the  auditory  nerve,  and  passes  out  of  the  cranial 


NINTH    NERVE;    GLOSSO-  P  H  A  R  YN  GE  A  L.  669 

cavity  through  the  jugular  foramen  in  company  with  the  pneumogas- 
tric  and  spinal  accessory  nerves.  As  the  glosso-pharyngeal  nerve 
passes  out  of  the  jugular  foramen,  it  expands  into  the  petrous  ganglion 
or  ganglion  of  Andersch  from  which  fine  filaments  are  given  off  to  the 
pneumogastric  and  sympathetic  nerves.  The  ganglion  gives  origin 
also  to  the  tympanic  or  Jacobson's  nerve;  the  latter,  ascending  through 
the  canal  of  the  same  name  in  the  petrous  portion  of  the  temporal 
bone,  expands  upon  the  promontory  of  the  tympanum  into  a  number  of 
branches  which  supply  the  lining  membrane  of  the  tympanum,  the 
round  and  oval  windows,  and  the  Eustachian  tube.  The  tympanic 
nerve  gives  off  also  two  small  branches  which  pass  respectively  to  the 
large  and  small  petrosal  nerves  and  filaments  to  the  sympathetic  plexus 
of  the  internal  carotid  artery.  From  the  ganglion  of  Andersch  the 
glosso-pharyngeal  nerve  descends  (Fig.  392)  between  the  jugular 
vein  and  the  internal  carotid  artery  to  the  root  of  the  tongue  on  the 
inner  side  of  the  stylo-pharyngeus  muscle  terminating  in  the  muscles 
and  mucous  membrane  of  the  pharynx,  soft  palate,  tonsils,  the  root  and 
mucous  membrane  of  the  tongue,  including   the  circuin vallate  papillae. 

During  its  course  the  glosso-pharyngeal  sends  off  filaments  to  the 
pneumogastric  and  sympathetic,  and,  as  already  mentioned,  receives 
filaments  from  the  facial.  That  the  glosso-pharyngeal  nerve  is  a 
sensory  nerve,  at  least  at  its  origin,  is  shown  by  the  loss  of  sensibility 
in  the  parts  to  which  it  is  distributed  and  loss  of  the  sense  of  taste  in 
the  posterior  third  of  the  tongue  following  its  division  in  a  living 
animal  or  paralysis  in  man,  and  that  stimulation  at  the  root  in  a  living 
animal  fails  to  produce  muscular  contractions.  Owing,  however,  to  its 
connections  with  the  facial  and  with  the  spinal  accessory  through 
the  pneumogastric,  the  glosso-pharyngeal  undoubtedly  receives  motor 
fibres,  to  which  are  due  the  muscular  contractions  following  irritation 
of  the  glosso-pharyngeal  when  stimulated  outside  of  the  cranium,  and 
the  difficulty  experienced  in  deglutition,  if  the  nerve  be  divided  in  an 
animal,  or  be  paralyzed  in  man.  It  has  already  been  mentioned  that 
the  contractions  of  the  muscles  involved  in  deglutition  following  stimu- 
lation  of  the  glosso-pharyngeal  are  reflex  in  character,  the  impressions 
made  upon  the  latter  nerve,  like  those  made  upon  the  palatine  branches 
of  the  fifth  nerve,  being  transmitted  to  the  medulla  and  thence  reflected 
through  the  petrosal  nerves  to  the  ganglion  of  Meckel,  and  the  otic 
ganglion  to  the  muscles  supplied  by  the  latter.  The  glosso-pharyngeal 
nerve  is  therefore  sensory  in  function,  endowing  the  tongue  and 
pharynx  with  sensibility,  and  the  posterior  third  of  the  tongue  with  the 
sense  of  taste,  any  motor  realities  that  it  may  exhibit  being  attributed 
to  the  facial  and  spinal  accessory  nerves  with  which  it  is  connected. 

The  tenth  nerve,  the  pneumogastric,  the  par  vagum  or  vagus,  arises 
probably  by  decussating  fibres  from  a  group  of  nerve  cells  situated 
beneath  the  lowest  part  of  the  floor  of  the  fourth  ventricle,  giving  rise 
to  a  promontory  on  the  surface  of  the  latter  (Fig.  o$5,  X).  At  the 
point  of  the  calamus  scriptorius,  the  symmetrically  disposed  nuclei  are 
in  contact  at  the  middle  line,  but  a  little  higher  up  are  separated  by 
the  nuclei,  giving  origin  to  the  hypoglossal  nerves.  From  this  origin 
the  fibres  pass  forward  through  the  medulla,  emerging  by  twelve  or 


670  THE     MEDULLARY    NERVES. 

more  roots  containing  about  9000  fibres  attached  to  the  rest  i form  body 
in  a  line  below  those  of  the  glossopharyngeal  nerve,  and  leave  the 
cranial  cavity,  as  already  mentioned,  in  company  with  the  glosso- 
pharnygealj  spinal  accessory  nerves,  and  the  internal  jugular  vein.  In 
the  jugular  foramen  (Fig.  392)  the  pneumogastric  nerve  presents  a  well- 
marked  enlargement  from  one-sixth  to  one-fourth  of  an  inch  in  length, 
the  ganglion  of  the  root  or  the  jugular  ganglion,  from  which  pass 
filaments  to  the  facial,  and  the  ganglion  of  the  glosso-pharyngeal  and 
superior  cervical  ganglion  of  the  sympathetic.  After  leaving  the 
cranial  cavity  the  pneumogastric  nerve  presents  another  enlargement 
from  half  an  inch  to  an  inch  in  length,  the  ganglion  of  the  trunk, 
from  which  filaments  pass  to  the  hypoglossal  nerve  and  occasionally  to 
the  arcade  formed  by  the  first  two  cervical  nerves.  Immediately 
after  leaving  the  cranial  cavity  the  pneumogastric  nerve  receives  an 
important  branch  from  the  spinal  accessory,  and  during  its  course 
gives  off  also  filaments  to  the  middle  and  superior  cervical  and  upper 
dorsal  ganglia  of  the  sympathetic,  and  together  with  fibres  from  the 
glosso-pharyngeal,  spinal  accessory,  and  sympathetic  forms  the  pharyn- 
geal plexus.  The  most  important  branches  given  off  by  the  pneu- 
mogastric, whose  functions  we  shall  study  seriatim,  are  as  follows  : 
the  auricular,  pharyngeal,  superior  and  inferior  laryngeal,  cervical  and 
thoracic,  cardiac,  anterior  and  posterior  pulmonary,  oesophageal,  and 
abdominal.  That  the  pneumogastric  is  exclusively  sensory  at  its 
origin,  whatever  may  be  the  functions  of  its  branches,  appears  to  be 
satisfactorily  shown,  even  though  indirectly,  by  experiments  like  those 
of  Longet1  made  upon  horses  and  dogs  just  dead,  in  which  stimulation 
of  the  nerve  at  its  root  failed  to  produce  muscular  contractions  if  the 
nerve  was  carefully  insulated  and  all  its  motor  connections  divided. 
That  irritation  should  be  followed  by  muscular  contractions  if  the  latter 
precaution  be  not  observed,  should  not  excite  surprise  when  it  is  re- 
membered that  the  pneumogastric  receives  motor  filaments  from  at  least 
five  sources,  viz.,  the  facial,  spinal  accessory,  hypoglossal,  and  first  and 
second  cervical  nerves,  not  to  speak  of  the  motor  fibres  derived  from 
the  sympathetic.  Any  muscular  contractions  ensuing  upon  irritation 
of  the  pneumogastric  must  therefore  be  either  reflex  in  character  like 
those  of  the  glosso-pharyngeal  already  referred  to,  or  be  attributed  to 
the  stimulation  of  fibres  derived  from  the  motor  sources  just  mentioned. 
The  auricular  or  Arnold's  nerve,  though  containing  fibres  derived 
from  the  facial  and  glosso-pharyngeal  nerves,  is  usually  described  as 
being  a  branch  of  the  pneumogastric  nerve,  being  given  off  from  the 
ganglion  of  its  trunk.  Passing  through  the  temporal  bone  by  the 
canal  of  the  same  name,  it  is  distributed  to  the  external  auditory 
meatus  and  the  membrana  tympani,  endowing  those  parts  with  sensi- 
bility. The  pharyngeal  branches  are  given  off  from  the  superior  portion 
of  the  ganglion  of  the  trunk  of  the  pneumogastric  nerve,  but  consist 
largely  of  filaments  derived  from  the  spinal  accessory,  reinforced, 
further,  during  their  course,  by  filaments  from  the  glosso-pharyngeal 
and    superior    cervical     ganglion    of   the   sympathetic     to    form    the 

1  Physiologie,  tome  iii.  p.  508.     Paris,  1869. 


TENTH    NERVE  ;    P  NEU  MO  GASTRIC  .  671 

pharyngeal  plexus,  which  supplies  the  muscles  and  mucous  mem- 
brane of  the  pharynx,  the  motor  filaments  being  derived,  as  we  shall 
see,  from  the  spinal  accessory,  and  the  sensibility  being  due  to  the  fila- 
ments of  the  pneumogastric  proper,  and  also  to  those  of  the  pharyngeal 
branches  of  the  fifth,  and  of  the  glossopharyngeal.  The  superior 
laryngeal  nerve  arising  from  the  ganglion  of  the  trunk  divides  into 
the  external  and  internal  branches,  the  external  branch  receiving  fila- 
ments from  the  inferior  laryngeal,  and  the  sympathetic  supplies  the 
mucous  membrane  of  the  ventricle  and  crico-thyroid  muscles  of  the 
larynx,  and  the  inferior  constrictor  of  the  pharynx.  The  internal 
branch,  also  receiving  filaments  from  the  inferior  laryngeal,  supplies, 
like  the  external  branch,  the  crico-thyroid  muscle,  and  is  distributed  to 
the  mucous  membrane  of  the  epiglottis,  the  base  of  the  tongue,  the 
aryteno-epiglottidean  folds,  and  the  mucous  membrane  of  the  larynx 
as  far  down  as  the  true  vocal  membranes.  From  the  anatomical  dispo- 
sition it  might  be  inferred  that  the  general  sensibility  of  the  upper  part 
of  the  larynx  and  the  surrounding  mucous  membrane,  as  well  as  the 
innervation  of  the  crico-thyroid  muscle,  was  due  to  the  superior 
laryngeal  nerve,  and  experiment  shows  that  such  is  the  case.  Thus, 
stimulation  of  the  superior  laryngeal  nerves  in  a  living  animal  gives 
rise  to  intense  pain,  and  causes  contraction  of  the  crico-thyroid  muscle. 
It  is  through  the  exquisite  sensibility  of  the  upper  part  of  the  mucous 
membrane  of  the  larynx  that  foreign  bodies  are  prevented  from 
entering  the  air  passages ;  impressions  made  by  such,  being  transmitted 
to  the  medulla,  are  thence  reflected  through  the  inferior  laryngeals 
back  to  the  larynx,  bringing  about  a  closure  of  the  glottis.  Every  one 
is  familiar  with  the  fact  that  if  a  crumb  of  bread,  etc.,  fall  upon  the 
aryteno-epiglottidean  folds  or  the  edge  of  the  vocal  membranes,  the 
sensibility  of  the  parts  is  such  as  to  excite  a  convulsive  cough,  by  which 
the  foreign  body  is  dislodged  and  expelled.  The  impression  conveyed 
by  the  superior  laryngeal  nerve  to  the  medulla  being  reflected  thence 
through  the  nerves  supplying  the  expiratory  muscles  of  the  chest  and 
abdomen,  by  which  the  coughing  is  accomplished.  That  this  reflex  action 
is  due  to  the  sensibility  of  the  laryngeal  mucous  membrane  is  shown  by 
the  fact  that,  after  division  of  the  superior  laryngeal  nerve,  impres- 
sions made  upon  the  mucous  membrane  fail  to  bring  about  such  action. 
The  superior  laryngeals,  also,  constitute  the  afferent  nerves  in  the 
reflex  mechanism  by  which,  through  contraction  of  the  constrictors  of 
the  pharynx,  the  act  of  deglutition  is  completed.  It  is  interesting  to 
observe  that  the  impressions  made  upon  the  mucous  membrane  of  the 
larynx,  and  the  surrounding  membrane,  and  by  which,  through  reflex 
action,  deglutition  is  brought  about,  cause,  at  the  same  time,  closure  of 
the  glottis,  and  arrest  of  respiration,  thereby  protecting  the  air-passages 
against  the  entrance  of  food  or  other  foreign  bodies. 

The  two  inferior  or  recurrent  laryngeal  nerves,  so  called  from  reascend- 
ingto  the  larynx  after  descending  from  the  pneumogastric,  differ  slightly 
in  their  course  on  the  two  sides,  that  of  the  left  side  passing  beneath  the 
aorta,  that  of  the  right  side  winding  from  before  backward  around  the 
subclavian  artery  before  they  ascend  in  the  groove  between  the  trachea 


672  THE    MEDULLARY    NERVES. 

and  the  oesophagus  to  the  larynx.  In  other  respects,  the  course  and  dis- 
tribution of  the  two  nerves  are  the  same.  The  curious  course  taken  by 
the  inferior  laryngeal  nerve,  whether  of  the  right  or  left  side,  is  due  to 
the  fact  that,  while  in  the  embryonic  condition,  the  larynx  and  heart 
are  in  close  proximity  ;  through  the  elongation  of  the  neck,  incidental  to 
development,  the  heart  and  great  bloodvessels  recede  from  the  larynx, 
and,  in  so  doing,  drag  down  with  them  the  inferior  laryngeal  nerves, 
which  pass,  loop-like,  around  them.  It  may  be  mentioned,  in  this  con- 
nection, as  observed  by  Owen,1  and  by  the  author,  in  four  individuals 
dissected  by  the  latter,  that  in  the  giraffe  the  inferior  laryngeal  nerves 
pass  directly  from  the  pneumogastric  to  the  larynx,  like  the  superior 
laryngeals.  The  significance  of  this  is  very  evident,  for,  were  the 
course  of  the  inferior  laryngeals  in  the  giraffe  the  same  as  in  man,  the 
nerve,  in  descending  and  ascending  through  so  many  feet,  would,  in  all 
probability,  be  so  stretched  and  tensed  as  to  render  it  incapable  of  per- 
forming its  functions.  As  the  inferior  laryngeal  nerves  ascend  they 
give  off  filaments,  which  join  those  of  the  cardiac  branches  of  the 
pneumogastric,  filaments  to  the  muscular  tissue,  and  mucous  membrane 
of  the  upper  part  of  the  oesophagus,  to  the  mucous  membrane  and 
inter-cartilaginous  muscular  tissue  of  the  trachea,  to  the  inferior  con- 
strictor of  the  pharynx,  and,  as  already  mentioned,  a  branch  which 
joins  the  superior  laryngeal,  terminating,  finally,  after  penetrating  the 
larynx  behind  the  posterior  articulation  of  the  cricoid,  with  the  thyroid 
cartilage,  in  all  of  the  intrinsic  muscles  of  the  larynx,  except  the  crico 
thyroid,  which,  it  will  be  remembered,  is  supplied  by  the  superior 
laryngeal  nerve.  Direct  stimulation  of  the  inferior  laryngeal  nerves 
proves  what  one  would  be  led  to  expect  from  their -distribution,  that 
they  are  principally  motor  in  function,  and  from  the  fact,  as  we  shall 
see  hereafter,  of  division  of  the  spinal  accessory  being  followed  by  loss 
of  voice,  the  respiratory  movements  of  the  glottis  being,  however,  un- 
affected, but  that  division  of  the  inferior  laryngeal  nerves  not  only 
involves  loss  of  voice,  but  paralysis  of  the  respiratory  movements  of  the 
larynx  as  well — that  their  motor  filaments  are  derived  at  least  from  two 
different  sources,  if  not  more.  To  anticipate  what  we  shall  see  more 
particularly  hereafter,  the  muscles  of  the  larynx  involved  in  the  pro- 
duction of  the  voice  are  the  arytenoid,  the  thyro-arytenoid,  and  the 
lateral  crico-arytenoid,  supplied  by  the  inferior  laryngeal  nerves,  and 
the  crico-thyroid,  supplied  by  the  superior  laryngeal  nerves.  The  pos- 
terior crico-arytenoid  muscles,  supplied  by  the  inferior  laryngeal  nerves 
opening  the  glottis,  are,  however,  respiratory  in  function.  Now,  while 
in  an  animal  the  voice  is  lost  after  division  of  the  internal  branch  of 
the  spinal  accessories,  nevertheless,  the  glottis,  though  not  closing  on 
irritation,  being  still  capable  of  dilatation,  respiration  is  not  interfered 
with.  Such  being  the  case,  if  the  inferior  laryngeal,  however,  be 
divided,  the  glottis  is  at  once  mechanically  closed  with  each  inspiratory 
effort,  and  the  animal,  if  young,  dies  of  suffocation.  In  adults,  how- 
ever, the  cartilages  of  the  larynx  being  rigid,  permit  of  respiration  even 
after  the  larynx  is  paralyzed.     The  only  inference  from  these  facts  is 

1  Op.  cit.,  vol.  iii.  p.  160. 


TENTH    NERVE;     PXEUJI06ASTRIC.  673 

that  the  fibres  of  the  inferior  laryngeal  that  innervate  the  muscles  of 
phonation  are  derived  from  the  spinal  accessory,  but  that  those  in- 
nervating the  respiratory  movements  of  the  glottis  are  derived  from 
some  other  source — from  the  facial,  in  all  probability,  or,  possibly,  from 
the  hypoglossal,  or  the  cervical  nerves  that  we  have  seen  give  off 
branches  to  the  pneumogastric  nerve.  Inasmuch,  also,  as  the  crico- 
thyroid muscle  is  involved  in  phonation,  and  as  we  have  seen  that  the 
superior  laryngeal  nerve  supplying  it  receives  fibres  from  the  inferior 
laryngeal,  in  all  probability  it  is  the  fibres  of  the  latter  nerve  that 
influence  the  crico-thyroid  muscle  in  phonation,  otherwise  it  is  difficult 
to  see  why  the  paralysis  of  the  voice  following  division  of  the  inferior 
laryngeal  nerve  should  be  so  complete.  The  cervical  cardiac  branches, 
two  or  three  in  number,  arising  from  the  pneumogastric,  pass  to  the 
cardiac  plexus,  which  consists  principally,  as  we  shall  see,  of  fibres 
derived  from  the  sympathetic.  The  thoracic  cardiac  branches  given  off 
below  the  origin  of  the  inferior  laryngeal  nerves  pass,  also,  to  the 
cardiac  plexus. 

Contrary  to  what  might  have  been  naturally-  expected  from  what  we 
have  hitherto  learned  as  to  the  effect  of  division  and  stimulation  of 
nerves,  division  of  the  pneumogastric  nerve  in  a  living  animal,  so  far 
from  arresting  the  action  of  the  heart,  actually  increases  the  rapidity  of 
its  pulsations,  while  electrical  stimulation  of  the  pneumogastric  nerve 
arrests  the  heart's  action  in  diastole,1  and  causes  a  fall  in  the  blood  pres- 
sure. The  effect  of  division  of  one  pneumogastric  nerve,  however,  in  a 
dog  or  a  rabbit,  for  example,  is  not  by  any  means  as  marked  as  when 
both  nerves  have  been  divided.  In  the  latter  case  the  action  of  the  heart 
is  tremulous,  the  number  of  its  beats  may  be  doubled,  while  the  respi- 
ration, from  being  momentarily  accelerated,  becomes  calm  and  profound, 
but  diminished  in  frequency.  That  the  influence  exerted  by  the  fibres 
of  the  pneumogastric  nerve  upon  the  heart  is  transmitted  centrifugally 
and  is  dependent  upon  its  motor  fibres  is  shown  by  the  fact  that  if 
the  pneumogastric  nerve  be  divided  in  a  living  animal  and  stimu- 
lated at  its  central  end  none  of  the  effects  such  as  those  just  described 
ensue:  stimulation  of  the  distal  end  alone  slowing  up  the  action  of 
the  heart  and  causing  a  fall  in  blood-pressure  :  and  that  if  the  stimu- 
lation be  continued  too  long,  so  as  to  exhaust  the  irritability  of 
the  motor  fibres,  the  heart  begins  to  beat  again,  their  inhibitory 
effect  being  lost.  Further,  in  animals  poisoned  with  curara,  which, 
as  is  well  known,  paralyzes  the  motor  nerves,  stimulation  of  the 
pneumogastric  nerve  fails  to  arrest  the  action  of  the  heart.  That 
the  motor  fibres  of  the  pneumogastric  nerve  influencing  the  heart's 
action  are  derived  from  the  spinal  accessory  can  be  shown  by  experi- 
ments like  those  of  Waller,2  in  which  after  division  of  the  spinal 
accessory  of  one  side  in  a  living  animal,  allowing  sufficient  time  to 
insure  disorganization  of  its  fibres,  stimulation  of  the  pneumogastric 
nerve  of  the  corresponding  side  failed  to  arrest  the  action  of  the  heart, 
the  usual  effect,  however,  being  observed  when  the  pneumogastric  nerve 

'  Weber:  Aivliiv  d'Anat.  Gen.  et  tie  Physiologie,  1846. 

2  Gazette  Medicale,  3ieme  serie,  tome  xi   p.  42U.    Paris,  1850. 

43 


674 


THE     MEDULLARY    NERVES. 


was  stimulated  on  the  one  side  in  which  the  spinal  accessory  was  still 
intact.  That  the  cardiac  branches  of  the  pneumogastric  nerves  have 
the  same  inhibitory  influence  upon  the  heart  in  man  as  they  have  been 
shown    experimentally    to    have    in    animals,    may    be    inferred    from 


Fra.  393 


\cce7ercent.  of 
,    ,  Med.  Obi. 
Vayalor       \  ^ 

exilra-carrl.iriJui.  central 


Heart,  lungs,  and  great  vessels  of  the  rab- 
bit, with  the  nerves  in  relation  with  them. 
V,  c,  d,  V,  c,  s.  Right  and  left  venae  cavae  supe- 
riores  ;  the  left  vena  cava  is  represented  as  if 
cut  away,  in  order  to  show  the  nerves.  G. 
Ganglion  eervicale  inferius.  s.  Sympathetic. 
v.  Vagus,  d.  Depressor.  The  dotted  lines  on 
each  side  indicate  the  position  of  the  phrenic. 
(Ludwig.) 


Diagram  to  aid  in  understanding  the  action  of  the 
nerves  upon  the  heart.  The  right  half  represents  the 
course  of  the  inhibitory,  and  the  left  the  course  of  the 
accelerating  nerves  of  the  heart ;  the  arrows  showing  the 
direction  in  which  impressions  are  conveyed.  The  ellipse 
at  the  upper  extremity  of  the  vagus  looking  like  the  sec- 
tion of  the  nerve  is  intended  to  represent  the  vagal 
nucleus  or  centre.  In  this  diagram  the  nerves  are  incor- 
rectly made  to  cross,  instead  of  passing  behind,  the  aorta. 


such  pathological1  cases  as  those  in  which  the  number  of  heart  beats 
have  been  known  to  be  reduced  to  three  or  four  per  minute  from 
the  compression  exerted  upon  the  nerve  by  pressing  upon  glands, 
tumors,  etc.  That  the  inhibitory  action  of  the  pneumogastric  upon 
the  heart  can  also  be  exerted  in  a  reflex  as  well  as  direct  manner, 
is  shown  by  those  cases  in   which  there  is  a  sudden  stoppage  of  the 


1  Muller's  Archiv,  1841,  Heft  3.     Jenaesche  Zeits.,  1C5,  S.  384. 


TENTH    NERVE;    PN  EUMO  GASTRIC  .  675 

heart  following  blows  upon  the  epigastrium,  especially  after  full  meals, 
draughts  of  cold  water,  the  body  being  overheated,  great  emotional 
excitement,  etc.,  the  impression  in  such  cases  being  transmitted  from 
the  general  sensory  surface  to  the  medulla,  and  thence  reflected  through 
the  inhibitory  fibres  of  the  pneumogastric  to  the  heart.  That  the 
pneumogastric  nerve  in  man  contains  also  special  afferent  fibres  passing 
from  the  heart  as  well  as  efferent  ones  to  it,  by  which  impressions 
are  transmitted  to  the  medulla,  and  thence  reflected  back  to  the 
heart  by  the  inhibitory  fibres,  appears  very  probable  from  what  has 
been  shown  to  be  experimentally  the  case  in  the  rabbit  and  other 
animals.  Thus,  if  in  the  rabbit,  the  so-called  depressor1  nerve  (Fig. 
393) — that  is,  the  nerve  arising  partly  from  the  pneumogastric,  and 
partly  from  the  superior  laryngeal  nerve,  be  divided,  and  its  distal  end 
stimulated,  no  effect  upon  the  heart  is  observed;  if,  however,  the  central 
end  of  the  nerve  be  stimulated,  the  action  of  the  heart  is  arrested,  and 
the  blood  pressure  falls  just  as  if  the  pneumogastric  nerve  or  the  cardio- 
inhibitorv  fibres  of  the  same  (corresponding  in  man  to  the  superior 
cardiac  nerve)  be  stimulated,  the  action  being  evidently  a  reflex  one ; 
the  impression  made  upon  the  central  end  of  the  depressor  nerve  is  trans- 
mitted to  the  medulla,  and  thence  reflected  back  through  the  cardiac 
inhibitory  fibres  of  the  pneumogastric  to  the  heart.  It  might  naturally 
be  supposed  that  the  inhibitory  influence  of  the  cardiac  fibres  of  the 
pneumogastric  is  directly  exerted  upon  the  heart.  That  such,  how- 
ever, is  not  the  case,  appears  from  the  fact  of  the  latent  period — that 
is,  the  time  elapsing  between  the  application  of  the  stimulus  and  the 
inhibitory  effect,  being  very  long,  nearly  one-fifth  of  a  second,  in- 
stead of  one-hundredth  of  a  second,  in  some  cases  even  two  entire 
beats  of  the  heart  intervening  before  its  arrest  occurred,  indicating  that 
some  resistance  must  be  overcome,  the  inhibitory  fibres  of  the  pneumo- 
gastric acting  upon  some  mechanism  inherent  in  the  heart  itself.  That 
such  is  the  case,  is  shown  -by  the  fact  that  the  action  of  the  heart  in 
the  eel  and  the  frog  can  be  arrested  by  direct  stimulation,  and  that 
in  the  mollusca,  although  no  pneumogastric  nerve  is  present,  the  heart 
can  be'  stopped  in  diastole2  by  direct  irritation.  Again,  if  nicotin  or 
curara  be  subcutaneously  injected  in  small  doses  into  a  living  animal  the 
heart  beats  slower,  but  on  account  of  the  extra  cardiac  inhibitory  cen- 
tres (Fig.  394)  of  the  pneumogastric  becoming  soon  paralyzed,  the 
heart  beats  faster;  if  now  muscarin  or  jaborandi  be  then  administered, 
the  heart  will  be  arrested  in  diastole,  the  latter  substances  appearing 
to  act  directly  upon  intracardiac  inhibitory  centres.  On  the  other 
hand,  if  atropia  be  injected,  then  neither  muscarin  nor  jaborandi  will 
have  any  inhibitory  effect  upon  the  heart,  atropia  appearing  to  paralyze 
both  the  extra-  and  intracardiac  inhibitory  centres.  Even  admitting 
the  existence  of  extra-  and  intra-cardio-inhibitory  centres,  and  cardio- 
motor  centres  which  the  intra-cardio-inhibitory  centres  act  upon,  such  as 
are  hypothetic-ally  represented  in  Fig.  394,  it  is  impossible  in  the  present 
state  of  our  knowledge  to  offer  any  explanation  of  the  inhibitory  effect 
of  the  pneumogastric  nerve  upon  the  heart;  it  would  be  useless,  there- 

1  Luilwig's  Arbeiten,  18G6.  2  Foster :  Pfluger's  Arcbiv,  Band  v.  S.  191. 


676  THE    MEDULLARY    NERVES. 

fore,  to  offer  any  further  reflections  upon  its  functions  in  this  respect, 
and  the  same  may  be  said  to  a  great  extent  of  the  fall  in  blood  pressure 
induced  through  stimulation  of  the  pneumogastric. 

The  most  plausible  explanation,  and  that  usually  offered,  is  as  follows: 
A  stimulus  being  applied  to  the  central  end  of  the  depressor  nerve,  the 
impulse  generated,  as  already  mentioned,  is  not  only  transmitted  to  the 
extra-cardiac  inhibitory  centres  (Fig.  394),  whence  it  is  reflected  through 
the  cardio-inhibitory  fibres  of  the  pneumogastric  nerve  to  the  heart, 
slowing  or  arresting  the  latter,  but  also  to  a  vaso-inhibitory  centre,  sup- 
posed to  exist  in  the  medulla,  which  exerts  a  restraining  or  inhibi- 
tory influence  upon  the  vasomotor  centre  of  the  medulla,  the  result  of 
which  is  that  the  blood  pressure  sinks  through  the  inhibition  of  the 
vasomotor  nerve  fibres  supplying  the  bloodvessels,  and  which  emanate 
from  this  centre.  To  anticipate  a  little  what  will  be  described  more  in 
detail  in  our  consideration  of  the  sympathetic,  it  may  be  mentioned, 
with  reference  to  the  explanation  just  offered  of  the  fall  in  blood  pressure, 
that,  under  ordinary  circumstances,  a  nervous  influence  emanates  from 
the  vasomotor  centre  in  the  medulla,  and  which,  being  transmitted 
through  the  spinal  cord,  spinal  and  splanchnic  nerves,  maintains  the 
bloodvessels  to  which  these  nerves  are  distributed  in  a  state  of  tonic 
contraction,  which  keeps  up  the  blood  pressure.  If,  however,  the 
vasomotor  centre  of  the  medulla  be  paralyzed  by  the  action  of  the  vaso- 
inhibitory  centre,  induced  through  the  stimulation  of  the  depressor 
nerve,  no  such  nervous  influence  being  then  exerted  upon  the  blood- 
vessels, the  latter  dilate,  and  the  blood  pressure  falls.  The  result  of 
this  is,  however,  that  the  medulla  receives  less  blood,  so  much  passing 
into  the  abdominal  vessels,  etc.,  the  consequence  of  which  is,  that  the 
extra-cardiac  inhibitory  centres  of  the  pneumogastric  become  less 
active,  and  the  heart  resumes  its  usual  activity.  That  it  is  to  the 
paralysis  of  the  splanchnic  nerve,  and  consequent  dilatation  of  the  great 
abdominal  vessels,  that  the  fall  in  blood  pressure  induced  by  stimulation 
of  the  depressor  nerve  is  principally  due,  is  shown  by  the  fact  that  if 
the  splanchnic  nerves  be  first  divided,  and  then  the  depressor  nerve  be 
stimulated,  the  blood  pressure  sinks  but  little  more  than  when  the 
splanchnics  are  alone  divided.  The  cardiac  fibres  of  the  pneumogas- 
tric nerve  not  only  consist  of  inhibitory  or  restraining  fibres,  but  also 
of  accelerating  ones  (Fig.  394).  The  latter  are,  however,  derived,  to 
a  considerable  extent,  also,  from  fibres,  which,  descending  from  the 
medulla  through  the  spinal  cord,  emerge  opposite  the  last  cervical  and 
first  dorsal  ganglia  of  the  sympathetic,  which  they  pass  before  termi- 
nating in  the  heart.  There  are  good  reasons,  also,  for  supposing  that 
just  as  there  are  extra-  and  intra-cardiac  inhibitory  centres,  so  there 
are  extra-  and  intra-cardiac  accelerating  centres,  which  act  upon  the 
cardiomotor  centre  just  as  the  inhibitory  centres  are  supposed  to  do. 
It  may  be  as  appropriately  mentioned  in  this  connection,  as  elsewhere, 
that  while  the  existence  of  intra-cardio-inhibitory  and  accelerating  gan- 
glia is  hypothetical,  an  inference  from  experiments,  but  not  yet  demon- 
strated, that,  apart  from  the  small  ganglia  and  nerves,  shown  by  dissec- 
tion to  be  distributed  through  the  substance  of  the  heart,  there  are  three 
well-developed  ganglia,  which  appear  to  be  the  centres   to  which  the 


TENTH  nerve;  pneumog  astric.  677 

efferent  nerves  convey  the  impressions  made  upon  the  endocardium  by 
the  circulating  blood,  and  which  transmitted  thence  through  efferent 
nerves  to  the  muscular  fibres  of  the  heart  excite  the  latter  to  activity. 
The  presence  of  these  ganglia  can  be  readily  demonstrated  in  the  heart 
of  the  frog,  and  their  functional  significance  shown  by  the  well-known 
experiment  of  Stannius.1  In  the  frog,  as  is  well  known,  the  two  venae 
cavre  unite  before  entering  the  right  auricle  to  form  a  dilatation — the 
sinus  venosus.  It  is  in  the  wall  of  the  latter,  near  the  opening  of  the 
inferior  vena  cava,  that  the  first  of  these  ganglia,  the  ganglion  of 
Remak,2  is  situated,  the  second,  or  the  ganglion  of  Bidder,3  being  found 
in  the  left  auriculo- ventricular  groove,  the  third  ganglion,  or  that  of 
Ludwig,  in  the  septum  between  the  auricles.  If  a  ligature  be  applied 
between  the  sinus  venosum  and  the  right  auricle,  the  heart  stops  beating, 
and  remains  in  a  state  of  diastole. 

The  sinus  venosus,  however,  continues  beating,  and  the  auricles  or  the 
ventricle  will  make  a  few  movements  in  response  to  direct  stimulation. 
If  now  a  second  ligature  be  applied  between  the  auricle  and  ventricle,  the 
ventricle  will  begin  beating  again,  the  auricles,  however,  still  remaining 
quiet.  Many  explanations  have  been  offered  of  the  phenomenon  just 
described,  one  of  the  simplest  and  most  plausible  being  that  which 
regards  the  ganglion  of  Ludwig  as  inhibitory  in  function  and  exerting 
greater  influence  than  that  of  Hemak  or  Bidder,  when  either  of  these 
ganglia  is  exerted  alone.  If  such  be  the  case,  it  follows  that  a  ligature 
being  applied  to  the  sinus  venosus  the  inhibitory  action  of  the  ganglion 
of  Ludwig  being  only  opposed  to  the  exciting  action  of  that  of  Bidder, 
the  heart  stops,  and  that  after  a  ligature  is  applied  between  the  auricles 
and  the  ventricle  then  the  inhibitory  action  of  the  ganglion  of  Ludwig 
being  cut  off",  and  there  being  nothing;  to  counteract  the  action  of  the 
ganglion  of  Bidder,  the  ventricle  begins  to  beat  again.  Whatever  the 
explanation  may  be  of  the  facts  just  described,  and  from  what  has  been 
said  of  the  cardiac  fibres  of  the  pneumogastric  nerve,  it  is  evident  that 
the  heart  possesses  an  intrinsic  nervous  mechanism  by  which,  in  response 
to  the  ^stimulus  exerted  by  the  blood,  its  fibres  are  excited  to  act,  and 
that  there  exists  an  extrinsic  one  by  which  the  action  of  the  heart  is 
inhibited  or  accelerated. 

The  pulmonary  branches  of  the  pneumogastric  nerve  are  given  off  as 
the  anterior  and  posterior  branches.  The  anterior  pulmonary  branches 
after  sending  a  few  filaments  to  the  trachea,  form  a  plexus  which, 
surrounding  the  bronchial  tubes,  is  continued  to  the  termination  of  the 
latter  in  the  pulmonary  air  cells.  The  posterior  pulmonary  branches, 
larger  and  more  numerous  than  the  anterior  ones,  together  with  fibres 
derived  from  the  upper  three  or  four  thoracic  ganglia  of  the  sympa- 
thetic, constitute  the  posterior  pulmonary  plexus.  After  giving  off 
fibres  to  the  inferior  and  posterior  portion  of  the  trachea,  to  the  mus- 
cular tissue  and  mucous  membrane  of  the  middle  portion  of  the 
oesophagus,  to  the  posterior  and  superior  portion  of  the  pericardium,  the 
posterior  pulmonary  plexus  surrounds  the  bronchial  tubes,  and,  like  the 

i  Zwei  Rcihcn  :  Phyaiologlsche,  Versuche,  1851.  -  Muller's  Archiv,  1S44,  S.  4G3. 

3  Archiv  f.  Aunt.  u.  Phys.,  18G8,  S.  1. 


678  THE  MEDULLARY  NERVES. 

.•interior  one,  is  continued  with  the  latter  to  the  air  cells.  The  pulmo- 
nary branches  of  the  pneumogastric  nerve  supply  the  lower  part  of  the 
trachea,  the  bronchi,  and  the  lungs,  with  both  sensory  and  motor  fibres, 
as  shown  by  experiments  like  those  of  Longet,1  in  which,  after  division 
of  the  pneumogastric  nerve  in  the  neck,  the  mucous  membrane  of  the 
trachea  and  bronchus  became  insensible,  while  stimulation  of  its  branches 
caused  the  muscular  fibres  of  the  bronchus  to  contract.  It  might  natu- 
rally be  supposed,  from  the  pneumogastric  nerve  giving  off  the  branches 
we  are  now  considering,  to  the  lungs,  that  the  latter  influence  in  some 
manner  respiration.  That  such  is  the  case  is  shown  by  the  fact  that 
after  division  of  the  pneumogastrics  in  a  living  animal,  the  division  of 
one  nerve  having  but  little  effect,  that  not  only  is  the  number  of 
respirations  diminished,  in  some  instances  being  reduced  one-half,  but 
that  their  character  is  changed,  as  may  be  seen  from  Fig.   395,  the 

Fig.  39-3. 


a.  Tracing  of  the  respiratory  movements  of  the  cat.    a  before,  6  after  division  of  both  vagi.    (Carpenter.) 

respiration  becoming  much  deeper,  and  that  although  the  same  quantity 
of  air  is  breathed  the  blood  becomes  decidedly  venous.  Death  usually 
takes  place  after  division  of  the  pneumogastrics  within  from  one  to  six 
days,  occasionally,  however,  recovery  takes  place  through  reunion  of  the 
divided  ends.  In  the  former  case  the  most  marked  symptoms  are  failure 
of  the  respiration  and  increasing  sluggishness.  After  death  from  di- 
vision of  the  pneumogastrics  in  a  mammal,  the  lungs  are  found  to  have 
become  leathery  and  resisting  to  the  touch,  destitute  of  crepitation,  of  a 
dark  purple  color,  sinking  when  cut  up  and  thrown  into  water,  engorged 
with  blood,  and  almost  empty  of  air.  This  peculiar  kind  of  solidification 
or  carnification,  as  it  is  called,  appears  to  be  due  to  a  traumatic  emphy- 
sema set  up  as  a  consequence  of  the  excessively  labored  and  profound 
inspirations  due  to  division  of  the  pneumogastrics;  the  pulmonary  capil- 
laries being  then  ruptured  through  the  distention  of  the  air  cells,  the 
blood  effused  coagulates  and  so  gives  rise  to  the  characteristic  post- 
mortem conditions.  That  this  explanation  of  carnification  suggested 
by  Bernard2  is  the  correct  one,  is  confirmed  by  the  fact  of  it  not  occur- 
ring in  birds  after  division  of  the  pneumogastric  nerves,  since  in  these 
animals  the  lungs  are  fixed  to  the  walls  of  the  thoracic  cavity,  and  their 
general  relations  are  such  as  not  to  be  exposed  to  great  distention  in 
respiration.  The  only  explanation  that  can  be  offered  of  the  diminution 
in  the  number  of  respirations,  etc.,  following  division  of  the  pneumo- 
gastric nerves  is  that  the  latter  contain  fibres,  the  pulmonary  branches, 
wdiich  convey  impressions  from  the  lungs,  generated  through  the  want 

1  Traite  de  Physiologie,  tome  iii.  p.  535.      Paris,  1809. 

2  Systeme  Nerveux,  tome  ii.  pp.  353,  3G8.     Paris,  1858. 


TENTH    NERVE;    P  NEU  MO  GASTRIC  .  679 

of  air  to  the  medulla,  which  thence  reflected  through  the  phrenic  and 
intercostal  nerves,  etc.,  excite  inspiratory  movements.  The  want  of  air 
being  supplied  by  the  filling  of  the  lungs  through  the  inspiratory  effort, 
and  the  stimulus  to  the  medulla  no  longer  being  generated,  the  passive 
movements  of  expiration  then  ensue.  Such  being  the  case,  it  follows, 
the  pneumogastrics  being  divided,  that  the  impression  due  to  the  want 
of  air  is  no  longer  conveyed  to  the  medulla;  the  respiratory  centre  of 
the  latter  lacking  its  usual  stimulus  acts,  therefore,  less  energetically, 
and  the  number  of  respirations  diminishes.  In  a  word,  the  animal  not 
feeling  the  need  of  breathing,  then  inspires  much  less  frecpuently  than 
ordinary.  From  what  has  been  said  of  the  function  of  the  inferior 
laryngeal  nerves,  it  is  evident  that  the  pneumogastric  nerves  being 
divided  in  the  neck  and  the  laryngeal  muscles  influencing  the  vocal 
cords  and  the  dilatation  of  the  glottis,  paralyzed,  that  the  quantity  of  air 
entering  the  lungs  will  be  diminished  through  the  collapse  of  the  glottis. 
The  aeration  of  the  blood  being,  therefore,  very  imperfect  from  this 
cause  as  well  as  from  the  carnification  of  the  lungs,  its  venous  condition 
and  the  general  sluggish  condition  of  the  system  already  referred  to,  is 
accounted  for. 

The  respiratory  centre  being,  of  course,  affected  in  this  way  is  less  sus- 
ceptible to  impressions  derived  from  other  afferent  nerve  fibres  than 
those  passing  from  the  lungs  to  the  medulla  in  the  pneumogastrics,  to 
be  mentioned  again  presently,  and  the  breathing  consequently  becoming 
slower  and  slower,  death  finally  ensues.  That  the  pneumogastric  nerves 
play  an  important  part  in  respiration  may  also  be  inferred  from  the 
respiratory  movements  being  accelerated  by  the  application  of  a  mod- 
erate electrical  stimulus  to  the  central  ends  of  the  divided  nerve,  no 
effect  following  the  stimulation  of  the  peripheral  ends;  the  action  is 
evidently,  therefore,  entirely  a  reflex  one.  It  should  be  mentioned, 
however,  in  this  connection,  that  the  effect  of  stimulation  of  the  pneumo- 
gastric nerves  will  not  only  vary  according  to  the  strength  of  the  stimu- 
lus, but  with  the  state  of  the  breathing.  Thus,  if  the  breathing  be 
natural,  the  effect  of  a  slight  stimulus  is  acceleration  of  the  respiration; 
if  the  stimulus  be  strong,  temporary  arrest  of  respiration  occurs,  and  if 
very  strong  the  diaphragm  passes  into  a  tetanic  condition.  In  apnoea, 
when  the  blood  is  overcharged  with  oxygen,  the  effect  of  the  stimulus 
is  negative ;  but  if  the  blood  be  deficient  in  oxygen,  as  in  dyspnoea, 
all  the  accessory  muscles  are  brought  into  play  and  the  chest  remains 
in  a  tetanic  condition.  From  the  fact  of  respiration  not  ceasing  en- 
tirely after  division  of  the  pneumogastric  nerves,  but  only  diminishing 
in  rapidity,  and  of  recovery  even  taking  place  after  such  an  operation, 
it  is  evident  that  there  must  be  stimuli  by  which  the  respiratory  centre 
of  the  medulla  is  called  into  action  other  than  those  emanating  in  the 
lungs  through  the  wTant  of  air  and  transmitted  by  the  fibres  of  the  pneu- 
mogastric  to  the  medulla.  Every  one  is  familiar  with  the  fact  that  the 
dashing  of  cold  water  in  the  face,  or  the  first  plunge  into  a  cold  bath, 
and  the  application  of  a  pungent  vapor  to  the  nostrils,  cause  involuntary 
respiratory  efforts.  It  is  well  known,  also,  that  the  first  inspiratory 
efforts  of  the  newborn  child  are  usually  made  in  response  to  the  stimu- 
lation of  the  cool  external  air  coining  in  contact  with  the  face,  and  that 


680  THE    MEDULLARY    NERVES. 

impressions  on  the  general  surface,  such  as  a  slap  on  the  face  or  upon 
the  buttocks,  will  frequently  excite  the  child  to  breathe  when  otherwise 
it  would  not  do  so.  It  would  appear,  therefore,  that  impressions  made 
upon  the  general  sensory  surface  when  transmitted  to  the  medulla  will 
cause,  through  stimulation  of  the  respiratory  centre  reflexly,  inspiratory 
movements,  as  well  as  stimuli  in  the  lungs  due  to  the  want  of  air  and 
transmitted  through  the  pneumogastrics.  Finally,  there  can  be  little 
doubt  that  blood  itself  when  deficient  in  oxygen  acts  as  a  stimulant  to 
the  respiratory  centre  of  the  medulla,  since  even  after  the  pneumo- 
gastrics are  divided  if  the  blood  becomes  venous  in  character  through 
artificial  respiration  being  not  kept  up,  the  chest  of  the  animal  being 
opened  or  the  blood  be  cut  off  from  the  medulla  by  opening  an  artery 
even  though  fresh  air  be  supplied  to  the  lungs,  in  either  case  violent 
respiratory  movements  are  made,  evidently  in  response  to  the  stimulus 
exerted  by  the  non-oxygenated  blood  upon  the  respiratory  centre  of  the 
medulla.1  The  oesophageal  branches  of  the  pneumogastric  given  off 
both  above  and  below  the  pulmonary  ones  unite  to  form  the  oesophageal 
plexus,  which  supplies  the  muscular  tissue  and  the  mucous  membrane 
of  the  lower  third  of  the  oesophagus.  These  branches  contain  both 
sensory  and  motor  fibres,  the  latter  being  probably  more  numerous, 
since  while  the  mucous  membrane  is  sensitive  to  heat  and  cold,  strong 
irritants,  etc.,  it  cannot  be  said  to  be  acutely  sensitive. 

That  the  motor  fibres  supplying  the  oesophagus  are  derived  from  the 
pneumogastric  nerve  can  be  shown  by  experiments  like  those  of 
Bouchardat  and  Sandras,2  Chauveau,3  Longet,4  Bernard,5  in  which,  after 
division  of  the  pneumogastric  nerve  in  a  living  animal,  the  oesophagus 
was  paralyzed  and  distended  by  the  food  vainly  endeavored  to  be 
swallowed.  It  is  still  a  question,  however,  from  wdiat  nerve  the  motor 
fibres  of  the  lower  third  of  the  oesophagus  are  derived,  since,  according 
to  Chauveau,6  stimulation  of  the  bulbar  roots  of  the  spinal  accessory, 
the  most  probable  source,  do  not  excite  contractions  of  the  oesophagus. 
The  abdominal  branches  of  the  pneumogastric  nerve  differ  somewhat 
in  their  course,  according  as  they  are  distributed  to  the  two  sides.  That 
of  the  left  side,  situated  anteriorly  to  the  cardiac  opening  of  the 
stomach,  immediately  after  passing  with  the  oesophagus  into  the 
abdominal  cavity,  gives  off  numerous  branches,  some  of  which  are  dis- 
tributed to  the  muscular  walls  and  mucous  membrane  of  the  stomach, 
while  others  pass,  in  company  with  the  sympathetic,  along  the  course 
of  the  portal  vein  to  the  liver.  That  of  the  right  side,  situated  pos- 
teriorly, passes  through  the  oesophageal  opening  of  the  diaphragm,  and, 
after  sending  a  few  filaments  to  the  muscular  coat  and  the  mucous  mem- 
brane of  the  stomach,  is  distributed  to  the  liver,  spleen,  kidneys,  supra- 
renal capsules,  and  the  whole  of  the  small  intestine,  giving  off,  also, 
filaments  to  the  left  pneumogastric.  If  the  pneumogastric  nerves  be 
divided  during  full  digestion  in  a  living  animal  in  which  a  gastric 
fistula  has  been  established,  so  that  the  interior  of  the  stomach  can  be 

1  Flint :  Physiology.  Nervous  System,  p.  237,  1872.        -  Comptes  Rendus,  tome  xxiv.  p.  59.  Paris,  1847. 

3  Journal  de  la  physiologie,  tome  v.  p.  312.     Paris,  1862. 

4  Traits  de  Physiologic,  tome  iii.  p.  547.     Paris,  18UI). 

5  Systeme  Nerveux,  tome  ii.  p.  422.     Paris,  1858.         6  Op.  cit.,  p.  205. 


TENTH   NERVE;    P  NE  U  MOG  ASTRIC.  681 

examined,  the  muscular  contractions  will  be  observed '  to  cease  in- 
stantly, the  mucous  membrane  to  become  pale  and  flaccid,  the  secretion 
of  the  gastric  juice  to  be  arrested,  and  the  organ  to  have  become  insen- 
sible. There  can  be  no  doubt,2  also,  that  stimulation  of  the  pneumo- 
gastric  nerves  causes  the  stomach  to  contract,  and  that  digestion  may, 
to  a  certain  extent  at  least,  be  reestablished  by  stimulation  of  the 
peripheral  extremities  of  the  divided  nerves.3  Inasmuch,  however,  as 
several  seconds  elapse  between  the  application  of  the  stimulus  and  the 
contraction  of  the  stimulus,  it  is  hardly  probable,  as  suggested 
by  Longet,  that  the  muscular  contractions  of  the  stomach  induced 
by  the  stimulation  of  the  pneumogastrics  are  due  to  its  sympathetic 
fibres,  rather  than  to  the  stimulation  of  the  nerve  fibres  of  the 
pneumogastric  proper,  the  tardiness  in  action  just  mentioned  being 
characteristic,  as  we  shall  see,  of  the  sympathetic.  If  such  be  the  case, 
it  would  appear  that  the  impressions  due  to  the  presence  of  food  in  the 
stomach  are  transmitted  by  the  abdominal  branches  of  the  pneumo- 
gastric to  the  medulla,  the  efferent  impulses  being  reflected  thence  to  its 
muscular  walls  by  sympathetic  fibres.  It  must  be  mentioned,  however, 
that  even  when  both  pneumogastric  nerves  are  divided,  if  the  animal 
survive  the  operation,  in  a  day  or  two  digestion  may  be  partly  reestab- 
lished4 if  the  food  be  finely  divided  and  carefully  introduced  into  the 
stomach.  It  is  quite  possible  that  the  impression  due  to  the  presence  of 
food  in  the  stomach  and  intestines,  after  reaching  the  plexus  of  Meissner, 
situated  in  the  submucous  tissue,  and  the  plexus  of  Auerbach,  lying 
among  the  fasciculi  of  the  longitudinal  muscular  coat,  is  at  once  reflected 
back  to  their  muscular  coats  without  being  transmitted  to  the  medulla. 
Whether  the  reflex  nervous  mechanism  involved  in  gastric  digestion  be 
such  as  just  mentioned  or  not,  there  can  be  no  doubt  that  digestion  in 
man  is  very  much  influenced  by  the  nervous  system.  Every  one  is 
familiar  with  the  fact  that  digestion  may  be  at  once  stopped  by  nervous 
excitement,  such  as  a  piece  of  bad  news,  etc.;  that  there  exists  an 
intimate  sympathy  between  the  brain  and  the  stomach  at  all  times,  and 
it  is  difficult  to  understand  by  what  avenues,  other  than  the  abdominal 
branches  of  the  pneumogastric  nerve,  impressions  are  carried  to  and 
from  these  organs.  That  the  abdominal  branches  of  the  pneumogastric 
influence  also  absorption  from  the  stomach  and  intestinal  digestion  may 
be  inferred  from  the  fact  that,  after  division  of  the  pneumogastric 
nerves,  the  absorption  of  poisons  is  retarded,  if  not  prevented,  and 
that  the  most  powerful  cathartics  fail  to  produce  their  characteristic 
purgative  effects,5  just  as.  under  similar  circumstances,  digitalis  fails  to 
diminish  the  action  of  the  heart.6  Division  of  the  pneumogastric  nerve 
through  its  abdominal  branches  produces,  also,  congestion  of  the  liver, 
renders  the  bile  watery,  and  arrests  its  glvcogenic  function,  the  latter 
being  exaggerated  by  stimulation  of  the  central  ends  of  the  divided 
nerves.     The  action   is   a  reflex  one,  as  stimulation  of  the   peripheral 

l  Bernard,  op.  cit.,  tome  ii.  p.  422.  -  Longet,  op.  cit.,  tome  iii.  p.  546. 

3  Tiedemann  et  Gmelin  :  Recherches  snr  la  digestion,  p.  373.     Paris,  1827. 

*  Scliiff  :  Lecons  sur  la  physiologie  de  la  digestion,  tome  ii.  389.  Florence,  1867.  Longet,  op.  cit.,  tome 
iii.  p.  549. 

5  Brodie  :  Phil.  Trans.,  vol.  xiv.  ;i.  101.  London,  1  *1 1.  Reid  :  Phvs.  Anat.  and  Path.  Researches, 
London,  1S48.     Wood:  American  Journal  of  the  Med.  Sciences,  vol.  l.\.  p.  75.     Phila.,  1870. 

0  Traube  :  Gesammelte  Beitrage  zur  Bath.  u.  Physiologie,  Bd.  i.  S.  I'M.     Berlin. 


682  THE  MEDULLARY  NERVES. 

ends  has  no  effect  in  this  respect,  and  the  efferent  impulses  are  trans- 
mitted from  the  centre,  in  the  medulla,  hy  the  sympathetic,  probably, 
and  not  by  the  pneumogastric  nerve,  since  division  of  the  latter  between 
the  lungs  and  liver  does  not  affect  the  production  of  sugar  by  the 
latter.1 

Resuming  what  has  been  said  of  the  functions  of  the  different 
branches  of  the  pneumogastric  nerve,  it  appears  that  the  auricular 
branches  endow  the  upper  portion  of  the  external  auditory  meatus  and 
the  membrana  tympani  with  sensibility  ;  that  the  pharyngeal  branches 
supply  the  muscles  of  the  pharynx  with  motor  filaments  derived  from 
the  spinal  accessory,  contributing  slightly,  also,  to  the  sensibility  of  the 
pharynx.  To  the  superior  laryngeal  branches  are  due  the  exquisite 
sensibility  of  the  upper  portion  of  the  larynx,  the  closing  of  the  glottis 
against  foreign  substances,  and  the  production,  partly,  of  the  movements 
of  deglutition,  and  arrest  of  the  diaphragm,  the  crico-thyroid  muscles 
being  also  supplied  by  these  nerves.  The  inferior  laryngeal  branches, 
through  fibres  derived  from  the  spinal  accessories,  influence  phonation, 
and,  through  fibres  derived  from  other  sources,  the  respiratory  move- 
ments of  the  glottis,  while  reflexly  they  cause  deglutition  and  arrest  of 
the  diaphragm.  The  cardiac  branches,  through  fibres  derived  from  the 
spinal  accessories,  arrest  the  action  of  the  heart,  and  through  depressor 
fibres  inhibit  the  vaso-motor  centre  of  the  medulla,  and  so  lower  the 
blood  pressure.  The  pulmonary  branches  are  to  a  certain  extent  the 
avenues  by  which  impressions,  due  to  the  want  of  air,  are  transmitted  to 
the  respiratory  centre  of  the  medulla,  and  thence  through  reflex  action 
excite  inspiratory  movements,  by  which  the  want  of  air  is  supplied. 
The  oesophageal  branches  supply  the  lower  third  of  the  oesophagus 
with  both  motor  and  sensory  fibres,  the  middle  portion  being  supplied 
by  the  posterior  pulmonary,  and  the  upper  portion  by  the  inferior 
laryngeal  nerves.  The  abdominal  branches  influence  the  production  of 
bile  and  sugar  by  the  liver,  and  gastric  and  intestinal  digestion,  proba- 
bly, through  conveying  impressions  from  the  stomach  and  intestine, 
which  transmitted  to  the  medulla  and  thence  reflected  through  the 
sympathetic,  cause  secretion. 

The  spinal  accessory  or  the  eleventh  nerve  (Fig.  381),  consisting  of 
from  2000  to  2500  fibres,  arises  by  two  distinct  sets  of  roots — upper 
and  lower.  The  upper  root  or  the  bulbar  portion,  originating  in  a 
nucleus  lying  close  to  the  central  canal,  and  continuous  with  the 
nucleus  of  the  pneumogastric  nerve  (Fig.  385,  XI),  emerges  from  the 
side  of  the  medulla  below  the  latter  nerve.  The  lower  roots  or  the 
spinal  portion,  originating  in  the  anterior  cornu  of  the  cord,  curve 
backward,  and,  passing  through  the  gray  substance  and  lateral  columns 
of  the  cord,  emerge  from  the  latter  as  six  or  eight  filaments  between 
the  anterior  and  posterior  roots  of  the  first  and  seventh  cervical  nerves 
inclusive.  The  spinal  accessory  nerve  so  formed  enters  the  cranial 
cavity  by  the  foramen  magnum,  and  leaves  the  latter  by  the  jugular 
foramen  in  company  with  the  pneumogastric  and  glossopharyngeal, 
and  the  jugular  vein.      During  its  course  the  spinal  accessory  receives 

1  Bernard,  op.  cit.,  tome  ii.  p.  432  ;  Lecons  de  physiologic  experimentale,  tome  i.  p.  324.   Berlin,  1855. 


ELEVENTH    NERVE;    SPINAL    ACCESSORY.  683 

from  or  gives  off  some  filaments  to  adjacent  nerves.  Frequently,  as  it 
enters  the  cranial  cavity,  it  receives  filaments  from  the  posterior  roots 
of  the  first  two  cervical  nerves,  to  which  its  recurrent  sensibility  is 
due;  occasionally  also  it  gives  off  a  filament  to  the  superior  ganglion  or 
ganglion  of  the  root  of  the  pneumogastric.  It  also  receives  filaments 
from  the  anterior  branches  of  the  second,  third,  and  fourth  cervical 
nerves.  After  emerging  from  the  jugular  foramen  the  spinal  accessory 
gives  oft'  also  two  branches — internal  and  external — meriting  special 
notice.  The  internal  branch,  consisting  principally,  if  not  entirely,  of 
the  fibres  derived  from  the  medulla,  passes  to  the  pneumogastric,  sub- 
dividing as  it  joins  the  latter  into  two  small  branches,  the  first  of  which 
constitutes  a  part  of  the  pharyngeal  branch  of  the  pneumogastric  as 
already  observed ;  the  second,  however,  becomes  so  intimately  united 
with  the  pneumogastric  nerve  that  its  final  distribution  cannot  be  made 
out  by  dissection  alone,  experiment  only  indicating  its  functional  sig- 
nificance, as  we  shall  see  presently.  The  external  branch  of  the  spinal 
accessory,  larger  than  the  internal,  and  derived  principally  from  the 
fibres  of  the  spinal  cord,  pass  through  the  posterior  portion  of  the  upper 
third  of  the  sterno-cleido-mastoid  muscle,  receiving  filaments  in  its  course 
through  the  muscle  from  the  second  and  third  cervical  nerves,  to  be 
finally  distributed  to  the  trapezius  muscle. 

That  the  spinal  accessory  nerve  is  essentially  motor  in  function, 
supplying  the  muscles  just  mentioned,  can  be  demonstrated  experiment- 
ally by  cutting  through  the  occipito-atloid  ligaments  and  stimulating 
the  roots  of  the  nerve  within  the  spinal  canal  by  electricity.  If,  how- 
ever, the  filaments  arising  from  the  medulla  only  be  stimulated  con- 
tractions of  the  muscles  of  the  larynx  and  pharynx  alone  ensue,  no 
movements  of  the  sterno-cleido-mastoid  or  trapezius  being  observed. 
On  the  other  hand,  if  the  filaments  arising  from  the  spinal  cord  only  be 
stimulated  then  the  sterno-cleido-mastoid  and  trapezius  muscles  alone 
contract,  the  laryngeal  and  pharyngeal  muscles  remaining  quiescent. 
Not  only  does  this  striking  experiment  confirm  what  the  distribution  of 
the  spinal  accessory  would  lead  us  to  suppose  as  to  its  general  motor 
functions,  but  it  also  clearly  shows  that  the  muscles  of  the  larynx  must 
be  supplied  by  the  spinal  accessory — that  is,  that  the  fibres  of  the  recur- 
rent laryngeal  nerves  supplying  the  muscles  of  the  larynx,  except  the 
crico-thyroid,  are  derived  not  from  the  pneumogastric  but  from  the  spinal 
accessory  nerve.1  The  spinal  accessory  nerve  appears  to  be  endowed 
also  with  a  certain  amount  of  direct,  apart  from  the  recurrent,  sensi- 
bility already  referred  to.  Whatever  sensibility  it  does  possess  is,  how- 
c\  er,  due  undoubtedly  to  those  filaments  derived  from  the  pneumogastric 
and  cervical  nerves.  In  speaking  of  the  functions  of  the  inferior  laryn- 
geal branches  of  the  pneumogastric  nerve  it  was  mentioned  that  those 
nerves  consisted  of  two  kinds  of  fibres,  one  set  influencing  the  respira- 
tory action  of  the  glottis,  another  regulating  phonation,  and  that  the 
latter  were  in  reality  derived  from  the  internal  branch  of  the  spinal 
accessory.  It  only  remains,  therefore,  to  describe  the  manner  in  which 
this   can  be   demonstrated,  since   the  fibres   of  the   inferior  laryngeal 

1  Bernard :  Systeme  Nerveux,  tome  ii.  p.  296. 


684:  THE     MEDULLARY    NERVES. 

nerves  influencing  phonation  cannot  be  traced  by  dissection  back  to  the 
spinal  accessory.  Bischoff  was  the  first  to  demonstrate  the  influence 
exerted  by  the  internal  branch  of  the  spinal  accessory  nerve  upon  the 
production  of  the  voice  by  opening  in  a  goat  the  spinal  canal  through 
the  occipito-atloid  space,  and  dividing  all  its  roots  on  both  sides,  the 
result  being  entire  extinction  of  the  voice,  whatever  sound  was  emitted 
after  the  experiment  being  one  which  in  no  wise  could  be  called  voice.1 
As  this  method  of  procedure  was  however  unsuccessful  in  the  six  pre- 
ceding experiments,  five  of  which  were  performed  upon  dogs  and  one 
upon  the  goat,  even  in  the  hands  of  such  a  skilful  anatomist  and  physi- 
ologist as  Prof.  Bischoff,  that  introduced  later  and  habitually  practised 
by  Bernard  is  a  far  more  satisfactory  one.  This  consists  in  following 
by  dissection  the  external  or  muscular  branch  of  the  spinal  accessory 
up  to  the  point  where  it  emerges  from  the  jugular  foramen,  and  where 
it  separates  from  the  internal  branch,  and  then,  after  seizing  the  com- 
bined trunk  between  the  blades  of  a  forceps,  by  steady  and  continuous 
traction  to  extract  the  whole  nerve  with  both  its  medullary  and  spinal 
roots  entire  ;  or  to  remove  the  medullary  portion  with  the  internal  branch 
alone,  leaving  the  spinal  portion  with  the  external  branch  intact,  in 
which  case  the  voice  is  entirely  lost;  or  to  remove  the  spinal  portion 
with  the  external  branch,  leaving  the  medullary  portion  with  the  internal 
branch  intact,  in  which  case  the  voice  is  unaffected  or  in  some  cases 
even  rendered  clearer.2  It  is  an  interesting  fact  that  in  a  chimpanzee 
dissected  by  Vrolik  the  internal  branch  of  the  spinal  accessory  was 
found  passing  directly  to  the  larynx  instead  of  to  the  pneumogastric. 
The  usual  disposition  in  this  anthropoid  appears,  however,  to  be  the 
same  as  obtains  in  man,  at  least  such  was  found3  to  be  the  case  in  three 
individuals  dissected  by  the  author.  After  what  has  been  said  of  the 
influence  exerted  by  the  pharyngeal  branches  of  the  glosso-pharyngeal 
and  of  the  pharyngeal  and  inferior  laryngeal  branches  of  the  pneumo- 
gastric in  deglutition,  and  of  the  inhibitory  effects  upon  the  heart  by 
the  cardiac  fibres  of  the  latter  nerve,  it  is  only  necessary  here  to  men- 
tion again  that  the  motor  fibres  involved  in  the  performance  of  the 
above  functions  are  derived  from  the  internal  branch  of  the  spinal  acces- 
sory, at  least  partly  so  in  the  case  of  deglutition,  and  entirely  so  in 
that  of  the  inhibition  of  the  heart.  As  to  the  function  of  the  external 
or  muscular  branch  of  the  spinal  accessory,  it  would  appear  that  its 
action  is  to  excite  contraction  of  the  sterno-cleido-mastoid  and  trapezius 
muscles,  synchronously  with  the  action  exerted  by  the  internal  branch 
upon  the  laryngeal  and  pharyngeal  muscles,  the  harmonious  action  of 
the  muscles  so  brought  about  beino-  of  advantage  under  certain  circum- 
stances.  Thus,  in  prolonged  vocal  efforts,  as  in  singing,  for  example, 
in  which,  as  which  we  shall  see,  the  vocal  membranes  are  put  on  the 
stretch,  the  upper  portion  of  the  chest  is,  at  the  same  time,  fixed  through 
the  action  upon  the  shoulders,  to  a  certain  extent  at  least,  of  the  sterno- 
cleido-mastoid  and  trapezius  muscles,  and  in  this  way  the  expulsion  of 

1  "  Qui  npiitirpiani  veil  appellari  potuit."    Bischoff  :  Nervi  Accessorii  Willisii  Anatomia  et  Physiologie, 
p.  94.     Darinsradii,  1832. 

2  Bernard,  op.  cit.,  tome  ii.  p.  296. 

3  Proo.  of  Acad,  of  Nat.  Sciences,  Philadelphia. 


TWELFTH    XERVE  ;    HYPOGLOSSAL.  685 

air  through  the  glottis,  and  upon  which  the  singing  depends,  can  be 
well  regulated.  In  the  same  manner,  when  one  makes  a  muscular 
effort,  the  glottis  is  closed  at  the  same  moment  that  the  chest  is  fixed, 
respiration  being  temporarily  arrested.  The  same  synchronism  in  the 
action  of  the  external  and  internal  branches  of  the  spinal  accessory 
obtain,  therefore,  in  this  instance,  as  in  the  former.  That  the  external 
branches  of  the  spinal  accessory  exert  some  influence  upon  the  respira- 
tory movement  is  well  seen  in  animals  in  which  the  branches  on  both 
sides  have  been  divided,  such  suffering  from  shortness  of  breath  after 
any  very  great  muscular  effort,  and  presenting,  also,  irregularity  in  the 
movements  of  the  anterior  extremities,  the  shortness  of  breath  being 
apparently  due  to  the  want  of  synchronous  action  of  the  sterno-cleido- 
mastoid  and  trapezius  muscles. 

The  twelfth  nerve,  the  hypoglossal  or  sublingual,  consisting  of  from  4500 
to  5000  fibres,  arises  probably  by  decussating  fibres  from  a  long  column 
of  nerve  cells,  the  lower  part  of  which  lies  in  front  of  the  central  canal 
on  each  side,  the  upper  part  forming  a  prominence  upon  the  floor  of 
the  fourth  ventricle  (Fig.  385,  xii).  Passing  thence  through  the  inner 
part  of  the  olivary  body,  the  fibres  emerge  as  eleven  or  twelve  filaments 
from  the  furrow  between  the  anterior  pyramid  and  the  olivary  body 
(Fig.  381),  which,  passing  as  two  distinct  bundles  through  two  distinct 
openings  in  the  dura  mater  into  the  anterior  condyloid  foramen,  unite 
into  a  single  trunk  as  they  emerge  from  the  cranial  cavity.  Occasion- 
ally, the  hypoglossal  nerve,  as  it  passes  through  the  foramen,  receives  a 
filament  having  a  ganglion  upon  it,  arising  from  the  postero-lateral 
portion  of  the  medulla.  This  ganglionated  filament,  or  posterior  root, 
so  to  speak,  of  the  hypoglossal  nerve,  while  exceptionally  present  in 
man,  is,  however,  found  normally  in  the  dog,  cat,  rabbit,  hog,  horse, 
and  calf,  and  is  sensory  in  function  in  these  animals,  the  anterior  por- 
tion of  the  common  trunk  corresponding  to  the  hypoglossal  in  man, 
being  motor.  After  the  hypoglossal  passes  out  of  the  cranial  cavity  it 
gives  off'  (Fig.  39G)  filaments  to  the  sympathetic,  to  the  pneumogastric, 
to  the  upper  two  cervical  nerves,  and  to  the  lingual  branch  of  the  fifth. 
Descending  behind  the  pneumogastric  nerve  it  curves  downward  and 
forward  to  the  outer  side  of  the  latter,  between  the  internal  carotid 
artery  and  the  jugular  vein,  and  penetrates  the  genio-hyo-glossal  muscle, 
which  it  supplies,  as  also  the  hyo-glossus,  lingualis,  genio-hyoid.  and 
stylo-glossus  muscles.  The  hypoglossal  gives  off,  also,  an  important 
branch,  the  descendens  noni,  but  which,  according  to  the  classification 
of  the  nerves  usually  adopted,  would  be  more  correctly  called  the 
descending  branch  of  the  twelfth,  supplying  the  sterno-thyroid,  sterno- 
hyoid, and  omo-hyoid  muscles,  the  thyro-hyoicl  muscle  being  supplied 
by  the  branch  of  the  same  name.  From  the  distribution  of  the  hypo- 
glossal nerve  it  might  naturally  be  inferred  that  it  is  essentially  motor 
in  function,  any  sensibility  that  it  possesses  being  due  to  the  filaments 
communicating  with  the  cervical  and  pneumogastric  nerves,  and  the 
lingual  branch  of  the  fifth.  That  such  is  the  case  is  shown  by  the 
effect  of  division  of  the  hypoglossal  in  a  living  animal,  and  of  its 
paralysis  in  man.  Under  such  circumstances,  through  paralysis  of  the 
tongue,  though  the  tactile  and  gustatory  senses  are  not  affected,  masti- 


686 


THE     ME  1)1  LI,  A  KY    NERVES, 


cation  is  rendered  very  difficult,  if  not  impossible,  while,  through 
paralysis  of  the  muscles  depressing  the  larynx  and  hyoid  bone,  deglu- 
tition is  made  difficult;   in  man  the  power  of  articulation  is  lost  as  well. 


Fie  306. 


Distribution ;of  the  sublingual  nerve.  I.  Root  of  the  fifth  nerve.  2.  Ganglion  of  Gasser.  3,4,5,6,7, 
9,10,12.  Branches  and  anastomoses  of  the  fifth  nerve.  11.  Submaxillary  ganglion.  13.  Anterior  belly 
of  the  digastric  muscle.  11.  Section  of  the  mylo-hyoid  muscle.  15.  Glosso-pliaryngeal  nerve.  16. 
Ganglion  of  Andersch.  17,  18.  Branches  of  the  glosso-pharyngeal  nerve.  19,19.  Pneumogastric.  20, 
21.  Ganglia  of  the  pneumogastric.  22,22.  Superior  laryngeal  branch  of  the  pneumogastric.  23.  Spinal 
accessory  nerve.  24.  Sublingual  nerve.  25.  Descemlens  noni.  26.  Thyro-hyoid  branch.  27.  Terminal 
branches.  28.  Two  branches,  one  to  the  genio-hyo-glossu.s,  and  the  other  to  the  genio-hyoid  muscle. 
(Sappky.) 

This  is  well  seen  in  cases  of  glosso-labio-laryngeal  paralysis,  in  which 
the  nuclei  of  origin  in  the  medulla  of  the  hypoglossal,  as  wTell  as  the 
facial,  spinal  accessory,  and  glosso-pharyngeal  nerves  are  affected  by 
disease,  which  involves  a  gradual  and  progressive  paralysis  of  the 
tongue,  palate,  lips,  and  laryngeal  muscles,  rendering  articulation,  and 
ultimately  deglutition,  impossible. 

In  cases  of  hemiplegia  the  hypoglossal  nerve  is  usually  more  or  less 
involved.  In  such  cases  the  patient  protrudes  the  tongue,  the  point 
being  deviated  to  the  side  affected  with  the  paralysis,  owing  to  the  unop- 
posed action  of  the  genio-hyo-glossus  muscle  of  the  sound  side.  That 
the  hypoglossal  nerve  is  a  motor  nerve — the  motor  nerve  of  the  tongue, 
etc. — is  further  shown  by  the  effect  of  stimulating  the  peripheral  end  of 
the  divided  nerve,  the  tongue,  and  the  muscles  to  which  the  nerve  is  dis- 


TWELFTH    NERVE;    HYPOGLOSSAL.  687 

tributed  at  once  contracting.  The  hypoglossal  nerve,  together  with  the 
small  or  motor  root  of  the  fifth  and  the  facial  nerves,  constitutes  the 
efferent  fibres  by  which  the  reflex  action  involved  in  mastication  is 
accomplished,  the  afferent  fibres  being  the  lingual  branch  of  the  fifth; 
and  the  glosso-pharyngeal  nerves,  together  with  the  small  root  of  the 
fifth,  facial,  pharyngeal,  and  inferior  laryngeal  branches  of  the  pneu- 
mogastric  and  cervical  plexus,  the  efferent  fibres  involved  in  the  perform- 
ance of  deglutiton,  the  afferent  fibres  being  constituted  by  the  palatine 
branches  of  the  fifth,  the  pharyngeal  branches  of  the  glosso-pharyngeal, 
the  superior  laryngeal  and  oesophagus  branches  of  the  pneumogastric. 

Having  described  the  distribution  and  function  of  the  ten  pairs  of 
cranio-medullary  nerves,  and  having  seen  that  they  arise  from  gray  nuclei 
in  the  medulla  oblongata,  it  is  evident  that  the  medulla  consists,  not  only 
as  we  have  seen,  of  fibres  passing  from  the  cord  to  the  ganglion  of  the 
base  of  the  brain,  but  may  be  regarded,  also,  as  being  composed  of 
so  many  distinct  reflex  centres,  of  which  the  cranio-medullary  and 
spinal  nerves  constitute  the  afferent  and  efferent  fibres  ;  the  existence  in 
the  medulla  of  about  fourteen  such  centres,  probably  more,  has  been 
established.  First.  That  for  closing  the  eyelids,  the  afferent  fibres  being 
contained  in  the  optic  nerve,  and  the  branches  of  the  fifth  distributed 
to  the  conjunctiva  and  to  the  skin  of  the  lids,  the  efferent  fibres  in  the 
facial.  Second.  The  centre  for  sneezing,  the  afferent  fibres,  being  in 
the  olfactory  and  the  fifth  nerve,  the  efferent  in  the  spinal  nerves  in- 
fluencing expiration.  Third.  The  centre  for  coughing,  the  afferent 
fibres  rising  in  the  pneumogastric,  the  efferent  being  the  same  as 
those  last  mentioned.  Fourth.  The  respiratory  centre,  or  nceud-vital 
of  Flourens.  Fifth.  The  masticatory  centre.  Sixth.  The  centre  of 
insalivation.  Seventh.  The  centre  of  deglutition.  Eighth.  The  cardio- 
inhibitory  centres,  the  afferent  and  efferent  fibres  of  which  have  already 
been  referred  to.  Ninth.  The  centre  for  sucking,  the  afferent  fibres  of 
which  are  in  the  fifth  and  glosso-pharyngeal  nerves,  the  efferent  the 
facial  supplying  the  lips.  Tenth.  The  centre  influencing  the  act  of 
vomiting,  the  afferent  fibres  being  in  the  pneumogastric,  the  efferent  in 
the  nerves  of  expiration.  Eleventh.  The  centre  of  speech — that  is, 
with  reference  to  the  movements  of  the  lips,  tongue,  and  larynx. 
Twelfth.  The  vaso-motor  centre.  Thirteenth.  The  centre  inhibiting 
the  reflex  centres  of  the  spinal  cord. 

The  medulla  oblongata  being  the  seat  of  the  centres  receiving  the 
afferent  fibres  and  giving  off  the  efferent  ones  involved  in  the  perform- 
ance of  mastication,  insalivation,  deglutition,  respiration,  circulation, 
etc.,  is,  therefore,  the  great  coordinating  centre  of  the  reflex  actions 
essential  to  the  maintenance  of  life.  Even  if  all  the  parts  of  the  brain 
above  the  medulla  be  removed  in  a  living  animal,  or  be  undeveloped,  as 
in  anencephalous  infants,  life  may  yet  be  maintained  by  artificial 
means,  since,  if  food  be  introduced  into  the  mouth  it  will  be  swallowed, 
the  respiratory  and  circulatory  movements  will  go  on  in  the  usual 
rhythmical  manner,  the  animal  or  infant  will  react  to  impressions  made 
upon  the  general  sensory  surface,  withdrawing  its  limbs,  etc.,  if  pulled 
or  pinched,  may  even  utter  a  cry,  as  if  in  pain,  and  yet  such  an  animal 
or  human  being  cannot  be  said  to  be  really  a  sentient,  still  less  an  in- 
telligent, being,  but  merely  a  nutritive  reflex  mechanism. 


CHAPTER    XL  II  I. 

THE  PONS  VAROLII.  CRURA  CEREBRI.  CORPORA  STRIATA. 
THALAMI  OPTICI.  CORPORA  QUADRIGEMINA.  CERE- 
BELLUM. 

Whether  reflex  action  of  the  spinal  cord  or  medulla  be  accompanied 
or  not  in  the  lower  animals  with  sensation,  volition,  consciousness, 
there  can  be  no  doubt  that  the  physical  seat  of  what  we  call  feeling, 
thinking,  etc.,  in  ourselves  is  situated  in  some  part  of  the  brain  above 
the  level  of  the  medulla  oblongata,  since  in  the  absence  of  such  parts 
one  neither  feels,  thinks,  nor  wills.  Now,  just  as  we  have  seen  that 
the  spinal  cord  and  medulla  consist  of  nervous  centres  as  well  as  of 
fibres  passing  through  them  to  the  ganglia  at  the  base  of  the  brain,  so 
may  the  pons  Varolii  or  mesencephalon  be  regarded  as  consisting, 
not  only  of  ascending  sensory  and  descending  motor  fibres  connect- 
ino-  the  cord  with  the  basal  ganglia,  and  of  bridging  fibres  connect- 
ing the  lateral  lobes  of  the  cerebellum — hence  its  name — but  of  gray 
matter  performing  the  functions  of  a  distinct  nervous  centre  or  centres. 
That  the  gray  matter  or  tuber  annulare  (Fig.  397, 1)  is  the  essential  part  of 

Fig.  397. 


Diagram  of  human  brain  in  transverse  vertical  section.     1.    Tuber  annulare.     2,  2.  Crura  cerebraj 
3,3.  Internal  capsule.     4,4.  Corona  radiata.     5,  6.  Cerebral  ganglia.      7.  Corpus  callosum.  (Dalton.) 

the  pons  Varolii  is  shown  by  the  fact  of  thebridging  fibres  of  the  pons  being 
absent  in  animals  in  which  the  lateral  lobes  of  the  cerebellum  are  unde- 
veloped as  in  birds.     That  the  tuber  annulare,  or  vesicular  matter  of  the 


CRURA     CEREBRI.  689 

pons  Varolii,  is  that  part  of  the  encephalon  in  which  consciousness  first 
awakens  in  response  to  impressions  transmitted  by  the  spinal  and 
cranial  nerves  from  the  external  world  appears  probable  from  ex- 
periments, such  as  those  of  Longet,1  Vulpian,2  etc.,  in  which,  after 
removal  of  the  whole  encephalon  except  the  pons,  medulla, -and  cere- 
bellum, sensibility  to  pain  still  persisted,  the  cries  emitted  by  an 
animal  so  mutilated  not  being  simply  reflex  in  character,  such  as  are 
heard  in  an  animal  possessing  only  the  medulla  already  referred  to, 
but  as  really  indicating  the  perception  of  painful  impressions.  While 
it  is  true  that  the  appreciation  of  painful  and  other  impressions  is  not 
acute,  but  obscure,  nevertheless  that  such  an  animal  is  conscious  to  a 
certain  extent  at  least,  there  can  be  little  doubt,  their  condition  being 
apparently  similar  to  patients  undergoing  a  severe  surgical  operation, 
but  imperfectly  under  the  influence  of  an  anaesthetic,  and  who,  while 
undoubtedly  suffering  pain  at  the  time,  have  no  recollection  of  it,  the 
impressions  due  to  the  operation  not  being  conveyed  to  the  cerebral 
hemispheres,  and  therefore  not  memorized. 

It  has  already  been  mentioned  that  the  motor  tract  beginning  in  the 
corpus  striatum  of  one  side  of  the  body  is  continued  downward  through 
the  anterior  or  inferior  portion  of  the  crus  cerebri  (crusta)  to  the  decus- 
sating fibres  of  the  medulla,  and  thence  to  the  antero-lateral  columns  of 
the  opposite  side  of  the  cord;  that  the  sensory  tract  of  the  cord  is  pro- 
longed upward  through  the  medulla  and  posterior  or  superior  portion 
of  the  crus  cerebri  (tegmentum)  to  terminate  in  the  thalamus  opticus  of 
the  same  side.  Such  being  the  case,  as  might  be  anticipated  if  both 
crura  (Fig.  397,  2,  2)  are  completely  divided,  sensation  and  voluntary 
movement  are  entirely  annihilated  throughout  the  body,  division  of  one 
of  the  crura  involving  paralysis  of  sensation  and  motion  on  the  opposite 
side  of  the  body  only.  The  constant  tendency  to  turn  toward  the  side 
opposite  that  of  the  lesion,  the  "evolution  du  manege"  of  Longet, 
observed  when  one  crus  is  imperfectly  divided  appears  to  be  due  to  the 
balance  of  the  muscular  action  being  destroyed  through  the  weakening 
of  the  sensori  motor  apparatus  of  the  opposite  side.  Division  of  the 
crus  cerebri  involves  also  paralysis  of  the  oculo-motoris  of  the  same 
side,  and  partial  paralysis  of  the  facial  nerve  of  the  opposite  side,  and  is 
also  followed  by  contraction  of  the  arteries,  a  rise  in  blood  pressure, 
and  the  loss  of  power  to  influence  voluntarily  the  action  of  the 
sphincter  ani,  and  the  constrictor  urethrse.  In  addition  to  the  motor 
and  sensory  fibres  just  referred  to,  the  crura  cerebri  contain  also  fibres 
passing  from  the  gray  matter  of  the  medulla  and  pons  to  the  hemi- 
spheres, and  of  fibres  passing  forward  and  backward  from  the  locus  niger, 
or  the  gray  matter  separating  the  crusta  from  the  tegmentum,  to  the 
cerebellum,  and  of  fibres  passing  from  the  corpora  quadrigemina  to  the 
cerebellum.  The  functions  of  these  fibres,  so  far  as  known,  appear  to  be 
commissural  in  character.  If  the  hemispheres  of  the  brain  be  removed 
to  the  level  of  the  corpus  callosum,  or  the  bridge  of  white  substance 
uniting  the  cerebral  hemispheres,  and  the  latter  be  divided  and  turned 
aside,  the  lateral  ventricles  will  be  exposed — that  is,  the  two  cavities 

1  Physiologic,  tome  iii.  p.  396  2  Systeme  Xerveux,  p.  542.     Paris,  1866. 

44 


690 


CORPORA    STRIA  T A . 


having  for  their  roof  the  corpus  callosum,  their  floor  the  fornix,  their  inner 
walls  the  septum  lucidum  with  its  enclosed  fifth  ventricle,  their  outer 
walls  the  corpora  striata.  Each  corpus  striatum,  so  called  from  present- 
ing a  striated  appearance  on  section,  projects  as  a  half  pyriform  prom- 
inence into  the  lateral  ventricle,  constituting,  as  just  said,  its  outer  wall, 
the  largest  anterior  portion  heing  known  as  the  head  ;  the  narrowest 
posterior  portion  the  tail,  the  latter  curving  backward  to  the  outer  side 
of  the  thalamus  opticus. 

Each  corpus  striatum  (Fig.  398)  consists  of  two  parts,  the  intraven- 
tricular, or  nucleus  caudatus  (6),  and  the  extraventricular,  or  nucleus 

Fig.  398. 


.- 


J 


- 


Horizontal  section  of  the  hemispheres  at  tin-  level  of  the  cerebral  ganglia.  1.  Great  longitudinal 
fissure,  between  frontal  lobes.  2.  Great  longitudinal  fissure,  between  occipital  lobes.  3.  Anterior  part 
of  corpus  callosum.    4.  Fissure  of  Sylvius.     5.  Convolutions  of  the  insula.    G.  Caudate  nucleus  of  corpus 

striatum.  7.  Lenticular  nucleus  of  corpus  striatum.  8.  Optic  thalamus.  9.  Internal  capsule.  ID.  Ex- 
ternal capsule.     11.  Claustrum.     (Dalton  ) 

lenticularis  (7),  the  two  being  separated  by  the  internal  capsule  (9),  or 
the  diverging  fibres  of  the  crus  cerebri,  to  which  the  corpus  striatum 
owTes  its  name,  the  external  capsule  (10)  with  the  claustrum  (11)  lying 
to  the  outer  side  of  the  nucleus  lenticularis  and  close  to  the  insula  or 


CORPOKA    STRIATA.  691 

island  of  Reil  (5).  While  it  is  quite  possible  that  some  of  the  divergent 
fibres  of  the  cms  cerebri  pass  directly  through  the  corpus  striatum  to 
the  gray  matter  of  the  convolutions  of  the  hemispheres,  it  appears  more 
probable  that  the  corona  radiata  (Fig.  397,  4),  or  the  cone  of  fibres 
radiating  out  to  the  convolutions,  originate  de  nova  in  the  corpus  stria- 
tum, and  are  not  merely  continuations  of  the  internal  capsule.  If  now 
the  fornix  or  floor  of  the  lateral  ventricle  be  removed,  a  narrow  trian- 
gular cavity  will  be  exposed,  the  third  ventricle,  communicating,  on  the 
one  hand,  with  the  lateral  ventricles  by  the  foramina  of  Monro,  and 
on  the  other  with  the  fourth  ventricle  by  the  iter,  the  latter  passing 
under  the  corpora  quadrigemina,  to  be  mentioned  presently.  The  floor 
of  the  third  ventricle  is  formed  from  before  backward  by  the  optic 
commissure,  infundibulum,  mammillary  eminences,  posterior  perforated 
space,  and  cerebral  crura ;  its  walls,  by  the  thalami  optici,  situated  on 
the  inner  side  of  the  crura  cerebri,  and  separated  from  the  corpora, 
striata  by  the  internal  capsule  and  taenia  semicircularis.  The  more 
prominent  portions  of  the  thalamus  opticus  anteriorly  and  posteriorly 
are  known  as  its  tubercles ;  beneath  the  posterior  ones  are  situated  the 
copora  geniculata,  giving  partial  origin  to  the  optic  tracts.  Each  thala- 
mus opticus  consists  internally  of  white  matter,  externally  of  both  white 
and  gray  matter,  and  is  connected,  like  the  corpus  striatum,  with  the 
convolutions  of  the  hemispheres  by  diverging  fibres.  It  will  be  observed 
from  this  brief  sketch  of  the  structure  and  relation  of  the  corpora  striata 
and  thalami  optici  to  the  crura  cerebri  on  the  one  hand,  and  the  cerebral 
convolutions  on  the  other,  that  there  are  three  distinct  sets  of  nerve 
centres,  and  three  distinct  sets  of  nerve  fibres  through  which  the  im- 
pressions from  the  periphery  are  transmitted  to  the  convolutions  of  the 
hemispheres  and  in  the  reverse  direction,  viz.,  nerve  centres,  first,  the 
graj  matter  of  the  cord,  second,  the  basal  ganglia,  and  third,  the  gray 
matter  of  the  convolutions  of  the  hemispheres;  nerve  fibres,  first,  the 
fibres  of  the  nerves  connecting  the  periphery  with  the  gray  matter  of 
the  cord,  second,  the  fibres  of  the  gray  matter  and  of  the  columns  of  the 
cord  connecting  the  gray  matter  of  the  cord  with  the  basal  ganglia,  and 
third,  the  fibres  of  the  corona  radiata  connecting  the  basal  ganglia  with 
the  gray  matter  of  the  convolutions  of  the  hemispheres.  Such  being 
the  case,  if  what  we  have  called  the  motor  and  sensory  tracts  of  the 
spinal  cord  in  man  have  the  functional  significance  attributed  to  them, 
and  if  the  corpus  striatum  is  the  beginning  of  the  motor,  and  the  thalamus 
opticus  the  ending  of  the  sensory  tract,  it  is  difficult  to  avoid  drawing 
the  conclusion  that  these  ganglia  are  respectively  motor  and  sensory  in 
function.  One  of  the  best  established  facts  in  human  or  animal  cerebral 
pathology  is  that  a  destructive  lesion  of  the  corpus  striatum,  whether  pro- 
duced by  disease  or  experimentally,  is  followed  by  a  paralysis  of  motion  of 
the  opposite  side  of  the  body,  sensation  remaining  unimpaired.  It  is  true 
that  in  some  exceptional  cases  the  paralysis  is  on  the  same  side  of  the 
body,  but  there  is  no  question  in  such  cases  as  to  the  paralysis  due  to 
the  lesion  of  the  corpus  striatum  being  that  of  motion.  Of  this  there  can 
be  no  doubt.  Apart  from  the  number  of  cases  that  have  been  recorded. 
the  author  has  had  ample  opportunities  afforded,  both  in  man  and 
animals,  of  satisfying  himself  as  to  this  point.    It  has  also  been  shown  by 


692  THALAMl    OPTICI. 

several  experimenters1  that  electrical  stimulation  of  the  corpus  striatum 
in  a  living  animal,  monkeys,  dogs,  cats,  etc.,  causes  a  general  unilateral 
contraction  of  the  muscles  of  the  opposite  side  of  the  body,  the  latter 
being  thrown  into  a  condition  of  pleurosthotonus,  in  which  it  is  bent 
to  the  opposite  side,  the  flexor  muscles  being  contracted  apparently  more 
than  the  extensor  ones.  It  is  well  known  also,  that  in  the  cetacea,  the 
whale,  dolphin,  the  elephant,  etc.,  very  muscular  animals,  the  corpora 
striata  are  not  only  absolutely  but  relatively  large  and  well  developed. 
The  facts  of  pathology,  experiment,  and  comparative  anatomy,  confirm, 
therefore,  the  view  based  upon  their  anatomy,  that  the  function  of  the 
corpora  striata  is  essentially  motor.  While  lesions  of  the  thalamus 
opticus  are  not  of  infrequent  occurrence  in  man,  from  the  fact  that  the 
corpus  striatum  and  adjacent  parts  of  the  hemispheres  are  usually 
involved,  conclusions  as  to  the  functions  of  these  ganglia,  based  upon  the 
loss  of  sensibility,  etc.,  following  their  destruction,  cannot  be  accepted 
with  the  same  confidence  as  in  the  case  of  the  corpora  striata.  Never- 
theless, if  the  lesion  be  limited,  as  is  sometimes  the  case,  to  the  corpus 
striatum  and  the  thalamus  opticus,  and  the  destruction  of  these  two 
ganglia  is  followed  by  loss  of  motion  and  of  sensibility  on  the  opposite 
side  of  the  body,  and  if  it  be  admitted  that  the  function  of  the  corpus 
striatum  is  motor,  the  conclusion  that  the  thalamus  opticus  is  sensory 
in  function  becomes  then  unavoidable.  Indeed,  it  could  not  be  other- 
wise, since  after  destruction  of  the  thalamus  opticus  no  other  avenue  is 
left  by  which  sensory  impressions  can  be  transmitted  from  the  general 
periphery  of  the  body  to  the  cerebral  hemispheres.  That  the  thalamus 
opticus  is  essentially  sensory  in  function  is  further  shown  by  the  fact 
of  its  destruction  in  man  being  followed  by  loss  of  general  and  special 
sensibility  on  the  opposite  side  of  the  body,  tactile  sensation  being 
impaired,  and  hearing  and  vision  in  some  cases  affected.2 

The  results  of  experiments  performed  upon  animals  are  unfortunately 
so  contradictory  and  unsatisfactory  that  they  throw  little  or  no  light 
upon  the  functions  of  the  optic  thalami  in  them  and  still  less  in  man. 
It  appears,  however,  to  have  been  established  by  the  fact  of  electrical 
stimulation  failing  to  produce  muscular  contractions  that  the  thalamus 
opticus  has  not  motor  significance,  confirming  what  has  just  been  said 
as  to  its  having  sensory  functions.  While  it  must  be  admitted  that  the 
evidence  adduced  in  favor  of  the  thalamus  opticus  being  sensory  is  not 
as  conclusive  as  that  in  favor  of  the  corpus  striatum  being  motor  in 
function,  nevertheless  what  positive  evidence  there  is  bearing  upon  this 
subject  favors  such  a  view  while  the  negative  evidence  is  not  against  it. 
That  the  paralysis  of  motion  and  sensation  following  lesions  of  the 
corpora  striata  and  thalami  optici  is  not  due  simply  to  the  motor  and 
sensory  impulses  being  normally  transmitted  through  these  ganglia  from 
or  to  the  convolutions  of  the  hemispheres,  and  that  after  the  destruction 
of  these  ganglia  no  avenues  are  left  fur  the  transmission  of  such  impulses, 
is  shown  by  the  fact  that  after  removal  of  the  cerebral  convolutions  in  a 

i  Ferrier:  The  Functions  of  the  Brain,  p.  237.  New  York,  1876.  Burdon  Sanderson:  Centralblatt, 
p.  51:;,  1,-74. 

2  Ley's  Recherches  sur  le  Systeme  Nerveux,  1865,  p.  538.  Crichton  Browne  :  West  Riding  Asylum 
Reports,  vol.  v.  p.  227, 1876.     Ferrier,  op.  cit.,  p.  239. 


THALAMI    OPTICI.  693 

mammal  the  power  of  movement  and  sensation  remains.  Thus,  for 
example,  in  a  rabbit  the  cerebral  hemispheres  having  been  removed, 
while  there  is  nothing  observed  to  indicate  that  its  sensations  ever  give 
rise  to  ideas — that  is,  that  it  perceives — nevertheless,  it  feels  even  it  does 
not  think ;  it  sees,  hears ;  if  pinched,  it  cries ;  when  stirred  up,  it  runs  or 
leaps  forward,  avoiding  with  more  or  less  success  obstacles  placed  in  its 
path.  The  animal  has  undoubtedly  possession  of  its  senses,  can  exe- 
cute all  its  bodily  movements,  but  its  intelligence  appears  to  be  gone, 
at  least  objects  which  would  have  ordinarily  pleased  or  terrified  it  make 
no  impression  whatever  upon  it.  It  must  be  borne  in  mind,  however, 
that  in  any  application  to  be  made  of  such  results  with  the  view  of  eluci- 
dating the  functions  of  the  basal  ganglia  in  man,  that  it  does  not  neces- 
sarily  follow  that  a  human  being,  or  even  a  dog  deprived  of  its  cerebral 
hemispheres,  should  be  in  exactly  the  same  mental  condition  as  a  rabbit 
under  similar  circumstances.  On  the  contrary,  there  is  good  reason  for 
supposing  that  as  we  pass  from  the  lower  to  the  higher  mammals  the 
seat  of  voluntary  motion  and  sensation  is  removed  to  higher  and  higher 
levels  in  the  encephalon ;  the  cerebral  convolutions  being  more  im- 
portant in  this  respect  in  man  than  in  a  dog,  and  the  basal  ganglia 
more  important  in  the  dog  than  in  the  rabbit,  and  so  on.  The  most 
marked  contrast  in  this  respect  is  presented  by  fishes,  in  which  the 
corpora  striata  are  relatively  well  developed,  the  cerebral  hemispheres 
but  little  so — in  fact,  the  latter  are  only  represented,  more  particularly  in 
the  cartilaginous  fishes,  by  the  thin  film  of  nervous  matter  covering  in 
the  cavity  or  ventricle,  of  which  the  corpora  striata  constitute  the  floor; 
the  so-called  optic  lobes  in  fishes  represent,  probably  also  not  only  the 
optic  lobes  of  the  higher  vertebrates,  but  also  the  thalami  optici  as  well. 
Undoubtedly  a  rabbit  can  do  more  without  its  basil  ganglia  and  cerebral 
convolutions  than  a  dog,  and  a  dog  with  its  basal  ganglia  but  without 
its  hemispheres  than  a  man  without  the  latter.  It  becomes,  therefore, 
a  very  difficult  matter  to  say  just  where  sensation  begins  in  man,  and 
still  more,  where  sensation  is  accompanied  or  gives  rise  to  ideation  and 
volition.  If  it  be  admitted,  however,  that  even  after  removal  of  all  the 
encephalon  above  the  pons,  feeling  even  if  obscure  persists  it  might  be 
expected  that  sensation  would  be  more  defined,  more  acute,  if  higher 
ganglia  such  as  the  thalami  optici  remain  intact.  While  it  cannot  be 
said  then  that  the  functions  of  the  basal  ganglia  have  been  established 
beyond  doubt,  in  all  probability  the  thalamus  opticus  is  the  ganglion  of 
general  sensibility,  the  corpus  striatum  of  motion,  and  in  the  lower 
mammals  of  voluntary  motion  very  probably.  Even  if  such,  how- 
ever, be  not  exactly  the  case,  and  it  be  supposed  that  an  impression 
made  upon  the  periphery  must  be  transmitted  to  the  cerebral  convolu- 
tions to  be  thoroughly  appreciated,  and  that  a  voluntary  impulse  de- 
veloped in  response  to  such  a  sensation  must  emanate  in  the  same,  the 
connections  of  the  basal  ganglia  through  the  corona  radiata,  with  the 
convolutions  of  the  hemispheres,  and  with  each  other,  offer  an  avenue 
for  the  performance  of  reflex  actions  already  referred  to,  which  origi- 
nally being  accompanied  with  both  sensation  and  volition,  in  time  come 
to  be  performed  without  either.  For  with  the  constant  repetition  of 
a  particular  action  involving  sensation  and  volition,  it  is  natural  to 


69-4 


CORPOEA    QUADR1GEMINA. 


suppose  that  the  circuit  traversed  might  become  shorter  and  shorter, 
and  that  impressions  which  originally  reached  the  cerebral  hemisphere 
before  being  reflected  back,  simply  passing  through  the  basal  ganglia  to 
and  fro,  gradually  take  a  shorter  course,  and  reaching  the  thalamus 
opticus  are  at  once  reflected  back  through  the  corpus  striatum,  short- 
circuited,  so  to  speak. 

Such  a  change  would  obviously  be  of  advantage  to.  the  economy, 
since  the  basal  ganglia,  taking  upon  themselves,  so  to  speak,  the  perform- 
ance of  the  work  done  formerly  by  the  hemispheres,  more  opportu- 
nity would  be  afforded  the  latter  of  doing  intellectual  work.  It  has 
already  been  mentioned  that  the  iter  or  way  by  which  the  third  and 
fouth  ventricles  communicate  with  each  other,  passes  underneath  the 
corpora  quadrigemina.  The  latter  consist  of  a  white  quadrate  mass 
more  or  less  divided  upon  its  upper  surface  by  a  crucial  depression  into 
four  eminences,  the  so-called  nates  and  testes,  optic  lobes,  or  quadri- 
gemina! bodies,  whence  their  name.  The  corpora  quadrigemina,  or 
the  optic  lobes,  as  we  shall  hereafter  for  brevity  designate  them,  are 
attached  laterally  to  the  thalami  optici  between  which  they  are  situated, 
and  also  to   the  geniculate  bodies,   and  therefore  indirectly  with  the 

Fig.  399. 


Diagram  of  the  optic  nerves  and  tracts,  in  man.  1.  Left  eyeball.  2.  Right  eyeball.  3,3.  Corpora 
geniculata interna.  4,  4.  Corpora  geniculata  externa.  5.  Tubercula  quadrigemina.  6,  6.  Centres  of 
vision  in  the  cerebral  hemispheres.   (Dalton.  ) 


optic  tracts,  and  inferiority  through  the  superior  penduncles  of  the  cere- 
bellum, between  and  attached  to  which  is  the  valve  of  Vieussens,  to  the 


FUNCTION    OF    CORPORA    QU  ADRI  GE  MI  NA  .  f)95 

cerebellum,  and  also  through  the  fibres  descending  through  the  pons  and 
embracing  the  olivary  body  to  the  motor  columns  of  the  cord.  Such 
being  the  anatomical  disposition  of  the  optic  lobes,  it  might  be  surmised 
that  with  their  destruction  sight  would  be  abolished  and  muscular 
action  affected,  which  is  found  to  be  the  case  in  those  instances 
where  the  optic  lobe  has  been  destroyed  by  disease  in  man,  or  by  ex- 
periment in  animals.  Further,  on  the  supposition  that  there  is  a  total 
decussation  of  the  optic  tracts,  and,  according  to  the  view  entertained 
by  Charcot  (Fig.  3P9),  it  becomes  intelligible,  not  only  why  destruc- 
tion of  the  optic  lobe  of  one  side  entails  the  total  loss  of  sight  in  the 
opposite  eye,  but  through  the  connections  of  the  optic  lobe  with  the 
thalamus  opticus  and  adjacent  fibres  of  the  corona  radiata  why  lesions 
situated  in  that  part  of  the  brain  should  be  accompanied  by  impairment 
of  sensibility  as  well  as  loss  of  vision.  The  optic  lobe,  as  might  be 
expected,  constitutes  also  an  important  part  of  the  reflex  mechanism  by 
which  the  coordination  of  the  eyeballs  and  the  contraction  of  the  pupil 
are  effected,  the  optic  nerve  being  the  afferent  nerve  and  the  oculo- 
motorius  the  efferent  nerve,  the  reflex  centres  being  situated  either  in 
the  optic  lobe  or  immediately  beneath  it.  Apart  from  the  anatomical 
fact  that  the  optic  lobes  are  connected  with  the  motor  tracts  of  the  spinal 
cord,  which  would,  as  already  remarked,  indicate  that  these  ganglia 
influence  muscular  action  in  some  way,  it  is  well  known  that  the  optic 
lobes  are  not  invariably  developed  in  proportion  to  the  eyes,  but,  on  the 
contrary,  may  be  quite  large,  though  the  eyes  and  optic  tracts  be  but 
small,  little  developed,  or  even  wanting  altogether,  as,  for  example,  in 
the  myxine  or  hag  fish,  and  the  aplerechthys  csecus  among  fishes,  in 
the  proteus  and  cecilia  among  batrachians,  and  in  moles  and  shrews 
among  mammals,  which  show  that  the  optic  lobes  have  other  func- 
tions beside  those  influencing  vision.  Xow,  while  the  experience  of  the 
author  has  been  like  that  of  other  experimenters,  that  destruction  of  the 
optic  lobes  involves,  in  addition  to  loss  of  sight,  disorders  of  equilibrium 
and  want  of  muscular  coordination,  nevertheless,  it  must  be  mentioned 
that  a  very  great  difference  prevails  in  this  respect  according  to  whether 
the  animal  upon  which  the  experiment  of  removing  the  optic  lobe  is 
performed  be  a  batrachian,  bird,  or  mammal,  the  optic  lobes  relatively 
to  the  cerebral  hemispheres  being  so  much  better  developed  in  the  lower 
than  in  the  higher  vertebrates.  Thus,  for  example,  a  frog  with  its  optic 
lobes  intact,  but  without  its  cerebral  hemispheres,  can  coordinate  its 
muscles  for.  the  performance  of  ordinary  actions  better  than  a  pigeon  or 
a  rabbit  similarly  conditioned,  and  the  latter  better  than  a  monkey  or 
man.  It  may  be  mentioned  also,  in  this  connection,  that  the  want  of 
coordinating  power,  etc.,  following  destruction  of  the  optic  lobes  is  not 
due,  as  might  be  supposed,  to  the  blindness  entailed,  since  in  the  frog, 
for  example,  if  the  eyes  be  destroyed  but  the  optic  lobes  be  left  intact, 
such  disoi'ders  as  those  ensuing  upon  the  destruction  of  these  ganglia 
are  not  observed.  It  is  well  known  that  if  all  the  encephalic  centres 
above  the  optic  lobes  be  removed  in  the  frog;,  g;entle  stroking-  of  the  back 
excites  the  animal  to  croak.  The  croaking  entirely  ceasing,  however, 
if  the  optic  lobes  be  removed,  the  natural  inference  is  that  these  ganglia 
contain  the  reflex  centres  through  which  the  croakim*  is  produced.     As 


696  CORPORA    QUADRIGEMINA. 

certain  plaintive  cries  emitted  by  the  rabbits  cease  after  removal  of  the 
optic  lobes,  it  is  possible  that  a  similar  reflex  centre  exists  in  the  optic 
lobes  of  mammals  as  well  as  in  those  of  frogs. 

Taking  this  latter  fact  into  consideration,  together  with  that  of  the 
circulation  and  respiration  being  modified  by  electrical  stimulation  of 
the  optic  lobes,  the  blood  pressure  being  increased,  the  heart  slowed, 
the  respiration  deepened  exactly  in  the  same  manner  as  when  the  sen- 
sory nerves  arc  powerfully  excited,  and  that  contractions  of  the  stomach, 
intestines,  and  bladder  also  follow,  it  would  appear  that  the  optic  lobes 
are  also  concerned  in  the  reflex  manifestation  of  motion,  as  well  as  of 
influencing  muscular  coordination  and  vision.  While  there  can  be  no 
doubt  that  destruction  of  the  optic  lobes  in  man  and  animal  entails  loss 
of  vision  and  impairs  the  power  of  muscular  coordination,  it  still  remains 
to  be  determined  whether  these  effects  are  due  simply  to  the  fact  that 
the  fibres  by  which  impressions  made  upon  the  retina  and  periphery 
reach  the  visual  and  coordinating  centres  pass  through  the  optic  lobes, 
or  whether  these  ganglia  are  themselves  the  seat  of  the  visual  and 
coordinating  centres.  That  the  latter  is  not  the  case  in  the  higher 
vertebrates,  whatever  it  may  be  in  the  lower  ones,  is  shown  by  the  fact 
that  destruction  of  the  angular  convolution,  or  gyrus,  in  a  mammal, 
the  monkey,  for  example,  entails  loss  of  vision  as  certainly  as  destruc- 
tion of  the  optic  lobe  itself;  on  the  other  hand,  it  cannot  be  denied 
that  even  after  destruction  of  the  angular  gyrus  in  a  mammal,  or  entire 
removal  of  the  cerebral  hemispheres  in  a  bird,  the  mere  sensation  of 
sight  persists — that  is  to  say,  the  impression  of  light  upon  the  retina 
still  gives  rise  to  the  mere  sensation  of  sight,  but  that  the  sensation  no 
longer  gives  rise  to  such  ideas  as  are  usually  developed  in  response 
to  the  stimulus  of  light — that  is  to  say,  the  animal  with  its  optic  lobes 
intact,  but  with  its  cerebral  hemispheres  removed,  may  see,  but  does 
not  think.  It  is  not  impossible,  however,  that  in  the  lower  vertebrates 
the  true  visual  and  simply  sensory  centres  may  be  located  together  in 
the  same  part  of  the  encephalon,  the  mass,  for  example,  representing 
in  fishes  the  optic  lobe  and  thalamus  opticus,  containing  also  the  repre- 
sentative of  the  angular  gyrus  of  the  higher  vertebrates.  The  relation 
of  the  optic  lobes  to  the  true  coordinating  centre  located,  in  all  proba- 
bility, at  least  in  birds  and  mammals  in  the  cerebellum,  can  be  more 
conveniently  discussed  after  the  functions  of  the  latter  organ  have  been 
considered.  It  may  be  mentioned,  however,  in  this  connection  that, 
after  removal  of  both  the  cerebral  hemispheres  and  cerebellum  in  the 
frog,  the  optic  lobes  being  still  intact,  the  power  of  muscular  coordina- 
tion remains  unaffected,  proving  that  in  such  animals  at  least  the  centre 
of  muscular  coordination  is  not  located  in  either  of  those  portions  of  the 
encephalon,  whatever  may  be  the  case  in  higher  vertebrates. 

It  has  already  been  mentioned  incidentally  that  the  optic  lobes  are 
connected  posteriorly  with  the  cerebellum  through  the  superior  pedun- 
cles of  the  latter.  The  fibres  of  the  superior  peduncles  passing  forward 
and  upward  to  the  testes  ascend  through  the  crura  cerebri  to  the  thala- 
mus opticus  and  corona  radiata,  some  of  the  fibres  decussating  beneath 
the  optic  lobes.  Inferiorly  the  superior  peduncles  are  connected  with 
the  vermiform  process  of  the  cerebellum  and  with  the  corpus  dentatum, 


CEREBELLUM 


697 


or  pouch-like  layer  of  gray  matter  within  the  white  matter  of  the  lateral 
hemispheres.  The  cerebellum,  constituting  about  one-eighth  of  the  bulk 
of  the  brain,  and  situated  in  the  posterior  fossae  of  the  cranial  cavity, 
consists  of  two  lateral  portions,  the  hemispheres,  the  anterior  rounded 
eminences  of  which  are  known  as  the  amygdalae,  or  the  tonsils.  The 
hemispheres,  though  separated  behind  and  below  by  a  wide  deep  groove, 
the  vallecula  or  valley,  are  connected  by  an  intermediate  worm-like 
ridge,  the  vermiform  process,  the  portion  of  the  latter  situated  between 
the  tonsils  being  called  the  uvula,  while  just  above  the  tonsils,  and  sepa- 
rated from  them  by  a  fissure,  may  be  seen  the  flocculi,  or  pneumogastric 
lobules,  so  called  from  their  vicinity  to  the  nerve  of  the  same  name. 
Each  lateral  hemisphere  and  vermiform  process  essentially  consists 
internally  of  a  prismoid  trunk  of  white  substance,  from  which  emanate 
about  a  dozen  broad  thin  laminoe;  the  latter  subdividing  again  into 
secondary  thinner  laminae,  and  the  gray  substance  enfolding  them, 
gives  rise  to  the  convolutions  and  fissures  observable  on  the  surface  of 
the  organ.  The  middle  peduncles  of  the  cerebellum  constituting,  as 
already  mentioned,  the  transverse  commissural  fibres  of  the  pons  Varolii 
connect  the  two  lateral  hemispheres,  while  the  inferior  peduncles  pass 
downward  into  the  restiform  bodies  of  the  medulla,  and  are  connected 
with  the  spinal  cord.  If  the  cerebellum  be  removed  in  a  bird,  a  pigeon, 
for  example  (Fig.  400),  though  the  animal  still  feels,  thinks,  wills,  it  is 

Fig.  400. 


Pigeon,  after  removal  of  the  cerebellum.     (Dalton.) 

unable  to  stand  or  fly.  If  placed  upon  the  back,  it  is  unable  to  rise. 
If  food  be  placed  within  its  reach,  though  it  sees  it,  it  cannot  pick  up 
the  food.  Instead  of  remaining  quiet,  it  is  in  a  continual  state  of  rest- 
lessness and  agitation.  In  a  word,  though  able  to  make  voluntary  move- 
ments, the  animal  has  lost  the  power  of  coordinating  its  movements  for 
the  performance  of  a  definite  object,  or  of  maintaining  its  equilibrium. 
Its  movements  highly  resemble  those  of  a  drunken  man.  Essentiallv 
the  same  results  are  obtained  if  the  cerebellum  be  removed  in  a  mammal. 
Undoubtedly,  then,  very  remarkable  disorders,  both  as  regards  the  main- 


698 


CEREBELLUM 


tenance  of  equilibrium  and  power  of  locomotion  ensue  upon  destruc- 
tion of  the  cerebellum  in  mammals  and  birds,  although,  as  already 
mentioned,  no  perceptible  change  is  observable  in  these  respects  in  the 
case  of  frogs,  in  which  the  cerebellum  has  been  removed. 

Differences  of  opinion  still  prevail  among  pathologists  as  to  whether 
lesions  of  the  cerebellum  in  man  give  rise  to  the  same  disorders  as 
observed  in  mammals  and  birds,  in  which  the  cerebellum  has  been 
removed,  and  even  though  it  be  admitted  that  entire  absence  of  the 
cerebellum,  as  shown  by  post-mortem  examinations,  was  not  accompanied 
during  life  with  loss  of  the  power  of  locomotion,  or  of  the  maintenance 
of  equilibrium,  nevertheless  it  may  be  questioned  whether  there  is  a 
well  authenticated  case  in  which  locomotion  and  equilibrium  remained 
unaffected,  extensive  lesions  of  the  cerebellum  existing.  Such  cases  as 
where  there  was  a  congenital  absence  of  the  cerebellum,  unaccompanied 
with  any  disorders  of  locomotion,  etc.,  being  explainable  on  the  suppo- 
sition that,  as  in  the  case  of  the  frog,  the  function  of  the  cerebellum 
was  performed  by  other  ganglia,  probably  the  optic  lobes.  On  the 
supposition  that  the  cerebellum  is  the  centre  for  the  maintenance  of 
equilibrium  and  of  muscular  coordination,  it  ought  to  be  best  developed 


Fig.  401. 


Fio.  402. 


Brain  of  kangaroo,  macorpos  major.  (Owen  ) 


Brain  of  chimpanzee. 


in  those  animals  which  exhibit  such  powers  in  a  marked  degree,  and  such 
we  find  to  be  the  case.  Thus  in  the  shark,  for  example,  in  which,  of 
all  fish,  the  muscular  system  is  best  developed,  and  the  power  of 
coordination  so  perfect,  as  shown,  for  example,  in  the  manner  in  which 
it  throws  itself  upon  its  back  at  the  instant  of  seizing  its  prey ;  the 
mouth  being  situated  beneath,  and  posteriorly,  the  cerebellum  is  larger 
and  more  complex  in  its  structure  than  in  any  other  fish.  Among  birds, 
also,  the  cerebellum   is  particularly  well  developed  in  the  carnivorous 


COORDINATING    POWER    OF    CEREBELLUM.  699 

raptores,  in  which  muscular  actions,  such  as  are  involved  in  the  swooping 
down  by  them  upon  prey  from  immense  heights,  require  very  nice 
adjustment  of  coordination.  Among  mammals  the  cerebellum  is  large; 
in  the  kangaroo  (Fig.  401),  whose  peculiar  mode  of  progression  necessi- 
tates considerable  muscular  coordination,  while,  in  the  elephant,  in 
which  great  muscular  coordination  is  demanded,  owing  to  the  enormous 
muscular  development,  and  in  the  case  of  the  posterior  extremities  to 
the  absence  of  the  round  ligament  of  the  hip-joint,  the  cerebellum  is 
very  large,  being  equal  to  one  of  the  hemispheres.  In  the  anthropoid 
apes,  also,  which  not  unfrequently  assume  the  semi-erect  attitude,  the 
cerebellum  is  larger  than  in  the  remaining  monkeys.  Indeed,  in  the 
chimpanzees  (Fig.  402)  and  orangs  dissected  by  the  author1  the  cere- 
bellum was  found  so  well  developed  as  to  extend  slightly  beyond  the 
posterior  lobes  of  the  cerebrum,  which  is  not  the  case  in  monkeys 
generally,  in  the  baboons,  macacques,  spider-monkeys,  etc.,  the  cere- 
bellum being  perfectly  covered  by  the  posterior  lobes  of  the  cerebrum, 
as  in  man.  That  the  cerebellum,  at  least  in  mammals,  birds,  and  fishes, 
is  the  centre  for  the  maintenance  of  equilibrium  and  muscular  coordina- 
tion is  not  only  shown  by  experiment,  pathology,  and  comparative 
anatomy,  but  from  the  fact  of  the  tactile,  visual,  labyrinthine,  and  per- 
haps visceral  impressions  upon  which  the  maintenance  of  equilibrium 
and  muscular  coordination  depend,  being  transmitted  from  the  periphery 
through  nerves  which  directly  or  indirectly  terminate  in  the  cerebellum, 
as  we  shall  now  endeavor  to  show.  It  has  already  been  mentioned 
that  a  frog  from  which  the  cerebral  hemispheres  have  been  removed, 
but  which  still  preserves  its  optic  lobes  and  cerebellum,  retains  the 
power  of  maintaining  its  equilibrium  and  of  muscular  coordination.  If, 
however,  the  skin  be  removed  from  the  hinder  legs  of  such  a  frog, 
the  animal  at  once  loses  this  power  and  falls  like  a  log  if  the  position  of 
its  support  be  changed,  the  removal  of  the  skin  making  impossible  the 
transmission  of  those  aiferent  tactile  impressions  which  through  some 
reflex  centre  give  rise  to  those  efferent  muscular  actions  requisite  for 
the  maintenance  of  equilibrium.  That  this  reflex  centre  is  situated  in 
man  in  the  cerebellum,  and  that  these  afferent  tactile  impressions  are 
transmitted  by  the  posterior  columns  of  the  spinal  cord,  is  rendered 
very  probable  from  the  fact  that  sclerosis  of  these  columns  causes  loco- 
motor ataxia,  a  disease  specially  characterized  not  by  a  loss  of  sensi- 
bility but  of  power  of  coordination,  and  that  the  posterior  columns  of 
the  cord  through  the  restiform  bodies  of  the  medulla  terminate  in  the 
cerebellum.  While  visual  are  not  as  important  as  either  tactile  or 
labyrinthine  impressions  in  the  maintenance  of  equilibrium,  since  the 
latter  almost  suffice  in  the  absence  of  the  former,  nevertheless  they 
exercise  a  certain  amount  of  influence.  Thus,  in  cases  of  locomotor 
ataxia,  for  example,  equilibrium  and  coordination  are  not  altogether 
impossible,  even  though  the  tactile  impressions  be  wanting,  so  long  as 
the  labyrinthine  and  visual  impressions  persist,  and  in  such  cases  when 
the  transmission  of  tactile  and  labyrinthine  impressions  are  perfect,  the 
absence  of  visual  ones  always  entails  some  slight  want  in  the    coordi- 

1  Proc.  Acad,  of  Nat.  Sciences,  1879. 


700  CEREBELLUM. 

nating  power.  That  such  visual  impressions  are  transmitted  to  the 
cerebellum,  is  rendered  very  probable  when  it  is  remembered  that  the 
optic  lobes  are  connected  with  the  cerebellum  both  through  the  superior 
peduncles  and  valve  of  Vieussens.  As  is  well  known,  remarkable  dis- 
turbances of  equilibrium  ensue,  if  the  membranous  semicircular  canals 
of  the  internal  ear  be  divided  in  a  bird  or  mammal,  or  if  they  are  dis- 
eased as  in  Meniere's  disease  in  man,  which  vary  according  to  the  seat 
of  the  lesion.  Thus,  if  the  horizontal  canals  be  divided  in  a  pigeon,  for 
example,  rapid  movements  of  the  head  in  a  horizontal  plane,  from  side 
to  side,  follow,  with  oscillation  of  the  eyeballs,  and  a  tendency  to  spin 
around  on  a  vertical  axis  is  manifested. 

If,  however,  the  posterior  or  inferior  vertical  canals  be  divided,  the 
head  is  moved  rapidly  backward  and  forward,  and  the  animal  tends 
to  turn  somersaults  backward  head  over  heels,  whereas  if  the  superior 
vertical  canals  be  divided,  the  head  is  moved  rapidly  forward  and  back- 
ward, and  the  animal  tends  to  make  forward  somersaults  heels  over 
head.  It  would  appear  from  the  researches  of  Goltz,1  Mach,2  Brewer,3 
and  Crum  Brown4  among  others,  that  the  character  of  the  impressions 
made  upon  the  vestibular  nerves  depends  upon  the  degree  and  relative 
variations  in  the  pressure  exerted  by  the  endolymph  upon  the  ampullae 
of  the  membranous  canals,  to  which,  as  we  shall  see  hereafter,  these 
nerves  are  distributed.  Such  being  the  case,  it  is  obvious  that  if  the  semi- 
circular canals  be  divided  disturbances  of  equilibrium  must  ensue,  the 
natural  tension  of  the  endolymph  being  thereby  altered,  which  will 
vary  according  to  the  particular  semicircular  canal  affected.  It  may  be 
mentioned  in  this  connection,  that  pigeons  in  which  the  semicircular 
canals  have  been  divided  on  one  side  in  time  regain  the  power  of  main- 
taining their  equilibrium,  but  if  the  canals  be  divided  on  both  sides, 
they  never  again  are  able  to  assume  their  natural  position,  the  most 
strange  and  bizarre  attitudes  being  taken.  Whatever  may  be  the 
nature  and  mechanism  of  the  labyrinthine  impressions,  there  can  be  no 
doubt  as  to  the  influence  exerted  by  them  in  the  maintenance  of  equi- 
librium, since  in  their  absence  the  same  becomes  impossible  even  though 
the  tactile  and  visual  impressions  persist.  That  the  membranous  semi- 
circular canals  and  the  auditory  nerve  together  constitute  an  afferent 
system  by  which  impressions  are  transmitted  to  the  cerebellum,  acting 
as  a  reflex  coordinating  centre,  appears  highly  probable  when  it  is  re- 
membered that  division  of  the  auditory  nerve  entails  disturbances  of 
equilibrium,  that  the  auditory  nerve  through  the  restiform  bodies  is 
directly  connected  with  the  cerebellum,  and  that  a  great  similarity 
exists  between  the  effects  of  destruction  of  the  cerebellum  and  division 
of  the  semicircular  canals.  Thus,  destruction  of  the  anterior  portion 
of  the  middle  lobe  of  the  cerebellum,  like  that  of  the  superior  vertical 
canal,  involves  displacement  of  equilibrium  forward  around  a  horizontal 
axis,  destruction  of  the  posterior  part  of  the  median  lobe  like  that  of  the 
posterior  vertical  canal,  displacement  backward  around  a  horizontal 
axis,  destruction  of  the  lateral  lobes  of  the  cerebellum,  like  that  of  the 

i  Pfluger's  Archiv,  1870.  *  Sitz.  u.  der  K.  Acad,  der  Wiss.,  Wion,  1873. 

8  Med.  Jahrbucher,  Heft  i.,  1874.  *  Journal  of  Auat.  and  Pbys.,  May,  1874. 


COORDINATING    POWER    OF    CEREBELLUM.  701 

horizontal  canals,  lateral  displacement  around  a  vertical  axis.  The 
cerebellum  appears,  therefore,  to  be  the  reflex  centre  by  which  the 
afferent  impressions  transmitted  by  the  cutaneous,  optic,  and  acoustic 
nerves  are  coordinated  with  the  efferent  ones  for  the  maintenance  of 
equilibrium  and  locomotion.  That  such  reflex  actions  are  accompanied 
now,  or  originally  at  least,  with  consciousness,,  and  that  the  cerebellum 
is  that  part  of  the  encephalon  in  which  the  ideas  of  space  are  developed, 
is  rendered  very  probable  when  it  is  remembered  that  many  actions 
involving  muscular  coordination,  which  are  performed  now  unconsciously, 
were  originally  accompanied  by  both  sensation  and  volition,  and  that 
the  disorders  of  equilibrium  and  locomotion  following  destruction  of  the 
cerebellum  or  of  the  afferent  system  leading  to  it,  imply  a  perversion  in 
the  ideas  of  space  relations. 

In  concluding  our  account  of  the  cerebellum  it  should  be  remembered 
that  as  its  lateral  peduncles  decussate  in  the  pons  Varoli  the  cerebellum 
is  connected  with  the  motor  tracts  of  the  opposite  side  of  the  cord,  but 
as  the  latter  decussate  in  the  medulla,  the  lateral  lobes  of  the  cerebellum 
in  this  way  influence  the  muscles  of  the  same  side  of  the  body. 


CHAPTER   XLIV. 

THE  CEREBRAL  HEMISPHERES. 

The  cerebral  hemispheres,  so  called  on  account  of  their  hemispherical 
form,  are  two  ovoidal  masses  flattened  at  their  mesial  surface,  where  they 
are  separated  by  the  great  longitudinal  fissure.  'They  consist  of  gray 
or  vascular  and  of  white  or  fibrous  nervous  tissue.  The  gray  substance, 
like  that  of  the  cerebellum  but  unlike  that  of  the  spinal  cord,  situated 
externally  and  varying  between  two  and  three  millimetres  in  thickness, 
sinks  at  intervals  into  the  white  substance  to  a  depth  of  from  ten  to 
twenty-five  millimetres,  invaginating  itself — that  is,  folds  inward  to 
return  upon  itself  again,  and  so  gives  rise  to  the  convoluted  and  fissured 
surface  so  characteristic  of  the  brain  of  man  and  of  many  mammals.  It 
is  evident  that  through  this  convoluted  arrangement  the  hemispheres 
contain  far  more  gray  matter  than  if  they  were  smooth,  on  the  same 
principle  that  a  pocket  handkerchief  occupies  much  less  room  when 
folded  up  than  when  laid  out  smooth,  and  that  the  deeper  and  more 
numerous  the  fissures  the  greater  the  amount  of  gray  matter  present. 
The  gray  matter  of  the  convolution  or  cortical  layer  of  the  hemispheres, 
consisting  of  a  granular  matrix  in  which  are  imbedded  nerve-cells,  con- 
nected through  their  prolongations  with  the  nerve  fibres  of  the  white  sub- 
stance, is  composed  of  six  or  more  layers  distinguished  by  the  character 
of  the  nerve  cells  they  contain.  Of  the  latter  may  be  mentioned  the  so- 
called  pyramidal  cells,  varying  between  10  micro-millimetres  and  40 
micro-millimetres  (25100th  to  -g^-th  of  an  inch),  characterized  by  their 
quadrangular  base  and  tail-like  extremity,  the  latter  pointing  outwardly, 
the  smallest  cells  being  the  most  superficial,  and  the  cells  constituting 
the  so-called  nuclear  layer  situated  beneath  the  pyramidal  cells  and  about 
10  micro-millimetres  (^gVirth  °f  an  inch)  in  diameter.  The  pyramidal 
cells  are  more  numerous  and  larger  in  the  anterior  portion  of  the  hemi- 
spheres in  the  convolutions  of  the  frontal  lobe,  for  example,  the  cells  of 
the  nuclear  layer  in  the  occipital  and  temporal  lobes.  Certain  so-called 
giant  pyramidal  cells,  probably  motor  in  function,  like  those  of  the 
anterior  cornu  of  the  spinal  cord,  are  also  found  more  particularly  in 
the  posterior  portion  of  the  frontal  lobe  in  the  anterior  convolution,  the 
processes  of  which  appear  to  be  prolonged  downward  as  the  axis-cylin- 
ders traversing  the  antero-lateral  columns  of  the  spinal  cord  emerging 
from  the  latter  as  the  anterior  roots  of  the  spinal  nerves,  while  other 
cells,  having  no  processes  or  axis-cylinders,  are  found  more  especially 
in  the  posterior  part  of  the  hemispheres  in  the  occipital  lobe.  Although 
the  convolutions  or  gyri  and  the  fissures  or  sulci  do  not  run  in  exactly 
the  same  manner  in  different  brains,  and  are  not  symmetrically  disposed 
even  in  the  two  hemispheres  of  the  same  brain,  nevertheless  the  general 
disposition  is  so  constantly  the  same  that  the  most  important  of  them 


CEREBRAL    FISSURES    AND    CONVOLUTIONS. 


'03 


can  be  readily  recognized  and  identified,  and  on  account  of  their  sup- 
posed functional  importance  demand  at  least  a  brief  description.  The 
most  striking  fissure  observable,  if  the  hemisphere  be  viewed  laterally, 
both  on  account  of  its  depth  and  constancy,  it  existing  not  only  in  man 
but  in  all  animals  whose  brain  is  fissured  at  all,  is  the  fissure  of  Sylvius. 
Beo-innino-  as  a  transverse  furrow  on  the  under  side  of  the  brain,  it  runs 
thence  outward,  backward,  and  upward,  separating  the  temporal  (T,  Fig. 
403)  from  the  frontal  lobe  (F),  and  divides  on  the  outer  side  of  the  hemi- 
sphere into  an  anterior  (S)  and  posterior  (S')  branch,  the  convolutions 
included  between  these  two  branches,  and  known  as  the  operculum, 


Fin.  403. 


Outer  surface  of  the  left  hemisphere.  F.  Frontal  lobe.  !\  Parietal  lobe.  0.  Occipital  lobe.  T.  Tem- 
poro-sphenoidal  lobe.  S.  Fissure  of  Sylvius.  S'  Horizontal,  S"  Ascending  ramus  of  the  same.  ■-.  Sulcus 
centralis  or  fissure  of  Rolando.  A.  Anterior  central  or  ascending  frontal  convolution.  1!.  Posterior 
central  or  ascending  parietal  convolution.  Fj  Superior,  F2  Middle,  and  F3  Inferior  frontal  convolution. 
/j  Superior,  and  u  Inferior  frontal  sulcus  ;  /3  Sulcus  pra?centralis.  Pj  Superior  parietal  of  postero-parietal 
lobule,  viz  :  P2  Gyrus  supramarginalis,  P'2  Gyrus  angularis.  ip.  Sulcus  intraparietalis.  cm.  Termina- 
tion of  the  calloso-marginal  Bssure.  02  first,  0]  second,  02  third  occipital  convolutions,  po.  Parieto- 
occipital fissure  O.  Sulcus  occipitalis  transversus,  0  Sulcus  occipitalis  longitudinalis  inferior.  T]  first,  T., 
second,  Ts  third  temporo-sphenoidal  convolutions.  <]  first,  t%  second  teniporo-sphenoidal  fissures.  (After 
Ecker  and  Duret.) 

covering  the  insula  or  island  of  Reil.  An  important  fissure,  readily 
identified  on  account  of  its  constant  course,  is  the  fissure  (c)  of  Rolando, 
or  central  fissure,  passing  from  about  the  middle  line  of  the  hemisphere 
downward,  outward,  and  forward,  reaching  very  nearly  the  fissure  of 
Sylvius,  and  serving  to  divide  the  frontal  from  the  parietal  lobe.  The 
fissure  of  Rolando  is  bordered  by  two  important  convolutions  running 


7(M 


THE    CEREBRAL    HEMISPHERES. 


parallel  with  itself  and  known  as  the  anterior  and  posterior  central  con- 
volutions, or  the  ascending  frontal  and  ascending  parietal  convolutions. 
Through  the  very  constant  presence  of  the  long  superior  frontal  (/j)  and 
inferior  frontal  fissure  (/2)  the  latter  running  into  the  precentral  fissure 
(/3).  the  anterior  portion  of  the  frontal  lobe  naturally  divides  itself  into  the 
superior  (Fj),  middle  (F2),  and  inferior  (F3)  frontal  convolutions.  Through 
the  presence  of  the  first  and  second  temporo-sphenoidal  fissures  in  the 
same  manner,  the  temporal  lobe  (T)  is  divided  into  the  first  (ri\),  second 
(T2),  and  third  (T3)  temporo-sphenoidal  convolutions.  The  most  impor- 
tant fissure  of  the  parietal  lobe  (P)  is  the  intraparietal  fissure  (ip).  Start- 
ing from  the  posterior  central  convolution,  it  extends  backward  and  down- 
ward, and  dividing  the  parietal  lobe  into  the  superior  (Px)  and  inferior 
(P2)  parietal  lobules,  terminates  toward  the  posterior  extremity  of  the 
hemisphere.  Beneath  the  intraparietal  fissure,  and  as  constituent  parts 
of  the  inferior  parietal  lobule,  are  situated  two  important  convolutions, 
the  supra-marginal  (P2)  convolution  arching  around  the  fissure  of  Sylvius 
and  the  angular  (P'2)  convolution   around  the  first  temporo-sphenoidal 


Fig.  404. 

-A  c  B 

-IDS 

(I 

or 

BE   *v-       * 

Inner  surface  of  right  hemisphere.     The  regions  bounded  by  the  line  ( )  represent  the  territories 

over  which  the  branches  of  the  anterior  cerebral  artery  are  distributed.    The  regions  bounded  by  the  line 

( )  represent  the  territories  over  which  the  brandies  of  the  posterior  cerebral  artery  are 

distributed.  CC.  Corpus  callosum,  longitudinally  divided.  Gf.  Gyrus  fornicatus.  II.  Gyrus  hippo- 
campi, h.  Sulcus  hippocampi.  U.  Uncinate  gyrus,  cm.  Sulcus  calloso-marginalis.  Fj.  Median  aspect 
of  the  first  frontal  convolution,  c.  Terminal  portion  of  the  sulcus  centralis,  or  fissure  of  Kolando.  A. 
Anterior.  B.  Posterior  central  convolution.  Pj".  Prsecuneus.  Oz.  Cuneus.  To.  Parieto-occipital  fissure, 
o.  Sulcus  occipitalis  transversus.  oc  Calcarine  fissure,  oc"  Inferior  ramus  of  the  same.  D.  Gyrus 
descendens.  T4.  Gyrus  occipito-temporalis  lateralis  (lobulus  fusiformis).  T6.  Gyrus  occipito-temporalis 
medialis  (lobulus  liugualis).     (After  Ecker  and  Duret.) 


fissure.     The  parietal  is  separated  from  the  occipital  (0)  lobe  by  the 
parieto-occipital  (Po)  fissure,  the  latter  being,  however,  just  visible  from 


CEREBRAL     TISSUES    AND    CONVOLUTIONS.  705 

a  lateral  view,  should  be  viewed  from  the  mesial  surface  of  the  hemi- 
sphere, as  in  Fig.  404,  where  it  (Po)  will  be  observed  to  descend  down- 
ward and  inward,  separating  the  cuneus  (Oz)  from  the  precuneus  (P'2) 
and  terminating  in  an  acute  angle  in  the  calcarine  fissure  (oc),  the  latter 
fissure  beino-  so  called  on  account  of  its  marking  the  inner  concave 
border  of  the  calcarius  or  hippocampus  minor  in  the  posterior  cornu 
of  the  lateral  ventricle.  The  occipital  lobe  (0)  is  made  up  of  the  first 
(Ot),  second  (02),  and  third  (03)  occipital  convolutions,  the  first  occi- 
pital being  separated  from  the  second  occipital  convolution  by  the  trans- 
verse occipital  fissure  (0),  and  the  second  occipital  convolution  from  the 
third  by  the  inferior  longitudinal  occipital  fissure  (02).  As  the  cal- 
carine fissure  (oc,  Fig.  404)  does  not  run  into  the  hippocampal  (p)  fissure, 
it  will  be  observed  that  the  convolution  lying  above  the  corpus  callosum, 
and  known  as  the  gyrus  fornicatus  (Gf),  passes  continuously  into  the 
convolution  of  the  hippocampus  (H).  The  latter  convolution  terminates 
anteriorly  in  a  crook-like  extremity  or  crotchet,  the  so-called  uncus 
gyri  fornicati  or  subiculum  cornu  ammonis  (V).  Below  the  calcarine 
fissure  are  situated  two  convolutions,  the  lobulus  fusiformis  (T4)  and 
lobulis  lingualis  (T5),  separated  by  the  occipito- temporal  fissure,  while 
above  the  gyrus  fornicatus  (Gf)  is  separated  from  the  mesial  surface  of 
the  first  (Fj)  frontal  convolution  by  a  well-marked  fissure,  the  calloso- 
marginal  (cm),  which,  like  the  parieto-occipital  fissure,  is  also  just  visible 
from  a  lateral  view  of  the  hemisphere.  It  must  not  be  supposed  from 
the  fact  of  names  being  given  to  certain  well-defined  convolutions  that 
the  latter  are  entirely  distinct,  or  do  not  run  into  each  other;  on  the  con- 
trary, as  may  be  seen  from  Figs.  403  and  404,  it  is  evident  that  directly 
or  indirectly  they  are  all  continuous  with  each  other.  Thus  the  third 
frontal  (F3)  runs  into  the  anterior  (A)  central,  the  latter  into  the  posterior 
(B)  central,  the  three  occipital  convolutions  into  the  superior  parietal 
lobule  (P),  the  angular  gyrus  and  third  temporo-sphenoidal  (T3)  convo- 
lutions respectively,  and  so  on.  In  addition  to  these  principal  fissures 
just  mentioned,  there  are  numerous  other  less  important  ones  which 
increase  considerably  the  number  of  convolutions  and  obscure  somewhat 
those  already  described.  That  these  fissures  are  of  a  secondary  char- 
acter, however,  becomes  at  once  evident  when  the  arachnoid  and  pia 
mater  are  removed,  they  being  then  seen  to  be  mere  superficial  indenta- 
tions and  not  deep  fissures  penetrating  into  the  brain. 

The  internal  or  white  substance  of  the  cerebral  hemispheres  is  com- 
posed largely  of  fibres  which  in  general  radiate  from  the  basal  ganglia 
internally  to  the  gray  or  cortical  substance  outwardly.  The  amount  of 
white  substance  varies  very  much  in  different  portions  of  the  hemisphere, 
thus,  in  the  region  of  the  island  of  Reil,  where  the  gray  substance  pene- 
trates to  a  considerable  depth,  but  little  of  it  is  present,  whereas,  in  the 
posterior  portions  of  the  hemisphere,  where  the  gray  matter  is  relatively 
less  well  developed,  the  white  substance  is  pi-esent  in  great  quantity. 
The  fibres  of  which  the  white  substance  consists  may  be  said  to  be 
essentially  of  three  kinds  :  First,  commissural  fibres,  such  as  those  com- 
posing the  corpus  callosum  or  the  broad  commissure  connecting  the 
two  hemispheres  at  the  bottom  of  the  great  longitudinal  fissure  or  the 
anterior  commissure  situated  a  little  in  front  of  the  thalami  optici  and 

45 


706 


THE     CEREBRAL    HEMISPHERES. 


spreading  out  from  the  latter  into  the  lower  and  anterior  parts  of  the 
temporal  lobes.  Second,  association  fibres,or  fibres  which,  lying 
just  beneath  the  gray  matter,  connect  the  different  convolutions  of  the 
same  hemisphere.  Third,  medullary  fibres  including  both  the  indirect 
fibres  passing  from  the  medulla  through  the  crura  cerebri  and  termi- 
nating in  the  corpora  striata  and  thalami  optici,  and  the  fibres  of 
the  corona  radiata,  which  beginning  in  the  basal  ganglia  spread  out 
to  terminate  in  the  convolutions  and  the  direct  fibres  which,  begin- 
ning in  the  convolutions  about  the  fissure  of  Rolando  and  probably 
motor,  pass  downward  through  the  middle  of  the  crura  to  the  pyramid 
tracts  of  the  cord,  or  beginning  in  the  cord  pass  upward  along 
the  outward  border  of  the  crura  to  terminate  in  the  convolutions  of 
the  occipital  lobe,  and  probably  sensory  in  function.  One  of  the 
most  striking  facts  with  reference  to  the  cerebral  hemispheres,  the 
bulk  of  the  latter  being  taken  into  consideration,  is  the  large  amount 
of  blood  which  they  receive,  one-fifth  of  the  whole  mass  of  the  blood, 
indeed,  according  to  Haller,1  going  to  the  encephalon.  The  manner 
in  which  the  blood  is  distributed  to  the  brain  is  also  very  remark- 
able, the  branches  of  the  basilar  (5)  and  internal  (1)  carotid  arteries 
anastomosing   so  freely,  as  the   circle  of  Willis  (Fig.   405),  that  the 


Fig.  40;' 


Circle  of  Willis.     (Quain  and  Sharpev.) 


supply  of  blood  to  any  one  part  of  the  brain  is  not  interrupted,  even 
though  the  principal  branch  supplying  such  a  part  be  obstructed.     The 


1  Elementa  Physiologic. 


WEIGHT    OF    BRAIN.  707 

importance  of  this  peculiarity  in  the  distribution  of  the  cerebral  blood- 
vessels becomes  at  once  apparent  when  it  is  remembered  that  with  the 
cessation  of  the  blood  supply  the  functional  activity  of  the  brain  at 
once  ceases,  and  it  may  be  appropriately  mentioned  in  this  connection 
that  while  in  all  probability  the  energy  of  the  brain  depends  largely 
on  the  size  of  its  arteries  and  the  freedom  with  which  the  blood  circu- 
lates through  them,  the  special  manifestation  of  brain  power  depends 
upon  the  particular  areas  of  distribution.  It  has  already  been  men- 
tioned that  the  gray  matter  of  the  nervous  system  is  more  vascular 
than  the  white,  and  that  in  all  probability  it  is  in  the  gray  or  vas- 
cular substance  that  the  nervous  force  is  generated,  the  white  or  fibrous 
substance  transmitting  it.  The  significance,  therefore,  of  the  develop- 
ment of  the  convolutions  just  described  produced  through  the  invagi- 
nating  of  the  gray  substance  into  the  white,  together  with  their  pia 
mater  or  vascular  tunic,  thereby  insuring  a  far  greater  supply  of  blood 
than  would  be  possibe  if  the  brain  were  smooth,  becomes  evident. 
Further,  when  it  is  borne  in  mind  that  the  brain  is  enclosed  in  a  bony 
unyielding  case,  and  that  the  amount  of  blood  sent  to  the  brain  from 
the  heart  must  vary  with  the  force  of  the  latter,  and  that  the  cerebral 
disturbances  ensue  with  any  increase  or  diminution  in  pressure  it 
might  be  anticipated  that  some  provision  must  exist  by  which  a  uniform 
pressure  within  the  cerebral  substance  is  maintained.  The  latter 
function  appears  to  be  fulfilled  by  the  cerebro-spinal  fluid  found  in  the 
subarachnoid  cavity  of  the  brain  and  cord,  since  if  this  fluid  be  with- 
drawn from  a  living  animal,  cerebral  disturbances  attributable  to 
changes  in  pressure  ensue.  The  cerebro-spirial  fluid  amounts  to  at 
least  two  ounces,  and  probably  more,  and  appears  to  be  as  rapidly 
absorbed  as  produced,  and  as  it  readily  passes  from  the  subarachnoid 
space  through  the  foramen  of  Magendie  or  the  triangular  orifice  in  the 
pia  mater  situated  at  the  inferior  angle  of  the  fourth  ventricle  into  the 
ventricles  of  the  brain  or  the  central  canal  of  the  cord,  it  evidently 
serves  to  equalize  the  pressure  in  the  cranial  cavity,  merely  allowing 
bloodvessels  to  expand  and  contract  within  such  limits  as  do  not  in- 
duce any  marked  change  in  the  pressure  to  which  the  brain  substance 
is  usually  subjected.1  The  entire  encephalon  in  the  adult  male  brain 
weighs  on  an  average  about  fifty  ounces,  that  of  the  female  a  little 
less,  about  forty-four  ounces.  On  this  supposition,  the  relative  weights 
of  the  cerebrum,  cerebellum,  etc.,  are  as  follows: 

Table  LXXIV.2 

Average  weight.  Male.  Female. 

Cerebrum 43.98  oz.  38.75  oz. 

Cerebellum  .....      5.25  ''  4.76  " 

Pens  and  medulla       ....       0.98"  1.01"' 


Entire  encephalon      ....     50.21  "  44.52  " 

Katio  of  cerebrum  to  cerebellum        .     1  to  8f-  1  to  81 

The  human  brain  is  absolutely  heavier  than  that  of  any  other  animal 
except  the  elephant  and  the  cetacea,  the  brain  of  the  elephant  usually 

1  Magendie:  Journal  de  Physiologie,  tome  v.  p.  27,  Paris,  1825';  tome  vii.  pp.  1-tJO,  1827. 
'-'  Quain'd  Anatomy,  8th  ed.,  vol.  2d,  p.  581. 


708 


THE    CEREBRAL    HEMISPHERES. 


weighing  from  eight  to  ten  pounds1  or  even  more,  that  of  the  young 
male  elephant  which  recently  died  al  the  Philadelphia  Zoological  Gardens 
having  been  found  by  the  author  to  weigh  immediately  after  removal 
from  the  skull  ten  and  a  half  pounds.  The  brain  of  the  whale  weighs 
about  five  pounds;2  that  of  a  grampus  delphinus,  as  found  by  the 
author,  seven  pounds.  Relatively,  however,  to  the  size  of  the  body  the 
brain  is  larger  in  certain  birds  and  mammals  than  in  man,  as,  for  ex- 
ample, in  the  canary  bird,  field  mouse,  and  ouisitite  monkey.  With 
reference,  however,  to  the  size  of  the  nerves  given  oft"  from  its  base,  the 
brain  of  man  is  larger  than  that  of  any  other  animal  without  exception. 
The  brain  consists  chemically3  of  about  75  per  cent,  of  water,  15  of 
fats,  7.5  albuminoids,  1.5  of  salts,  1  of  extractives,  including  such 
principles  as  cerebrin  (Cj-H^NC^),  lecithin  (C44H9irNT09),  choles- 
terin,  fats,  fatty  acids,  phosphorus,  sodium  chloride,  salts  of  lime,  potash, 
and  magnesia.  The  relative  amounts  in  which  cholesterin,  fat,  and 
cerebrin  are  found  in  the  gray  and  white  substance  of  the  brain  are 
worthy  of  mention.  Thus,  while  gray  substance  contains  18.7  per 
cent,  of  cholesterin  and  fat  and  only  0.5  of  cerebrin.  the  white  sub- 
stance contains  51.9  per  cent,  of  cholesterin  and  9.5  of  cerebrin.  The 
quantity  of  phosphorus  is  very  noticeable,  amounting  to  from  1.3  to 
1.7  per  cent.  Its  presence  as  an  indispensable  condition  of  a  healthy 
brain  cannot  be  overestimated.  Indeed,  it  has  been  truly  said  wt  with- 
out phosphorus  no  thought."4  In  considering  the  functions  of  the 
medulla,  pons,  cerebellum,  and  basal  ganglia,  we  have  necessarily 
anticipated  somewhat,  by  a  process  of  exclusion,  the  functions  of  the 
cerebral  hemispheres.  It  only  now  remains  for  us  to  offer  the  positive 
evidence  bearing  upon  the  questions  and  confirming  the  general  con- 
clusions already  reached  by  the  manner  just  mentioned. 

Fig.  406. 


Pigeon,  after  removal  of  the  hemispheres.  (Dalto.v.) 

If  the  cerebral  hemispheres  be  removed  in  a  pigeon,  for  example,  the 
animal    at  once  falls  into  a   condition  of  stupor,   its  whole  appearance 


l  Ovcloripedia  of  Aunt.  Phys.,  vol.  iii.  n.  B6*.     Lond.  1SH9-4T. 

-  Rudolplii  :  Gmndrisa  der  Physiologie,  B.  ii.  S.  12.     Berlin.  1823. 

::  Cnrpenter'a  Physiology,  1S81,  p.  529. 

4  Moleschott :  Leiire  derNahrungemittel,  S.  115.     Erlangen,  1850. 


INJURY    TO     THE    CEREBRAL    HEMISPHERES.  709 

being  very  peculiar  and  most  characteristic  (Fig.  406).  With  its  head 
almost  buried  within  the  feathers  of  the  neck,  with  closed  eves,  the 
pigeon  stands  sufficiently  firmly,  but  without  moving,  apparently  utterly 
indifferent  to  its  surroundings.  From  time  to  time  it  opens  its  eyes, 
stretches  its  neck,  or  smooths  its  feathers,  but  soon  again  relapses  to  its 
former  condition  of  apathy.  That  the  pigeon,  however,  still  feels  there 
can  be  no  doubt.  Pinch  its  neck  or  one  of  its  toes  and  a  persistent 
effort  is  made  to  withdraw  the  part  from  the  grasp.  Fire  off  a  pistol, 
the  pigeon  will  open  its  eyes  and  turn  its  head  round  as  if  it  had  heard 
the  report  and  was  looking  whence  it  came.  The  report  of  the 
pistol,  however,  causes  no  alarm,  for  the  pigeon  makes  no  effort  to 
escape.  While  the  animal  undoubtedly  hears  and  sees,  the  sensations  do 
not  give  rise  to  the  usual  ideas  associated  with  or  developed  out  of  them, 
the  pigeon  feels  but  does  not  perceive  the  sensation  of  sound ;  the  report 
of  the  pistol  does  not  give  rise  to  any  idea  of  danger  usually  associated 
with  the  production  of  sound.  In  the  same  way  the  presence  of  food, 
though  seen  and  smelt  by  the  pigeon,  does  not  excite  the  idea  of  hunger, 
the  animal  making  no  effort  to  feed,  starving  to  death  amidst  plenty. 
That  this  entire  loss  of  memory,  volition,  and  conscious  intelligence,  fol- 
lowing loss  of  the  cerebral  hemispheres  in  a  pigeon  and  a  mammal  is  not 
due  simply  to  the  effects  of  shock,  hemorrhage,  etc.,  is  shown  not  only 
by  the  entirely  different  effect  following  destruction  of  the  cerebellum,  but 
that  a  pigeon  from  which  the  cerebral  hemispheres  have  been  removed 
can  be  kept  alive  for  months  by  artificial  feeding,  and  a,  mammal 
usually  for  a  short  period,  and,  although  the  effects  of  shock  have  long 
since  passed  away,  nevertheless,  the  animal  never  regains  its  intelligence, 
remaining  ever  afterward  in  this  characteristic  condition  of  stupor  and 
apathy.  Although  the  effects  of  destruction  or  compression  of  the 
cerebral  hemispheres  in  man,  whether  due  to  disease  or  injury,  are  not 
as  well  established  as  in  the  case  of  birds  and  mammals  through  the 
imperfect  localization  of  the  disease,  the  basal  ganglia,  etc.,  being 
usually  involved  as  well  as  the  cerebral  hemispheres ;  nevertheless,  a 
sufficient  number  of  cases  have  been  observed  by  pathologists  which 
show  that  loss  or  compression  of  the  cerebral  hemispheres  in  man  in- 
volves, as  in  the  case  of  birds  and  mammals,  the  loss  of  memory,  volition, 
conscious  intelligence,  the  negative  functions,  however,  remaining  un- 
impaired.  Among  such  cases  may  be  mentioned  that  of  the  sailor 
related  by  Sir  Astley  Cooper,1  who,  having  fallen,  probably  from  the 
yard-arm,  was  picked  up  on  the  deck  insensible,  practically  deprived  of 
all  powers  of  mind,  volition,  or  sensation,  in  which  condition  he  re- 
mained for  thirteen  months,  being  kept  alive  all  this  time  by  artificial 
feeding,  the  grinding  of  the  teeth  and  the  sucking  of  the  lips  indicating 
to  his  attendants  the  necessity  of  giving  food  and  drink.  During  this 
period  the  man  lived  almost  entirely  a  vegetable  existence,  the  only 
movements  he  made,  with  the  exceptions  of  the  lips,  etc.,  being  with  the 
fingers,  which  he  moved  to-and-fro  to  the  time  of  the  pulse.  In  this 
condition  the  sailor  was  seen  by  Dr.  Cline,  the  famous  surgeon  of  the 
day,  who,  satisfying   himself  that  a  depression   in   the   skull   existed, 

1  Lectures  on  the  Principle*  and  Practice  of  Surgery,  p.  138.     Philadelphia,  1839. 


710  THE    CEREBRAL    HEMISPHERES. 

trephined,  and  with  the  happy  result  that  within  a  short  time  after  the 
operation  the  patient  was  able  to  get  out  of  bed,  talk,  and  tell  where 
he  came  from,  his  mind  having  been  restored  through  the  removal  of 
the  pressure  exerted  by  the  depressed  bone  upon  the  cerebral  hemi- 
spheres. 

In  general,  it  may  be  said  that  injury  or  disease  of  the  cerebral  hemi- 
spheres in  man  entails  disturbance  or  loss  of  the  intellectual  powers, 
according  to  the  seat  and  extent  of  the  lesion.  Impairment  and  then 
loss  of  memory,  weakening  and  failure  of  the  reasoning  powers  and  of 
the  judgment,  invariably  follow  disease  or  injury  of  the  cerebral  hemi- 
spheres, while  the  facts  that  under  such  circumstances  there  is  no  loss  of 
sensation  or  motor  power,  and  that  the  vegetative  functions  also  remain 
unimpaired,  as  in  the  case  of  idiots  and  the  insane,  clearly  show  that  the 
cerebral  hemispheres  are  indispensable  to  the  manifestation  of  the  intel- 
ligence. On  the  other  hand,  the  fact  already  mentioned  of  animals 
deprived  of  their  cerebral  hemispheres  living  indefinitely  when  supplied 
with  food,  and  of  human  beings  being  born  anencephalous  and  yet 
were  kept  alive  some  time,  and  who  sucked  and  cried  like  ordinary 
infants,  proves  that  the  cerebral  hemispheres  are  not  concerned  in  the 
performance  of  those  functions  not  involving  intellection,  which  have 
been  assigned  to  other  parts  of  the  encephalon.  That  the  intellectual 
powers  depend  upon  the  development  of  the  encephalon  is  also  shown 
by  the  facts  of  comparative  anatomy,  the  encephalon  of  the  more 
intelligent  animals  being  much  heavier  both  absolutely  and  relatively, 
with  reference  to  the  weight  of  the  body,  than  that  of  the  less  intelligent 
ones.  Thus,  in  fishes  the  ratio  of  the  encephalon  to  the  body  is  as  1 
to  5668,  in  the  reptiles  as  1  to  1321,  in  birds  as  1  to  212,  in  mammals 
1  to  189, x  and  in  man  as  1  to  50,  supposing  the  body  of  the  man  to 
weigh  150  pounds  and  the  brain  about  48  ounces,  or  three  pounds. 
Further,  the  brain  of  the  lower  races  of  mankind  is  not  as  heavy  as 
that  of  the  higher  and  more  intellectual  ones,  weighing  on  an  average 
only  about  46  ounces,  and  is  much  less  bulky,  occupying  perhaps  a 
space  within  the  skull  of  only  63  cubic  inches,2  while  that  of  the  higher 
races  may  occupy  a  space  of  114  cubic  inches.3  It  is  also  well  known 
that  individuals  distinguished  by  great  intellectual  power  possessed  large 
and  heavy  brains,  thus,  the  brain  of  Abercrombie  weighed  63  ounces,4 
that  of  Cuvier  64.33  ounces.4  On  the  other  hand,  the  brain  of  idiots  has 
been  found  in  some  instances  to  weigh  not  more  than  20  ounces.  It 
will  be  observed  also  from  a  comparison  of  the  brain  of  the  lower  with 
that  of  the  higher  vertebrates,  that  it  is  the  greater  development  of  the 
cerebral  hemispheres  in  the  latter  to  which  are  due  the  greater  bulk  and 
weight  of  the  encephalon.  Thus,  as  we  pass  from  the  brain  of  the  fish 
(Fig.  407)  to  that  of  the  reptile  (Fig.  408),  from  the  brain  of  the  reptile 
to  that  of  the  bird  (Fig.  409),  from  the  latter  to  the  brains  of  mammals 
(Fig.  410),  including  that  of  man,  one  cannot  but  be  impressed  with 
the  fact  that  the  cerebral  hemispheres  become  successively  more   and 

1  Leuret:  Anatomie  Comparee  flu  Svsteme  Nerveux,  pp.  lo3,  'I'll,  284,  422.   Paris,  1839. 
-  Morton  :  Crania  Americana,  p   'Ji:i.     Philadelphia,  1839 
3  Edinburgh  Med.  ami  Surg.  Journal,  1845,  vol    Ixiii.  p.  448. 

*  "Trois  livres  onze  oncea  quatrea  gros  et  demi,"  is  the  number  given  in  the  account  of  the  autopsy  of 
Cuvier  io  the  Archives  geuerales  de  Medeciue,  tome  xxix.  p.  144.     Paris,  1832  . 


COMPARATIVE    DEVELOPMENT    OF    THE    BRAIN".       711 

more  developed,  until  in  the  monkeys  (Fig.  411)  (excepting  young  and 
possibly  also  adult  anthropoids)  and  in  man  they  completely  cover  the 


Fig.  407. 


Fig.  409. 


Brain  of  carp.  A.  Cere- 
bral hemispheres.  B.  Op- 
tic lubes.     C.   Cerebellum. 


Brain  of  lizard.     (Owen.) 


Brain  of  the  pigeon.  A.  Cere- 
bral hemispheres.  B.  Optic  lubes. 
C.  Cerebellum.     (Ferrier.) 


cerebellum.  Further,  it  may  also  be  seen  from  such  a  comparison  that 
Avliile  the  brain  in  fish,  reptiles,  birds,  and  the  lower  orders  of  animals, 
such  as    the    marsupiala,  rodentia,  suenia  (Fig.  412),  etc.,  is    smooth 


Fro.  410. 


Fig.  411. 


Brain  of  the  rabbit.  A.  The  smooth 
cerebral  hemisphere.  B  The  olfactory 
bulb.     C.  The  cerebellum.     (Ferrier.) 


Base  of  brain  of  baboon.     (Owen.) 


or  nearly  so,  in  the  higher  orders,  including  the  proboscidea,  cetacea, 
the  ungulata  (Figs.  413,  414),  the  carnivora  and  primates  (Fig.  415), 
it  is  more  or  less  convoluted.  Indeed,  so  much  is  this  the  case  that 
in  the  proboscidea  it  is  particularly  convoluted,  even  more  so  than  in 
man.  In  general,  it  may  be  said  that  the  development  of  the  intel- 
lectual powers  depends  not  only  upon  that  of  the  encephalon,  but  more 
particularly  upon  that  of  its  cerebral  hemispheres,  and  especially,  as 
affirmed  long  ago  by  Erasistratus,1  upon  the  number  and  depth  of  the 


1  Galenus  De  Usu  Partium,  Lib.  8,  Cap.  13. 


1V1 


T  1 1  E    G  E  H  E  15  K  A  L    H  E  M  I S  P  H  K  R  E  S . 


convolutions  of  the  gray   matter  of  the  same.      Further,  in  the  savage 
races  of  mankind,  characterized  by  a  low  order  of  intelligence,  the  con- 


Pig.  412. 


Brain  of  manatee. 


Fig.  413. 


Fig.  414. 


Brain  of  the  horse.     (Owbn.) 


Brain  of  pecca  i  \ 


COMPARATIVE    DEVELOPMENT    OF    THE    BRAIN 


713 


volutions  are  not  so  deep,  are  less  numerous,  and  are  more   simply 
disposed    than    in    the    civilized    races  distinguished    by  the  develop- 


Fig.  415. 


Brain  of  the  orans 


ment   of  their    mental    faculties,  while    in    individuals    especially  re- 
markable  among  the  latter   for  intellectual  power,  as  in  the  case  of 


Fig.  41(5. 


Fig.  417. 


Cerebrum 


-—Cerebrum 


_   Corp. 
quadrig. 

--Cerebellum 


*» Med.  oblonfi 


Med.  oblong. 


Brain  of  human  embryo,  three  months. 


Brain  of  human  embryo,  five  months. 


Gauss,1  for  example,  one  of  the  most  distinguished  mathematicians  that 
ever  lived,  the  convolutions  of  the  cerebral  hemispheres  were  found  to 


1  Quain  :  Anatomy,  1878,  vol.  ii.  pp.  .529,  581. 


714  THE    CEREBRAL    HEMISPHERES. 

be  very  numerous  and  deep,  and  far  from  simply  arranged.  On  the 
other  hand,  in  idiots  the  convolutions  are  few,  comparatively  superficial, 
and  simply  disposed.  The  development  of  the  brain' also  confirms  the 
conclusions  based  upon  the  facts  of  comparative  anatomy  and  ethnology, 
the  transitory  stages  through  which  the  foetal  brain  passes  being  per- 
manently retained  in  the  brains  of  the  lower  animals.  Thus,  at  about 
three  weeks  of  intrauterine  life  the  brain  of  the  human  fcetus  resembles 
that  of  the  adult  fish,  there  being  but  little  difference  at  this  early  period 
in  the  relative  development  of  the  cerebral  hemispheres,  optic  lobes, 

Fig.  418. 


Lateral  view  of  the  right  cerebral  hemisphere.  1  Fissure  of  Rolando.  2.  Ascending  frontal  codvo- 
lution.  3  Superior,  3'j  middle,  and  7,  inferior  frontal  convolutions.  4.  A  bridging  convolution  between 
the  superior  and  middle  frontal  convolutions.  5.  Ascending  parietal  convolution.  6,  8  Supramarginal 
convolution  (8  in  front  points  to  part  of  the  inferior  frontal  convolution).  9,  9.  Superior  temporo- 
sphenoidal  convolution.  10,  11,  12.  Convolutions  of  the  island  of  Keil,  or  central  lobe.  13.  Orbital 
convolutions.  11.  Lower  extremity  of  middle  temporo-sphenoidal  convolution.  15.  Occipital  lobe. 
(From  Sappey  after  Foville.)    %. 

cerebellum,  etc.  As  development  advances  the  hemispheres  enlarge 
and  grow  backward ;  at  three  months  (Fig.  416),  though  still  smooth, 
they  slightly  overlap  the  optic  lobes,  the  latter  not  having  yet  divided 
into  the  corpora  quadrigemina.  At  about  the  fifth  month  (Fig.  417) 
the  cerebral  hemispheres  in  the  human  fcetus  overlap  the  cerebellum, 
and  here  and  there  exhibit  a  rudimentary  fissure,  though  their  surface 
is  still  almost  entirely  smooth,  as  in  those  of  the  rodentia.  Finally,  at 
about  the  seventh  month,  the  optic  lobes  are  subdivided  into  the  corpora 
quadrigemina,  while  at  full  term  or  at  birth  the  convolutions  are  all 
formed. 

The  brain  of  the  human  foetus,  however,  at  this  period,  both  as 
regards  the  number,  depth,  and  simplicity  of  arrangement  of  the 
cerebral  convolutions,  resembles  rather  the  brain  of  the  chimpanzee 
than  that  of  the  adult  man,  while  the  brain  of  the  uneducated  child 
resembles,  in  similar  respects,  that  of  the  savage  races  of  mankind 
rather  than  that  of  the  civilized  ones ;  a  physical  correspondence  in 
harmony  with    their    intellectual    acquirements.      While    the  facts  of 


LOCALIZATION    OF    FUNCTIONS.  715 

experiment,  pathology,  comparative  anatomy,  etc.,  with  but  few  excep- 
tions, and  those  usually  more  apparent  than  real,  undoubtedly  agree  in 
establishing  the  view  that  associates  intellectual  power  with  the  develop- 
ment of  the  cerebral  hemispheres,  and  more  particularly  with  that  of  the 
convolutions,  or  the  gray  matter  of  the  same,  it  must  be  borne  in  mind 
that  the  quality  of  the  chemical  composition  of  the  latter  is  quite  as 
important  a  condition  as  its  mere  quantity.  Further,  that  the  exercise 
of  the  mental  faculties  necessitates  the  connections  between  the  gray 
or  vascular  substance  of  the  convolutions  and  the  fibres  of  the  white 
substance  being  maintained  in  their  normal  condition,  just  as  the  action 
of  a  muscle  depends  on  the  position  and  manner  of  insertion ;  and, 
above  all,  upon  the  free  supply  of  blood  and  active  circulation,  both 
that  the  materials  for  the  nourishment  of  the  hemispheres  and  the  pro- 
duction by  them  of  thought,  may  be  supplied  in  sufficient  quantity,  and 
that  the  effete  and  worn-out  materials  incidental  to  mental  activity  may 
be  carried  away  to  the  proper  emunctories  as  rapidly  as  produced.  As  we 
have  already  seen  that  the  different  structures  of  which  the  encephalon 
consists,  medulla,  pons,  cerebellum,  basal  ganglia,  cerebral  convolu- 
tions, etc.,  have  undoubtedly  different  functions,  it  is  reasonable,  there- 
fore, to  suppose  that  the  different  convolutions,  or  the  gray  matter 
of  the  cerebral  hemispheres,  have  also  special  faculties  or  functions. 
Phrenology  has,  therefore,  a  basis  worthy  of  consideration.  Phrenology, 
however,  as  understood  by  the  vulgar,  is  based  upon  the  untenable 
assumption  that  the  form  of  the  surface  of  the  brain  can  be  inferred 
from  the  external  configuration  of  the  skull,  that  any  protuberance,  or 
"bump,"  of  the  latter  is  to  be  taken  as  an  indication  of  a  similar 
excessive  development  of. the  former,  and  the  possession  of  some  par- 
ticular well-developed  mental  faculty.  Apart,  however,  from  the  facts 
that  the  skull  consists  of  two  tables,  and  that  the  outer  surface  of  the 
brain  is  separated  from  the  inner  surface  of  the  skull  by  the  dura 
mater,  arachnoid,  pia  mater,  and  cerebro-spinal  fluid,  the  latter  vari- 
able, in  quantity,  the  figure  of  the  brain,  except  in  a  general  way,  does 
not  correspond  to  the  figure  of  the  skull.  So  much  so  is  this  the  case 
that  in  certain  animals,  as  in  the  elephant,  for  example,  through  the 
enormous  development  of  the  frontal  sinuses  the  anterior  portion  of  the 
skull  is  no  indication  of  the  form  of  the  brain  whatever.  Further,  the 
surface  of  the  brain  is  not  elevated  into  bumps,  the  convolutions,  as  we 
have  seen,  being  formed  through  the  invagination,  or  dipping  down  of 
the  gray  matter  into  the  white.  Even  though,  then,  osseous  "  bumps" 
be  ever  so  well  developed,  there  are  never  any  cerebral  "bumps"  with 
special  functions  or  faculties  corresponding  to  the  osseous  ones.  Phre- 
nology, as  such,  must  be  relegated,  then,  to  the  charlatan  and  itinerant 
showman,  who  amuse  their  audience  by  feeling  their  heads,  and  illus- 
trating their  views  by  showing  plaster  casts  of  the  heads  of  Napoleon, 
Schiller,  noted  murderers,  idiots,  and  the  like.  Within  recent  years, 
however,  another  kind  of  phrenology  has  been  developed  and  estab- 
lished, more  or  less  satisfactorily  based  upon  entirely  different  methods 
of  investigation,1  such  as  exposing  the  brain  in  a  living  animal,  and 

1  Fritsch  and  Ilitzig:  Archiv  f.  Anat..  Physiologic,  etc.,  S.  300.  Leipzig,  1870.  Ferrier  :  Functions  of 
the  Brain,  IS76.  Carville  and  Duret :  Archives  de  Physiologie  2eime  serie,  tume  ii.  p  352.  Paris,  1875. 
Dalton  :  New  York  Medical  Journal,  187o,  p.  225. 


710 


THE     CEREBRAL     HEMISPHERES, 


stimulating  with  a  weak  electrical  current  a  particular  convolution,  and 
so  determining  whether  the  latter  is  excitable,  and  whether  its  stimu- 
lation  causes  sensory  or  motor  effects;  or,  destroying  a  particular 
convolution  by  cutting,  corrosion,  etc.,  and  observing  whether  the  animal 
is  deprived  of  any  of  its  faculties,  and  so  learning  whether  the  convo- 
lution has  motor  or  sensory  functions.  By  such  experimental  methods 
particular  functions  have  been  assigned  in  animals  to  the  different  con- 
volutions of  the  brain,  and  there  can  be  little  doubt  that  such  convo- 
lutions of  the  brain  in  man  as  are  homologous  with  the  brain  in 
monkeys  and  the  higher  mammalia  have  essentially  the  same  functions  as 
in  the  latter;  the  results  obtained  by  post-mortem  examination  and  the 

Fig.  419. 


The  left  hemisphere  of  the  monkey.     (Fekrier.) 

clinical  study  of  disease  of  the  brain  in  man  confirm  the  results  obtained 
by  experimentation  upon  animals;  destruction  of  the  convolutions  by 
injury  or  disease  entailing  the  loss  of  motor  or  sensory  faculties.1  Thus, 
electrical  irritation  of  the  convolutions  bordering  the  fissure  of  Rolando 
in  the  brain  of  the  monkey  (Fig.  419,  1,  2,  3,  4,  5,  6,  7,  8,  a,  b,  c,  d) 
and  in  man  (Fig.  420),  at  least  in  the  only  case  recorded,2  gives  rise  to 
certain  well-defined  constant  movements  of  the  hands,  feet,  arms,  legs, 
facial  muscles,  mouth,  and  tongue,  on  the  opposite  side  of  the  body. 

That  the  muscular  contractions  induced  through  electrical  stimulation 
of  these  or  other  convolutions  are  not  due  to  an  escape  or  diffusion  down- 
ward of  the  electrical  current,  and  so  affecting  the  corpus  striatum, 
etc.,  is  shown,  apart  from  the  fact  that  stimulation  by  chemical  agents 
produces  the  same  effect,  by  several  considerations,  among  which  may 
be  mentioned  the  feebleness  of  the  current  used,  the  close  approxima- 
tion of  the  electrodes,  the  imperfect  conductivity  of  the  brain  substance, 
the  muscular  contractions  occurring  on  the  opposite  side  of  the  body, 
and  not  occurring  at  all  when  other  convolutions  were  stimulated. 
That  these  convolutions  are  in  reality  motor  centres,  constituting  the 
indispensable  physical  substratum  for  the  volitional,  psychical  initiation 
of  movements  corresponding  to  those  induced  by  electrical  stimulation, 


1  Forrier :  Localization  of  Cerebral  Disease,  p.  42.  London,  1879.  Grasset  :  Des  Localisations  dans 
les  Maladies  Cerebrates,  p.  143.  Pari-,  188D.  Charcot  :  Lecons  sur  les  Localisations  dans  les  Maladies 
du  Cerveiiu,  p.  166.     Paris,  ls78.     Rendu  Revue  des  Sciences  Medicates,  tome  xiii.  p.  314.     Paris,  1879. 

"  Bartholovv  :  American  Journal  of  the  Medical  Sciences,  April,  1874. 


LOCALIZATION    OF    FUNCTIONS.  717 

the  latter  acting   in  the  same  manner  as  the   stimulus  of  the  will,  is 
further  shown  by  the  fact  that  destruction  of  these  convolutions  in  the 

Fig.  420. 


Bateral  view  of  the  human  brain.     The  circles  and  letters  have  the  same  significance  as  those  in  the 
brain  of  the  monkey,  Fig.  453.     (Ferrier.) 

Fig.  -121. 


Brain  of   dog;  showing  excision  of  angular  convolution  an  1  two  adjacent  anterior  convolutions  on  left 
side.     Blindness  of  right  eye.     (Ferrier.) 

monkey1  by   experiment   (Fig.  421)   and   in   man2  by   disease    causes 
complete  hemiplegia  of  the  opposite  side  of  the  body  without  affecting 

1  Ferrier:  Functions  of  the  Brain,  1876,  p.  201. 

-  Leiiine  :    De  In  TiOC»li<mti  >n  dans  lea  Maladies  Cerebrates,  p.  S3.     Paris,  lS7o.      Gliky  :    Deutsches 
Archiv  fur  kiin.  Med.,  Dec.  1875. 


718  THE    CEREBRAL    HEMISPHERES. 

sensation.     On  the  other  hand,  destruction  in  the  monkey1  of  certain 
convolutions,  like  the  angular  gyrus  (Fig.  422),  for  example,  while  not 

Fig.  422. 


Brain  of  dog,  showing  excision  of  angular  convolution  and  adjacent  posterior  convolution   in  right 
side.     Blindness  of  left  eye.     (Ferrier.) 

aifecting  at  all  its  motor  powers,  entails  in  the  opposite  eye  loss  of  per- 
ceptive vision — that  is,  the  loss  of  visual  ideas  as  distinguished  from 
mere  visual  sensations,  the  corpora  quadrigemina,  as  we  have  already 
seen,  being  the  centres  of  the  latter.  An  animal  with  its  optic  lobes 
intact  undoubtedly  sees — that  is,  the  physical  ray  of  light  becomes  the 
mental  subjective  conscious  sensation  of  sight,  but  the  latter,  in  the 
absence  of  the  angular  gyrus,  gives  rise  to  no  ideas  such  as  are  nor- 
mally developed  out  of  the  sensation  of  light.  Under  such  circum- 
stances familiar  objects  are  seen,  but  do  not  suggest  the  ideas  of 
pleasure  or  pain,  for  example,  usually  associated  with  them.  In  a  word, 
the  animal  sees,  but  does  not  perceive,  it  is  only  psychically  blind  ;  with 
the  destruction  of  the  optic  lobes  it  becomes  absolutely  so.  Now,  while 
in  man,  at  least  at  present,  the  localization  of  a  sensory  function  like 
that  of  perceptive  vision  in  a  particular  convolution,  the  angular  gyrus, 
has  not  been  as  definitely  established  by  chemical  and  pathological 
investigation,  as  in  the  case  of  the  monkey,  the  dog,  etc.,  nevertheless, 
cases  of  cerebral  hemianaesthesia — that  is,  loss  of  sensibility,  without  loss 
of  motion,  accompanied  also  by  loss  of  perceptive  vision,  on  the  oppo- 
site side  of  the  body,  due  to  cerebral  lesions — go  to  show2  that  there  are 
special  sensory  as  well  as  motor  convolutions  in  the  brain  of  man. 
The  condition  of  aphasia,  whether  presented  in  the  usual,  or  agraphic, 
or  amnesic  form,  depending,  as,  without  doubt,  it  does,  upon  disease  in 
the  region  of  the  posterior  extremity  of  the  third  left  frontal  convolu- 
tion, where  the  latter  abuts  on  the  fissure  of  Sylvius,  and  overlaps  the 
island  of  Reil,  is  a  most  convincing  argument  in  favor  of  the  view  of 
the  cerebral  functions  being  localized  in  the  convolutions  of  the  hemi- 
spheres.     Merely  referring    incidentally  to   the    researches  of  Petit,3 

1  Ferrier,  ibid.,  p.  167.  "  Ferrier,  op.  cit.,  pp.  170,  181. 

3  Recueil  d'observations  d'anatomie  et  de  chiiurgie,  p.  74.     Paris,  1766. 


APHASIA.  '719 

Bouillaud,1  Dax,2  Broca,3  Hughlings  Jackson,4  etc.,  upon  the  subject  of 
aphasia,  the  detailed  consideration  of  which  belongs  rather  to  the  study 
of  clinical  medicine  and  pathological  anatomy,  it  may  be  briefly  said 
that  a  person  presenting  the  condition  of  aphasia  as  exhibited  in  its 
most  usual  form  is  deprived  of  the  faculty  of  articulate  speech,  though 
such  a  person  comprehends  perfectly  the  meaning  of  words  spoken  by 
others  ;  having  a  clear  idea  of  language  and  of  the  meaning  of  words, 
and  being  able  to  write  perfectly  well.  In  other  cases,  however,  the 
patient  cannot  express  ideas  in  writing,  or  cannot  remember  the  words 
wanted ;  in  those  of  aphasia,  agraphia,  or  amnesia,  the  idea  even  of 
language  is  lost.  That  the  inability  to  speak  exhibited  by  the  person 
suffering  from  aphasia,  whether  simple  or  combined  with  the  amnesic 
or  agraphic  form,  is  not  due  to  paralysis  of  the  muscles  of  articulation 
is  shown  by  the  fact  that  the  aphasic  individual  makes  use  of  these 
muscles  in  mastication  and  deglutition.  Though  the  centre  for  the 
coordination  of  the  muscles  effecting  articulation  be  diseased,  since  the 
action  of  the  centre  of  the  articulating  muscles  is  bilateral — that  is, 
the  centre  in  one  hemisphere  innervating  the  muscles  of  articulation 
of  both  sides — there  is  no  difficulty  in  understanding  that  such  should 
be  the  case. 

While  disease  of  the  centre  of  articulation  of  the  left  hemisphere,  for 
the  reason  just  given,  does  not  entail  paralysis  of  the  muscles  of  articu- 
lation, it  does  entail  paralysis  of  articulation  or  speech,  the  centre  for 
the  coordination  of  the  muscles  involved  in  the  production  of  speech 
being  then  affected.  When  it  is  remembered,  however,  that  speech  is 
gradually  acquired  through  the  constant  and  continual  association  in 
the  mind  of  sounds  or  written  signs  with  the  corresponding  spoken 
words,  that  the  acquisition  of  speech,  physiologically  speaking,  is  the 
development  in  the  brain  of  an  organic  nexus  between  the  sound  or 
symbol,  and  the  articulation,  it  becomes  intelligible  why  if  this  nexus 
be  broken,  that,  though  the  sound  be  heard  and  the  svmbols  seen, 
and  the  corresponding  ideas  developed,  the  words  expressing  the  ideas 
cannot  be  uttered, — the  individual  is  speechless,  because,  as  Ferrier 
expresses  it,5  the  motor  part  of  the  sensori- motor  cohesion,  sound- 
articulation  situated  in  the  inferior  frontal  convolution,  is  broken. 
Further,  owing  to  the  close  proximity  of  the  motor  centre  of  the  hand 
and  facial  muscles,  it  is  easy  to  see,  therefore,  why  dextral  and  facial 
paralysis  are  so  often  present,  though  not  necessarily  so  in  the  case  of 
aphasia.  At  first  sight  it  may  appear  strange  that  the  centre  for 
coordinating  the  muscles  effecting  articulation  should  be  located  ex- 
clusively  in  one  hemisphere ;  in  reality,  however,  there  is  nothing  more 
strange  in  this  than  that  most  persons  are  right-handed.  Dextral 
movement,  like  articulate  speech,  is  gradually  acquired,  and  there  is 
no  more  reason  to  doubt  that  in  the  absence  of  the  coordinating  cen- 
tres of  articulation  of  the  left  hemisphere  that  of  the  right  could  be 
educated,  than  that  in  the  absence  of  the  right  hand  one  could  learn  to 
usf  the  left.  Indeed,  it  has  been  found  that  in  left-handed  persons 
suffering  with  aphasia    the  inferior   frontal  convolution   affected  is  situ- 

Irchivos  de  Mfidecine,  1825.  -  Gazette  oebdomadaire,  April,  1865. 

:;  Bulletin  de  la  Bociete  anatomique,  tome  it.  1861.  4  London  Hos]  ital  Reports,  vol.  i. 

■'•  Op.  <it.,  p.  -74. 


720  THE    CEREBRAL    HEMISPHERES. 

ated  in  the  right  hemisphere  instead  of  the  left  hemispheres  as  is  usually 
the  case.  By  the  same  methods  made  use  of  in  determining  the  func- 
tions of  the  convolutions  about  the  fissure  of  Rolando,  the  angular 
gyrus,  the  inferior  frontal  convolution,  etc.,  the  functions  of  the  re- 
maining convolutions  have  been  more  or  less  satisfactorily  made  out, 
and  may  be  resumed  according  to  Ferrier,1  as  follows  (Fig.  420): 

1.  Postero-parietal  lobule:  movement  of  the  hind  loot,  as  in  walking. 

2,  3,  4.   Convolutions  bounding  the  fissure  of  Rolando:   movements  of 
the  arm  and  leg,  as  in  climbing,  swimming,  etc. 

5.  Posterior  extremity  of  the  superior  frontal  convolution:  extension 
forward  of  the  arm  and  hand. 

6.  Anterior  central  convolution  :   supination  and  flexion  of  the  fore- 
arm through  action  of  biceps. 

7.  8.  Anterior  central  convolution  :    elevation  and  depression  of  the 
angle  of  the  mouth,  respectively. 

9,  10.  Inferior  or  third  frontal  convolution  :    movements  of  the  lips 
and  tongue,  as  in  articulation,  disease  of  whjch  causes  aphasia. 

11.  Posterior  central  convolution :    retraction  of  the  angle    of  the 
mouth. 

a,  b,  c,  d.  Posterior  central  convolution :  movements  of  the  hand  and 
wrist,  as  in  clinching  the  fist. 

12.  Superior  and  middle  frontal  convolutions :   lateral  movements  of 
the  head  and  eyes,  elevation  of  the  eyelids,  and  dilatation  of  the  pupil. 

13.  13'.   Supramarginal  lobule,  angular  gyrus :  centre  of  vision. 

14.  Superior  temporo-sphenoidal  convolution:  centre  of  hearing. 
V.   Subiculum  cornu  ammonis :    centres  of  smell,  taste,  etc. 

11.  Hippocainpal  region :   centre  of  touch. 

0.  Occipital  lobes :  centres  of  organic  sensations,  hunger. 

F.  Frontal  lobes:   intellectual  and  reflective  powers. 

In  concluding  this  necessarily  brief  account  of  the  functions  of  the 
convolutions  of  the  hemispheres,  inasmuch  as  the  surgeon  at  the  present 
day  may  be  called  upon  at  any  moment  to  trephine  the  skull  and  ex- 
pose a  particular  convolution  with  the  object  of  removing  some  morbid 
growth  causing  epileptiform  convulsion,  etc.,  the  character  of  the 
latter  indicating  the  convolution  to  be  sought  for,  it  may  not  appear 
superfluous  if  the  general  relations  of  the  convolutions  to  the  skull  be 
pointed  out.  Taking  certain  easily  recognized  structures,  such  as  the 
occipital  protuberance,  the  parietal  and  frontal  eminences,  the  external 
angular  processes  of  the  frontal  bone,  as  landmarks,  and  making  use 
further  of  the  coronal,  lambdoidal,  and  sagittal  sutures,  and  by  means  of 
an  imaginary  line  drawn  from  the  squamosal  suture  vertically  upward 
through  the  parietal  eminence  to  the  sagittal  suture,  the  skull  may  be 
conceived  as  being  mapped  out  into  ten  areas,  within  which  may  be 
found  the  most  important  of  the  fissures  and  convolutions. 
|  The  brain,  like  every  other  organ  in  the  body,  from  time  to  time  must 
rest,  not  only  that  the  waste  incidental  to  its  functional  activity  may  be 
repaired,  but  that  its  cells  or  whatever  other  structural  elements  may  be 
concerned  in  the  elaboration  of  consciousness  may  not  be  overtaxed, 

l  Op.  cit.,  p.  305. 


CAUSATION    OF    SLEEP.  721 

worn  out  by  constant  activity.  This  need  of  rest  is  especially  manifest  in 
the  case  of  the  brain,  for  no  work  is  so  exhausting  as  brain  work,  and  when 
once  the  brain  is  fagged,  worn  out,  nothing  is  so  difficult  as  to  restore  to 
it  its  natural,  healthy  activity.  This  necessity  of  periods  of  rest  rhythmi- 
cally alternating  with  those  of  activity,  is  undoubtedly  the  underlying 
cause  of  sleep — "Tired  nature's  sweet  restorer,  balmy  sleep'' — however 
the  latter  may  be  brought  about,  and  concerning  which  there  still  pre- 
vails considerable  difference  of  opinion  among  physiologists.  Thus  it  is 
held  by  Sommer1  that  as  oxygen  appears  to  be  gradually  stored  up 
during  sleep,  as  shown  by  the  experiments  of  Pettenkofer,  after  a 
time  it  will  have  accumulated  in  such  an  amount  as  to  accelerate  mate- 
rially the  nutritive  changes  going  on  in  the  brain,  etc.,  the  effect  of 
which  is  that  awakening  occurs.  On  the  other  hand,  during  the  waking 
state  this  store  of  oxygen  is  gradually  used  up,  as  shown  by  increase 
in  the  amount  of  carbonic  acid  eliminated,  the  consequence  of  which  is 
that  exhaustion  and  general  relaxation  are  experienced,  followed  by  a 
desire  to  sleep.  According  to  Pfliiger,2  the  combination  of  this  intra- 
molecular oxygen  with  the  carbon  of  the  brain  tissue  is  so  violent  as  to 
amount  to  an  explosion,  which,  taking  place  at  successive  intervals, 
maintains  the  brain  in  a  waking  condition  ;  as  the  stored-up  oxygen, 
however,  is  gradually  used  up  the  explosions  diminish  in  frequency  and 
violence  until  they  cease  altogether,  and  as  a  consequence  sleep  follows. 
A  very  plausible  theory  of  the  causation  of  sleep  is  that  advanced  by 
Dr.  Cappie,3  who  holds  that  the  molecular  activity  of  the  cerebral  cells 
is  diminished  through  less  blood  being  supplied  to  them  by  the  capil- 
laries, and  that  consequently  the  brain  occupies  less  space.  But  inas- 
much as  the  brain-case  must  be  full,  the  veins  of  the  pia  mater  become 
proportionally  distended,  the  effect  of  which  is  that  although  the  absolute 
quantity  of  blood,  and  consequently  the  pressure,  remains  the  same,  the 
direction  of  the  pressure  is  modified,  being  less  from  within  and  more 
on  the  surface  of  the  brain,  the  latter  or  the  altered  direction  of  the 
pressure  giving  rise  to  sleep.  This  view  is  confirmed  by  the  researches 
of  Durham,4  by  whom  it  was  shown  that  the  brain  during  sleep  is  in  an 
essentially  bloodless  condition,  that  not  only  the  quantity  of  the  blood 
but  the  velocity  of  its  flOAV  is  diminished,  and  also  by  the  observations 
of  Dr.  Hughlings  Jackson,5  who  showed  by  ophthalmoscopic  examina- 
tion that  the  optic  disk  during  sleep  was  whiter,  the  arteries  smaller, 
the  veins  larger  and  the  adjacent  parts  of  the  retina  more  anaemic  than 
during  the  waking  state.  The  amount  of  sleep  required  is  affected  by 
so  many  conditions,  such  as  age,  temperament,  habit,  mental  and  physical 
exhaustion,  that  it  is  absurd  to  lay  down  any  rule  upon  the  subject.  In 
this  respect,  as  in  all  others,  physiological  nature  is  our  best  guide.  Go 
to  bed  when  you  feel  sleepy  and  rise  up  when  you  awake.  The  mere  fact 
that  some  individuals  get  along  with  only  four  or  five  hours'  sleep  with- 
out their  health  being  affected  is  no  argument  whatever  that  such  a 
small  amount  of  sleep  is  only  required  and  should  suffice  for  every  one. 
Xo  greater  mistake  is  made,  and  that  so  often,  by  students  of  medicine, 

i  Zeits.  f.  Rat.  Med.,  Band  xxxii.  S.  214,  1868.  2  ArctaiT,  1875,  S.  468. 

3  The  Causation  of  Sleep,  Edinburgh,  1882.  i  Guy's  Hospital  Krpoits  3  1  s.r.  vol.  vi 

Royal  London  Ophth.  Hosp.  Reports. 

46 


722  THE    CEREBRAL    HEMISPHERES. 

physicians,  and  literary  men  generally,  than  to  rol>  themselves  of  their 
natural  sleep,  with  the  laudahle  desire,  it  is  true,  of  distinguishing 
themselves,  but,  unfortunately,  at  the  cost  of  broken-down  health  and  lost 
spirits,  too  often  never  to  be  regained. 

Resuming  what  has  been  said  of  the  functions  of  the  cerebro-spinal 
axis  in  man,  it  may  be  stated  in  general  that  the  spinal  cord  and 
medulla  oblongata  are  the  seat  of  excito-motor  actions,  the  functions  of 
the  medulla  differing  from  those  of  the  cord  rather  in  degree  than  in 
kind,  the  rhythmical  performance  of  such  complex  functions  as  deglu- 
tition, circulation,  and  respiration,  depending  upon  the  medulla,  from 
the  fact  of  the  nerves  distributed  to  the  tongue,  fauces,  larynx,  heart, 
and  lungs  emanating  from  that  portion  of  the  spinal  axis;  that  the 
pons  Varolii,  being  that  portion  of  the  encephalon  in  which  external 
impressions  first  become  conscious  ones,  is  the  seat  of  excito-sensori- 
motor  actions,  as  are  also  the  basal  ganglia,  the  corpora  striata  and 
thalami,  being  the  centres  of  motion  and  sensation,  respectively,  the 
optic  lobes  the  centres  of  vision  ;  that  the  cerebellum  is  a  reflex  centre  for 
the  maintenance  of  equilibrium  and  coordination  of  locomotion ;  that 
the  cerebral  hemispheres,  being  the  portion  of  the  encephalon  in  which 
perceptions,  ideas,  emotions,  and  volition  are  developed,  are  the  seat  of 
excito-sensori-ideo-motor  actions.  It  will  be  observed  that  up  to  the 
present  moment,  in  our  exposition  of  the  functions  of  the  encephalon,  we 
have  endeavored  to  offer  only  what  appears  to  us  to  be  well-established 
anatomical  and  physiological  facts,  merely  mentioning,  or  not  referring 
at  all,  to  the  remaining  portions  of  the  encephalon,  whose  functions  have 
not  as  yet  been  made  out — to  describe  simply  the  physical  substratum  of 
consciousness.  It  is  needless  to  say,  however,  that  whether  or  no  the 
different  parts  of  the  encephalon  and  the  different  convolutions  of  the 
hemispheres  really  possess  the  functions  assigned  to  them,  that  the 
phenomenon  of  consciousness  is  thereby  in  no  wise  explained.  Admit- 
ting, for  example,  that  the  optic  lobe  is  the  centre  of  the  sensation  of 
sight,  and  that  the  exact  nature  of  the  molecular  changes  occurring  in 
its  cells  when  the  sensation  of  sight  is  experienced  were  understood,  we 
would  be  still  unable  to  understand  how  the  vibrations  of  light  falling 
upon  the  retina  give  rise  to  visual  sensations — that  is,  the  manner  in 
which  a  physical  impression  becomes  a  conscious  sensation.  In  the 
present  state,  at  least,  of  the  development  of  our  consciousness  it 
appears  impossible  even  to  conceive  of  how  the  gap  between  matter  and 
mind,  the  objective  and  subjective,  can  ever  be  bridged  over.  At  all 
events,  the  phenomenon  of  consciousness  can  never  be  explained  by  a 
purely  physiological  investigation.  We  can  say  that  the  brain  is  the 
organ  of  the  mind,  even  that  it  converts  heat  into  thought,  but,  as 
viewed  subjectively,  the  functions  of  the  brain  are  synonymous  with 
mental  operations.  The  phenomenon  of  consciousness  must  be  studied, 
not  only  objectively  by  the  physiologist,  but  subjectively  by  the  psycholo- 
gist ;  nevertheless,  too  much  stress  must  not  be  laid  upon  the  distinc- 
tion of  matter  and  mind,  of  object  and  subject,  as  made  by  the  meta- 
physician, since  the  existence  of  matter  or  mind,  as  shown  by  ultimate 
analysis,  is  only  an  inference.  We  are  conscious  of  the  sensations  of 
color,  hardness,   roundness,  weight,   extension,  etc.,  and  we  infer  the 


FUNCTIONS    OF    CEREBEAL    HEMISPHERES.  723 

existence  of  something  underlying  these  qualities,  which  we  call  matter, 
and  which  produces  in  us  these  sensations.  We  are  directly  conscious 
of  these  sensations,  not  of  the  matter  supposed  to  cause  them.  The 
existence  of  matter  being,  therefore,  an  inference  from  our  conscious- 
ness, it  is  impossible  to  say,  not  knowing  anything  whatever  about  its 
nature,  whether  it  is  akin  to  mind  or  not.  On  the  other  hand,  suppose 
that  matter  does  exist,  it  is  certain  that  the  various  modes  of  motion 
ordinarily  known  as  heat,  light,  sound,  etc.,  are  transformable  in  us 
into  equivalent  modes  of  consciousness,  and  we  infer  from  these  modes 
of  motion  the  existence  of  something,  the  mind  underlying  these  modes 
of  consciousness,  but  of  whose  nature  we  know  just  as  little  as  that  of 
the  matter,  from  the  effects  of  which  its  existence  is  inferred.  The 
idealist  may  argue  that  there  is  no  such  thing  as  matter  apart  from 
mind,  since  material  forces  are  only  cognizable  as  modes  of  conscious- 
ness, and  the  materialist  may  argue  that  there  is  no  mind  apart  from 
matter,  that  the  modes  of  consciousness  are  material,  since  what  exists 
in  us  as  consciousness  is  transformable  into  modes  of  motion,  but  it  is 
evident  that  the  forces  of  the  inner  are  correlated  with  those  of  the  outer 
world,  the  forces  of  the  outer  with  those  of  the  inner  world,  that  if  we 
besin  with  mind  Ave  end  with  matter,  if  with  matter  we  end  in  mind  ; 
matter  and  mind  being  merely  symbols  of  the  unknown  reality  under- 
lying both. 


CHAPTER   XL Y. 

SYMPATHETIC  NEEVOUS  SYSTEM. 

The  sympathetic  system  of  nerves,  or  the  system  of  organic  vegetative 
life,  also  known  as  the  trisplanchnic  nerve,  great  intercostal  nerve,  etc., 
consists  of  a  double  chain  of  symmetrically  disposed  ganglia  extending 
the  entire  length  of  the  vertebral  column,  which,  gradually  converging, 
terminates  finally  as  a  single  ganglion,  the  ganglion  impar,  resting  upon 
the  coccyx.  While  there  is  no  doubt  as  to  the  manner  in  which  the 
double  ganglionated  cord  of  which  the  sympathetic  consists  ends,  it  has 
not  as  yet  been  made  out  exactly  how  it  begins ;  the  observation  of 
Ribes1  that  it  begins  as  it  ends,  in  a  ganglion  impar  situated  upon 
the  anterior  communicating  artery,  not  having  been  confirmed  by  other 
anatomists.  It  may  be  mentioned,  however,  in  this  connection,  that 
the  author  in  dissecting  various  genera  of  monkeys,  in  more  than  one 
instance  found  such  a  ganglion,  though  he  has  failed,  like  others,  to 
find  it  in  man.  Intercommunicating  with  the  nerves  of  the  cerebro- 
spinal system,  and  giving  off  during  its  course  numerous  branches  form- 
ing intricate  plexuses,  such  as  the  cardiac,  solar,  and  hypogastric,  the 
sympathetic  nerves,  as  a  general  rule,  follow  the  course  of  the  great 
bloodvessels,  entwining  the  latter  as  the  ivy  the  oak,  to  supply  the 
viscera  of  the  great  cavities  of  the  body,  etc. 

The  nerves  of  the  sympathetic  system  are  usually  much  smaller,  softer, 
and  less  distinctly  seen  than  those  of  the  cerebro-spinal  system,  present 
a  grayish  aspect,  and  adhere  closely,  by  connective  tissue,  to  contiguous 
structures.  While  consisting  of  medullated  nerve  fibres,  they  are  largely 
composed  of  the  pale  gray,  gelatinous  fibres  of  Remak,  the  latter  resem- 
bling embryonic  nerve  fibres  and  the  nerve  fibres  developed  in  the 
reunion  of  nerves.  The  ganglia  of  the  sympathetic,  whether  of  the 
ganglionated  cord  or  its  branches,  do  not  differ  essentially  in  structure 
from  the  ganglia  of  the  posterior  roots  of  the  spinal  nerves,  large  root 
of  the  fifth,  trigeminal,  glossopharyngeal,  pneumogastric,  etc.  They 
consist  of  a  mass  of  nerve  cells  smaller  than  those  of  the  spinal  ganglia, 
imbedded  in  a  stroma  of  connective  tissue,  which  is  traversed  by  nerve 
fibres,  the  whole  being  enclosed  by  a  tightly  adherent  membrane  con- 
tinuous with  the  sheath  of  the  nerves  upon  which  the  ganglia  occur,  the 
latter  looking  like  so  many  grayish-white  or  reddish-gray  swellings  or 
knots.  The  main  ganglia  and  branches  of  the  sympathetic  being  situ- 
ated in  the  cervical,  thoracic,  abdominal,  and  pelvic  regions,  we  may 
begin  in  our  necessarily  brief  account  of  the  physiological  relation  of  the 
parts  involved  with  the  ganglia  of  the  cervical  region,  and  first  with  the 
superior  cervical  ganglion  (Fig.  423). 

1  Mem.  de  la  Soc.  Med.  d'Emnlation,  tome  viii.  p  606 


SYMPATHETIC    NERVE. 
Fig.  423. 

11 


725 


:t 


41 

11 


Ml! 

'•,  fly  .:■' 


Cervical  and  thoracic  portion  of  the  sympathetic.  1,1,  1.  Right  pneumogastric.  2.  Glossopharyngeal. 
3.  Spinal  accessory.  4.  Divided  trunk  of  the  sublingual.  5,5,5.  Chain  of  ganglia  of  the  sympathetic. 
6.  Superior  cervical  ganglion.  7.  Branches  from  this  ganglion  to  the  carotid.  8.  Nerve  of  Jacobson. 
9.  Two  filaments  from  the  facial,  one  to  the  spheno-palatine  and  the  other  to  the  otic  ganglion.  10. 
Motor  oculi  externus.  11.  Ophthalmic  gangli receiving  a  motor  filament  from  the  motor  uculi  com- 
munis and  a  sensory  filament  from  the  nasal  branch  of  the  fifth.  12.  Spheno-palatine  ganglion.  13. 
Otic  ganglion.  14.  Lingual  branch  <>f  the  fifth  nerve.  15.  Submaxillary  ganglion.  16,  17.  Superior 
laryngeal  nerve.  18.  External  laryngeal  nerve.  19,20.  Recurrent  laryngeal  nerve.  21,22,23.  Anterior 
branches  of  the  upper  four  cervical  nerves,  sending  filaments  to  the  superior  cervical   sympathetic  gan- 


726  SYMPATHETIC    NERVOUS    SYSTEM. 

glion.  24.  Anterior  brandies  of  the  fifth  and  sixth  cervical  nerves,  sending  filaments  to  the  middle 
cervical  ganglion.  25,20.  Anterior  branches  of  the  seventh  and  eighth  cervical  and  the  first  dorsal 
nerves,  sending  filaments  to  the  inferior  cervical  ganglion.  27.  Middle  cervical  ganglion.  28.  Cord 
connecting  the  two  ganglia.  29.  Inferior  cervical  ganglion.  30,  31.  Filaments  connecting  this  with  the 
middle  ganglion.  32.  Superior  cardiac  nerve.  33.  Middle  cardiac  nerve.  lit.  Inferior  cardiac  nerve. 
35,35.  Cardiac  plexus.  3(5.  Ganglion  of  the  cardiac  plexus.  37  Nerve  following  the  right  coronary  artery. 
38,  38.  Intercostal  nerves,  with  tlieir  two  filaments  of  communication  with  the  thoracic  ganglia.  30,  40, 
41.  Great  splanchnic  nerve.  42.  Lesser  splanchnic  nerve.  4:5,  43.  Solar  plexus.  44.  Left  pneumogastric. 
45.  Right  pneumogastric.  46.  Lower  end  of  the  phrenic  nerve.  47.  Section  of  the  right  bronchus.  48. 
Arch  of  the  aorta.  49.  Right  auricle.  50.  Right  ventricle.  51,52.  Pulmonary  artery.  53.  Right  half 
of  the  stomach.     54.  Section  of  the  diaphragm.       (Sappey.) 

The  superior  or  first  cervical  ganglion,  lying  upon  the  rectus  major 
muscle  opposite  the  second  and  third  cervical  vertebrae  and  behind  the  in- 
ternal carotid  artery,  is  connected  by  intervening  filaments  with  the  upper 
four  spinal  nerves — the  ganglia  of  the  glossopharyngeal,  pneumogastric, 
and  the  hypoglossal  nerves.  In  addition  to  its  cord  of  communication 
with  the  second  cervical  ganglion,  the  superior  cervical  gives  off' an  ascend- 
ing branch,  vascular  and  pharyngeal  branches,  and  the  superior  cardiac 
nerve.  The  ascending  branch  accompanying  the  internal  carotid  artery 
through  the  carotid  canal  divides  into  two  branches,  which,  subdividing 
and  communicating  with  each  other  around  the  artery,  so  form  the 
carotid  plexus.  From  the  latter  are  given  oft"  filaments  to  the  abducens 
nerve,  and  the  deep  petrosal  which  passes  to  the  spheno-palatine,  or 
Meckel's  ganglion,  the  latter  connected  with  the  spinal  system  by  the 
superior  maxillary  and  great  petrosal  nerve.  Continuing  upward  around 
the  artery,  on  reaching  the  cavernous  sinus,  the  sympathetic  plexus  is 
then  known  as  the  cavernous  plexus,  an  important  one,  since  it  commu- 
nicates with  the  semilunar  ganglion  and  ophthalmic  branch  of  the 
trigeminal  with  the  ophthalmic  ganglion,  the  latter  connected  with  the 
spinal  system  by  the  ophthalmic  and  oculo-motor  nerves,  and  with  the 
oculo-motor  and  pathetic  nerves.  From  the  carotid  and  cavernous 
plexuses  fine  filaments  are  also  given  off  which  entwine  themselves 
around  all  the  branches  of  the  internal  carotid  artery.  The  vascular 
branches  of  the  superior  cervical  ganglion  form  plexuses  upon  the  in- 
ternal carotid  artery  and  its  branches.  By  the  plexuses  on  the  internal, 
maxillary,  and  facial  arteries  the  sympathetic  communicates  with  the  otic 
and  submaxillary  ganglia  respectively,  the  otic  ganglion  being  connected 
with  the  spinal  system  by  the  small  petrosal,  the  submaxillary  ganglia 
by  the  chorda  tympani.  The  pharyngeal  branches,  two  or  three  in 
number,  descending  to  the  side  of  the  pharynx,  together  with  branches 
from  the  glossopharyngeal  and  pneumogastric  nerves,  form  the  pharyn- 
geal plexus,  which,  as  we  have  already  mentioned,  supplies  the  mucous 
membrane  and  constrictor  muscles  of  the  pharynx.  The  superior  cardiac 
nerve,  derived  from  the  first  cervical  ganglion  and  from  the  cord  below 
it,  descends  behind  the  great  bloodvessels  of  the  neck,  and  entering  the 
thorax  passes  on  the  right  side  either  in  front  of  or  behind  the  sub- 
clavian artery,  thence  along  the  innominate  to  the  back  of  the  arch  of 
the  aorta,  to  end  in  the  cardiac  plexus.  On  the  left  side  of  the  nerve 
follows  the  carotid  artery  in  its  course  to  the  cardiac  plexus. 

The  superior  cardiac  nerve  communicates  with  the  pneumogastric, 
and  gives  off  filaments  to  the  inferior  thyroid  artery.  The  middle,  or 
second  cervical  ganglion,  resting  upon  the  inferior  thyroid  artery,  and 


CERVICAL    GANGLIA     AND    CARDIAC    NERVES. 


^27 


situated  opposite  the  fifth  cervical  vertebra,  is  connected  with  the  third 
cervical  ganglion  by  several  branches,  and  gives  off  filaments  to  the 
fifth  and  sixth  spinal  nerves,  branches  which  follow  the  inferior  thyroid 
artery  to  the  thyroid  body,  and  the  middle  cardiac  nerve.  The  latter, 
as  it  descends  the  neck,  receives  filaments  from  the  superior  and  inferior 
cardiac  and  pneumogastric  nerve,  and  ends  in  the  cardiac  plexus. 
Occasionally  the  middle  cervical  ganglion  is  indistinct,  or  even  absent; 
in  such  cases  it  appears  to  be  fused  with  the  inferior  or  third  cervical 
ganglion.  The  latter,  situated  behind  the  vertebral  artery  and  between 
the  transverse  process  of  the  last  cervical  vertebra  and  the  first  rib,  gives 
oft0,  in  addition  to  the  branches  going  to  the  first  thoracic  ganglion, 
branches  to  the  seventh  and  eighth  spinal  nerves,  to  the  vertebral 
artery,  and  the  inferior  cardiac  nerve,  which,  after  receiving  filaments 
from  the  middle  cardiac  and  inferior  laryngeal  nerves,  and  sometimes 
from  the  first  thoracic  ganglion,  terminates  in  the  cardiac  plexus. 
Occasionally  the  inferior  cardiac  nerve  of  the  left  side  becomes  blended 
with  the  middle  cardiac  nerve.  The  three  cardiac  and  pneumogastric 
nerves,  together  with  branches  from  the  first  thoracic  ganglion,  form  the 
cardiac  plexus.  The  latter,  situated  behind  and  beneath  the  arch  of 
the  aorta,  gives  off'  branches  which,  accompanying  the  coronary  arteries, 
constitute  the  coronary  plexuses. 

Fig.  424. 


Solar  JileXUS.       (HlRSCHFELD.) 

While  the  cervical  portion  of  the  sympathetic  consists,  as  we  have 
seen,  of  three  ganglia,  etc.,  the  thoracic  portion  consists  of  usually 
twelve  ganglia,  resting  upon  the  heads  of  the  ribs,  and  covered  by  the 
pleura.  The  first  thoracic  ganglion,  as  already  mentioned,  is  connected 
with  the  last  cervical,  and  the  last  thoracic  with  the  first  lumbar,  the 
connecting  cord  of  the  latter  passing  through  the  diaphragm.  Each 
thoracic  ganglion  usually  gives  oft'  two  narrow  cords,  the  rami  commu- 


728  SYMPATHETIC    NERVOUS    SYSTEM. 

nicantes,  which  pass  to  the  nearest  intercostal  nerve.  The  upper  six 
thoracic  ganglia  give  off,  also,  branches  to  the  aorta,  intercostal  blood- 
vessels, and  the  oesophageal  and  pulmonary  plexuses  of  the  pneumo- 
gastric  nerve.  The  lower  six  thoracic  ganglia  give  off,  in  addition  to 
the  branches  going  to  the  aorta,  branches  which  go  to  form  the  three 
splanchnic  nerves.  The  great  splanchnic  nerve,  deriving  its  roots  from 
the  sixth  to  the  tenth  thoracic  ganglia,  inclusive,  perforates  the  crus 
of  the  diaphragm,  and  terminates  in  the  semilunar  ganglion.  The 
small  splanchnic  nerve,  deriving  its  roots  from  the  tenth  and  eleventh 
thoracic  ganglia,  passes  through  the  diaphragm  with  the  preceding 
nerve,  and  terminates  in  the  solar  plexus.  The  third  splanchnic,  some- 
times absent,  coming  from  the  twelfth  thoracic  ganglion,  pierces  the 
diaphragm,  and  terminates  in  the  renal  plexus. 

The  solar  plexus  (Fig.  424),  so  called  on  account  of  the  numerous 
filaments  radiating  from  it,  is  situated  behind  the  stomach  and  in  front 
of  the  aorta  and  crura  of  the  diaphragm,  and  surrounding  the  coeliac 
and  commencement  of  the  superior  mesenteric  artery,  extends  to  between 
the  suprarenal  bodies.  It  consists  of  an  intricate  mixture  of  nerves 
and  ganglia ;  among  the  former  may  be  mentioned  the  great  and  small 
splanchnics,  as  well  as  filaments  from  the  pneumogastric  nerve  ;  among 
the  latter  the  semilunar  ganglion  (Fig.  425),  so  called  on  account  of  its 
being  situated  on  each  side  of  the  plexus,  at  the  side  of  the  coeliac  and 
superior  mesenteric  arteries.  From  the  solar  plexus  emanate  numerous 
plexuses,  named  after  the  vessels  around  which  the  branches  entwine 
themselves,  as  follows :  the  phrenic,  coronary,  hepatic,  splenic,  supra- 
renal, renal,  and  spermatic,  superior  mesenteric,  and  aortic  plexus.  The 
aortic  plexus,  descending  upon  the  aorta  from  the  solar  plexus,  of  which 
it  is  the  continuation,  after  giving  off  the  inferior  mesenteric  plexus 
terminates  below  in  the  hypogastric  plexus.  The  latter  very  intricate 
plexus,  situated  between  the  common  iliac  bloodvessels,  extends  down- 
ward as  the  inferior  hypogastric  plexuses  on  each  side  of  the  rectum, 
and  after  receiving  branches  from  the  lower  lumbar  and  sacral  ganglia, 
the  lower  two  or  three  sacral  nerves,  and  the  inferior  mesenteric  plexus, 
gives  off  the  vesico-prostatic,  or  the  vesico-vaginal  and  uterine  plexuses, 
according  to  the  sex  respectively. 

The  lumbar  portion  of  the  sympathetic  consists  of  four  or  five  ganglia 
situated  at  the  sides  of  the  vertebrae  which  communicate  with  each 
other,  and  with  the  adjacent  lumbar  nerves,  as  in  the  case  of  the 
thoracic  ganglia,  and  give  off  branches  to  the  aortic  and  hypogastric 
plexus.  The  sacral  ganglia,  usually  four  in  number,  are  connected 
likewise  with  the  spinal  nerves,  and  give  off  branches  to  the  hypogas- 
tric plexus.  As  already  mentioned,  the  single  coccygeal  ganglion  or 
ganglion  impar,  with  connections  similar  to  those  of  the  sacral  ganglia, 
is  common  to  the  two  sympathetic  nerves.  While  considerable  differ- 
ence of  opinion  prevailed  at  one  time  as  to  whether  the  ganglia  of  the 
sympathetic  were  sensitive,  there  is  no  doubt  on  this  point  at  present; 
mechanical  or  chemical  irritation  of  the  thoracic  or  semilunar  ganglia 
in  dogs,  calves,  and  rabbits,  having  been  shown  by  Flourens,1  Brachet,2 

i  Recherches  experimentale  sur  Lea  propri6t6s  et  les  functions  du  systeme  nerveux.  p.  230.  Paris,  1842. 
2  Recherches  experimentale  sur  les  functions  du  systeme  gauglionaire,  p.  305.     Bruxelles,  1834. 


LUMBAR    AND    SACRAL    GANGLIA. 


729 


Muller,1  Longet,2  etc.,   to  give  rise  to  pain.      The   sensibility  of  the 
sympathetic,  however,  is  far  from  acute,  being  indeed,  dull,  as   com- 


Fig.  425. 


20 


Lumbar  ami  sacral  portions  of  the  sympathetic.  1.  Section  of  the  diaphragm.  2.  Lower  end  of  the 
cesophagus.  3.  Left  half  of  the  stomach.  4.  Small  intestine.  5.  Sigmoid  flexure  of  the  colon.  6.  Rec- 
tum. 7.  Bladder.  8.  Prostate.  9.  Lower  end  of  the  left  pneumogastric.  ID.  Lower  end  of  the  right 
pneumogastric.  11.  Solar  plexus.  12.  Lower  end  of  the  great  splanchnic  nerve.  13.  Lower  end  of  the 
lesser  splanchnic  nerve.  14,14.  Last  two  thoracic  ganglia.  15,15.  The  four  lumbar  ganglia.  16,16, 
17,  17  Branches  from  the  lumbar  ganglia.  18.  Superior  mesenteric  plexus.  19,  21,  22,  23.  Aortic  lum- 
bar plexus.  20.  Inferior  mesenteric  plexus  24,24.  Sacral  portion  of  the  sympathetic.  25,25,26,26, 
27,27.  Hypogastric  plexus.  28,29,30  Tenth,  eleventh,  and  twelfth  dorsal  nerves.  31,32,33,34,35, 
36,37,38,39.  Lumbar  and  sacral  nerves      (Sapi 


i  Muller:  Physiology,  vol.  i.  p.  712.     London,  1841 


-  Physiologie,  tome  iii.  p.  593.     Taris,  1869. 


730  SYMPATHETIC    NERVOUS    SYSTEM. 

pared  with  that  of  the  cerebro-spinal  system.  As  regards  the  excita- 
bility of  the  sympathetic,  if  has  also  been  shown  by  Mailer,1  Longet,2 
and  others,  that  stimulation  of  the  ganglia,  splanchnic  nerves,  etc.,  by 
electricity  or  chemical  irritants  causes  contractions  of  the  muscular  coat 
of  the  intestines.  Inasmuch,  however,  as  the  muscular  coat  of  the 
intestine  consists  of  unstriated  muscular  tissue,  the  contraction  does 
not  immediately  follow  the  simulation,  as  in  the  case  of  the  cerebro- 
spinal system  and  striated  muscle,  and  further,  the  contraction  lasts 
longer,  another  characteristic  of  the  effect  of  stimulating  unstriated 
muscular  tissue.  Since,  however,  the  most  important  effects  following 
stimulation  of  the  sympathetic  can  be  obtained,  as  we  shall  see  presently, 
by  the  stimulating  of  the  cerebro-spinal  system,  and  as  the  ganglia 
and  fibres  of  the  sympathetic  lose  their  properties  through  atrophy, 
degeneration,  etc.,  when  separated  from  the  cerebro-spinal  system, 
with  which  we  have  just  seen  they  are  invariably  connected,  as  shown 
by  the  experiments  of  Bernard,3  Courvoisier,4  etc.,  it  would  appear 
that  whatever  properties  are  possessed  by  the  sympathetic  are  due  to 
its  connections  with  the  cerebro-spinal  system.  That  the  sympathetic 
system,  in  fact,  is  only  an  appendage  of  the  cerebro-spinal  system,  is 
not  only  shown  by  the  facts  just  referred  to,  but  also  by  the  very  im- 
portant one  in  this  connection  that  in  the  lowest  fishes,  amphioxus, 
myxine,  the  sympathetic  system  is  undeveloped  or  absent,  which  would 
not  be  the  case  were  its  presence  an  indispensable  element  in  the  nervous 
organization  of  a  vertebrate.  Up  to  the  beginning  of  the  eighteenth 
century  it  may  be  said  that  absolutely  nothing  had  been  definitely 
established  with  regard  to  the  functions  of  the  sympathetic  system.  In 
1712,  however,  Pourfour  du  Petit5  divided  the  cervical  sympathetic  in 
a  dog,  repeating  the  experiment  in  1725,  in  the  presence  of  Winslow 
and  Senac,  and  called  attention  among  its  consequences  to  the  redness 
and  injected  condition  of  the  conjunctiva,  the  contracted  condition  of 
the  pupil,6  etc.  The  conclusion  drawn  by  Petit  from  his  experiments 
and  observations  was  that  the  intercostal  nerve,  as  the  sympathetic  was 
then  called,  "furnished  spirits  to  the  conjunctiva,  to  the  glands,  and  to 
the  vessels  which  are  found  in  these  parts,  the  relaxation  of  the  parts 
being  so  evident  that  there  almost  always  ensues  a  slight  inflammation  of 
the  conjunctiva  due  to  the  swelling  of  the  vessels;"  that  the  influence 
exerted  by  the  sympathetic  was  propagated  from  below  upward  toward 
the  brain,  and  not  from  the  brain  downward,  as  was  often  supposed. 
Notwithstanding  the  importance  of  the  conclusions  correctly  drawn 
from  his  experiments  by  Petit  with  reference  to  the  influence  of  the 
sympathetic  upon  the  circulation,  nutrition  of  the  eye,  etc.,  nearly  a 
century  passed  without  anything  further  being  added  to  our  knowledge 
of  the  functions  of  the  sympathetic.  In  1812,  however,  Dupuy,  of 
Alfort,  having  removed  the  superior  cervical  ganglion  in  horses,  called 
attention  among  the  effects  of  the  experiment,  particularly  to  the  in- 

1  Op.  cit.,  p.  713,  -  Op.  tit.,  p.  595.  Systeme  Nerveux,  tome  ii.  p.  568.     Paris,  1842. 

3  Journal  de  la  physiologie,  tome  v  p.  407.     Paris,  1862. 
«  Archiv  of  Micros.  Anat.,  Band  ii.  S.  30.     Bonn,  18X6. 
6  Memoires  de  l'Arad.  des  Sciences,  p.  1.     Paris,  1727. 

6  Due  to  the  unopposed  action  of  the  third  pair  of  nerves  supplying  the  circular  muscular  fibres  of 
the  iris. 


EFFECTS    OF    DIVISION    OF    CERVICAL    SYMPATHETIC.    731 

jected  condition  of  the  occular  conjunctiva,  and  to  the  elevation  of 
temperature  in  the  ears,  head,  and  neck,  which  were  bathed  in  sweat; 
the  general  conclusion  arrived  at  by  Dupuy1  being  that  the  sympa- 
thetic exercises  a  great  influence  on  the  nutritive  functions.  While 
Petit  described  the  effects  of  cutting  the  cervical  sympathetic,  and 
Dupuy  of  removing  the  superior  cervical  ganglion  neither  of  these  ex- 
perimenters offered  any  definite  explanation  of  the  hyperemia  noted 
in  both  cases,  nor  Dupuy  of  the  rise  in  temperature  in  the  latter  one. 
Indeed,  the  true  explanation  of  the  phenomena  at  that  period  would 
have  been  impossible,  the  structure  of  the  arteries  not  yet  being  under- 
stood. 

Even  though  Valentin2  had  shown,  in  1839,  that  the  arteries  con- 
tracted in  response  to  stimulation  of  the  nerves  distributed  to  them,  it 
was  not  admitted  that  the  middle  coat  of  the  arteries  contained  mus- 
cular fibres  until  1840,  when  such  was  actually  demonstrated  to  be  the 
case  beyond  doubt  by  Henle.3  During  the  same  year,  Stirling,4  like 
Henle,  was  led  to  the  conclusion  that  there  existed  nerves  comparable 
to  those  distributed  to  the  muscles  generally,  which  act  upon  the  blood- 
vessels, either  directly  or  reflexly,  and  which  he  called  "  vasomotor 
nerves."  In  1852  Brown-Sequard5  divided  the  cervical  sympathetic 
on  one  side  in  rabbits,  and  called  attention,  as  Bernard6  had  done  in  the 
previous  year,  to  the  hypericin  ia  and  elevation  of  temperature,  often 
amounting  to  as  much  as  11°  F.  on  the  corresponding  side  of  the  head 
and  ear,  and  for  the  first  time  gave  the  true  explanation  of  the  phe- 
nomena in  attributing  the  rise  in  temperature  of  the  parts  affected  to 
the  supply  of  blood  being  increased  through  the  dilatation  of  the  blood- 
vessels, and  by  showing  that  while  section  of  the  sympathetic  in  para- 
lyzing the  muscular  coats  of  the  arteries  permits  of  their  dilatation,  elec- 
trieal  stimulation  of  the  central  cut  end  of  the  sympathetic  causes  their 
contraction  again,  and  with  the  latter  the  restoration  of  the  parts  to 
their  normal  condition.  To  Brown-Sequard  must  be  accorded,  there- 
fore, the  discovery,  not  exactly  of  vaso-motor  nerves,  since  the  existence 
of  such  had  been  previously  indicated  by  Henle  and  Stirling,  but  of 
the  vasomotor,  or,  more  especially,  of  the  vaso-constrictor  nerves  of  the 
cervical  sympathetic,  and  of  their  mode  of  action  in  influencing  the 
temperature,  etc.,  of  the  parts  to  which  the  latter  are  distributed.  It 
should  be  mentioned,  however,  injustice  to  Bernard,  that  three  months 
after  Brown-Sequavd's  discovery,  and  without  being  aware  of  it,  Ber- 
nard7 offered  the  same  explanation  of  the  experiments  performed  by 
him  during  the  previous  year  (1851),  but  at  that  time  by  him  incor- 
rectly interpreted.  The  vaso-motor,  or  vaso-constrictor  nerves,  as  we 
shall  hereafter  call  them,  since,  through  their  constringing  effect  upon 
the  muscular  coat  of  the  bloodvessels,  the  normal  calibre  of  the  latter 
are  maintained,  and  the  tissues  supplied  with  the  proper  amount  of 
blood,  are  found,  not  only  in  the  cervical,  but  also  in  the  thoracic  and 

1  Journal  de  Oonvisart  et  Leroux,  1816,  tome  xxxvii.  p.  340.     Medhel's  Archiv,  1818,  Band  iv.  S.  105. 
-  De  B,nucti"nJbu8  Nervorum  Cerebral  in  m  et  Nervi  Sympathetici,  (>.  153.     Bernae,  1839. 

3  Wofhenachrift  fur  die  gesamnite  Heilkunde,  1  4n,  No   29,  S.  329. 

4  Recberches  path,  et  med    pratiques  sur  ['irritation.     Leipzig,  1>40. 

5  The  Medical  Examiner,  New  Series,  vol.  viii    p.  189      Philadelphia,  August,  1852. 
c  Comptes  reudue  de  la  SOCie'te'  de  biologie,  tome  iii.  p.  103.     Paris,  1851. 

Ibid.,  1862,  tome  iv.  p.  ion. 


732  SYMPATHETIC    NERVOUS    SYSTEM. 

abdominal  portions  of  the  sympathetic  and  in  the  brachial  and  sciatic 
plexuses,  supplying  the  upper  and  lower  extremities.  While  the  vaso- 
constrictor  nerves  are  apparently  given  off  as  fibres  from  the  sympa- 
thetic ganglia,  in  reality  they  are  derived,  as  shown  by  recent  investiga- 
tion,1 from  the  spinal  cord,  since  division  or  stimulation  of  the  latter,  or 
of  certain  spinal  nerves  in  certain  definite  regions,  is  followed  by  dilata- 
tions or  contractions  of  the  bloodvessels,  just  as  if  the  vaso-constrictor 
nerves  had  themselves  been  divided  or  stimulated.  Thus,  for  example, 
while  the  vaso-constrictor  nerves  of  the  head  are  apparently  derived  from- 
the  superior  cervical  ganglion,  they  can  be  traced  by  their  division  and 
electrical  stimulation  through  the  cervical  cord  of  the  sympathetic  to 
the  anterior  roots  of  the  first  three  dorsal  spinal  nerves,  and  thence  into 
the  anterior  columns  of  the  cord.  Further,  according  to  Bernard,2 
whilst  the  fibres  distributed  to  the  dilating  muscular  fibres  of  the  iris, 
thereby  causing  dilatation  of  the  pupil,  are  derived  from  the  first  two 
dorsal  nerves  (cilio-spinal  centre),  those  distributed  and  influencing  the 
calibre  of  the  bloodvessels  are  derived  from  the  third  dorsal  nerve. 
In  the  same  manner,  the  vaso-constrictor  nerves  supplying  the  blood- 
vessels of  the  upper  extremity,  while  apparently  emanating  from  the 
first  thoracic  ganglion,  are,  in  reality,  derived  from  the  spinal  cord, 
passing  off  from  the  latter  with  the  anterior  roots  of  the  third  to  the 
seventh  dorsal  nerves  inclusive,  and  thence  traversing  the  thoracic  por- 
tion of  the  sympathetic  and  the  inferior  thoracic  ganglion,  reach  the 
brachial  plexus  by  the  rami  communicantes,  to  be  finally  distributed 
with  the  branches  of  the  plexus,  while  such  of  the  vaso-constrictor 
nerves  as  are  derived  from  the  plexus  itself  are  given  off  with  the  ante- 
rior roots  of  the  cervical  nerves.  The  vaso-constrictor  nerves  supplying 
the  bloodvessels  of  the  abdominal  viscera,  more  especially  the  splanchnic 
nerves,  are  largely  derived  from  the  dorsal  and  lumbar  portion  of  the 
cord  ;  the  latter,  together  with  the  sacral  portion  of  the  cord,  giving  off 
fibres  which  pass  through  the  lumbar  and  sacral  plexuses  to  the  sym- 
pathetic, and  thence  into  the  lower  extremities,  supplying  the  blood- 
vessels of  the  latter.  Inasmuch,  then,  as  the  vaso-constrictor  nerves 
are  derived  from  the  spinal  cord,  traversing  more  particularly  its  ante- 
rior columns,  it  might  naturally  be  supposed  that  all  these  nerve  fibres 
at  some  point  of  the  cord,  the  upper  portion  most  probably,  would  be 
brought  to  a  focus,  so  to  speak,  and  that  stimulation  of  such  a  portion 
of  the  cord  would  cause  all  of  the  bloodvessels  to  contract,  and  a  corre- 
sponding rise  in  blood  pressure  and  division  of  the  same,  a  dilatation  of 
the  vessels  and  fall  in  blood  pressure. 

Such  a  focus  or  vaso-motor  centre  has  indeed  been  found  in  animals, 
not  exactly  by  anatomical  demonstration,  but  by  means  of  successive 
sections  of  the  cord  below  upAvard,  and  from  above  downward,  and 
localized  in  the  rabbit,  for  example,  by  Owsjanikow3  in  the  floor  of  the 
fourth  ventricle  on  either  side  of  the  middle  line  just  one  millimetre 
behind  the  optic  lobes,  and  between  four  and  five  millimetres  in  front  of 

1  Badge  and  Waller :  Oomptes  Rendus,  tome  xxxiii.  p  372.  Paris,  1851.  Ludwig  and  Thiry  :  Wiener 
Sitznngsberichte,  1861,  Band  xlix.  II.  Abtheilung,  S.  421,  Vulpian  :  Let;ons  sur  l'Appareil  vaso  moteur, 
p.  180.     Paris,  1875. 

2  Comptes  Rendus,  tome  iv.  p.  383.  3  Ludvvig's  Arbeiten,  1871,  S.  210. 


VASO-DILATOR    NERVES.  733 

the  nib  of  the  calamus  scriptorius.  From  this  centre  emanate  impulses, 
which  transmitted  through  the  anterior  columns  of  the  cord  and  anterior 
roots  of  the  spinal  nerves  pass  thence  to  the  sympathetic  ganglia  and 
vaso-constrictor  nerves,  and  through  the  latter  maintain  the  normal 
calibre  of  the  vessels  or  the  vascular  tonus.  Inasmuch  as  the  muscular 
fibres  of  the  middle  coat  of  the  bloodvessels  is  disposed  in  a  circular 
manner  at  right  angles  to  the  long  axis  of  the  vessel,  it  is  not  difficult  to 
understand  why  stimulation  of  the  vaso-constrictor  nerves  is  followed  by 
contraction  of  the  vessels — indeed,  the  disposition  of  the  nervous  and 
muscular  fibres  being  such,  it  can  hardly  be  conceived  how  it  should  be 
otherwise,  and  yet,  strange  as  it  may  appear,  as  first  shown  by 
Bernard1,  there  are  also  nerves  the  stimulation  of  which  causes  dilatation 
of  the  bloodvessels  instead  of  contraction,  and  which  may  therefore  be 
called  vaso-dilator  nerves  ;  among  such  may  be  mentioned  the  chorda- 
tympani,  the  auriculo-temporal,  the  nervi-erigentes  of  the  penis;  stimula- 
tion of  these  nerves  causing  dilatation  of  the  vessels  of  the  tongue,2  of  the 
ear,  and  of  the  corpora  cavernosa  of  the  penis,3  respectively.  Though 
numerous  explanations  have  been  offered  of  the  manner  in  which  the 
vaso-dilator  nerves  act,  it  must  be  admitted  that  none  of  them  are  satis- 
factory, and  that  it  is  not  yet  understood  how  their  stimulation  causes 
dilatation  of  the  bloodvessels.  Thus,  it  has  been  said  that  the  stimulation 
of  a  vaso-dilator  nerve  causes  the  vein  of  the  part  to  contract,  and  that 
in  consequence  an  obstacle  is  offered  to  the  passage  of  the  blood  from 
the  artery  to  the  capillary,  which  is  the  cause  of  the  dilatation  of  the 
artery.  As  a  matter  of  fact,  however,  the  vein  does  not  contract,  but 
dilates  as  much  as  the  artery.  It  has  also  been  suggested  that  the 
stimulation  of  a  vaso-dilator  nerve  excites  the  activity  of  the  anatomical 
elements  of  the  part  to  which  the  nerve  is  distributed,  the  effect  of 
which  in  the  case  of  a  salivary  gland,  for  example,  would  be  that  its 
secretory  activity  being  increased  more  blood  would  flow  to  the  part, 
and  the  vessels  would  dilate.  Unfortunately,  however,  for  this  hypothe- 
sis, in  the  absence  of  all  secretion,  as  in  the  case  of  an  animal  poisoned 
with  atropine,  the  vessels  of  the  tongue  will  still  dilate  if  the  chorda 
ivmpani  be  stimulated.  Another  explanation,  a  too  common  one  when 
physiological  phenomena  remain  unexplained,  is  that  of  inhibition,  it 
being  held  that  vaso-dilator  nerves  inhibit  or  paralyze  the  vaso-constrictor 
nerves.  Apart,  however,  from  the  fact  that  the  dilatation  of  an  artery 
following  stimulation  of  a  vaso-dilator  nerve  is  greater  than  that  follow- 
ing paralysis  of  the  vaso-constrictor  nerve,  to  say  that  the  one  nerve 
inhibits  the  other  is  rather  another  way  of  stating  the  fact  to  be  ex- 
plained than  an  explanation  of  it.  Whatever  value  may  be  attached  to 
the  explanations  offered,  whether  they  be  accepted  or  not,  nevertheless, 
there  can  be  no  question  as  to  the  fact  of  their  being  vaso-dilator  as  well 
as  vaso-constrictor  nerves,  and  that  in  all  probability  they  emanate  from 
a  focus  or  centre  close  to  the  vaso-motor  or  constrictor  one,  already 
described,  if  not  actually   in  the  latter.       The  vaso-constrictor  or  vaso- 

1  Systeme  Nerveux,  tome  ii.  p.  144.     Pari?,  185S.     Liquides  tie  l'Organisme,  tome  i.  p.  312. 
-   \  r  Ipian,  op  cit.,  p.  158. 

3  Eckpard  :  Untersuchungen  uber  die  Erection  dea  Penis  beim  Hunde.  Beitrage  zurAu.it.  u.  Pbys. 
Abband.  vii.     Giesseu,  1S6'2. 


734  SYMPATHETIC    NERVOUS    SYSTEM. 

dilator  nerves   c;m  be  excited   reflexly  as  well   as   directly.       Thus,  as 
firsl  shown  by  Brown- Sequard1  and  Tholozan,  if  a  thermometer  be  held 

ii e  hand  and  the  other  hand  surrounded  by  ice  or  very  cold   water, 

in  a  very  short  time  the  temperature  of  the  hand  holding  the  thermome- 
ter will  fall,  the  general  temperature  of  the  body,  however,  remaining 
unaffected,  an  effect  which  can  only  be  explained  on  the  supposition  that 
the  impression  due  to  the  cold  is  transmitted  by  the  sensory  nerves  to 
(he  spinal  cord  and  thence  reflected  by  the  vaso-constrictor  nerves  to 
the  vessels  of  the  hand  holding  the  thermometer.  For  the  same  reason, 
according  to  Brown-Sequard,2  if  one  foot  be  immersed  in  water  ataboul 
41°  F.,  the  temperature  of  the  other  foot  will  fail  in  a  few  minutes  per- 
haps 7°  F.  It  has  also  been  shown  by  Vulpian3  that  if  the  sciatic  nerve 
be  divided,  as  in  a  dog,  for  example,  and  the  central  end  stimulated,  not 
only  the  vessels  of  the  limb  contract,  but  also  almost  all  the  vessels  of 
the  body,  the  under  surface  of  the  tongue  even  becoming  pale  through 
constriction  of  its  vessels.  The  same  reflex  effect  can  also  be  induced 
by  stimulation  of  almost  any  of  the  sensory  nerves,  of  the  posterior 
roots  of  the  spinal  nerves,  and  even  by  irritation  of  the  skin.  As  illus- 
trations of  reflex  vaso-dilator  action  may  be  mentioned,  the  dilatation  of 
the  internal  saphenous  artery  following  stimulation  of  the  central  cut 
end  of  the  dorsal  nerve  of  the  foot,  and  the  dilatation  of  the  vessels  of  the 
ear,  brought  about  through  excitation  of  the  central  end  of  the  auriculo- 
temporal nerve,  or  through  stimulation  of  the  central  end  of  the  sciatic 
nerve. 

While  the  functions  that  we  have  attributed  to  the  sympathetic  nerve 
are  those  possessed  by  that  of  animals,  there  is  no  doubt  that  the 
functions  of  the  sympathetic  in  man  are  essentially  the  same.  The 
blush  and  pallor  due  to  emotion  are  familiar  examples  of  reflex  vaso- 
motor actions  in  man.  A  number  of  cases  have  been  now  recorded 
by  J.  W.  Ogle,4  Panas,5  Verneuil,6  Trelat,7  Poiteau,8  W.  Ogle,9 
Bartholow,10  Seeligrauller,11  Nicati,12  Eulenberg,13  in  which  rise  of 
temperature,  unilateral  sweating  of  the  neck  and  head,  hyperemia  of 
the  conjunctiva,  contraction  of  the  pupil,  were  all  observed  more  or  less 
in  consequence  of  paralysis  of  the  sympathetic  due  to  pressure  exerted 
by  aneurisms,  tumors,  etc.,  while,  according  to  Vulpian,14  lesions  of  the 
spinal  cord  may  be  localized  from  the  vascular  dilatation  developed  in 
the  upper  extremities  as  a  consequence  of  the  injury  to  the  vasomotor 
nerves  arising  from  it.  It  may  be  also  mentioned  in  this  connection 
that  before  most  of  these  observations  had  been  made,  Wagner15  had 
noticed  that,  in  the  case  of  a  decapitated  woman,  powerful  galvanization 
of  the  sympathetic  caused  dilatation  of  the  pupil.  While  the  scope  of 
this  work  does  not  permit  of  a  detailed  account  of  the  influence  exerted 

1  Journal  de  Brown-Sequard,  1858,  tome  i.  p.  497.  2  Ibid.,  p.  502. 

3  Op.  cit.,  p.  237.  4  Med.-Chir.  Trans.,  vol.  xli.  p.  397. 

5  Mem.  de  laSoc.  de  Chirurgie,  1864,  t.  vi.  p.  383. 

6  Bui.  de  la  Soc   de  Chirnrgie,  1864,  2d  serie,  t.  v.  p.  167 

•  Gaz.  des  hopitaux,  Paris,  2  Juin,  1868  8  These  de  Paris,  1869,  No.  2. 

9  Med.-Chir.  Trans.,  vol.  Hi.  p.  150.     London,  1869. 
i°  Quarterly  Journal  of  Psych.  Medicine,  vol.  iii.  p.  134.     New  York,  1869. 

11  Berlin   klin.  Wochenschrit't,  1872.     No.  2. 

12  La  paralysie  du  nerf  sympathetique.     Lausanne,  1873. 

«  Berlin,  klin.  Woehenschtift,  1869,  S.  287.  14  Op.  cit.,  p.  195. 

15  Journal  de  physiologie,  tome  iii.  p.  175.     Paris,  1860. 


ONCOMETER. 


735 


by  the  sympathetic  nervous  system  upon  nutrition,  it  will  have  been 
seen,  no  doubt,  from  what  has  been  already  said,  that  its  influence  must 
be  very  great,  since  the  amount  of  blood  distributed  to  the  stomach, 
intestine,  liver,  kidney,  etc.,  is  regulated  by  the  vasomotor  nerves.  The 
reflex  flow  of  the  alimentary  secretions  in  response  to  the  excitement 
developed  through  the  presence  of  food,  their  natural  stimulus,  the 
great  vascularity  of  the  liver,  spleen,  pancreas,  during  digestion,  is 
brought  about  through  the  influence  of  the  sympathetic  nerves  distrib- 
uted to  these  organs.  The  rapidity  and  extent  with  which  the  absorp- 
tion of  the  digested  food  takes  place  depends  largely  upon  the  condition 
of  the  portal  circulation,  as  influenced  by  the  vaso-motor  nerves,  and 
more  particularly  by  the  splanchnic.  The  circulation  of  the  blood,  as 
we  have  already  seen,  is  modified  by  the  combined  effects  of  the  depressor 
and  vasomotor  nerves.  It  is  also  through  the  intermediate  action  of 
the  latter  that  the  cerebro-spinal  centres,  more  especially  those  of  the 
medulla,  as  shown  by  Bernard1  and  Vulpian,2  influence  the  biliary  and 
glycogenic  functions  of  the  liver  and  the  secretion  of  urine  by  the 
kidneys.  That  the  amount  of  blood  circulating  through  the  latter,  and 
therefore  the  amount  of  urine  secreted,  is  influenced  by  the  vaso-motor 
nerves,  can  be  readily  demonstrated  by  means  of  the  oncometer  and 
oncograph,  by  which  the  volume  of  the  kidney  in  the  living  animal  can 
be  shown  to  vary  with  the  blood  circulating  through  it,  the  amount  of 
the  latter  being  regulated  by  the  vasomotor  nerves. 

The  oncometer  (Fig.  426)  is  a  metallic  capsule,  shaped  like  a 
kidney,  composed  of  two  halves  moving  on  a  hinge  (/*),  by  which  the 
kidney  is  introduced,  the  renal  vessels  (a,  v,  u)  passing  out  by  the  oppo- 


Fig.  42"; 


Oncometer,  K.  Kidney  ;  the  thick  line  is 
the  metallic  capsule.  /(.Hinge.  I.  Tube  for 
filling  apparatus.  T.  Tube  to  connect  with 
T,.  a,  v,  u.  Artery,  vein,  ureter.  (Stirling, 
after  Roy.) 


Oncograph.  C  Chamber  filled  with  oil,  communi- 
cating by  T,  with  T.  p.  Pioton.  /.  Writing  lever 
(Stirling,  alter  Roy.) 


site  opening,  The  kidney  (K)  is  sur- 
rounded with  a  thin  membrane,  and 
the  space  (o)  between  the  latter  and 
the  inner  surface  of  the  capsule  filled  with  warm  oil  introduced  through 
the  tube  I,  which  can  be  closed  with  a  stopcock.  The  tube  T  being 
adapted  to  the  tube  T,  leading  into  the  metallic  chamber  C  of  the 
oncograph  (Fig.  427),  also  filled  with  oil,  any  increase  in   the  volume 


Systeme  Nerveux,  tome  i.  pp.  398-163.     Physiolugie  Experimental,  tome  i.  p.  345. 
-  Op.  cit.,  tome  i.  pp.  541,  556. 


736  SYMPATHETIC     NERVOUS    SYSTEM. 

of  the  kidney  will  force  the  oil  from  the  space  o  into  the  chamber  C, 
and  the  piston  p  will  be  elevated,  and  with  it  the  recording  pen.  On 
the  other  hand,  any  diminution  in  the  volume  of  the  kidney  through 
stimulation  of  the  vaso-constrictor  nerves  will  cause  the  oil  to  flow  from 
C  into  o  and  the  piston,  and  with  it  the  recording  pen,  will  fall.      By 

Fig.  428. 

AMAAMWV/UWV 


adapting  the  pen  to  the  cylinder  Ave  can  get  a  trace  of  the  so-called 
kidney  curve  (Fig.  428). 

We  have  already  seen  that  through  the  contractions  and  dilatations  of 
the  cutaneous  bloodvessels  the  blood  either  remains  in  the  deeper  por- 
tions of  the  skin,  or  comes  to  the  surface  of  the  body,  the  heat  produced 
in  the  body,  in  the  one  case  being  retained  within  it,  and,  in  the  other 
lost  by  either  radiation,  conduction,  etc.,  and  that  the  application  of 
cold  to  the  general  surface  so  constringes  the  cutaneous  bloodvessels 
that  the  blood  does  not  rise  to  the  surface,  the  heat  thereby  being 
retained,  which  would  otherwise  be  lost.  That  this  effect  is  due  to 
the  impression  made  by  the  cold  being  transmitted  by  the  sensory 
nerves  to  the  spinal  cord,  and  thence  reflected  by  the  vaso-constrictor 
nerves  to  the  cutaneous  bloodvessels,  is  shown  by  the  fact  of  a  curarized 
hot-blooded  animal  losing  this  compensating  power,  through  which  the 
heat  of  the  body  is  normally  retained,  even  though  the  latter  be  exposed 
to  cold,  the  temperature  of  the  curarized  animal  not  being  a  constant 
one,  but,  like  that  of  the  cold-blooded  one,  varying  within  narrow  limits 
with  the  temperature  of  its  surroundings. 


CHAPTER    XLYI 


THE  SKIN  AND  ITS  APPENDAGES.     PERSPIRATION. 
AND  TACTILE  SENSIBILITY. 


(rEXERAL 


The  Skin. 


Fig.  429. 


The  skin  or  integument  constitutes  a  general  protective  and  sensory 
covering  for  the  surface  of  the  body.  In  addition  to  these  important 
functions,  however,  in  eliminating  the  sweat,  carbonic  acid,  urea,  etc., 
the  skin  acts  also  as  an  excretory  organ, 
supplementing,  in  this  respect,  the  action 
of  the  lungs  and  kidneys.  As  we  have 
already  seen,  the  skin,  too,  in  a  great 
measure  regulates  the  production  and  dis- 
tribution of  heat.  To  a  certain  extent, 
also,  the  skin  acts  as  an  absorbing  surface. 
Further,  through  special  modifications  of 
its  sensory  structure,  the  skin  is  endowed 
with  tactile  sensibility,  and  thereby  minis- 
ters to  the  sense  of  touch.  The  skin  in 
addition,  then,  to  being  sensory  and  pro- 
tective, possesses,  as  well,  excretory,  calor- 
ific, absorbing,  and  tactile  functions.  The 
general  appearance  of  the  skin,  its  exten- 
sibility, flexibility,  elasticity,  and  color  are 
sufficiently  familiar  to  all.  It  may  be 
mentioned  in  this  connection,  however, 
that  the  color  of  the  skin  in  the  different 
races  of  mankind,  and  the  varieties  of 
complexion  observed  in  different  indi- 
viduals of  the  same  race,  are  due  to  the 
amount  of  pigmentary  matter  present  in 
the  deeper  layers  of  the  epidermis,  and 
that  the  color  of  the  true  skin,  or  dermis,  is 

whitish  and  semi-transparent,  its  apparent  of  eurous  tissue.  2.  Epidermis.  3.  its 
pinkish  color  being  due  rather  to  that  of  cuticle.  .  its  soft  layer.  5.  subcu- 
underlying  parts  and  the  blood  circulating 
through  the  latter.  The  furrows  and  folds 
of  the  skin  are  caused  partly  by  the 
muscles  and  joints  and  partly  by  loss  of 
elasticity  in  the  skin  itself,  and  by  the 
deposition  in  it  of  fat.  Faint,  irregular  lines  are  also  observed  on  most 
parts  of  the  surface  of  the  skin,  upon  the  palms  of  the  hand  and 
soles  of  the  feet,  and  particularly  upon  the  palmar  surface  of  the  last 

"  47 


Vertical  section  of  the  skin  of  the  fore- 
finger across  two  of  the  ridges  of  the 
surface,  highly  magnified.  1.  Dermis 
composed  of  an  intertexture  of  bundles 


taneous  connective  and  adipose  tissue. 
G.  Tactile  papillae  7.  Sweat  glands.  K. 
Duct.  9.  Spiral  passage  from  the  latter 
through  the  epidermis.  10.  Termina- 
tion of  the  passage  on  the  summit  of 
ridge.     (Lf.idy.) 


738  SKIN     AND    APPENDAGES. 

phalanges;  these  lines  are  well  marked  in  the  latter  situation,  being 
disposed  as  concentric  curves  depending  upon  the  regular  arrangement 
of  the  underlying  papillae  of  the  true  skin  or  dermis.  According  to 
Sappey,1  the  cutaneous  surface,  on  the  average  in  man,  is  equal  to  about 
ten  square  feet,  in  woman  from  six  to  eight,  though  in  men  above  the 
ordinary  size  it  may  amounl  in  extent  to  from  twelve  to  even  eighteen 
square  feet.  '  The  significance  of  such  variations  physiologically  will 
become  apparent  presently  when  we  consider  the  excretory  functions  of 
the  skin. 

In  harmony  with  the  protective  functions  of  the  skin,  its  thickness 
varies  very  much  in  different  parts.  Thus,  where  naturally  exposed  to 
constant  pressure  and  friction,  as  on  the  soles  of  the  feet  or  the  palms 
of  the  hands,  the  skin,  as  we  shall  see,  is  much  thicker  than  that  of  the 
face,  eyelids,  etc. 

The  skin  consists  of  two  layers,  the  dermis  and  epidermis,  special 
modifications  of  the  latter  constituting  the  hair  and  nails,  the  sebaceous, 
mammary,  and  sweat  glands.  The  dermis  or  true  skin,  also  known  as 
the  cutis  vera,  corium,  etc.  (Fig.  429),  constituting  the  deeper  layer  of 
the  skin,  is  more  or  less  closely  connected  to  the  underlying  parts  by 
the  connective  tissue  of  the  adipose  layer  of  the  superficial  fascia,  or 
when  the  adipose  layer  is  absent,  by  the  loose  connective  tissue  to  the 
deeper  layer  of  the  fascia  or  subjacent  structure,  thereby  allowing  the 
skin  a  certain  amount  of  movement  backward  and  forward.  The  thick- 
ness of  the  adipose  layer  varies  very  much  in  different  individuals  and 
in  different  parts  of  the  same  individual.  Thus  while  there  is  no  fat 
beneath  the  skin  of  the  eyelids,  the  upper  and  outer  part  of  the  ear, 
the  penis,  and  the  scrotum,  a  layer  about  the  twelfth  of  an  inch  in  thick- 
ness is  usually  present  beneath  the  skin  of  the  cranium,  the  nose,  the 
neck,  the  knee  and  elbow,  and  the  dorsum  of  the  hand  and  foot;  the 
adipose  layer,  on  an  average,  in  other  situations,  measuring  from  a 
sixth  to  one-half  an  inch.  In  fat  persons,  however,  it  may  attain  a 
thickness  of  one  inch  or  even  more.  There  is  no  well-defined  line  of 
demarcation  between  the  dermis  and  the  underlying  adipose  tissue, 
and  after  separating  the  two  the  dermis  looks  like  a  coarsely  corded 
network,  the  meshes  being  occupied  by  small  round  masses  of  adipose 
tissue.  The  dermis  consists  principally  of  a  dense  intertexture  of 
bundles  of  fibrous  tissue  crossing  one  another  at  acute  angles  in  different 
directions,  mingled  with  amorphous  matter  and  some  elastic  tissue,  the 
latter  being  most  abundant  on  the  front  of  the  body  and  around  the 
joints.  It  contains  also  unstriated  muscular  fibres  which,  passing  down- 
ward from  the  more  superficial  part  of  the  dermis  are  inserted  into  the 
hair  follicles,  and  which,  when  excited  to  contract  through  the  stimulus 
of  cold,  emotions  of  fear,  or  electricity,  elevate  the  hairs  and  so  give  rise 
to  the  condition  known  as  "goose  flesh."  In  consequence  of  the  gradual 
transition  of  the  dermis  into  the  subjacent  tissues,  its  exact  thickness  is 
difficult  to  estimate.  It  may  be  said,  however,  to  be  about  y^d  of  an 
inch  thick  on  the  eyelids,  from  the  -^g-th  to  -^th  of  an  inch  on  the  front 
of  the  body,  and  from  the  -gVth  to  tue  ¥*n  °*  an  *ncn  on  tne  Dac^  °^ tne 

1  Anatomic,  tome  ii.  p.  447.     Paris,  1852. 


DERMIS,    OR    TRUE    SKIN.  739 

body  and  the  heels,  being  thickest  where  the  entire  skin  presents  that 
condition. 

The  dermis  is  thinner  in  the  female  than  in  the  male,  about  half  as 
thick  in  children  as  in  adults,  and  becomes  thinner  in  old  age.  At  its 
outer  surface  the  dermis  is  quite  dense,  being  denned  by  a  more  homo- 
geneous layer  or  basement  membrane,  and  projects  here  and  there  as 
small  eminences,  the  papilla,  into  the  deeper  layers  of  the  dermis. 
The  papillae  on  which  the  perfection  of  the  skin  as  an  organ  of  touch 
largely  depends,  they  being  highly  developed  where  the  sense  of  touch 
is  exquisite,  and  vice  versa,  are  of  two  kinds,  simple  and  compound, 
the  latter  consisting  of  two,  three,  or  more  simple  papillae  springing 
from  a  common  base.  The  papillae  composed  of  a  continuation  of  the 
fibrous  and  amorphous  structure  of  the  dermis  and  defined  by  the 
basement  membrane  of  the  latter  vary  in  number  and  size  in  different 
parts  of  the  body.  They  are  most  numerous  and  longest  in  the  palms  of 
the  hands  and  soles  of  the  feet,  attaining  in  these  situations  a  length  of 
the  -gl-jyth  to  the  yyo-th  of  an  inch,  and  being  here  disposed  in  double 
rows  on  the  ridges  of  the  dermis,  of  which  they  are  the  continuation, 
and  give  rise,  as  already  mentioned,  to  the  curved  lines  so  noticeable 
on  the  palmar  surfaces  of  the  skin  of  the  last  phalanges  of  the  fingers 
and  toes.  The  papilla  are  also  quite  numerous  on  the  prepuce,  glans 
penis,  nymphse,  clitoris,  and  nipple.  In  other  portions  of  the  body 
they  are  less  numerous  and  small,  measuring  only  from  the  ^-Q-th  to 
the  -g-^-jj-th  of  an -inch.  In  the  face,  for  example,  the  papilla  are  so 
little  developed  as  to  be  hardly  recognizable.  Most  of  the  papilla  of  the 
palms,  fingers,  soles,  toes,  and  nipples,  especially  the  compound  kind, 
contain  tactile  corpuscles  in  which,  as  already  mentioned,  the  cutaneous 
nerves  terminate.  It  will  be  remembered  also  that  the  digital  nerves 
of  the  fingers  and  toes  appear  to  terminate  in  similar  shaped,  though 
larger  bodies,  the  Pacinian  corpuscles,  situated  in  the  subcutaneous 
tissue,  and  the  nerves  supplying  the  skin  of  the  glans  penis  and 
clitoris  in  the  Krause  corpuscles,  resembling  the  tactile  and  Pacinian 
corpuscles,  though  smaller  than  either.  The  dermis  with  its  papillae  is 
richly  supplied  with  bloodvessels  and  lymphatics,  as  well  as  nerves. 
The  arteries  penetrating  the  dermis  from  beneath  end  in  a  capillary 
network,  the  latter  extending  as  single  loops  into  the  papilla,  while 
the  veins,  more  numerous  and  larger  than  the  arteries,  terminate  in 
the  superficial  venous  trunks.  The  lymphatics  already  referred  to  are 
most  numerous  on  the  fore  and  inner  part  of  the  body  and  limbs, 
being  particularly  well  developed  in  the  palms  and  soles.  The  dermis 
consisting  largely  of  white  fibrous  tissue  is  by  boiling  resolved,  in 
a  great  measure,  into  gelatine,  the  ordinary  source  of  glue,  hence, 
also  its  conversion  into  leather  by  tanning.  The  fibrous  structure  of 
the  dermis,  the  papilla,  the  mouths  of  hair  follicles,  etc.,  may  usually 
be  seen  in  the  cut  edge  and  rough  surface  of  a  piece  of  leather.  De- 
prived of  its  fatty  matters,  etc.,  the  dermis,  when  properly  thinned, 
forms  also  parchment. 

The  epidermis,  also  known  as  the  cuticle  or  scarf  skin,  constituting 
the  superficial  layer  of  the  skin,  bears  the  same  relation  to  the  dermis 
that   the  epithelium   does  to  the  deeper  layer  of  mucous  membranes. 


740 


SKIN    AND    APPENDAGES. 


Indeed,  the  transition  of  skin  into  mucous  membrane  at  the  mouth 
and  anus  is  so  gradual,  that  it  is  impossible  to  say  where  one  ends 
and  the  other  begins;  in  fact,  as  "well  known,  if  the  skin  be  inverted 
in  these  places,  it  becomes  mucous  membrane,  and  if  the  mucous 
membrane  be  everted,  it  becomes  skin.  The  internal  surface  of  the 
epidermis  is  applied  directly  to  the  papillae  (Fig-  480)  of  the  dermis, 

Fig.  430. 


Epidermis  elevated  so  as  to  show  papillae.     (Hirschfeld,) 


and  follows  closely  all  their  inequalities ;  its  external  surface  is  marked 
by  very  shallow  grooves  corresponding  to  the  furrows  between  the  latter. 
The  epidermis  is  entirely  destitute  of  bloodvessels  and  lymphatics, 
deriving  its  nutritive  fluid  (like  all  other  vascular  parts),  by  osmosis, 
from  the  blood  of  the  dermis.  It  was  for  a  long  time  supposed  that 
the  epidermis  was  also  without  nerves.  Recent  investigations,  how- 
ever, make  it  probable  that  some  of  the  cutaneous  nerves  pass  through 
the  dermis,  terminating  as  non-medullated  nerve  fibres  among  the 
deeper  layers  of  the  epidermis  in  slightly  bulbous-like  extremities,  or 
in  a  plexus  of  fine  fibrils.  However  this  may  be,  impressions  made 
upon  the  epidermis  will  be  appreciated,  whether  the  latter  be  provided 
with  nerves  or  not,  being  transmitted  through  pressure  to  the  ex- 
quisitely sensitive  dermis  beneath.  The  epidermis  serves  as  a  protective 
covering  to  the  soft  and  delicate  dermis,  which  would  be  otherwise 
constantly  exposed  to  laceration  and  drying. 

Indeed,  if  the  epidermis  be  removed,  contact  of  the  atmosphere  alone 
will  inflame  the  dermis,  which,  after  death,  rapidly  dries.  The 
epidermis  is  therefore  thicker  in  those  parts  which  are  most  exposed, 
as  in  the  palms  and  soles,  where  it  may  measure  as  much  as  the  yV**1  of 
an  inch  or  more,  being  very  thin,  on  the  other  hand,  upon  the  face,  the 
eyelids,  and  in  the  external  auditory  meatus,  attaining  in  these  situa- 
tions only  a  size  of  the  g^th  to  the  y^-th  of  an  inch.  The  whole  skin 
then,  including  the  dermis,  in  its  thickest  part  would  measure  about 
the  4-th  of  an  inch,  and  in  its  thinnest  part  about  the  -g^-th  of  an 
inch.     The  thickness  of  the  epidermis  is,  however,  dependent  to  a  great 


EPIDERMIS.  741 

extent  upon  the  amount  of  pressure  to  which  the  skin  is  subjected, 
being  very  thick  in  the  palm  of  the  laborer  and  the  sole  of  the  plowman. 
Corns  are  thickened  portions  of  the  epidermis,  and  are  due  to  the  parts 
affected  being  exposed  to  excessive  pressure  or  friction,  hence  they  are 
developed  not  only  in  the  feet  by  tight  shoes,  but  on  the  knee  of  the 
shoemaker  by  constant  hammering,  and  in  front  of  the  clavicle  of  the 
soldier  by  the  pressure  of  the  musket.  The  pain  caused  by  corns  is 
due  to  inflammation  of  the  dermis,  which  they  excite  by  pressing  upon 
its  delicate  structure,  just  as  any  foreign  body,  a  small  stone,  will  do 
under  similar  circumstances.  The  epidermis  consists  of  two  layers,  the 
rete  mucosum  and  the  cuticle.  The  rete  mucosum  or  Malpighii,  with  a 
thickness  varying  from  theyyL^th  to  the  yX-th  of  an  inch,  constituting  the 
deeper  internal  soft  layer  of  the  epidermis,  is  moulded  upon  the  ad- 
joining surface  of  the  dermis,  and  when  separated  by  maceration  or 
putrefaction  presents  impressions  corresponding  exactly  with  the 
papillae,  furrows,  depressions,  etc.,  of  the  latter,  the  more  prominent 
irregularities  of  the  dermis  being,  as  already  mentioned,  visible  upon 
the  outer  surface  of  the  cuticle,  but  less   distinctly  (Fig.  431).      The 

Fig.  431. 


jr—  V 


Rete  mucosum. 


rete  mucosum  consists  of  several  irregular  layers  of  cells  of  different 
forms,  more  or  less  agglutinated  together.  Those  lying  next  to  the 
dermis  are  somewhat  elongated  in  figure,  varying  in  length  from  the 
^Q-Q-th  tothe-j-gVg-th  of  an  inch,  and  disposed  perpendicularly,  while  the 
succeeding  ones  are  of  a  rounded  form  and  often  marked  with  rid o-es 
and  furrows,  in  sections  appearing  as  spines.    As  the  cells  are  gradually 


>-"  a  I, 


742  SKIN    AND    APPENDAGES. 

pushed  from  below  upward  through  the  continual  development  of 
new  cells  at  the  surface  of  the  dermis,  they  become  more  and  more 
flattened,  lose  their  soft  granular  contents  and  nucleus,  and,  becoming 
keratose,  give  rise  to  the  different  layers  of  the  rete  mucosum,  and 
are  finally  transformed  into  the  dry  horny  scales  of  the  cuticle.  While 
in  the  white  race  the  cells  of  the  rete  mucosum  are  colorless  and  like 
those  of  the  cuticle  translucent,  allowing  the  color  of  the  underlying 
dermis  to  be  seen,  in  those  of  the  black  races,  the  negro  especially,  the 
deeper  ones  (Fig.  432)  are    filled    with    brown  or    black  pigmentary 

matter,  which  gives  rise  to  their  char- 
Fig.  432  acteristic  dark  color,  and,  when  present 

in   smaller    quantities,    to    the    various 
shades  of  complexion  of  other  races,  of 
different    individuals,    and  of   different 
parts  of  the  skin  of  the  same  individual, 
while  the  accumulation  of  this  pigmen- 
tary  matter    in  spots    causes    freckles. 
As  the  cells  of  the  deeper  layers  of  the 
rete  mucosum  are  gradually  transformed 
WE-       into  those  of  the  cuticle,  the  pigmentary 
^Mfft,       matter  gradually  diminishes  and  finally 
Wk       disappears.        It   is  interesting  in  this 
Wij,        connection   to    note   that    the    color   of 
the  dermis  in  the  negro  is  the  same  as 
that  of  the  white,  and  that  the  whole 
skin  of  the   negro  foetus  is  as  pale    as 
that    of    the    white    one.        The    fact 
skin  of  the  negro,  vertical  section,  mag-      of  the  pigment  being  developed  in  the 

nified  250  diameters  »,  a.  Cutaneous  pa-  deep  Cells  of  the  rete  muCOSUm  Only  at  01" 
pill*.  b.  Undermost  and  dark-colored  after  bjrth  wou](1  int|icate  f^at  the  l^k 
layer   of    oblong    vertical   epidermis-cells.  1       .      .  ,     -    „  .  .  . 

c  mucous  or  Maipighian  layer.  ,/.Homy  race  had  descended  from  the  white  one 
layer,   (kblmkee.)  rather  than  the  reverse.     Further,  since 

in  the  dark  races  and  the  semi-burnt 
ones  of  the  white  races,  the  pigment  is  developed,  not  in  the  superficial, 
but  in  the  deep  layers  of  the  rete  mucosum,  it  is  to  be  inferred  that  the 
pigment  is  eliminated  by  the  cells  of  the  rete  mucosum  from  the  blood 
of  the  dermis,  and  that  the  effect  of  the  heat  of  the  sun  in  temperate  or 
tropical  climates  is  not  to  modify  directly  the  color  of  the  skin,  but  in 
rendering  the  liver  torpid,  to  throw  upon  the  skin  the  elimination  of 
the  coloring  and  other  matters  of  the  bile,  and,  hence,  only  indirectly 
affecting  it.  That  such  is  the  case  is  rendered  probable  also  from  the 
fact  of  the  cutaneous  pigment  being  essentially  carbonaceous  in  nature, 
as  is  that  of  bile.  While  there  is  no  doubt  that  the  cells  of  the  rete 
mucosum  are  gradually  transformed  into  those  of  the  cuticle,  there  is 
considerable  doubt  as  to  whether  they  themselves  are  derived  from  those 
of  the  dermis,  since,  as  wre  shall  see  hereafter,  the  epidermis  is  derived 
from  the  epiblast  or  external  blastodermic  membrane  of  the  embryo, 
and  the  dermis  from  the  mesoblast  or  middle  blastodermic  membrane. 
Such  being  the  case,  it  is  more  probable  that  the  deep  epidermal  cells 


THE    NAILS. 


743 


of  the  adult  are  derived  by  unbroken  descent  from  the  original  epiblastic 
ones  of  the  embryo  than  from  those  of  its  dermal  mesoblastic  ones. 

The  cuticle,  or  cuticula,  constituting  the  most  external  superficial 
portion  of  the  epidermis,  consists  of  numerous  layers  of  hard,  flattened, 
nearly  dry,  yellowish  translucent  cells,  irregularly  polygonal  in  form, 
generally  granular,  but  without  nuclei,  measuring  from  the  ^-^j-fj-th 
to  yl-o-th  °f  an  mcn  m  diameter,  and  composed  chemically  of  keratin, 
or  horny  matter;  the  deeper  cells  being  rather  thicker  and  rounder 
than  those  of  the  superficial  layers.  As  the  deeper  surface  of  the  cuti- 
cle is  being  continually  renewed  by  fresh  cells  from  the  rete  mucosum. 
its  free  surface  is  as  constantly  worn  away,  or  shed  off  in  flakes,  con- 
stituting the  so-called  scurf  (Fig.  438)  and  dandruff  (Fig.  484).     In 


Fig.  433. 


Fig.  434. 


Scurf  from  the  leg  1.  A  fragment  of 
scurf,  consisting  of  dried,  Battened,  aon- 
nucleated  cells  or  scales.  2.  A  few  cells 
with  a  nucleus.  3.  A  cell  more  highly 
magnified,  to  exhibit  its  polyhedral  form. 
(Leidv.) 


Fragment  of  dandruff  from  the  head.  1.  Portion  of 
dandruff,  consisting  of  non-nucleated  cells.  2.  Several 
fragments,  consisting  of  nucleated  cells.  3.  Isolated  cells, 
some  with  and  without,  nuclei.  4  A  cell  more  highly 
magnified,  exhibiting  granular  contents  ami  a  nucleus. 
(Leidv.  ) 


many  of  the  lower  animals,  as  in  snakes,  for  example,  the  cuticle  exfol- 
iates from  time  to  time  entire.  By  treating  the  cuticle  with  a  solution 
of  potash  its  scales  separate  from  one  another,  swelling  up  into  vesicles; 
it  is  for  this  reason  that  alkaline  solutions  remove  the  epidermis.  In 
tanning,  for  example,  the  epidermis  is  removed  by  macerating  the  skin 
in  lime.  etc.  A  blister  or  burn,  in  producing  inflammation  of  the  dermis 
and  effusion  of  liquid,  breaks  up  the  soft  cells  of  the  rete  mucosum, 
ami  so  elevates  the  cuticle.  If  the  skin  be  macerated  after  death,  the 
cuticle,  through  disorganization  of  the  rete  mucosum,  detaches  itself, 
and  when  under  such  circumstances,  it  is  thick- and  strong,  as  in  the 
case  of  the  hand  and  foot,  it  may  be  stripped  oif  like  a  glove. 

The  Nails. 


The  nails,  or  ungues,  appendages  of  the  skin,  corresponding  to  the 
claws  and  hoofs  of  other  animals,  and  situated  upon  the  dorsal  surfaces 
of  the  distal  phalanges  of  the  fingers  and  toes,  not  only  serve  to  pro- 
tect these  parts,  but  are  also  important  as  prehensile  organs,  in  civilized 
races  more  especially,  in  the  case  of  the  fingers,  but  in  certain  barbar- 
ous ones,  in  that  of  the  toes  as  well.  The  nails  are  thin,  flexible,  trans- 
lucent quadrilateral  plates,  continuous  with  the  epidermis  (Fig.  435), 


744 


SK  I  N     AND    AIM'KN  DA  CMS. 


FlQ.  435. 


Fig.  4m. 


'■;    >    »  km-,  2  7    >   a 


Vertical  section  of  the  end  of  a  finger.  1. 
Epidei  mis  on  the  back  of  the  linger.  -.  Point 
at  which  it  Is  reflected  to  become  continuous 
with  the  nail.  :f.  The  nail.  4.  Epidermis  at 
the  end  of  the  ringer.  5,  6,  7,  8  Surface  of 
the  dermis  corresponding  with  the  position  of 
the  soft  epidermic  layer.  9,10,11,  12.  Dermis. 
13.  Last  phalanx.  14.  Flexor  tendon. 
(IiEmy.  i 


•I     I 


.J3 


Vertical  transverse  section  through  a  small  portion 
of  the  nail  and  matrix,  highly  magnified.  A.  Corium 
of  the  nail-bed,  raised  into  ridges,  or  laminae,  «.  fitting 
in  between  coi  responding  lamina?,  b,  of  the  nail.  B  Jlal- 
pighian,  and  C,  horny  layer,  d.  Deepest  and  vertical 
cells,  e.  Upper  flattened  cells  of  Malpighian  layer. 
(Kolliker.) 


with  which  they  are  detached  if 
the  latter  be  separated  by  mac- 
eration from  the  dermis.  The 
nail  resting  upon  the  depressed 
surface  of  the  dermis,  known  as 
the  matrix,  or  bed,  as  described  by  anatomists,  consists  of  the  root, 
body,  and  free  border.  The  root  is  lodged  in  a  deep  groove  of  the 
matrix,  the  vallecula  unguis,  while  the  lateral  borders  of  the  body  of  the 
nail  fit  into  rather  shallow  grooves,  the  free  border  of  the  nail  being 
that  part  detached  from  the  skin.  The  color  of  the  nail  is  due 
to  its  translucency,  which  allows  the  color  of  the  highly  vascular,  or 
underlying  dermis,  or  matrix,  to  be  seen ;  the  lunula,  or  whitish 
spot  at  the  root,  defined  by  the  semicircular  line,  is  due  to  the 
matrix  being  there  less  vascular.  The  grooves  exhibited  more  particu- 
larly on  the  under  surface  of  the  nail  are  the  impressions  made  by  the 
fine  longitudinal    ridges  and  papillae   of  the   dermis   of  matrix   upon 

Fig.  437. 


.'/ 


Longitudinal  section  through  the  middle  of  the  nail  and  bed  of  the  nail.  «.  Bed  of  the  nail,  and  cutis 
of  the  back  and  points  of  the  fingers,  b.  Mucous  layer  of  the  points  of  the  fingers,  c.  Of  the  nail.  <l. 
Of  the  bottom  of  the  fold  of  the  nail.  e.  Of  the  back  of  the  finger.  /.  Horny  layer  of  the  points  of  the 
fingers,  g.  Beginning  of  them  under  the  edge  of  the  nail.  h.  Horny  layer  of  the  back  of  the  fingers 
i.  Ends  of  it  upon  the  upper  surface  of  the  root  of  the  nail.  k.  Body  /.  Koot.  in.  Free  edge  of  the 
proper  substance  of  the  nail.    Magnified  8  diameters. 

which  the  nail  is  moulded.     The  nail,  like  the  epidermis,  consists  of 
two  layers — a  horny  layer,  and  a  soft  layer.      The   soft   layer  corre- 


THE    HAIRS. 


745 


sponding  to  the  rete  mucosum  of  the  epidermis,  consists,  like  the  latter, 
of  delicate,  polyhedral  nucleated  cells,  averaging  from  the  3  ^  0 th  to 
the  1 7l0 0 th  of  an  inch  in  length,  which  are  being  continually  trans- 
formed into  the  scales  of  the  horny  layer.  The  latter,  corresponding 
to  the  cuticle  of  the  epidermis,  consists  of  a  number  of  layers  of 
flattened  nucleated  cells,  or  scales,  varying  from  the  y^Vjjth  to  the 
y-^jth  of  an  inch  in  diameter,  but  so  intimately  associated  that  they 
can  only  be  recognized  under  the  microscope,  after  separation  from  one 
another  by  treatment  with  alkalies,  etc.  The  thickness  of  the  true 
nail — that  is,  of  its  horny  layer  at  the  root — is  from  the  ^fth  to 
the  y-fnjth  of  an  inch,  and  at  the  middle  of  the  body  of  the  nail, 
from  the  375-th  to  the  375-th  of  an  inch.  Through  the  constant  addition 
of  cells,  the  root  of  the  nails  grows  in  length,  and  through  addition  of 
the  cells  beneath,  in  thickness — the  free  cut  edge  of  the  nail  consisting 
of  the  horny  layer  only.  (Fig.  437.)  The  average  rate  of  growth  of 
the  nails  is  said  to  be  -jVcl  of  an  inch  per  week,  and  to  be  more  rapid 
in  summer  than  in  winter.1 


The  Hairs 


Fig   438. 


The  hairs,  or  pili,  like  the  nails,  appendages  of  the  skin,  and  more 
particularly  of  the  rete  mucosum  of  the  epidermis,  are  first  noticed  at 
about  the  third  or  fourth  month  of  intra-uterine  life,  as  little  black 
specks  beneath  the  cuticle,  consisting  of  a  mass  of  cells,  defined  by  a 
basement  membrane  (Fig.  438),  developed  through  invagination,  or 
the  growing  downward  of  the  cells  of  the 
rete  mucosum  into  the  dermis.  As  devel- 
opment advances,  the  cells  of  which  this 
flask-like  body  consists  are  differentiated 
into  a  central  and  a  lateral  portion  (Fig. 
43!  >,  A),  the  former  the  rudiment  of  the 
future  hair,  the  latter  the  root-sheath,  or 
the  lining  of  the  hair  follicle,  while  the 
projecting  of  the  dermis  into  the  bottom 
of  the  flask-like  hair  forms  its  papillae. 
With  the  gradual  upward  growth  of  the 
hair  and  the  development  of  the  differ- 
ent parts,  of  which,  as  we  shall  see,  it 
consists  (Fig.  439,  B,  C),  the  root-sheath 
divided  into  the  inner  and  outer  root- 
sheaths,  the  former,  except  at  the  bottom, 
subdividing   into   Huxley's   and    Henle's 

layers,  the  latter  being  surrounded  and  defined  by  a  fibrous  membrane, 
derived  from  the  dermis,  and  constituting  the  wall  of  the  hair  follicle. 

Finally,  the  hair,  being  fully  formed,  penetrates  the  cuticle,  the 
papilla  to  which  it  is  attached  having  been  provided  with  nervous  fila- 
ments and  capillary  bloodvessels.  The  hair  is  usually  described  as 
consisting  of  a  root  beginning  in   the  skin  as  a  club-like  expansion, 


Rudiment  of  tlie  hair  from  the  brow 
of  a  human  embryo,  sixteen  weeks  old; 
magnified  350  diameters.  ".  Horny  layer 
of  ili»-  epidermis.  6.  Its  mucous  layer. 
i.  Structureless  membrane  surrounding 
the  rudiment  of  the  hair,  and  continued 
between  the  mucous  layer  and  the  cor- 
ium.  m  Roundish,  partly  elongated  cells 
which  especially  compose  the  rudiments 
of  the  hair. 


Quain's  Anatomy,  1--78,  vol.  ii.  p.  219. 


746 


SKIN    AND    APPENDAGES'. 

Fig.  4^,9. 


A.  Hair  rudiment  from  an  embryo  of  six  weeks.  ".  Horny,  and  ft,  mucous  or  Malpighian  layer  of  cuticle. 
i.  Basement  membrane,  ire.  Cells,  some  of  which  are  assuming  an  oblong  figure,  which  chiefly  form 
the  future  hair.  B.  Hair  rudiment,  with  the  young  hair  formed,  but  not  yet  risen  through  the 
cuticle,  n.  Horny,  ft.  Malpighian  layer  of  epidermis,  c.  Outer,  d,  inner  root  sheath,  e.  Hair-knob. 
/.  Stem,  and  g,  point  of  the  hair.  7i.  Hair-papilla,  n,  n.  Commencing  sebaceous  follicles.  C.  Hair- 
follicle  with  the  hair  just  protruded.     (ScHAFEn.) 


Fio.  440. 


the  bulb  and  a  shaft  or  stem  projecting 
from  the  skin,  and  terminating  in  the  end 
or  point.  It  is  composed  (Fig.  440)  usually 
of  a  medulla,  or  central  axis,  around 
which  are  concentrically  disposed  the 
cortical  substance  and  cuticle.  The  me- 
dulla consists  of  cuboidal  cells,  having  a 


diameter  of  from  the 


2000  "'  *° 


1  2  0  0 


ih 


Diagram  of  structure  of  the  root  of  a 
hair  within  its  follicle.  1.  Hair  papilla. 
2.  Capillary  vessel.  3.  Nerve  fibres.  4. 
Fibrous  wall  of  the  hair  follicles.  5.  Base- 
ment membrane.  6.  Soft  epidermis,  lining 
of  the  follicle.  7.  Its  elastic  cuticular 
layer.  8.  Cuticle  of  the  hair.  9.  Cortical 
substance  10  Medullary  substance.  11. 
Bulb  of  the  hair  composed  of  soft  poly- 
hedral cells  12.  Transition  of  the  latter 
into  the  cortical  substance,  medullary  sub- 
stance, and  cuticle  of  the  hair.     (Leidy.) 


of  an  inch,  with  granular  contents,  and 
an  indistinct  nucleus,  usually  intermin- 
gled with  small  bubbles  of  air,  which 
have  penetrated  from  the  ends  of  the 
hair,  and,  wh'en  present,  giving  rise  to 
the  white  silvery  lustre  of  the  latter.  In 
downy  hairs  the  medulla  is  absent.  The 
cortical  substance,  or  the  cortex,  consti- 
tutes the  chief  bulk  of  the  hair,  and  is 
that  part  upon  which  the  color  of  the 
hair  principally  depends  in  different  in- 
dividuals and  races.  It  is  composed  of 
several  layers  of  flexible  fibres,  the  latter 
consisting  of  elongated  fusiform  cells. 
With  the  loss  of  the  coloring  matter, 
which  is  generally  diffused  through  the 
cortical  substance,  the  latter  becomes 
white.  The  cuticle  consists  of  a  single 
layer  of  thin  colorless  quadrilateral  cells, 
overlapping  each  other  like  the  shingles 
of  a    roof.      The  edo-es  of  these  scales 


THE    HAIRS.  747 

being  directed  upward  and  outward  along  the  shaft  offer  an  obstacle  to 
any  movement  of  the  hair  otherwise  than  with  its  root  forward  when 
rubbed  between  two  surfaces.  It  is  upon  this  fact  that  the  felting  of 
hair  ami  wool  of  various  animals  depends.  The  hair,  like  the  epidermis, 
being  destitute  of  bloodvessels,  derives  its  nutritive  liquid  by  osmosis 
from  the  blood  of  the  vessels  of  the  papilla.  While  analogy  would  lead 
one  to  suppose  the  nerve  filaments  of  the  papilla  penetrate  the  hair,  as 
a  matter  of  fact,  no  nervous  filaments  having  as  yet  been  demonstrated 
in  it,  any  sensibility  that  the  hair  may  possess  must  depend,  therefore, 
upon  that  of  the  papilla  which  the  hair  bulb  tightly  encloses  or  caps. 
The  hairs  are  continually  renewed  by  constant  growth.  In  some 
instances,  especially  after  disease,  they  are  cast  off  or  shed,  new  ones 
being  produced.  Permanent  baldness  is  due  to  atrophy  of  the  papillae, 
while  the  sudden  blanching  of  the  hair,  occurring  sometimes  in  a  single 
night,  is  due  to  the  greater  part  of  the  medulla  and  cortex  becoming- 
filled  with  air.1 

Chemically,  hairs  are  composed  of  fats,  a  gelatine-like  substance, 
albuminous  matters,  containing  a  large  proportion  of  sulphur,  peroxide 
of  iron,  traces  of  manganese,  silica,  sodium,  and  potassium  chlorides, 
calcium  sulphate  and  phosphate,  and  magnesium  sulphate.2  With  the 
exception  of  the  palms  of  the  hands  and  soles  of  the  feet,  the  palmar 
surface  of  the  fingers  and  toes,  the  lips,  lining  of  the  prepuce  ami  glans 
penis,  hairs  cover  nearly  every  part  of  the  surface  of  the  body.  The 
hairs  generally  project  obliquely  from  the  skin,  and  are  regularly  dis- 
posed, usually  in  curving  lines  from  particular  points.  They  differ 
very  much  as  regards  their  size,  fineness,  color,  form,  and  number,  in 
different  races,  sexes,  individuals,  and  parts  of  the  body.  Of  the  long 
hairs,  attaining  sometimes  in  women  a  length  of  three  feet  or  more, 
and  a  diameter  of  from  the  ysVo^1  to  tne  TFotn  °^  an  mc^1-  the  finest 
are  found  upon  the  head.  The  short,  stiff  hairs  of  the  nostrils  and  edges 
of  the  eyelids,  are  from  the  4-3-g-th  to  the  yyiyth  of  an  mc^1  m  diameter, 
the  fine  downy  ones  from  the  -.Jy^th  to  the  121ootk.  While  the  fine 
silken  hair  of  the  head  in  the  white  race  is  cylindrical,  the  crisp  hair 
of  the  head  and  beard  of  the  negro  is  more  or  less  flattened  cylin- 
drical. It  has  been  estimated3  that  upon  a  square  inch  of  scalp  there 
are  about  1000  hairs,  the  number  upon  the  entire  head  amounting  to 
120,000.  The  hairs  are  elastic,  readily  electrified  by  friction,  especially 
in  cold,  dry  weather,  and  very  hygrometric.  The  latter  property  is 
taken  advantage  of  in  the  making  of  delicate  hvurometers,  the  hair  elon- 
gating  through  the  absorption  of  moisture.  The  hairs  not  only  serve 
to  protect  the  general  surface,  as  in  shielding  the  head  from  excessive 
cold  or  heat,  but  also  guard  certain  orifices,  as  those  of  the  ears  and 
nose.  The  eyebrows  prevent  the  perspiration  from  the  forehead  running 
on  to  the  lids,  the  eyelashes  the  surface  of  the  conjunctiva  from  dust, 
etc.  Hair,  being  a  bad  conductor  of  heat,  serves  also  to  retain  that 
produced  within  the  body.  It  has  already  been  mentioned  that  the 
hairs  are  quite  regularly  disposed,  and  it  will  be  further  observed  that 

1  Landois:  Virchow's  Arch.,  1866,  Band  xv.w   s   375.     Wilson:  Proc.   Roy.  Soc.  Loud.,  1867,  vol.  xv. 
p.  I  16. 
•  Quain's  Anatomy,  vol.  ii.  p.  226.  V!  ila  m  :   Healthy  Skin.  p.  si.     Philadelphia,  1854. 


748  SKIN     AND    APPENDAGES. 

if  a  man  assume  a  crouching  attitude,  with  elbows  upon  the  knees,  and 
the  chin  resting  upon  the  hands,  thai  their  general  direction  upon  the 

extremities  is  obliquely  downward,  a  disposition  such,  that  if  the 
person  be  exposed  to  wet  weather,  the  rain  will  be  drained  off",  an 
effect  obviously  of  advantage  to  the  primitive  man,  as  well  as  to  those 
who  go  naked  at  the  present  day.  Finally,  the  hairs  may  be  regarded, 
to  a  certain  extent  at  least,  as  so  many  excretory  organs,  since  their 
growth  necessarily  involves  the  excreting  from  the  blood  the  different 
principles  of  which  we  have  seen  that  they  chemically  consist,  and 
which,  if  retained  within  the  system,  in  all  probability  would  give  rise 
to  disease. 

Sebaceous  Glands. 

The  sebaceous  glands,  like  the  nails  and  hair,  are  appendages  of  the 
epidermis,  being  developed  during  the  fourth  and  fifth  months  of 
intra-uterine  life  as  outgrowths  of  the  hair  follicles,  into  which,  with 
but  few  exceptions,  they  eventually  open.  Each  sebaceous  gland  begins 
(Fig.  441,  A)  as  a  solid  bud  sprouting  out  into  the  dermis  from  the  external 

A  Fig.  441.  B 


A 


The  development  of  the  sebaceous  glands  in  a  six  months' foetus.  •<.  Hair.  6.  Inner  root-sheath,  here 
more  clusely  resembling  the  horny  layer  of  the  epidermis,  c.  Outer  root-sheath,  d.  Rudiments  of  the 
sebaceous  glands.  A.  Flask-shaped  rudiments  of  the  gland,  with  tat  developed  in  the  central  cells.  B. 
Larger  rudiments.     (Kolliker. ) 

root  sheath  of  the  hair  follicle,  and  consists  entirely  of  nucleated  cells. 
As  development  advances,  however,  the  cells  in  the  central  portion  of 
the  flask-like  (Fig.  441,  B)  bud  develop  fat,  which,  gradually  ex 
tending  themselves,  penetrate  the  root-sheaths  of  the  hair  follicle,  and 
so  pass  into  the  cavity  of  the  latter  as  the  primitive  sebaceous  secre- 
tion, while  through  the  further  division  and  subdivision  of  the  primitive 
bud  the  latter  assumes  the  form  of  a  simple  or  compound  racemose 
gland.  The  sebaceous  gland  when  fully  developed  consists  of  a  deli- 
cate wall  of  fibrous  tissue  defined  by  a  basement  membrane  lined  with 
an  epithelium   consisting  of  polyhedral  nucleated  cells,  with  granular 


SEBACEOUS    GLANDS. 


'49 


contents,  the  cavity  of  the  gland  being  filled  with  sebaceous  matter, 
the  chemical    composition  of  which  is  given  in    Table  LXXV.,   and 

Table  LXXV.1 — Composition  of  Sebaceous  Matter. 

Water 357 

Olein 270 

Margarin         ..........     135 

Sodium  butyrate  and  butyric  acid  .....        3 

Casein 129 

Albumen .2 

Gelatin   . 

Cakimn  }   Phosphate 

Sodium  chloride      .........         5 

Sodium  sulphate 5 


1000 


consisting  physically  of  cells  and  oil  globules,  the  cells  containing 
granular  matter  and  more  or  less  distended  with  oil.  The  sebaceous 
glands  are  very  numerous,  existing  almost  everywhere,  except  in  the 
palms  and  soles.     Usually  associated  with  the  hair  follicles  (Fig.  442), 


Fig.  442 


m 


A  large-  gland  from  the  nose,  with  a  little  hair-sac  opening  into  it;  magnified  fifty  diameters. 

(KoLLIKER.) 

they  are  disposed  around  the  latter  in  groups  varying  from  two  to 
eight  to  each  follicle,  and  imbedded  in  the  more  superficial  part  of  the 
dermis,  appearing  as  round  whitish  bodies,  and  measuring  on  an 
average  from  the  y^uth  to  the  ^th  of  an  inch  in  diameter.  The  largesl 
sebaceous  glands  are  those  of  the  nose,  concha  of  the  ear,  skin  of  the 
penis,  the  scrotum,  labia,  and  areola  surrounding  the  female  nipple. 

The  use  of  the  sebaceous  matter  is  to  smear  the  hairs  with  oil  as 
they  gi'ow  out  of  the  skin  and  thoroughly  to  imbue  the  cuticle  with 
the    same,    through    which    it    is    rendered    repellant  of  water.      The 


1  Robin  :  Leeons  snr  Ies  humeurs,  p.  509.     Paris,  18G7 


'50 


S  K  I  X     A  XI)     A  I'  I'  K  X  PAGES. 


greasiness  of  the  skin  thus  produced  is  the  cause  of  smut  and  dirt 
adhering  to  the  person  so  readily  and  necessitating  the  use  of  soap  for 
the  removal  of  the  same.  The  too  free  use  of  alkaline  washes,  how- 
ever, in  depriving  the  cuticle  of  its  natural  oil  renders  the  skin  dry 
and  harsh.  The  sebaceous  matter  often  becoming  inspissated,  dis- 
tends the  glands  producing  it,  especially  in  those  of  the  nose,  and 
becoming  incorporated  at  the  mouth  of  the  duct  with  dirt  if  squeezed 
out  is  often  regarded  on  account  of  the  shape  as  a  worm,  the  dirt  being 
supposed  to  be  the  head.  It  should  be  mentioned,  however,  that  the 
sebaceous  matter  frequently  contains  the  so-called  pimple  mite,  the 
acarus  or  Demodex  folliculorum.  The  sebaceous  glands  somewhat 
modified  constitute  also  the  Meibomian  glands  of  the  eye,  the  descrip- 
tion of  which  will  be  deferred,  however,  till  the  organ  of  vision  is 
considered. 

Mammary  Glaxds  and  Milk. 


The  mammary,  like  the  sebaceous  glands  just 
appendages  of  the   epidermis,  being  developed  in 


Fig.  443. 


J 


C 


described,  are  also 
the  fourth  or  fifth 
month  of  intrauterine  life  (Fig.  443,  1,  2) 
as  solid  invaginations  or  projections  of  the 
rete  mucosum  into  the  dermis,  the  latter  fur- 
nishing the  dense  layer  investing  them.  As 
development  advances  each  primitive  gland 
gives  off  a  number  of  buds,  the  future  lobes, 
numbering  at  birth  from  twelve  to  fifteen, 
which,  through  continued  division  and 
subdivision  into  lobules,  and  the  latter  into 
acini  or  secreting  vesicles,  ultimately  assume 
the  constitution  of  a  racemose  gland  (Fig. 
444),  such  as  the  parotid  or  submaxillary, 
the  wdiole,  however,  being  so  closely  asso- 
ciated by  connective  tissue  as  to  give  the 
appearance  of  being  homogeneous  rather  than 
lobulated.  Just  before  the  ducts  from  the 
lobes  reach  the  nipple  they  expand  beneath 
the  areola  into  the  so-called  lactiferous  sin- 
uses, especially  observable  in  the  human 
female  during  lactation,  and  constituting  the 
large  milk  reservoirs  in  the  cow.  As  the 
lacteal  or  galactophorous  ducts  from  each 
lobe  terminate  at  the  summit  of  the  nipple 
in  a  small  orifice,  the  number  of  the  latter, 
usually  twelve  to  fifteen,  correspond  with 
the  number  of  lobes.  The  mamma,  as  a 
whole,  is  of  a  firm  consistence :  of  a  pinkish- 
white  color,  of  circular  form  with  its  external 
surface  convex  and  prolonged  to  the  nipple.  The  latter,  provided  with 
sensitive  papillae,  is  highly  vascular  and  capable  of  erection.  The 
nipple,  reddish  or  brownish,  is  surrounded  by  an  areola  of  skin  usually 


Development  of  the  lacteal  gland. 
1,  rudiment  of  the  gland  in  a  male 
embryo,  at  five  months;  a,  horuy 
layer  ;  b,  mucous  layer  of  the  epi- 
dermis ;  e,  process  of  the  latter  or 
rudiment  of  the  gland;  il,  fibrous 
membrane  around  the  same.  2,  lac- 
teal gland  of  a  female  foetus,  at 
seven  months,  seen  from  above  ;  a, 
central  substance  of  the  gland,  with 
larger  (b)  and  smaller  (<•)  solid  out- 
growths, the  rudiments  of  the  large 
gland  lobes. 


MAMMARY    GLAXDS    AND    MILK. 


751 


of  the  same  color,  and  containing  sebaceous  glands  appearing  as  whitish 
eminences,    which,   during   sucking,    secrete  a  fatty    substance   which 


Fig.  444. 


protects  the  part  from  excoriation.  The  mammae  exist  in  the  male,  but 
usually  only  in  a  rudimentary  condition.  Their  presence  in  animals 
gives  rise  to  the  name  mammalia,  the  highest  order  of  vertebrates,  and 
while  as  a  general  rule,  they  are  attached  in  such  to  the  abdominal 
Avails,  in  man  and  monkeys  they  are  situated  on  the  anterior  part  of 
the  thorax. 

Table  LXXVI.1— Composition  of  Human  Milk. 


Water 

.  902.717 

Casein  (desiccated)     . 

.     29.000 

Lacto-protein 

.       1.000 

Albumen    . 

Butter 

.     25.000 

Sugar  of  milk    . 

.     37.000 

Sodium  lactate  . 

.       0.420 

Sodium  chloride 

.       0.240 

Potassium  chloride    . 

.       1 .440 

Sodium  carbonate 

.       0.053 

Calcium  carbonate     . 

.      0.069 

Calcium  phosphate 

.       2.310 

Magnesium  phosphate 

<i.42(i 

Sodium  phosphate 

0.225 

Ferric  phosphate 

.       0.032 

Sodium  sulphate 

.       0.074 

Potassium  sulphate    . 

100.000 

n         ■      ("Oxygen     ....        1.29)  OA 
( rases  in    '  VT./                                            !  ,  ,_     30  p 
,     •         Nitrogen  .                                12.n  i-      .r 

arts  per  1000 

solution  ,  n    ,  °  ■        •  ! 
(Carbonic  acid 

.       1 

5.54  J      m 

volume. 

The  secretion  of  the  mammary  glands  or  milk  constituting  a  sort  of 
emulsion,  whose  average  composition  is  given  in  Table  fcXXVL,  con- 
sists of  a  colorless  liquid,  the  milk  plasma,  composed  of  water,  holding 
in    solution   casein,    milk,   sugar,  salts,   etc..  and   innumerable  fat-like 


'•  Robin,  op.  cit.,  1867,  p.  95.    Somewhat  modified  and  authenticated.    Error  coirected. 


752  SKIN    AND    APPENDAGES. 

bodies,  the  milk  corpuscles,  or  globules.  The  latter,  to  which  the 
opaque,  whitish  color  of  milk  is  due  are  very  variable  in  size  (y2oo0^1 
to  the  i .,'-  Ah  of  :ui  inch),  and  consist  of  minute  drops  of  fat  surrounded 
apparently  by  a  thin  film  of  coagulated  casein.  With  the  exception  of 
the  water,  and  salts,  the  importanl  constituents  of  the  milk  are  elabo- 
rated by  the  cells  of  the  mammary  gland,  they  not  existing  as  such  in 
the  blood,  which,  as  they  successively  pass  into  the  lactiferous  ducts, 
burst,  giving  up  their  contents  as  milk.  The  quantity  of  milk  secreted 
in  twenty -four  hours  varies  very  much,  depending  upon  the  condition 
of  the  female,  kind  of  food,  etc.  Perhaps  it  may  be  assumed  that  the 
daily  production  of  milk  amounts  to  from  two  to  six  pints.  When  milk 
coagulates  spontaneously,  or  through  the  action  of  lactic  acid  upon  the 
casein,  it  separates  into  the  curd,  composed  of  casein  and  most  of  the 
fat,  and  a  greenish-yellow  serum — the  whey — the  phenomenon  taking 
place  more  readily  in  warm  than  in  cold  weather.  The  milk  formed  at 
the  beirinnino:  of  lactation — the  colostrum — differs  from  the  latter  milk 
in  being  thinner,  yellowish  in  color,  and  containing  many  of  the  milk 
cells  in  an  entire  condition;  the  colostrum  corpuscles  are  somewhat  in 
chemical  composition,  as  given  in  Table  LXXVII. 

Table  LXXVII.1 — Composition  of  Colostrum. 

Water 945.24 

Albumen 29.81 

Butter 7.07 

Sugar  of  milk       .........     17.27 

Sodium  }     i  i     •  i  I 

-r,  ,       .  -  chloride       ... 

Potassium       ) 

Potassium        I  | 

Calcium  -  phosphate  and  sulphate    | 

Magnesium     ) 

Ferric  phosphate  ....       J 

During  the  intervals  of  lactation  the  mammary  glands  secrete  only  a 
small  quantity  of  viscid  mucus. 

Sudoriferous  Glands. 

The  sudoriferous  or  sweat  glands,  like  the  sebaceous  and  mammary 
glands,  are  appendages  of  the  epidermis,  beginning  about  the  fifth 
month  of  intrauterine  life  as  flask-like  involutions  of  the  cells  of  the 
rete  mucosum  of  the  epidermis  into  the  dermis  (Fig.  445).  As  develop- 
ment advances  this  solid  flask-like  rudiment  becomes  transformed  into  a 
hollow  tube,  which,  extending  itself  through  the  dermis  to  the  subcuta- 
neous adipose  tissue,  terminates  at  the  one  end  in  a  coil,  and  at  the 
other  end  as  the  sweat  pore  on  the  surface  of  the  skin,  a  passage-way 
in  the  meantime  being  formed  in  the  epidermis  leading  from  the  latter 
into  the  hollow  tube.  Each  sweat  gland,  when  fully  formed,  consists 
of  a  tube  convoluted  at  its  commencement,  the  secreting  portion  of  a 
yellowish-red  color,  spheroidal  in  form,  with  an  average  diameter  of 
the  one-twentieth  of  an  inch,  and  passing  thence  upward,  as  the  sweat 

1  Robin,  op.  cit.,  p.  409. 


SUDORIFEROUS    GLANDS, 


75; 


Fig.  445. 


duct,  in  a  slightly  tortuous  manner  to  the  external  surface  of  the  dermis. 
The  tube  consists  of  an  external  fibrous  layer,  succeeded  by  a  basement 
membrane,  the  latter  supporting  an  epithelium  of  polyhedral  nucleated 
cells  containing  granular  and  yellowish  pigment  matter.  As  just  men- 
tioned, at  the  point  -where  the  sweat  duct  opens  on  the  surface  of  the 
dermis  a  passage-way  is  continued  through  the  epidermis  to  the  exterior. 
Where  the  epidermis  is  thin  the  passage  way 
is  straight,  but  where  thick,  as  in  the  palms  and 
soles,  it  takes  a  spiral  course,  terminating  at 
the  surface  in  a  funnel-shaped  orifice.  The 
openings  of  the  sweat  ducts  may  be  distinctly 
seen  disposed  in  a  single  row  of  the  summits 
of  the  ridges  of  the  skin  of  the  palms  and  soles, 
if  the  latter  be  viewed  with  a  common  pocket 
lens.  In  other  situations,  however,  they  are 
far  less  apparent.  With  the  exception  of  the 
concave  surface  of  the  concha  of  the  ear,  the 
glans  penis,  the  inner  layer  of  the  prepuce,  and 
perhaps  a  few  other  places,  the  sweat  glands 
are  found  in  every  part  of  the  skin.  The  num- 
ber varies,  however,  very  much  according  to  the 
part  of  the  skin  examined.  Thus,  while  ac- 
cording to  Krause,1  in  the  palmar  surface  of  the 
hand  there  may  be  as  many  as  2736  sweat  glands 
to  the  square  inch  of  skin,  in  that  of  the  nates 
there  may  be  as  few  as  417  per  square  inch.  It 
is  this  variation  in  the  number  of  sweat  glands 
existing  in  different  parts  of  the  skin  that  renders  any  determination  as 
to  their  total  number,  as  estimated,  for  example,  by  Krause  at  2,381,248, 
so  very  uncertain.  Assuming  that  the  secreting  portion  of  the  coil 
of  each  sweat  duct,  when  unravelled,  measures  the  one-sixteenth  of  an 
inch  in  length  on  the  above  estimate,  if  the  tubes  were  placed  end  to 
end  they  would  extend  a  distance  of  two  and  one-third  miles.  It  should 
be  mentioned,  however,  with  reference  to  this  last  estimate,  that  the 
length  of  the  excretory  portion  of  the  duct  is  not  taken  into  consid- 
eration, which  will  depend  on  the  thickness  of  the  skin.  Supposing  the 
latter  to  be  one-fifth  of  an  inch,  the  mean  of  its  thickest  and  thinnest 
parts,  the  total  length  of  the  excretory  portion  of  the  sweat  ducts  wrould 
amount  to  seven  and  one-half  miles,  a  somewhat  exaggerated  estimate, 
and  very  approximate,  it  must  be  admitted.  The  sweat  glands,  some- 
what modified,  constitute  the  ceruminous  glands  of  the  ear,  which  will 
be  referred  to  again  in  our  account  of  that  organ,  and  also  the  odori- 
ferous glands  of  the  axilla. 

In  the  latter  situation  they  form  a  patch  in  the  subcutaneous  con- 
nective and  adipose  tissue  often  an  inch  and  a  half  or  more  in  diameter, 
being  largest  in  the  centre  of  the  patch  and  gradually  diminishing 
toward  the  circumference,  where  they  become  undistinguishable  from 
the  ordinary  sweat  glands.     The  odoriferous  glands  of  the  axilla  not 


Rudiment  of  a  sudoriparous 
gland  of  a  human  embryo  at 
five  months.  Magnified  350 
diameters.  <i.  Horny  layer  of 
the  epidermis.  b.  Mucous 
layer,  c.  Corium.  <?.  Rudi- 
mentary glands,  as  yet  without 
any  cavity,  and  consisting  of 
small  round  cells. 


1  Wagner's  Physiology,  Band  ii.  S.  131.     Braunschweig,  1844. 

48 


751  SKIN    AND    APPENDAGES. 

only  secrete  sweat  but  a  strongly  odorous  substance,  hence  their  name, 
which  varies  somewhat  in  character  in  the  different  races  of  mankind. 
Indeed,  it  is  to  this  secretion  that  the  peculiar  odor  of  negroes  is  to  a 
great  extent  to  be  attributed,  the  glands  as  a  general  rule  being  better 
developed  in  the  negro  than  in  the  white  man  as  shown  first  by  the  late 
Professor  Horner,1  attaining  in  the  negro  the  size  of  a  pea. 

Perspiration. 

The  secretion  of  the  sudoriferous  or  sweat  glands,  the  perspiration 
or  sweat,  although  being  continually  elaborated  by  the  latter  from  the 
blood,  does  not  always  appear  as  such  upon  the  surface  of  the  skin, 
passing  from  the  body  in  the  form  of  an  insensible  vapor  as  rapidly  as 
produced.  If,  however,  through  the  amount  of  the  sweat  secreted 
being  increased,  or  from  the  condition  of  the  atmosphere,  as  regards 
temperature  and  moisture,  the  whole  of  the  sweat  produced  evaporates, 
the  residue  remains  in  the  form  of  minute  drops,  and  constitutes  what  is 
commonly  understood  as  sweat  or  perspiration.  There  is  no  difference, 
therefore,  between  the  insensible  and  sensible  perspiration,  the  form  in 
which  it  may  be  exhaled,  whether  as  liquid  or  vapor,  depending  simply 
upon  the  conditions  just  mentioned. 

Sweat  is  a  clear  watery  liquid,  of  a  specific  gravity  of  1.003  to  1.004, 
having  a  saline  taste  and  a  peculiar  odor  according  to  the  part  of  the 
skin  from  which  it  is  obtained.  The  reaction  of  the  sweat  appears  to 
be  alkaline,  the  acidity  often  observed  being  due  probably  to  decompo- 
sition and  to  the  presence  of  certain  volatile  acids,  such  as  the  acetic, 
formic,  butyric.  , 

Sweat,  as  shown  in  Table  LXXVIIL,  is  composed  in  by  far  the 
greater  part  of  water,  urea,  fatty  matters,  salts,  epidermic  scales  in 
small  quantities,  together  with  from  the  7^5-th  to  the  y^g-th  0I*  the 
carbonic  acid  produced  in  the  system,  using  the  word  sweat  in  its  fullest 
acceptation. 

Table  LXXVIII. '— Composition  of  Sweat. 


Water         .... 

Urea 

Fatty  matters 
Alkaline  lactates 

"         sudorates 
Sodium  chloride 
Potassium  chloride    . 
Alkaline  sulphates     . 

"         phosphates  . 

''         albuminates 

"         earthy  phosphates 
Debris  (epidermis)     . 


995.573 
0.043 
0.014 
0.317 
1.562 
2.230 
0.244 
0  012 

0.005 

oob.'ooo 

10000.000 


So  far  as  known  to  the  author,  the  celebrated  Sanctorius  was  the  first 
to  endeavor  to  determine  experimentally,  during  the  seventeenth  century, 
the    amount  of  the  perspiration,  the    method    made    use  of  being  to 

1  American  Journal  of  Med.  Sciences,  184<>,  p.  13. 

-  Faivre :  Archiv  Generates  de  Medeciue,  5  ieme  serie,  tome  ii.  p.  1.     Paris,  1853. 


PERSPIRATION.  755 

weigli  daily  the  body  and  all  the  solid  and  liquid  ingesta  and  egesta, 
and  from  the  loss  of  •weight  experienced  by  the  body  to  deduce  the 
amount  of  vapors  transpired.  Thus,  if  from  every  8  pounds  of  ingesta 
taken  in  24  hours  there  were  3  pounds  of  sensible  egesta,  44  ounces  of 
urine,  and  4  ounces  of  feces,  it  was  inferred  that  the  remaining  5 
pounds  of  ingesta  passed  from  the  body  insensibly  in  the  form  of  vapor. 
Unfortunately,  however,  as  the  latter  included  the  vapor  exhaled  from 
the  lungs  as  well  as  that  from  the  skin,  and  the  observation  simply  on- 
bodied  as  aphorisms,1  no  numerical  tables  given,  the  results  obtained 
have  now  but  little  value,  although  Sanctorius  experimented  daily  in 
the  manner  described  for  a  period  of  thirty  years.  Although  numerous 
and  interesting  observations  and  experiments  were  made  during  the 
eighteenth  century  by  Dodart,  Keill,  Rye,  Gorter,  Lining,  Hales, 
Stark,  with  a  view  of  determining  the  amount  of  the  perspiration  and 
the  conditions  affecting  it;  it  will  not  be  necessary  to  dwell  upon  them, 
since  the  pulmonary  and  cutaneous  perspiration  were  estimated  together 
by  these  observers.  The  first  attempt  to  estimate  separately  the  vapor 
exhaled  by  the  skin  from  that  by  the  lungs  was  made  by  Lavoisier"  and 
Seguin  in  1790,  the  experiments  consisting  in  enclosing  Seguin  in  a 
bag  of  gummed  taffeta  which  was  tied  above  the  head,  an  aperture  in 
the  coat  when  fixed  around  the  mouth  by  a  mixture  of  turpentine  and 
pitch  enabling  Seguin  to  inspire  fresh  air  and  exhale  the  breathed  air, 
but  only  permitting  the  pulmonary  vapor  of  the  latter  to  escape  from 
the  body.  By  then  deducting  the  amount  of  the  pulmonary  vapor  as 
determined  by  the  loss  of  weight  when  enclosed  in  the  gum  coat  from  the 
total  quantity  of  vapor  exhaled  as  determined  by  the  loss  of  weight 
when  so  enclosed,  the  amount  of  the  cutaneous  vapor  was  at  last  experi- 
mentally determined,  and  was  found  to  be  nearly  two  pounds,  one 
pound  and  fourteen  ounces,  which  does  not  differ  very  considerably  from 
the  later  results  obtained  by  Krause3  and  Valentin.4 

The  amounts  of  perspiration  exhaled  by  the  skin,  as  shown  by 
Lavoisier  and  Seguin  and  subsequent  observers,  vary  very  considerably, 
however,  depending  upon  the  quantity  and  temperature  of  the  liquid 
food,  the  relative  dryness  or  moisture  and  temperature  of  the  atmos- 
phere, the  amount  of  exercise  taken,  and  the  activity  of  the  lungs  and 
kidneys,  with  which  the  skin  acts  vicariously.  The  skin,  however,  not 
only  supplements  the  action  of  the  lungs  as  regards  the  exhalation  of 
•watery  vapor  and  carbonic  acid,  but  that  of  the  kidneys  also,  and  not 
only  with  reference  to  the  water  but  to  the  urea  eliminated  as  well. 
Thus,  according  to  Carpenter,5  in  one  experiment  the  entire  quantity 
of  perspiration  for  the  whole  body  being  in  one  hour  3320  grains,  6^ 
grains  of  urea,  containing  3.03  N,  were  obtained.  It  is  not  likely, 
however,  that  the  excretion  of  urea  would  have  continued  during  the 
whole  twenty-four  hours  at  such  a  rate.  It  should  be  mentioned  in  this 
connection  also,  according  to  Funkc,"  that  through  the  desquamation 
of  the  epidermic  scales  about  eleven  grains  of  nitrogen  are  also  daily 

i  Sanctorii  Sanctorii :  De  Statica  Medecina  aphorismorum.     Lugduni  Batavorum,  MDCCIII. 

-  Mem.  de  I' Acad,  des  Sciences,  p.  609      Paris,  lT'.iT.  ::  Waguer  :  Physio logie,  Band  II.  S.  319. 

i  Physi  ilogy,  Band  i   S.  174.     Braunschweig,  1814. 

■'  Physiologie,  p.  491.  6  Moleschott  Unters,  1838,  Band  iv.  S.  56. 


756  SKIN    AND    APPENDAGES. 

eliminated  from  the  system  by  the  skin.  The  fatty  matters  of  the  sweat 
are  probably  produced  by  the  sebaceous  glands,  while,  as  regards  the 
inorganic  principles,  the  most  notable  is  sodium  chloride,  existing  in  the 
proportion  of  2.2  parts  per  thousand.  That  the  sweat,  however,  contains 
other  substances  than  those  already  mentioned  is  rendered  very  proba- 
ble from  the  fact  that  death  soon  ensues  when  the  perspiration  is  sup- 
pressed, as,  for  example,  when  the  skin  is  varnished  in  animals1  and 
also  in  human  beings,  as  in  the  celebrated  case  of  the  child,  who,  being 
covered  with  gold-leaf  to  personate  an  angel  at  the  coronation  of  Leo  X., 
died  a  few  hours  afterward.2  While  death  in  such  cases  is  no  doubt 
partly  due  to  the  imperfect  arterialization  of  the  blood  and  the  rapid  fall 
of  temperature,  the  varnish  favoring  the  loss  of  heat  in  producing  a  cuta- 
neous hyperemia  similar  to  that  induced  through  paralysis  of  the  vaso- 
motor nerves,  symptoms  like  that  of  ursemic  poisoning,  tremors,  tetanic 
cramps,  movements  of  rotation,  increased  reflex  excitability,  present  as 
well,  lead  one  to  suppose  that  urea  and  other  poisonous  substances  not 
yet  isolated  are  retained  in  the  system  which  are  usually  carried  away 
in  the  sweat.  That  such  is  the  case  is  shown  by  the  fact  that  if  human 
sweat  be  injected  into  the  blood  of  the  rabbit3  the  pulse  of  the  latter 
may  be  increased  from  192  beats  per  minute  to  326,  the  respiration 
from  82  to  105,  and  the  temperature  raised  from  99.2°  to  104.3°  F. 
Even  if  it  be  admitted  that  the  exact  cause  of  death  is  not  yet  positively 
determined  there  can  be  no  doubt  that  imperfect  action  of  the  sweat- 
glands  must  be  a  source  of  disease,  various  matters  then  accumulating 
in  the  system  which  would  otherwise  be  eliminated.  Indeed,  too  much 
stress  cannot  be  laid  upon  the  importance  of  keeping  the  skin  clean — 
of  the  free  use  of  water.  Especially  is  such  the  case  in  tropical  climates 
where  the  true  secret  of  maintaining  one's  health  lies  in  attending  to  the 
condition  of  the  skin,  and  where  febrile  diseases  are  more  successfully 
treated  by  active  diaphoresis  than  in  any  other  way.  The  great  impor- 
tance of  daily  baths  in  the  maintenance  of  health  cannot  be  exaggerated, 
and  apparently  was  more  appeciated  by  the  ancients  than  the  moderns, 
as  the  ruins  of  the  magnificent  baths  of  Caracalla  and  Diocletian, 
at  Rome,  still  to  this  day  testify.  Noble  institutions  they  were ;  the 
baths  or  thermae  fed  by  stupendous  aqueducts  stretching  for  miles  across 
the  Campagna,  their  perpetual  streams  of  hot  and  cold  water  flowing 
through  mouths  of  solid  silver  into  capacious  basins,  accommodating  at 
one  time  thousands  of  bathers,  and  where  for  the  eighth  of  an  English 
penny  the  meanest  Roman  of  them  all  could  enjoy  the  luxury  that 
might  have  well  excited  the  envy  of  the  kings  of  Asia.4 

The  secretion  of  sweat,  like  other  secretions,  is  influenced  by  the 
nervous  system,  the  sweat  centre  or  centres  being  situated,  according 
to  Luchsinger,5  in  the  anterior  horns  of  the  gray  matter  of  the  spinal 
cord  and  medulla.  From  these  centres  nerve  fibres  arise,  which,  pass- 
ing down  the  cord,  emerge  principally  with  the  anterior  roots  of  the 
third,  fourth,  and  fifth  cervical  nerves  to  pass  with  the  brachial  plexus 

i  Fourcanet :  Comptes  Rendus,  tome  vi.  p.  369.  Paris,  1838.  Ibid.,  1843,  tome  xvi.  p.  139.  Valentin  : 
Archiv  f.  Physiologie  Heilkuiide,  1858,  Band  ii.  S.  433.  Bernard  :  Liquides  de  l'Organisme,  tome  ii.  p. 
177.     Paris,  1859. 

"-  Laschkewitsch  :  Du  Bois-Reymond's  Arch.,  1868,  S.  61. 

s  Ruhrig:  Jabrb.  f  Balneologie,  1873,  Band  i.  S    1. 

4  Gibbon  :  Decline  and  Full  of  the  Roman  Empire,  vol.  v.  p.  237.     London.  1807. 

&  PlUiger's  Archiv,  Band  xiii.  S.  2i2 ;  Band  xiv.  S.  545  ;  Band  XV.  S.  482  ;  Band  xvi.  S.  538. 


PERSPIRATION.  ibt 

to  the  skin  of  the  upper  extremity,  and  with  the  anterior  roots  of  the 
lumbar  nerves  to  supply  the  lower  extremity.  The  sweat  centres  may 
be  stimulated  directly  and  reflexly.  It  is  in  the  latter  manner  that  the 
sweat  centres  are  excited  in  man  by  motion,  fear,  heat,  various  sub- 
stances such  as  pilocarpin,  nicotin,  muscarin,  and  inhibited  by  cold, 
and  atropin. 

The  manner  in  which  the  skin  regulates  the  temperature  of  the  body 
through  the  radiation,  conduction,  etc.,  of  the  heat  produced  within  it 
having  already  been  sufficiently  considered,  it  will  not  be  necessary  to 
treat  further  of  the  function  of  the  skin  in  this  respect.  While  there 
can  be  no  doubt  that  absorption  in  the  lower  animals  and  in  many  of 
the  higher,  is  to  a  considerable  extent  carried  on  by  the  skin,  frogs, 
lizards,  etc.,  rapidly  gaining  in  weight  when  immersed  in  water,  some 
difference  of  opinion  still  prevails  among  physiologists  as  to  what  extent 
the  skin  in  man  normally  acts  as  an  absorbing  surface.  It  may  not 
appear  superfluous,  therefore,  if  attention  be  called  to  those  instances  or 
conditions  in  which  absorption  does  take  place  in  man  by  the  skin.  It 
is  well  known,  as  already  mentioned,  in  speaking  of  the  cause  of  thirst, 
that  in  the  case  of  the  shipwrecked  sailor  the  thirst  was  very  much,  if 
not  entirely,  temporarily  relieved  by  the  immersion  of  the  body  in  the 
sea,  or  by  wearing  clothes  wet  with  the  same.1  In  certain  cases  also, 
where  the  introduction  of  solid  or  liquid  food  by  the  mouth  had  become 
impracticable,  immersion  of  the  patient  in  a  bath  of  tepid  milk  morning 
and  evening  not  only  relieved  the  thirst,  but  for  some  time  maintained 
life,  the  weight  gained  being  unaccounted  for  by  the  enemata  also  given.2 
It  has  also  been  shown  that  not  only  does  the  body  gain  in  weight  after 
immersion  in  a  bath  through  the  absorption  of  the  liquid,  but  that  the 
skin  will  also  absorb  certain  salts  when  dissolved  in  the  same.  That 
the  skin  is  permeable  by  gas  is  also  well  known,  it  having  been  shown 
by  Bichat  that  if  a  limb  be  immersed  in  a  putrid  gas  the  latter  will  be 
absorbed  by  the  skin,  and  by  Aubert  that  the  skin  absorbs  about  the 
Y^th  of  the  oxygen  absorbed  by  the  lungs.  Admitting,  then,  that 
under  certain  circumstances  the  skin  undoubtedly  can  absorb,  it  still 
remains  undetermined  to  what  extent,  under  normal  conditions,  it  does 
absorb.  Covered,  as  the  skin  usually  is  in  man,  almost  entirelv  with 
more  or  less  clothing,  it  is  difficult  to  comprehend  how  or  what  the 
skin  under  such  circumstances  can  absorb,  the  gain  in  weight  of  the 
body  through  absorption  of  the  watery  vapor  of  the  atmosphere  some- 
times instanced3  being  due  to  the  absorption  of  the  vapor  by  the  lungs 
rather  than  by  the  skin.  We  have  further  seen  that  through  the 
presence  of  the  sebaceous  matter  the  skin  is  rendered  repeliant  of 
water,  Avhich  thereby  renders  it  very  insusceptible  to  the  taking  up  of 
foreign  substances.  Indeed,  it  is  very  questionable  whether  such  are 
ever  introduced  into  the  system  unless  the  epidermis  be  disintegrated, 
the  view  sometimes  advanced4  that  substances  are  absorbed  by  the  sweat 
ducts  being  very  improbable,  since  the  latter  are  already  filled  with 
sweat,  and  the  movement  of  the  sweat,  being  from  below  upward,  would 

1   Madden  :  Experimental  Enquiry  into  the  Physiology  of  Cutaneous  Absorption,  p.  64.     Edinb.,  1838. 
-  Currie:  Medical  P.. -ports,  vol.  i   pp.  30K-326.     Watson:  Chemical  Essays,  vol.  iii.  p.  mo. 
:   Lining:  Phil.  Trans.,  174:;,  p.  496.     Klapp :  Inaugural  Essay  on  Cuticular  Absorption,  p  30.    Phila- 
delphia, lso:,. 

1  iuspita:   Wiener  med.  Jahrb.,  1871.     Neumann;  Wiener  med.  Wochenschrift,  1871. 


758  SKIN     AND    APPENDAGES. 

tend  to  wash  away  foreign  substances  rather  than  favor  their  absorption. 
It  would  appear,  therefore,  as  Ave  pass  from  the  lower  to  the  higher 
animals,  that  the  skin  loses  its  significance  as  an  absorbing  surface, 
becoming  essentially  protective  and  excretory  in  function.  Neverthe- 
less, though  the  absorbing  power  of  the  skin  in  the  economy  of  the 
higher  animals  may  have  been  superseded  by  that  of  the  lungs  and 
alimentary  canal,  under  certain  conditions  it  may  even  in  them  act 
vicariously  with  the  same,  as  no  doubt  it  does,  as  regards  the  excretion 
of  water  by  the  kidneys  as  well  as  the  lungs. 

The  skin  acts  not  only  as  a  general  sensory  surface  through  the  im- 
pressions made  upon  the  epidermis  being  transmitted  thence  to  the  more 
deeply  situated  cutaneous  nerves,  but  through  its  tactile  Pacinian  and 
Krause  corpuscles  it  is  endowed  with  a  special  modification  of  sensibility 
— the  tactile  sensibility,  or  the  sense  of  touch,  by  means  of  which  we  not 
only  feel  but  appreciate  to  a  certain  extent  the  form,  size,  character  or 
surface,  weight,  and  temperature  of  objects.  While  the  skin  as  a  whole, 
therefore,  is  endowed  with  a  general  sensibility  more  or  less  acute  in 
different  parts  of  the  body,  its  tactile  sensibility,  however,  is  restricted 
to  certain  portions  of  it,  and  most  delicate  in  those  situations  where  the 
corpuscles  are  most  abundant.  Thus,  if  the  blunt  but  fine  ends  of  a 
pair  of  dividers  provided  with  a  graduated  bar,  or  the  eesthesiometer,  be 
applied  to  the  tip  of  the  tongue — the  individual  being  blindfolded — the 
two  ends  of  the  dividers,  though  only  separated  by  so  much  as  the  -^ th 
of  an  inch,  will  be  appreciated  as  two  distinct  objects.  If,  however,  the 
dividers  be  approximated  until  they  are  separated  by  less  than  that  dis- 
tance, the  two  impressions,  a  moment  previous  distinctly  appreciated  as 
such,  now  fade  into  one,  as  if  but  a  single  object  was  touching  the  tongue. 
Experimenting  in  this  manner,  it  was  first  shown  by  Weber,1  and  after- 
ward by  Valentin,2  that  the  sense  of  touch  varies  very  much  in  different 
parts  of  the  body,  being  most  acute  at  the  tip  of  the  tongue  and  ends  of 
the  fingers ;  least  so  in  the  back,  as  shown  in  Table  LXXIX. 

Table  LXXIX.3 — Tactile  Sensibility. 

Both  points  of  dividers  felt 
Part  of  surfaces.  when  separated  by 

these  distances. 

Tip  of  tongue 0.50  of  a  line. 

Palmar  surface  of  third  phalanx  of  fingers       .       1.00 

"   second        "         "         "  .       2.00     "      " 

Dorsal       "         "   third  "         "         "  .       3.00     "       " 

Middle  of  dorsum  of  tongue        ....       4.00 

End  of  the  great  toe 5.00     "      " 

Centre  of  hard  palate  ......       6.00 

Dorsal  surface  of  first  phalanx  of  fingers    .         .       7.00 

"        quarter  of  heads  of  metacarpal  bones      .       8.00 

Back  of  the  heel 10.00     "      " 

Dorsum  of  the  hand 14.00     "      " 

foot 18.00     '•      " 

Sternum 20  00     "      " 

Five  upper  dorsal  vertebrae .....  24.00 

Middle  of        "  " 30.00     "      " 

When  points  of  dividers  are  brought  closer  than  these  distances 

they  are  felt  as  one. 

1  Wagner  :  Physiologic,  Band  iii    Zweite  Abth.  S   524.  i  Physiologie,  Band  ii.  S.  558. 

3  Carpenter,  article  Touch,  Cycloptedia  of  Anat.  and  Phys.,  vol.  iv.  part  2d,  p.  1169. 


GENERAL    SENSIBILITY    OF    SKIN.  759 

It  was  also  shown  by  Weber,1  as  a  general  rule,  that  differences  in 
pressure  and  weight  are  appreciated  most  acutely  by  those  parts  of  the 
skin  which  are  most  sensitive  to  the  impressions  of  touch,  as  that  of  the 
fingers,  for  example,  and  that,  while  by  the  sense  of  pressure  alone,  a 
difference  in  weight  of  not  less  than  one-eighth  can  only  be  determined 
by  making  a  muscular  effort,  as  well  as  in  lifting,  a  difference  of  one- 
sixteenth  can  be  accurately  appreciated.  It  may  be  mentioned  in  this 
connection,  however,  that  the  appreciation  by  the  skin  of  the  tempera- 
ture of  the  surrounding  atmosphere,  or  of  bodies  applied  to  it,  does  not 
appear  to  depend  upon  nerves  other  than  those  of  general  sensibility,  or 
that  the  fact  of  our  appreciating  the  density,  immobility,  elasticity,  etc., 
offered  by  bodies  that  we  grasp  or  tread  upon,  or  which,  through  their 
weight,  offer  a  resistance  to  the  exercise  of  muscular  power,  implies  the 
existence  of  a  special  muscular  sense.  The  ataxic  symptoms  present  in 
certain  cases  of  paralysis,  often  referred  to  as  proof  of  the  existence 
of  a  special  muscular  sense  normally,  are  perfectly  well  accounted  for 
by  the  loss  of  general  sensibility.  Since  the  impression  made  by  the 
foreign  body,  whether  it  be  the  ground  we  tread  upon  or  the  child  we 
hold  in  our  arms,  not  being  transmitted  to  the  encephalon,  in  such  cases 
it  will  not  be  reflected  consciously  or  otherwise  to  the  appropriate  mus- 
cles whose  action  enables  us  to  stand  securely  or  grasp  firmly,  hence 
our  inability  to  walk  upon  the  ground  or  hold  a  child  in  our  arms 
unless  we  look  at  the  one  or  the  other,  the  essential  reflex  action  beins; 
then  effected  by  the  eye  and  optic  nerve  instead  of  the  skin  and  cuta- 
neous nerves. 

The  sense  of  touch,  like  the  other  senses,  can  be  very  much  improved 
by  attention  and  practice.  Thus,  it  is  said2  that  the  female  silk 
throwsters  of  Bengal  can  distinguish  twenty  different  degrees  of  fineness 
in  the  unwound  cocoons  by  the  touch  alone,  and  that  the  Indian  muslin 
weaver  makes  the  finest  cambric  with  a  loom  of  such  simple  construc- 
tion that,  if  worked  by  the  hands  of  a  European,  would  turn  out  but 
little  better  than  canvas.  It  is  also  a  well-known  fact,  that  those 
persons  who  are  employed  in  mints,  etc.,  in  the  daily  habit  of  handling 
coins,  detect  at  once,  and  with  certainty,  a  light  piece.  As  might  be 
expected,  the  sense  of  touch  is  very  much  developed  in  those  who  have 
lost  the  sense  of  sight,  or  who  have  been  blind.  One  of  the  most  remark- 
able of  such  cases  is  that  of  Giovanni  Gonelli,  who,  at  twenty  years 
of  age  lost  his  sight,  but  who,  nevertheless,  after  a  lapse  of  ten  years, 
developed  a  great  talent  as  a  sculptor,  modelling  such  an  excellent 
statue  out  of  clay  of  Cosmo  de  Medici  from  feeling  one  of  marble  that 
the  Grand  Duke  of  Tuscany  sent  him  to  Rome  to  make  a  statue  of 
Pope  Urban  VIII.,  which  was  a  very  successful  one,  the  likeness 
being  said  to  be  excellent.  Stranger  still,  even  a  good  knowledge  of 
botany  and  conchology  has  been  acquired  through  the  sense  of  touch 
by  persons  who  have  been  born  blind,  or  who  had  lost  their  sight  early 
in  life.  It  is  well  known,  also,  as  in  the  case  of  Baczko,3  that  the 
blind  can  learn  to  distinguish  the  colors  of  fabrics  by  the  sense  of  touch. 

I  Weber,  op.  eit..  Band  iii  ,  ZvveitK  Alitli.  S.  543.  2  Carpenter,  op.  cit.,  p.  1177. 

■:  Rudolphi :  Physiologie,  Band  ii.  S.  85. 


760  SKIN    AND    APPENDAGES. 

It  is  related  that  Sanderson,  the  Mind  professor  of  mathematics  at  Cam- 
bridge, could  not  only  distinguish  different  medals,  but  could  detect 
imitations  of  them  often  better  than  professed  connoisseurs,  while  his 
appreciation  of  variations  of  temperature,  it  may  he  mentioned  also,1  was 
so  acute  that  he  could  tell,  through  slight  modifications  in  the  tempera- 
ture of  the  air,  when  very  slight  clouds  were  passing  over  the  sun's  disk. 
It  is  a  familiar  fact,  also,  that  the  blind  learn  to  read  with  great  facility 
by  passing  their  fingers  over  raised  letters  of  about  the  size  of  those  of  a 
folio  Bible.  Terrible  a  calamity  as  the  loss  of  sight  is,  it  should  not  be 
forgotten,  as  the  above  examples  teach  us,  what  a  delicate  sense  in  that 
of  touch  we  possess  if  cultivated,  and  that  sources  of  pleasure  and  recre- 
ation through  its  development  may  be  offered  to  those  who  are  born 
blind,  or  who  have  lost  their  sight  later  in  life. 

i  Dunglison  :  Physiology,  vol.  i.  p.  697.     Phila.,  1856. 


CHAPTER    XL  VII. 

THE  NOSE  AND  OLFACTION.     THE  TONGUE  AND  GUSTATION. 

Just  as  we  have  seen  that  the  skin,  in  addition  to  its  other  functions, 
acts  as  a  general  sensory  organ,  so  we  shall  soon  learn  through  the 
study  of  Development,  that  parts  of  it  being  especially  modified  become 
wry  susceptible  to  certain  external  impressions,  and  that  such  modifica- 
tions, together  with  corresponding  ones  developed  in  the  terminal  nerves 
supplying  the  parts,  constitute  special  sensory  organs,  such  as  the  nose, 
tongue,  eye;  and  ear,  and  inasmuch  as,  of  such  organs,  the  nose  is  the 
most  simple  in  structure,  we  will  begin  the  consideration  of  the  special 
senses  Avith  the  study  of  Olfaction. 


Olfaction. 

The  nose,  the  special  organ  of  the  sense  of  smell,  is  regarded  anatomi- 
cally as  being  limited  to  the  pyramidal  eminence  of  the  face,  extending 
from  the  forehead  to  the  upper  lip;  physiologically,  however,  the  nose — 
that  is,  the  organ  of  olfaction — includes  not  only  the  parts  just  mentioned, 
consisting  of  the  septum,  cartilages,  etc.,  but  of  the  nasal  cavities  as 

Fig.  446. 


Distribution  of  nerves  in  the  nasal  passages.     1.  Olfactory  ganglion,  with  its  nerves.     2.  Nasal  branch 
of  fifth  pair.     3.  Spheno-palatine  ganglion.     (Dalton.) 

well ;  the  mucous  membranes  lining  the  latter  being  endowed  not  only 
with  general  sensibility,  as  we  have  seen,  but  with  the  special  sense  of 
olfaction,  its  upper  half  being  supplied  (Fig.  446)  by  the  olfactory  nerve, 
the  special  nerve  of  the  sense  of  smell.     The  skin  of  the  nose,  thin 


762      NOSE    AND    OLFACTION;    TONGUE     AND    GUSTATION. 

above  but  thick  below,  as  elsewhere,  is  furnished  with  sudoriferous  and 
sebaceous  glands  and  hairs;  the  hairs  are  usually  small  except  within 
the  margin  of  the  nostrils,  in  the  latter  position,  however,  they  are  well 
developed  from  all  sides,  and  to  a  certain  extent  act  like  a  fine  sieve  in 
keeping  out  dust,  etc.  The  nasal  cavities  communicating  with  the  ex- 
terior, in  front,  by  the  anterior  nares,  and  with  the  pharynx,  behind,  by 
the  posterior  nares,  are  lined  with  a  highly  vascular  mucous  membrane, 
the  Schneiderian  or  pituitary  membrane  closely  applied  to  the  adjacent 
periosteum  and  perichondrium,  which  becomes,  at  the  nostrils,  continuous 
with  the  skin,  at  the  posterior  nares  with  the  mucous  membrane  of  the 
pharynx,  and  at  the  lachrymo-nasal  duct  and  lachrymal  canals  with  the 
conjunctiva.  The  nasal  mucous  membrane  varies  very  much  as  regards 
its  thickness  and  vascularity.  Thus  upon  the  turbinated  processes  and 
turbinated  bone  it  is  very  thick  and  vascular,  and  forming  doublings  at 
their  inferior  borders,  and  posterior  extremities  of  the  above,  increases 
very  much  the  extent  of  the  nasal  surface.  Further,  while  the  epithe- 
lium within  the  region  of  the  external  nostrils  is  of  the  squamous  char- 
acter, that  lining  the  remaining  portion  of  the  nasal  cavities  is  of  the 
columnar  kind,  being  non-ciliated,  however,  in  the  olfactory  region,  or 
that  corresponding  to  the  convex  surface  of  the  turbinated  processes 
and  the  surface  of  the  nasal  plate  of  the  ethmoid  bone.  The  nasal 
mucous  membrane  is  also  provided  with  racemose  glands  whose  secretion 
keeps  the  surface  moist,  a  condition  essential  to  the  accurate  perception 
of  odoriferous  impressions.  The  glands  of  the  true  olfactory  membrane 
are,  however,  usually  of  a  simpler  character  than  those  found  in  the 
remaining  portion  of  the  nasal  mucous  membrane.  The  special  nerves 
of  the  sense  of  smell  or  the  true  olfactory  nerves  are  given  off  as  fifteen 
to  eighteen  filaments  from  the  olfactory  bulb  to  the  olfactory  region. 
The  olfactory  tract,  of  which  the  ganglionic  bulb  is  the  expansion,  is 
usually  described  as  the  olfactory  nerve,  but  improperly,  since,  as 
development  shows,  the  olfactory  tracts  are  outgrowths  of  the  cerebral 
hemispheres,  their  morphological  significance  masked  in  man  by  the 
excessive  development  of  the  former.  The  olfactory  tracts  are  two  cords 
or  bands,  soft  and  friable,  consisting  of  both  white  and  gray  nervous 
matter,  which,  passing  forward  and  inward  on  the  under  surface  of  the 
anterior  lobe  of  the  cerebrum  to  the  ethmoid  bone,  expand  at  the  side 
of  the  crusta  galli  into  the  olfactory  bulbs,  from  which  are  given  off,  as 
just  mentioned,  the  true  olfactory  nerves,  which,  passing  through  the 
cribriform  foramina  of  the  ethmoid  bone,  are  distributed  to  the  inner  and 
outer  walls  of  the  upper  parts  of  the  nasal  cavities.  Each  olfactory  tract 
arises  apparently  by  three  roots,  from  the  inferior  and  internal  surface  of 
the  anterior  lobe  of  the  cerebrum  in  front  of  the  anterior  perforated  space, 
the  external  and  internal  roots  being  composed  of  white  matter,  the 
middle  of  gray,  the  large  proportion  of  the  gray  substance,  one-third, 
entering  into  the  composition  of  the  olfactory  tract,  confirming  what  has 
just  been  said  as  to  the  true  nature  of  the  latter.  While  the  anterior 
root  can  be  traced  into  the  middle  lobe  and  the  middle  and  internal 
roots  into  the  anterior  lobe,  considerable  obscurity  still  prevails  as  to  the 
deep  origin  of  all  three  roots.  It  would  appear,  however,  that  the  long 
or  external  root  originates  in  the  island  of  Reil,  the  thalamus  opticus 


OLFACTION. 


763 


Fig.  447. 


and  the  nucleus  in  the  tempo-ro-sphenoidal  lobe  in  front  of  the  hippo- 
campus, the  middle  or  gray  root  in  the  gray  substance  of  the  anterior 
perforated  space,  the  inner  root  in  the  gyrus  fornicatus.  The  true 
olfactory  nerves,  or  the  filaments  given  oft"  from  the  olfactory  bulb,  as 
they  descend  from  the  cribriform  plate  ramify,  and,  uniting  in  a  plexi- 
form  manner,  spread  out  laterally  in  brush-like  and  flattened  tufts  (Fig. 
486).  In  their  minute  structure,  the  olfactory  differ  from  the  ordinary 
cerebral  and  spinal  nerves  in  being  pale  and  finely  granular,  in  not 
possessing  a  substance  of  Schwann,  in  adhering  to  one  another,  and  in 
pi-esenting  oval  corpuscles. 

Their  manner  of  termination  is  also  peculiar,  each  olfactory  fibre 
appearing  to  pass  into  the  spindle-shaped  bodies  (b)  interspersed 
between  and  among  the  epithelial  cells  (a)  of  the  olfactory  membrane 
(Fig.  447),  which  present  a  very  characteristic  appearance.  These 
olfactory  cells,  so-called  on  account  of 
their  supposed  function,  present  a  very 
characteristic  appearance,  the  central 
nucleated  portion  passing  on  the  one 
hand  internally  into  a  beaded  varicose- 
like  thread  (d)  apparently  continuous 
with  the  terminal  olfactory  fibril,  and, 
on  the  other,  externally  into  a  rod- 
like structure  (e),  which  in  the  frog  is 
prolonged  into  fine  hairs.  That  the 
olfactory  cells,  nerves,  bulbs,  and  tracts 
constitute  the  essential  structures  by 
which  external  impressions  are  trans- 
mitted to  the  subiculum  cornu  of  the 
hippocampal  convolution  in  which  the 
sense  of  smell  is  supposed  to  be  local- 
ized, is  proved  by  the  harmonious  re- 
sults of  experiments  performed  upon 
animals,  of  pathological  cases  observed 
in  man,  and  of  the  facts  of  comparative 
anatomy.  Thus,  among  the  numerous 
experiments  in  which  the  olfactory 
tracts  were  divided,  and  the  loss  of  the 
sense  of  smell  noticed,  may  be  men- 
tioned those  performed  upon  hunting 
dogs  by  Vulpian1  and  Philipaux,  in 
which  cases  the  animals,  although  de- 
prived of  food  for  thirty-six  hours  after 
complete  recovery  from  the  effects  of 
the  operation  failed  to  find  the  cooked 
meat  concealed  in  the  corner  of  the  lab- 
oratory. That  destruction  of  the  olfactory  nerves,  bulbs,  or  tracts  in 
man  due  to  disease  or  injury  involves  the  impairment  or  loss  of  the 
sense  of  smell  is  well  known  to  pathologists,  a  number  of  such  cases 


i'cll.-  ;iih!  terminal  nerve-fibres  of  the 
olfactory  region  highly  magnified.  1,  from 
the  frog;  2,  from  man;  a,  epithelial  cell, 
extending  deeply  into  a  ramified  process; 
h.  olfactory  cells;  <■,  their  peripheral  rods: 
e,  their  extremities,  seen  in  1  to  be  pro- 
longed into  fine  hairs  ;  '',  their  central  fila- 
ments ;  3,  olfactory  nerve-fibres  from  the 
dog;  (i,  the  division  into  fine  fibrillse. 
(Frey  after  Sciiultze.  ) 


'■   Lerons  sur  la  physiologie  generale  et  eumparee  dn  -ystem  ■  nerveux,  J).  SS2,  note.      Paris,  1806. 


764      NOSE    AND    OLFACTION;    TONGUE    AND    GUSTATION. 

having  been  observed  by  Schneider,  Rolpinck,  Eschricht,  Fahner, 
Valentin,  Rosenmnller,  Ceneti,  Pressat,1  Hare,2  Notta,3  Ogle,4  Flint.5 
That  the  olfactory  bulbs  and  nerves  are  the  essential  organs  of  the 
special  sense  of  smell  is  still  further  shown  by  the  fact  that  they  are 
usually  best  developed  in  animals  in  which  the  sense  of  smell  is  most 
acute,  being  better  developed,  for  example,  in  the  mammalia  than  in  the 
remaining  vertebrates,  while  of  the  former  class  it  is  among  those 
orders  as  in  the  carnivora,  in  which  the  sense  of  smell  is  very  acute, 
that  the  olfactory  region  is  most  developed,  in  the  dog,  for  example, 
in  which  the  sense  of  smell,  as  well  known,  is  very  remarkable.  The 
olfactory  nerves,  though  readily  impressed  by  odorous  emanations,  are 
but  little  affected  by  ordinary  ones,  while  the  olfactory  tracts  appear 
entirely  insensible  to  the  latter.6  That  the  appreciation  of  odors  or 
olfaction  is  due  to  the  material  emanations  given  off  by  odoriferous 
substances  being  carried  by  the  inspired  air  to  the  terminal  filaments 
of  the  olfactory  nerves,  the  olfactory  cells,  is  shown  by  the  manner  in 
which  one  sniffs  the  air  in  order  to  perceive  an  odor,  and  from  the  fact 
that  if  the  air  does  not  pass  through  the  nostrils,  as  in  occlusion  of 
the  posterior  nares  or  in  division  of  the  trachea,  the  sense  of  smell  is 
abolished.  In  every  case  where  odorous  emanations  are  perceived,  the 
latter  must  impinge  upon  the  olfactory  membrane,  come  in  contact, 
excite  the  peripheral  ends  of  the  olfactory  nerves.  As  a  general  rule, 
persons  having  offensive  emanations  from  the  respiratory  organs  are 
not  aware  of  such,  not  appearing  to  be  affected  by  odors  passing  from 
within  outward  through  the  nostrils.  This  is  due,  not  so  much  to  the 
odor  being  carried  by  the  air  expired  through  the  nostrils  instead  of 
by  that  inspired,  as  to  the  fact  that  one  becomes  in  time  accustomed 
to  such  odors,  and  ceases  to  notice  them,  however  fetid  they  may  be. 
Like  the  sense  of  touch,  and  the  other  special  senses,  that  of  smell 
may  be  very  much  developed  by  practice ;  as  exemplified  in  the  dis- 
crimination of  the  quality  of  wine,  drugs,  etc.  The  sense  of  smell  is, 
however,  far  more  acute  in  the  lower  races  of  mankind  than  in  the 
higher  ones,  to  whatever  extent  in  the  latter  it  may  have  been  devel- 
oped by  cultivation.  Thus  it  is  said  that  the  Mincopies  of  the  An- 
daman Islands  scent  the  ripeness  of  the  fruits ;  that  the  Peruvian 
Indians  distinguish  the  different  races  of  mankind  by  scent  alone ; 
that  Arabs  can  smell  a  fire  thirty  miles  off;  that  the  North  American 
Indians  pursue  by  smell,  their  enemies  or  their  game.  However 
the  sense  of  smell  may  be  developed  in  man,  it  is  far  surpassed  in 
acuteness  by  that  of  animals.  Every  sportsman  is  aware  that  odors 
are  recognized  by  hunting  dogs,  to  which  he  is  entirely  insensible. 

The  sense  of  smell  is  intimately  related  to  that  of  taste,  so  much  so, 
indeed,  that  if  the  nose  be  held,  or  plugged  up,  the  characteristic  taste 
of  certain  substances  when  swallowed,  is  not  appreciated  at  all,  as 
illustrated  in  drinking  different  kinds  of  wine,  it  being  difficult,  usually 
impossible,  to  distinguish  the  same  under  such  circumstances.     Further, 

1  Cited  by  Longet,  Anat.  et  Pliys.  dn  systeme  nerveux,  tome  ii.  p.  38.     Paris,  1842. 

-'  A  View  of  the  Structure,  etc.,  of  the  Stomach  and  Alimentary  Organs,  p.  145.     London,  1821. 

■'!  Archives  generates  de  medecine,  p.  385.     Paris,  Aviil,  187U. 

4  Medico-Chirur.  Trans.,  Lond.,  2d  ser.  vol.  xxxvii.  p.  203.         ■''  Flint:  Physiology,  1874,  vol.  v.  p.  39. 

0  Magendie  :  Journal  de  physiologic,  tome  iv.  p.  1G9.     Paris,  1824. 


THE    TONGUE    AND    GUSTATION. 


765 


it  has  been  observed  in  those  cases  in  which  the  sense  of  smell  is  lost, 
that  of  taste  is  usually  lost  also. 

The  influence  exercised  by  the  nose  upon  respiration  has  already 
been  mentioned.  We  shall  see,  hereafter,  that  the  nose,  also,  modifies 
very  much  the  quality  of  the  voice. 

The  Tongue  and  Gustation. 


The  sense  of  taste  or  gustation,  enabling  us  to  appreciate  the  savor 
of  sapid  substances  when  introduced  into  the  mouth,  is  due  to  the  sus- 
ceptibility of  the  terminal  filaments  of  the  chorda  tympani  and  glosso- 
pharyngeal nerves,  of  being  impressed  by  contact  of  the  same.  The 
influence  of  the  tongue  in  mastication  and  deglutition,  the  origin,  dis- 
tribution, and  general  functions  of  the  chorda  tympani  and  glosso- 
pharyngeal nerves  having  been  considered,  it  only  remains  for  us  now 
to  point  out  the  manner  in  which  gustation  is  performed  through  the 
parts  just  mentioned.  That  the  tongue  is  the  organ  of  gustation  there 
can  be  no  doubt.  It  would  appear,  however,  from  experiments  such  as 
those  performed  by  Longet1  and  others,  in  which  different  parts  of  the 
mucous  membrane  are  touched 
with  a  sponge  soaked  in  a  sapid 
solution,  that  the  sense  of  taste, 
probably  in  man  at  least,  is  lim- 
ited to  the  dorsal  surface  of  the 
tongue,  and  from  the  experiments 
of  Oamerer,2  in  which  solutions 
were  applied  through  fine  glass 
tubes,  more  particularly  to  the 
circum vallate  and  fungiform  pa- 
pillae, the  parts  around  the  latter 
not  appearing  to  be  impressed  by 
sapid  substances.  The  circum- 
vallate  papillae  (Fig.  448),  so 
called  on  account  of  each  papilla 
being  surrounded  by  a  trench  or 
fossa,  from  seven  to  twelve  in 
number,  are  disposed  in  two  rows,  in  the  form  of  a  reversed  V  on  the 
back  part  of  the  tongue.  Each  papilla  is  covered  by  numerous  small 
secondary  papillae,  the  latter,  however,  being  concealed  by  the  thick 
and  stratified  epithelium.  The  fungiform  papillae,  more  numerous  than 
the  circumvallate,  and  readily  distinguished  during  life  by  their  deep 
red  color,  while  found  in  the  middle  and  forepart  of  the  dorsum  of  the 
tongue,  are  most  numerous  and  closely  set  together  at  the  apex  and 
near  the  borders.  Each  fungiform  papilla,  while  narrow  at  its  attach- 
ment (Fig.  449),  at  its  free  extremity  is  blunt  and  rounded,  and,  like 
the  circumvallate  papillae,  is  covered  with  secondary  papillae  and  epi- 
thelium, imbedded  in  the  epithelium,  and  more  particularly  in  that  of 


Vertical  section  uf  circumvallate  papilla,  from  the 
calf.  35  diameters.  A.  The  papilla  B.  The  sur- 
rounding wall.  The  figure  shows  the  nerves  of  the 
papilla  spreading  toward  the  surface,  and  toward  the 
taste-buds  which  are  imbedded  in  the  epithelium  at 
the  sides;  in  the  sulcus  on  the  left  the  duct  of  a  gland 
is  seen  to  open.     (Exgelmann  ) 


1  Physiologic,  tome  iii.  p.  52.     Paris,  187;i. 


2  Zeitschrift  fiir  Biologie,  1S70,  Band  vi.  S.  440. 


766      NOSE    AND    01, FACTION  ;    TONGUE    AND    GUSTATION. 


the  circum vallate  papillae,  are  found  ovoidal  flask-shaped  bodies  (Fig. 
450),  having  a  length  of  the  3^75-th  of  an  inch,  and  a  diameter  of  the 


Pig.  449. 


Surface  and  sectional  view  of  a  fungiform  papilla.  A.  The  surface  of  a  fungiform  papilla  partial!}' 
denuded  of  the  epithelium.  135  diameters.)  p.  Secondary  papillae,  e.  Epithelium.  B  Section  of  a  fun- 
giform papilla  with  the  bloodvessels  injected,  a.  Artery,  v.  Vein.  c.  Capillary  loops  of  simple 
papillae  in  the  neighborhood,  covered  by  the  epithelium,  d.  Capillary  loops  of  the  secondary  papillae. 
e.  Epithelium.    (From  K.u.i.ikeh,  aftei  Todd  and  Bowman.) 

yg^QQ-th  of  an  inch,  consisting  apparently  of  modified  epithelial  cells, 
which,  with  good  reason,  are  supposed  to  be  the  special  organs  of  the 
sense  of  taste.    Each  ovoid  body,   surrounded  by   flattened   epithelial 

V\a.  4-r,(). 


Two  taste-buds  from  the  papilla  foliata  of  the  raM.it.     450  diameters.     (Engelmanx.) 

cells,  consists  of  a  cortical  and  a  central  part,  the  former  being  com- 
posed of  long,  flattened,  tapering  cells,  disposed  edge  to  edge,  and 
coming  to  a  point  at  the  taste-pore,  the  latter  of  spindle-shaped  cells 
and  taste  cells,  resembling  very  closely  the  olfactory  cells  ;  the  distal 
end  of  the  cell  projecting  from  the  orifice  of  the  taste-bud,  and  the  cen- 
tral beaded,  varicose,  and  continuous  with  the  terminal  filament  of  the 
gustatory  nerve.  Such  being  the  disposition  of  the  taste  cells,  it  would 
appear  that  the  terminal  filaments  of  the  gustatory  nerves,  of  which 
the  former  are  the  continuation,  are  excited  by  the  flow  of  sapid  solu- 
tions through  the  taste- pore  into  the  interior  of  the  taste-bud  ;  the  taste 
cells  being  especially  susceptible  to  impressions  made  by  sapid  sub- 
stances, whence  the  impression  is  transmitted  by  the  chorda  tympani 
and  glossopharyngeal  nerves  to  the  centres  of  taste  localized  in  the 


THE    TONGUE    AND    GUSTATION 


767 


subiculum  cornu  of  the  hippocampus,  when  they  are  perceived.  That 
the  chorda  tympani  and  the  glossopharyngeal  nerves  are  the  special 
nerves  of  the  sense  of  taste,  the  former  more  particularly  for  the  ante- 
rior two-thirds  of  the  tongue,  the  latter  for  the  posterior  third,  can  be 
shown,  as  already  mentioned,  both  by  experiments  performed  upon 
animals,  and  by  pathological  cases  observed  in  man,  division  or  dis- 
ease of  these  nerves  involving  loss  of  the  sense  of  taste.  The  glosso- 
pharyngeal differs  from  the  chorda  tympani,  however,  in  this  respect, 
in  that  it  is  a  nerve  of  general  sensibility,  as  well  as  that  of  taste,  the 
chorda  tympani  (gustatory  fibres)  being  a  nerve  of  taste  alone,  the  sen- 
sory fibres  of  the  lingual  nerve  bearing  to  the  chorda  tympani  the  same 
relation  that  the  sensory  fibres  of  the  glosso-pharyngeal  bear  to  its 
gustatory  ones.  In  conclusion,  it  may  be  mentioned,  and  as  might  be 
expected,  that  since  at  the  anterior  two-thirds  of  the  tongue  the  fungi- 
form papillae  are  supplied  by  the  chorda  tympani  at  the  posterior  third, 
and  the  circumvallate  papillae  by  the  glosso-pharyngeal,  the  taste  of  a 
substance  might  be  different  as  it  was  placed  upon  the  anterior  or  pos- 

"Fm.  451. 


a    I    A   f       a 


Filiform  papillae.     (Quain.) 


terior  part  of  the  tongue.     Such  has  been  experimentally  found  to  be 
the  case ;  thus,  according  to  Lussana,1  potassium  chloride  tastes  cool  and 


1  Archives  de  Pbytiologie,  tomt-  ii.  p.  208.     Paris,  1869. 


768      NOSE    AND    OLFACTION;    TONGUE    AND    GUSTATION. 

saltish  at  the  anterior  part  of  the  tongue,  and  sweetish  at  the  posterior 
part;  potassium  nitrate  cool  and  piquant  at  the  anterior,  and  bitter 
and  insipid  at  the  posterior  end.  Certain  substances,  like  mineral 
acids,  ferric  sulphate,  jalap,  and  colocynth,  while  but  little  appreciated 
at  the  anterior  part  of  the  tongue,  are  appreciated  very  acutely  at  the 
posterior  portion.  On  the  other  hand,  meats,  milk,  and  wines,  are 
equally  well  appreciated  at  both  ends  of  the  tongue.  It  may  be  men- 
tioned, incidentally,  that  the  filiform  papillae  the  minute  conical  emin- 
ences densely  set  over  the  greater  part  of  the  dorsum  of  the  tongue  and 
disposed  in  lines  diverging  from  the  raphe,  are  tactile  in  function. 


CHAPTER    XL VIII. 

THE  EYE  AND  VISION. 

The  organ  of  vision  includes  the  optic  nerve,  the  eve,  and  its  append- 
ages.    The  optic  nerves — consisting  of  medullated,  together  with  some 
gray  nerve  fibres — are  usually  described  as  arising  from  the  optic  chi- 
asma,  or  commissure.      Regarded,  however,  as  the  continuation  of  the 
optic  tracts,  the  optic  nerves  in  reality  arise,  as  we  have  seen,  from  the 
optic  lobes,  and  to  a  certain  extent  also  from  the  tlialami  optici,  corpora 
geniculata.  cerebral  peduncles,  and  tuber  cinereum ;   the  root  fibres  from 
these  different  points  of  origin,  converging  form  flattened  bands,  which, 
winding  obliquely  around  the  under  surface  of  the  crura  cerebri,  cross 
each  other  to  pass  to  the  opposite  eyes,  the  decussation  of  the  nerves, 
or  tracts,  which,  we  have  seen,  is  complete  giving  rise  to  the  chiasma. 
It  should   be  mentioned,  however,  that  the  fibres  constituting  the  an- 
terior portion  of  the  chiasma  are  not  derived  from   the  optic  tracts, 
but  simply  pass  from  one  eye  to  the  other,  Avhile  the  fibres  constituting 
the   posterior  part — and  sometimes  wanting — pass  from  tract  to  tract 
without  being  connected  with  the  eyes.     The  optic  nerves  proper,  aris- 
ing from  the  anterior  and  outer  border  of  the  chiasma,  curved  in  direc- 
tion and  rounded  in  form,  enclosed  in  a  double  fibrous  sheath,  derived 
from  the  dura   mater  and   arachnoid,  pass   into   the   orbit  through    the 
optic  foramina,  piercing   the  sclerotic  coat  of  the  eye  at  its  posterior, 
inferior,  and  internal  portions;    the  thin,  but  strong  membrane  through 
which   the   nervous   filaments   pass   into   the   sclerotic,    known  as    the 
lamina  cribrosa,  being   partly  derived   from   the  sclerotic,  and   partly 
from  the  coverings  of  the  nerve  fibres  which  are  lost  at  this  point.      At 
about  one-third  or  one-fourth  of  an  inch  behind  the  globe  of  the  eye, 
the  optic  nerve  receives  the  central  artery  and  vein  of  the  retina,  which, 
together  with  a  delicate  filament  from  the  ophthalmic  ganglion,  is  thence 
transmitted   within  the  centre  of  the  nerve  by  a   minute  canal,  lined 
with  fibrous  tissue.      That  the  optic  nerves  are  the  special  nerves   of 
the  sense  of  sight  there  can  be  no  doubt,  since  their  injury  or  division 
always  involves  impairment  or  loss  of  sight.     While  the  optic   nerves 
are  the  avenues  or  paths  by  which  the  impressions  due  to  the  presence 
of  light   are  transmitted    to  the  optic   lobes  and   angular  gyri,  there  to 
become,  as  we  have  seen,  conscious,  intelligent  vision,  they  are,  however, 
absolutely    insensible   to   ordinary  impressions.      Not   only   have  these 
nerves  been  pinched,  cut,  and  cauterized  in  animals,  without  the  latter 
evincing  any  pain,  but  their  insensibility  in  man  has  often  been  observed 
also,  as  in  surgical  operations,  for  example,  in  which   the  nerves  have 
been  exposed.     That  the  optic  nerves  are  especially  susceptible  to  the 
impressions  of  the  rays  of  light  is  still  further  shown  from  the  fact  of 
their  excitation,  however  caused,  always  giving  rise  in  consciousness  to 

49 


7/<>  THE    K  Y  K     AND     VISION. 

I  lie  idea  of  light — a  severe  blow  on  the  orbit  making  one  sec  stars,  as 
often  said,  the  mind  having  associated  so  uniformly  the  excitement 
of  the  optic  nerve  with  the  presence  of  light,  that  in  time  it  becomes 
impossible  to  disassociate  the  two;  the  presence  of  the  one  invariably 
suggesting  that  of  the  other. 

The  Eyeball. 

The  eyeball,  a  spheroidal  body,  partly  imbedded  in  a  cushion  of  fat, 
protected  by  the  surrounding  bony  orbit  and  the  eyelids,  moistened  by 
the  lachrymal  secretion,  and  moved  by  various  muscles,  is  composed  of 
several  coats,  concentrically  disposed,  and  enclosing  several  refractive 
media.  Were  it  not  for  the  fact  of  the  cornea  being  set  in  the  sclerotic, 
like  a  crystal  into  the  rim  of  the  face  of  a  watch,  the  eyeball  would 
present  the  form  of  a  spheroid.  Owing,  however,  to  the  cornea  con- 
stituting one-tenth  of  the  outer  circumference  of  the  eye,  and  to  the  fact 
just  mentioned,  the  longest  diameter  is  in  the  antero-posterior  direction, 
as  may  be  seen  from  the  results  obtained  by  Sappey  (Table  LXXX.). 

Table  LXXX.1 — Diameter  of  Eyeball  in  Fractions  of  an  Inch. 

Ant.  post.  Transverse.  Vertical.  Oblique. 

Mean  of  12  females  from 

18  to  81  years  of  age,    0.1)41  0.911  0.905  0.937 

Mean  of  14  males  from 

20  to  79  years  of  age,    0.968  0.941  0.925  0.949 

It  will  be  observed,  from  the  above  Table,  that  all  the  diameters  are 
less  in  the  female  than  in  the  male.  It  may  be  appropriately  mentioned 
in  this  connection,  also,  that  all  such  measurements  should  be  made  as 
soon  as  possible  after  death,  within  from  one  to  four  hours,  owing  to 
the  eyeball  losing  so  soon  its  normal  form  and  dimensions. 

The  Sclerotic  and  Cornea. 

The  sclerotic  (Fig.  452,  2),  the  outer  protective  coat  of  the  eyeball, 
covering  the  posterior  five-sixths  of  the  latter,  varying  in  thickness 
from  the  ^gth  to  the  j-g-th  of  an  inch,  is  a  dense  white,  opaque  tunic, 
composed  of  ordinary  connective  tissue,  mixed  with  small  elastic  fibres 
and  a  few  bloodvessels,  and  yielding,  on  boiling,  gelatine.  The  cornea, 
the  first  of  the  refractive  media,  constituting  the  anterior  sixth  of  the 
outer  circumference  of  the  eyeball,  and  varying  in  thickness  from  the 
■^d  to  the  gLjd  of  an  inch,  is  the  transparent  projecting  tunic  (Fig. 
452,  3,)  attached  to  the  periphery  of  the  sclerotic,  of  which,  indeed, 
it  may  be  regarded  as  the  continuation,  consisting,  like  the  latter,  of 
layers  of  connective  tissue,  though  somewhat  modified,  both  struc- 
turally and  chemically,  since  it  is  transparent,  admitting  light  into  the 
interior  of  the  eye,  and  yielding  chondrine  on  boiling.  The  cornea 
may  be  described  as  consisting  of  three  parts:  a  stratified  epithelium 
anteriorly,  continuous  with  that  of  the  conjunctiva,  a  middle  portion,. 

1  Traite  d'Anatomie,  tome  troisicme,  p.  747.    Paris,  ls"7. 


THE    CHOROID. 


771 


the  cornea  proper,  continuous  with  the  sclerotic,  consisting  of  modified 
connective  tissue,  posteriorly,  of  a  homogeneous,  elastic  lamella,  covered 
with  epithelium-like  cells,  the  membrane  of  Demours  or  Descemet,  the 
part  of  the  membrane  passing  to  the  anterior  surface  of  the  iris,  more 
noticeable  in  the  eyes  of  the  sheep  and  ox  than  in  man,  being  known  as 
the  ligamentum  pectinatum  iridis.     In  a  state  of  health  in  the  adult,  ves- 

Fig.  452. 


Horizontal  section  of  the  right  eyeball.  1.  Optic  nerve.  2.  Sclerotic  coat.  3.  Cornea.  4.  Canal  of 
Schlemm.  5.  Choroid  coat.  6.  Ciliary  muscle.  7.  Iris.  8.  Crystalline  lens.  9.  Ketina.  10.  Hyaloid 
membrane.     11.    Canal  of  Petit.     12.    Vitreous  body.     13.  Aqueous  humor.     (Dalton.) 

sels  are  not  found  in  the  cornea,  except  at  its  circumference,  where  they 
are  disposed  in  capillary  loops,  nutrition  apparently  being  carried  on 
by  means  of  the  corneal  corpuscles.  The  nerves  of  the  cornea  are, 
however,  very  numerous,  and  are  derived  from  the  long  and  short  cili- 
ary nerves.  Entering  the  sclerotic,  and  crossing  the  choroid,  they  pass 
into  the  cornea,  extending  almost  through  to  its  free  surface. 

The  Choroid. 


Removing  the  sclerotic  in  the  manner  represented  in  Fig.  453,  the 
second  coat  of  the  eyeball  from  without  inward,  the  choroid  with  its 
anterior  prolongation,  the  ciliary  muscle  will  then  be  exposed.  The 
choroid  may  be  regarded  essentially  as  the  vascular  pigmental  tunic  of 
the  eyeball ;  its  inner  or  pigmental  layer  in  reality,  however,  constitutes 
the  outer  coat  of  the  retina,  being  developed,  as  we  shall  see  hereafter, 
like  the  latter  from  the  invaginated  portion  of  the  optic  vesicle.  The 
choroid,  varying  in  thickness  from  the  YFoth  to  the  2Vtn  °f  an  mcn>  an(i 
covering  the  eyeball  to  the  same  extent  as  the  sclerotic,  is  connected  by 


772 


THE    EYE    AND    VISION. 


its  outer  surface  with  the  latter  tunic  by  connective  tissues,  vessels,  and 
nerves,  the  so-called  membrana  fusca,  and,  like  the  sclerotic,  is  traversed 
posteriorly  by  the  optic  nerve.  The  arteries  of  the  choroid,  the  short 
ciliary,  comparatively  large  after  piercing  the  sclerotic  close  to  the  optic 


Fig.  4? 


Choroid  membrane  and  iris  exposed  by  the  removal  of  the  sclerotic  and  cornea.  Twice  the  natural 
size.  a.  One  of  the  segments'of  the  sclerotic  thrown  back.  b.  Ciliary  muscle,  c.  Iris.  e.  One  of  the 
ciliary  nerves.    /.  One  of  the  vasa  vorticosa  or  choroidal  veins.  (Quain.) 

nerve,  break  up  into  branches,  which  pass  forward  and  then  inward 
to  end  in  the  capillaries,  the  latter  being  sometimes  known  as  the  tunic 
of  Ruysch.  The  veins  situated  externally  to  the  other  vessels  are  very 
numerous,  and,  being  disposed  in  curves  converging  into  four  trunks, 
present  a  peculiar  appearance,  which  has  given  rise  to  the  name  of 
vasa  vorticosa.  Among  the  vessels  of  the  choroid  are  also  found  elon- 
gated and  stellated  pigment  cells,  with  branches,  which,  intercommuni- 
cating, constitute  a  sort  of  network.  The  nerves  supplying  the  choroid 
are  derived  from  the  long  and  short  ciliary.  The  inner  surface  of  the 
choroid  is  smooth  and  is  covered  with  the  hexagonal  pigmental  cells  of 
the  retina,  which  will  be  considered  as  the  outer  layer  of  the  tunic 
rather  than,  as  formerly,  as  the  inner  layer  or  tapetum  nigrum  of  the 
choroid  for  the  reason  just  given. 

Ciliary  Processes. 

It  will  be  observed  from  Fig.  453  that  the  choroid  passes  forward 
into  the  ciliary  muscle,  the  latter  in  turn  passing  into  the  iris,  constitut- 
ing, in  fact,  one  continuous  layer — the  second  tunic  of  the  eyeball.  If, 
however,  the  choroid  be  viewed  from  behind,  as  represented  in  Fig.  454, 
in  which  the  eyeball  is  supposed  to  have  been  divided  transversely,  it 
will  be  seen  that  the  choroid  passes  forward  and  posteriorly  into  the 
ciliary  processes,  just  as  we  have  seen  it  passes  forward  but  anteriorly 
into  the  ciliary  muscle.    Or,  briefly,  the  relation  of  the  parts  may  be 


CILIARY    MUSCLE — THE    IRIS.  773 

expressed  by  saying  that  the  choroid  splits  at  its  anterior  termination 

into  the  ciliary  muscle  in  front,  and  the  ciliary  processes  behind,  the 

Fig.  4-34. 


mB>  y 


Ciliary  processes  as  seen  from  behind.  1.  Posterior  surface  of  the  iris,  with  the  sphincter  muscle  of  the 
pupil.  2.  Anterior  part  of  the  choroid  coat  3.  One  of  the  ciliary  processes,  of  which  about  seventy-one 
are  represented.      %,    (<t>iTAlN.) 

ciliary  muscle  being  continued  into  the  iris,  hence  the  general  term  of 
uvea  applied  to  all  of  these  parts  by  the  older  anatomists.  The  ciliary 
processes  or  plications,  about  seventy  in  number,  disposed  radially  behind 
the  ciliary  muscle  and  the  iris,  and  fitting  posteriorly,  as  we  shall  see, 
into  corresponding  plications  of  the  suspensory  ligament  of  the  lens, 
more  particularly  into  that  part  of  it  known  as  the  zone  of  Zinn, 
consists  of  large  and  small  thickenings  of  the  choroid,  the  small  folds 
alternating,  though  irregularly,  with  the  large  ones,  the  latter  measuring 
about  the  -j^th  of  an  inch  in  length  and  the  -^th  in  depth,  and  com- 
posed like  the  choroid  proper  of  vessels  and  pigment,  the  latter,  though, 
being  absent  in  the  rounded  inner  ends. 

Ciliary  Muscle. 

The  ciliary  muscle  (Fig.  453,  6),  the  continuation  anteriorly  of  the 
choroid,  about  the  |th  of  an  inch  wide,  consisting  of  longitudinal  and 
circular  fibres,  the  latter,  however,  present  at  the  periphery  of  the  iris 
only,  may  be  regarded  as  arising  from  the  inner  side  of  the  junction  of 
the  sclerotic  and  cornea,  close  to  the  canal  of  Schlemm,  and  inserted 
into  the  choroid  opposite  the  ciliary  processes.  Such  being  its  disposi- 
tion, it  is  evident  that,  in  contracting,  the  nerves  supplying  it  being 
the  long  and  short  ciliary  nerves,  will  draw  the  choroid  forward,  thereby 
compressing  the  vitreous  humor  and  relaxing  the  suspensory  ligament 
of  the  crystalline  lens,  the  significance  of  which  action  will  be  better 
appreciated  when  the  subject  of  accommodation  has  been  considered. 

The  Iris. 

The  iris  (Fig.  453,  e),  the  circular,  contractile,  and  colored  mem- 
brane seen  through  the  transparent  cornea,  to  which  the  characteristic 


774  THE    EYE    AND     VISION. 

color  of  the  eye  is  due,  is  the  muscular  diaphragm  of  the  eye,  the  aper- 
ture in  its  centre  or  pupil  permitting  and  regulating  the  passage  of  light 
into  the  interior  of  the  eye.  The  iris,  about  as  thick  as  the  choroid, 
is  attached  by  its  circumferential  border  to  the  line  of  junction  of  the 
cornea  and  sclerotic  at  the  origin  of  the  ciliary  muscle,  and  measures 
about  one-half  an  inch  across,  and  in  a  state  of  rest  about  the  one-fifth  of 
an  inch  from  the  circumference  to  the  pupil.  The  iris  consists  essentially 
of  a  stroma  of  connective  tissue  and  muscular  fibres,  the  latter,  disposed  as 
a  ring  around  the  pupil,  constituting  the  sphincter,  and  as  rays  from  the 
centre  to  the  circumference,  the  dilator  muscles,  of  the  iris.  The  pupil, 
or  aperture  in  the  iris  regulating  the  amount  of  light  admitted,  varies  in 
size  according  as  the  muscular  fibres  are  contracted  or  relaxed,  from  the 
one-twentieth  to  the  one-third  of  an  inch,  and  during  foetal  life  is  closed 
by  a  delicate  transparent  membrane.  The  iris  is  supplied  by  the  two 
long  ciliary  and  anterior  ciliary  arteries,  the  latter  being  derived  from 
the  muscular  branches  of  the  ophthalmic.  The  two  long  ciliary  arteries 
having  pierced  the  sclerotic,  one  on  each  side  of  the  optic  nerve,  pass 
between  the  latter  tunic  and  the  choroid  to  the  ciliary  muscle,  and  each 
vessel,  just  before  reaching  the  iris,  divides  into  an  upper  and  lower 
branch,  which,  anastomosing  with  the  corresponding  vessels  of  the  oppo- 
site side,  and  with  the  anterior  ciliary  arteries,  forms  avascular  ring,  the 
circulus  major  of  the  ciliary  muscle,  from  which  small  branches  are 
given  off,  some  of  which  supply  the  muscle,  while  others,  converging 
toward  the  pupil,  from  a  second  vascular  circle — the  circulus  minor ; 
from  the  latter  capillaries  are  given  off  which  terminate  in  veins.  The 
veins  of  the  iris  terminate  in  the  circular  venous  sinus  known  as  the 
canal  of  Schlemm,  situated  at  the  junction  of  the  cornea  with  the 
sclerotic.  The  nerves  of  the  iris  are  the  long  ciliary,  which,  as  we  have 
already  seen,  are  given  off  from  the  nasal  branch  of  the  ophthalmic  and 
the  short  ciliary  nerves  derived  from  the  ciliary  ganglion.  The  ciliary 
nerves,  after  piercing  the  sclerotic,  pass  forward  on  the  surface  of  the 
choroid,  to  which  tunic  they  give  branches,  to  the  ciliary  muscle,  in 
which  they  form  a  plexus  continued  forward  into  the  iris  ;  they  appa- 
rently terminate  at  the  pupil  in  a  plexus  of  non-medullated  fibres.  It 
has  already  been  mentioned  that  the  fibres  of  the  third  pair  of  nerves  and 
of  the  sympathetic  exercise  an  antagonistic  influence  upon  the  pupil ;  divi- 
sion of  the  third  pair  being  followed  by  dilatation,  and  that  of  the  sym- 
pathetic by  contraction  of  the  pupil;  and  that  the  ciliary  ganglion  giving 
off  the  ciliary  nerves  supplying  the  muscular  fibres  of  the  iris,  is  made 
up  to  a  considerable  extent  of  fibres  derived  from  the  third  pair  and 
sympathetic.  Putting  together  these  facts,  and  further  supposing  that 
the  fibres  of  the  third  pair  and  sympathetic  pass  through  the  gan- 
glion, thence,  as  the  ciliary  nerves,  to  terminate  in  the  circular  and 
dilator  fibres  of  the  iris  respectively,  it  becomes  evident  why  the  pupil 
dilates  if  the  third  pair  be  divided,  since  there  is  nothing  then  to 
antagonize  the  dilating  effect  of  the  sympathetic,  and  why  the  pupil 
contracts  if  the  sympathetic  be  divided,  since  then  there  is  nothing  to 
antagonize  the  constricting  effect  of  the  third  pair.  Inasmuch,  how- 
ever, as  the  nasal  branch  of  the  ophthalmic  contributes,  as  we  have  seen, 


THE    IE  IS.  775 

to  the  formation  of  the  ciliary  ganglion,  the  only  question  about  which 
there  can  still  be  any  doubt,  is  as  to  whether  the  sympathetic  fibres 
passing  to  the  ganglion  of  Grasser  and  thence  to  the  nasal  branch  of  the 
ophthalmic,  influence  the  radiating  fibres  of  the  iris  in  the  same  manner 
as  those  of  the  sympathetic,  just  contrasted  with  the  fibres  of  the  third 
pair.  Now.  while  it  is  very  possible  that  some  of  the  fibres  of  the  nasal 
branch  of  the  ophthalmic  passing  into  the  ciliary  ganglion  are  derived 
from  the  sympathetic  and  influence  the  radiating  fibres  of  the  iris,  it  is 
probable  that  most  of  its  fibres  are  derived  from  the  ophthalmic,  and 
endow,  through  the  short  ciliary  nerves,  together  with  the  long  ciliary, 
the  iris  and  cornea  with  sensibility.  We  shall  see  presently  that  in  the 
accommodating  of  the  eye  for  near  objects,  and  in  the  converging  of  the 
axes  of  the  eyes  for  the  same  purpose,  that  the  pupil  is  contracted,  and 
that  such  is  the  case  when  the  eye  is  exposed  to  a  bright  light,  the  pupil 
being  widely  dilated,  however,  when  the  light  is  dim.  If  what  has  just 
been  said  with  reference  to  the  influence  of  the  third  pair  of  nerves  be 
accepted,  it  becomes  intelligible  why  the  pupil  contracts  under  the 
stimulus  of  light,  since  the  impression  made  upon  the  retina  by  the  light 
being  transmitted  by  the  optic  nerve  to  the  optic  lobe  is  thence  reflected 
by  the  third  pair  to  the  circular  fibres  of  the  iris,  causing  the  latter  to 
contract  the  pupil.  If  such  be  the  reflex  mechanism,  then  the  pupil 
should  be  uninfluenced  by  light  if  either  the  optic  or  third  pair  of 
nerves  be  divided,  and  such  has  been  experimentally  shown  to  be  the 
case.  It  should  be  mentioned,  however,  that  light,  apart  from  any 
nervous  influence,  will  exercise  a  direct  stimulating  effect  upon  the  iris, 
causing  the  pupil  to  contract  even  after  the  eye  has  been  removed  from 
the  orbit  several  hours  after  death.     In  connection  with  the  influence 

Fru.  455. 


Diagrammatic  section  of  the  eyeball,  showing  difference  of  refraction  for  direct  and  indirect  vision. 

i;  ijrs  from  a  point  in  the  line  of  direct  vision,  focussed  at    the  retina.     6,  y,  z.  Kays  from  a  point 

outside  the  line  of  direct  vision,  brought  to  a  focus  and  dispersed  before  reaching  the  retina.     (Dalton.) 

exerted  by  the  third  pair  of  nerves  upon  the  iris,  this  fact  is  an  impor- 
tant one,  since  it  offers  an  explanation  of  the  pupil  contracting  even 


776 


THE    EYE    AND    VISION, 


after  division  of  the  third  pair.  The  contraction  of  the  pupil  in  response 
to  the  direct  stimulus  of  light  is,  however,  very  different  from  that 
observed  when  the  action  is  a  nervous,  reflex  one,  taking  place  very 
slowly  and  requiring  a  long  exposure.  It  need  hardly  be  men- 
tioned that  section  or  electrical  stimulation  of  the  nerves  supplying  the 
iris,  involving  as  they  do  sympathetic  fibres,  must  modify  the  vascularity 
of  the  iris.  Indeed,  it  has  been  held  that  contraction  of  the  pupil  is  due 
to  a  congestion  of  the  vessels,  dilatation  to  a  depletion  of  the  same;  the 
change  in  the  diameter  of  the  pupil  is,  however,  too  great  to  be  accounted 
for  in  that  way.  While  the  function  of  the  iris  is  without  doubt  that  of 
a  diaphragm,  regulating,  through  the  pupil,  the  amount  of  light  admitted 
to  the  interior  of  the  eye,  it  will  be  observed,  from  Fig.  455,  that  not 
only  will  the  light  enter  the  eye  from  a  point  (a)  in  the  line  of  direct 
vision,  but  from  a  point  (b)  outside  that  line,  and  that  the  latter  rays 
being  brought  too  soon  to  a  focus,  are  dispersed  again  before  reaching 
the  retina,  and  so  give  rise  to  confused  vision. 

The  Retina. 

If  the   choroid,  including  the   tapetum  nigrum,  be   removed   under 
water  in  the  same  manner  as  the  sclerotic,  the  third  tunic  of  the  eye 


Mem.br 


Fig.  456. 
Lamina  cribrosa 


' 


Section  through  the  middle  of  the  optic  nerve  and  the  tunics  of  the  eye  at  the  place  of  its  passage 

through  them.     (EcKER.) 


from  without  inward,  or  the  retina,  will  be  then  exposed  as  a  very 
delicate  and  transparent  membrane,  through  which  will  be  seen  the 
posterior  portion  of  the  underlying  vitreous  humor.  Within  a  short 
time  after  death,  however,  the  retina  loses  its  transparency  and  be- 
comes opaline,  the  change  being  hastened  by  the  action  of  water,  alcohol, 


THE    RETINA 


777 


and  other  fluids.  The  retina,  varying  in  thickness  from  the  g^th  to 
the  27rTrtn  °f  an  incn^  extends  over  the  posterior  portion  of  the  eyeball 
to  within  a  distance  of  about  the  Y5tn  °f  an  *ncn  °f  *ne  ciliary  pro- 
cesses, and,  if  torn  from  its  anterior  attachment,  presents  a  finely  indented 
edge,  the  so-called  ora  serrata.    As  a  matter  of  fact,  however,  the  retina 


Fig.  4")7. 


Fig.  458. 

Outer  or  choroidal  sm  far 


The  posterior  half  of  the  retina  of  the  left  eye 
viewed  from  before.  Twice  its  natural  size.  s. 
Cut  edge  of  the  sclerotic,  eft.  Choroid.  >-.  Retina: 
in  the  interior  at  the  middle  the  macula  lutea  with 
th»  depression  of  the  fovea  centralis  is  represented 
by  a  >li'^ht  oval  shade;  toward  the  left  side  the 
light  spot  indicates  the  colliculus  or  eminence  at 
the  entrance  of  the  optic  nerve,  from  the  centre  of 
which  the  arteria  centralis  is  seen  sending  its 
branches  into  the  retina,  leaving  the  part  occupied 
by  the  macula  comparatively  free.     (Hexle.) 

does  not  terminate,  as  often  said, 
at  the  ora  serrata,  but  is  continuous 
forward  as  a  thin  layer  of  trans- 
parent columnar  nucleated  cells, 
the  pars  ciliaris  retinee,  which, 
reaching  the  tips  of  the  ciliary  pro- 
cesses, then  disappears.  The  retina. 
the  nervous  tunic  of  the  eve.  and  inner  surface. 

.1  ,•  n      -,  '-1  i  r       Diagrammatic  section  of  the  human  retina.      1. 

that  portion    oi    it    susceptihle    ot  T    „    ,  t.      .       ,    .,     „  T         ,     . 

1  r  Layer  of  the  pigment  cells.     2.  Layer  of  rods  and 

being    impressed    by  light,  may     be    cones.     .  .  Membrana  limitans  externa.     3.   Outer 
regarded    as     an     expansion     Of     the    nuclear  layer.     4.  Outer  molecular  layer.    5.  Inner 

Optic    nerve,    though    it     is    USUally    "UC'ear  ,a)7"    6.  Inner  mol«cnlar  layer.  7.  Layer 

1  '        .        O  «       of  nerve  cells.     8.  Layer  of  nerve  fibres.     •■  Mem- 

described  as  being  traversed  by  the  brana  limitans  interna.   (Sc.u-i.tze.) 

latter,  like  the  sclerotic  and  choroid. 

The  optic  nerve  apparently,  then,  penetrates  the  retina  about  the  -|-th 

of  an  inch  within,  and  the  ^th  of  an  inch  below  the  antero-posterior 

axis  of  the  eye.      The  nerve  fibres  being  at  this  point,  the  porus  opticus, 

slightly  elevated,  give  rise  to  a  small  eminence  (Fig.  456),  the  colliculus 


778  THE    EYE    AND    VISION. 

nervi  optici,  between  "\vliicli  the  central  artery  of  the  retina  aopears,  and 
spreads  out  arborescent-like,  over  the  inner  surface  of  the  retina  (Fig. 
457),  and  the  branches  of  the  central  veins  converge  and  disappear. 
To  the  outer  side  of  the  optic  nerve,  about  the  yL-th  of  an  inch,  may- 
be also  seen  on  the  inner  surface  of  the  retina,  a  yellow  spot,  somewhat 
elliptical  in  shape,  about  the  -|th  of  an  inch  long,  and  A-th  of  an 
inch  broad,  its  long  diameter  being  horizontal,  the  so-called  macula 
lutea  or  limbus  lutens  of  Sommering,  presenting  in  its  centre  a  depres- 
sion, the  fovea  centralis,  which  is  situated  in  the  axis  of  vision.  As 
the  retina  is  so  thin  at  this  point  that  the  pigmental  layer  can  be  seen 
clearly  behind  it,  the  fovea  centralis  gives  the  impression  that  it  is  a 
hole  that  has  been  made  in  the  retina.  It  is  an  interesting  fact,  that 
the  yellow  spot  of  Sommering  has  only  been  found  in  the  eye  of  the 
primates.  The  sensitiveness  of  the  retina  to  light  varies  very  much, 
being  greatest  at  the  yellow  spot,  and  gradually  diminishing  toward  the 
periphery.  The  difference  can  be  determined  experimentally  on  the 
same  principle  as  the  tactile  sensibility  of  the  skin  was  determined. 
Thus,  if  two  wires  be  placed  close  together,  but  sufficiently  far  apart  to 
enable  us  to  distinguish  one  from  the  other,  and  then  the  eye  be  so 
directed  that  the  image  of  the  wires  shall  fall,  first  upon  the  yellow 
spot,  and  then  upon  the  great  circle  of  the  eye;  in  the  latter  case,  the 
wires,  to  be  seen  distinctly,  must  be  separated  at  a  distance  150  times 
greater  than  in  the  former  one.  It  is  evident,  therefore,  why  the 
movements  of  the  eyeball  all  tend  to  bring  the  image  of  external  objects 
upon  the  yellow  spot,  and  as  the  latter  only  constitutes  about,  the 
gJj-Q-th  of  the  retina,  it  follows  that  but  a  small  portion  of  the  latter 
is  actually  made  use  of  in  distinct  vision.  As  an  illustration,  may 
be  mentioned  the  familiar  fact  that,  in  reading,  we  see  one  or  two 
words  at  a  time,  and  that  the  eye  must  pass  over  the  whole  line  in  order 
to  read  it. 

The  retina  consists,  microscopically,  of  a  connective  tissue  scaf- 
folding, so  to  speak,  supporting  eight  distinct  layers  disposed  from 
without  inward,  as  follows  (Fig.  458):  1,  pigmentary  layer;  2,  co- 
lumnar layer ;  3,  outer  nuclear  layer ;  4,  outer  molecular  layer  ;  5, 
inner  nuclear  layer ;  6,  inner  molecular  layer:  7,  ganglionic  layer; 
and  8,  nerve  layer.  The  first  outer,  or  pigmentary,  layer  of  the  retina, 
formerly  described  as  the  inner  layer,  or  tapetum  nigrum  of  the  cho- 
roid, consists  of  a  single  stratum  of  hexagonal  nucleated  epithelium 
cells.  The  outer  surface  of  each  cell,  that  lying  next  to  the  choroid, 
is  smooth,  flattened,  and  usually  free  from  pigment ;  the  inner 
portion,  prolonged  as  fine  straight  filamentous  processes  between  the 
rods  and  cones  of  the  second  or  columnar  layer  is,  however,  loaded 
with  pigment.  The  second,  or  columnar  layer,  also  known  as  the 
the  baciilary  layer,  Jacob's  membrane,  consists  of  millions  of  elongated 
bodies,  the  so-called  rods  and  cones,  disposed,  in  a  palisade-like  man- 
ner, between  the  pigmentary  layer  and  the  so-called  membrana  lim- 
itans  externa,  which  is  not  a  continuous  membrane,  but  is  formed 
through  the  connective  tissue  fibres  of  the  retina,  uniting;  more  or  less 
along  a  definite  line  at  the  boundary  of  the  third,  or  outer  nuclear  layer. 


THE    RETINA.  779 

The  rods  exceed  the  cones  in  number,  there  being  usually  about  four 
rods  to  one  cone,  except  at  the  macula  lutea,  where  cones  only  are  pres- 
ent; they  have  an  elongated  cylindrical  form  with  a  diameter  of  about 
T2To~o"tn  °f  an  ^ncn  an^  a  length  of  -^Q-th  of  an  inch.  The  cones 
on  the  other  hand,  are  shorter  and  thicker,  having  a  diameter  of  about 
4iWtn  °f  an  incn5  bulge  out  at  the  inner  end  or  base,  and  termi- 
nate externally  by  a  fine  tapering  portion.  The  cones  are  usually 
separated  by  a  distance  of  -g-^Voth  of  an  inch,  the  intervening  por- 
tion being  filled  by  rods.  Through  delicate  fibre-like  prolongations 
the  inner  ends  of  the  rods  and  cones  are  connected  with  the  third  or 
outer  layer  of  the  retina,  the  outer  nuclear  layer,  which  consists  of 
several  strata  of  clear  oval  elliptical  nucleated  corpuscles  or  granules, 
from  both  ends  of  which  delicate  fibres  are  prolonged.  These  outer 
granules,  presenting  marked  differences,  are  of  two  kinds,  known 
as  rod  granules  and  cone  granules,  according  as  they  are  connected 
with  the  rods  or  cones,  respectively.  While  the  outer  fibres  of  the 
outer  nuclear  layer  are  prolonged  into  the  rods  and  cones,  the  inner 
fibres  of  the  same  are  prolonged  into  the  outer  molecular  layer ;  the 
latter  in  turn  appears  to  be  connected  through  fibrils  with  the  granules 
of  the  inner  nuclear  layer,  the  latter  being  connected  with  the  inner 
molecular  layer.  The  seventh  layer  of  the  retina  from  without  inward, 
the  ganglionic  or  layer  of  nerve  cells,  consists  of  a  stratum  of  nerve 
cells  of  a  spheroidal  or  pyriform  figure,  which  appears  to  be  connected 
by  fibres  on  the  one  hand,  with  the  preceding  inner  molecule  layer, 
and,  on  the  other,  with  the  fibres  of  the  optic  nerve.  The  latter,  con- 
stituting the  eighth  layer  of  the  retina,  appears  to  be  bounded  by  a 
distinct  membrane,  the  membrana  limitans  interna,  which,  however,  is 
not  a  continuous  structure,  as  its  appearance  would  lead  one  to  sup- 
pose, but  is  formed,  like  that  of  the  membrana  limitans  externa,  by 
the  terminal  fibres  of  the  sustenacular  or  connective  tissue  framework 
of  the  retina  being  united  together  at  this  point.  From  this  necessarily 
brief  description  of  the  minute  structure  of  the  retina  it  will  be  seen 
that  the  layer  of  the  rods  and  cones,  or  Jacob's  membrane,  bounded 
externally  by  the  pigmentary  layer,  may  be  regarded  as  the  termination 
of  the  optic  nerve  fibres.  It  has  already  been  mentioned  that  at  the 
macula  lutea  the  rods  are  absent,  the  cones  only  being  present;  the 
latter  are,  further,  much  longer  and  narrower  than  elsewhere,  especially 
opposite  the  fovea.  At  this  portion  of  the  retina  the  various  layers  of 
which  it  consists  are  also  very  much  thinned.  The  yellow  color  of  the 
macula,  deepest  at  the  centre,  is  due  to  a  coloring  matter  diffused 
through  all  the  layers  except  that  of  the  cones  and  the  outer  nuclear 
layer.  It  might  naturally  be  supposed  that  the  anterior  layer  of  the 
retina,  that  facing  the  light,  would  be  the  sensitive  layer — as  a  matter 
of  fact,  of  all  the  layers  of  the  retina,  however,  that  of  the  rods  and 
cones  is  most  sensitive  to  light,  as  can  be  shown  experimentally  by 
so  illuminating  the  eye  that  one  is  able  to  perceive  the  shadows  of  the 
vessels  of  his  own  retina,  which  are  cast  upon  the  layer  of  rods  and 
cones.  The  vessels  of  the  retina  being  situated  in  its  anterior  layer, 
necessarily  cast  their  shadows  on  one  of  its  posterior  layers,  and  the 
only  reason  that  we  do  not  ordinarily  see  these  shadows  is  probably 


'80 


THE    EYE    AND    VISION. 


that  we  have  become  so  accustomed  to  them  that  they  no  longer  attract 
our  attention.  If,  however,  the  source  of  light  be  placed  in  an  unusual 
position,  as  in  Fig.  4/39,  then  the  shadows  of 
the  vessels  falling  on  an  unusual  portion  of  the 
layer  of  rods  and  cones  will  be  perceived,  and 
will  be  seen  by  one  looking  at  a  very  dark  sur- 
face in  a  dark  room,  as  if  projected  at  D'  C, 
and  resembling  exactly  the  vessels  of  the  retina, 
the  picture  of  the  retina  so  seen  being  known  as 
the  vascular  tree  of  Purkinje.  Now  it  was  shown 
by  H.  Muller,1  that  the  distance  between  the 
anterior  layer  of  the  retina,  and  the  layer  of  rods 
and  cones,  was  about  equal  to  that  between  the 
retinal  vessels  ami  their  shadows ;  necessarily, 
then,  the  layer  of  rods  and  cones  must  be  sensi- 
tive to  light.  Now,  it  being  remembered  that 
the  layer  of  rods  and  cones  lies  next  to  the  pig- 
mental layer,  and  that  the  retina,  with  the  excep- 
tion of  the  latter  layer,  is  transparent,  it  follows 
that  a  ray  of  light  passes  through  the  retina  until 
it  reaches  the  pigmental  layer,  when  it  ceases  to 
be  light,  being  transformed  into  either  heat, 
chemical  or  nervous  force  ;  the  latter  exciting  the 
rods  and  cones,  gives  rise  to  an  impression  which 
is  then  transmitted  back  to  the  optic  fibres  on  the  anterior  surface  of 
the  retina,  where  it  is  again  reflected  along  the  optic  nerve  fibres  to  the 
optic  lobes,  etc. 

Beyond  the  statement  that  the  rods  and  cones  are  excited  by  the 
heat  or  nerve  force,  or  whatever  the  force  may  be  into  which  the  light 
is  transformed  in  the  pigmental  layer,  little  can  be  said  as  to  the  spe- 
cial role  they  play  in  vision.  Such  facts,  however,  as  that  in  the  bat, 
hedgehog,  and  mole,  nocturnal  animals,  and  night  birds,  also,  the  retina 
consists  solely  of  rods;  whereas,  in  day-birds,  especially  in  those  which 
live  on  insects,  of  brilliant  colors,  the  retina  contains  a  much  larger 
number  of  cones  than  the  mammalia,  would  lead  one  to  suppose  that 
the  rods  are  affected  by  differences  in  the  intensity  of  the  light,  the 
cones  by  differences  in  its  quality — that  is,  its  color.  While  there  can 
be  no  doubt  that  the  fibres  of  the  optic  nerve  transmit  luminous  impres- 
sions, or  their  modifications,  in  the  manner  described,  it  can  be  shown 
experimentally  that  the  part  of  the  retina  where  these  fibres  appear  is 
insensitive  to  light,  and  is  called,  for  that  reason,  the  punctum  caecum. 
Thus,  if  two  black  points  (Fig.  460,  A,  B),  on  a  piece  of  paper,  separ- 

Fig.  460. 


B,  a  candle   placed  at  the 

side  of  the  eye — that  is,  as 
much  to  the  Bide  of  the  cen- 
tra ot  the  cornea  as  possible. 
B',  interior  luminous  source, 
formed  by  the  rays  of  light 
concentrated  by  the  crystal- 
line lens  upon  the  extreme 
lateral  portion  of  the  eye. 
CD,  two  vessels  of  the  retina 
(the  size  of  the  retina  is  here 
greatly  exaggerated).  The 
shadow  of  these  two  vessels 
is  seen  as  if  projected  at  D' 
ami  C.     Experiment  by  Pur- 

KIN.TE. 


ated  by  a  distance  of  two  inches,  be  viewed  at  a  distance  of  six  inches 
by  the  right  eye,  the  left  eye  being  closed,  the  point  B  will  be  invisible, 
being  then  opposite  the  punctum  caecum,  or  blind  spot. 


1  Verhand.  der  physik  med.  Gessellschaft  zu  Wurzburg,  v.  S.  411. 


THE    CRYSTALLINE    LENS.  <81 


The  Vitreous  Humor  and  Hyaloid  Tunic. 

The  vitreous  humor,  while  enclosed  by  the  retina,  does  not,  however, 
lie  loosely  in  the  cavity  of  the  eyeball,  being  invested  by  a  delicate 
membranous  capsule,  about  the  ^^^th  of  an  inch  in  thickness — the 
hyaloid  tunic.  The  latter  is  thicker  in  advance  of  the  retina  than 
elsewhere,  and,  as  already  mentioned,  is  impressed  by  the  ciliary  pro- 
cess of  the  choroid,  the  zone  so  formed  around  the  crystalline  lens,  and 
well  defined  by  the  staining  of  the  process,  being  known  as  the  zone  of 
Zinn.  Anteriorly  the  hyaloid  tunic  splits  into  two  laminae,  which, 
diverging  at  the  border  of  the  crystalline  lens,  becomes  confluent  with 
the  anterior  and  posterior  surfaces  of  its  capsule,  the  two  laminae  adher- 
ing at  intervals;  if  the  space  between  them  be  inflated,  it  will  assume 
the  appearance  of  a  beaded  canal,  surrounding  the  circumference  of  the 
lens — the  canal  of  Petit.  Such  being  the  disposition  of  the  hyaloid 
tunic,  it  is  evident  that  not  only  does  it  support  the  vitreous  humor, 
through  investing  the  latter,  but  acts  also,  from  what  has  just  been  said, 
as  the  suspensory  ligament  of  the  lens.  The  vitreous  humor,  one  of 
the  refractory  media  of  the  eye,  occupying  about  the  posterior  two- 
thirds  of  the  globe,  consists  of  a  clear,  glassy,  gelatinous  matter,  divided 
into  compartments  by  delicate  membranous  processes,  which,  given  off* 
by  the  hyaloid  tunic,  penetrate  its  substance.  The  specks  that  one  sees 
occasionally  floating  about,  as  it  were,  in  the  field  of  vision,  the  so-called 
muscie  volitantes,  are  due  to  the  shadows  cast  upon  the  retina  by  the 
connective  tissue  elements  suspended  in  the  vitreous  humor. 

The  Crystalline  Lens. 

The  crystalline  lens  (Fig.  452,  8).  the  most  important  of  the  refracting 
media  of  the  eye,  transparent  and  very  elastic,  is  situated  in  the  hyaloid 
fossa  of  the  vitreous  humor,  behind  the  pupil,  and  is  enclosed,  as  already 
mentioned,  between  the  laminpe  of  the  hyaloid  tunic,  the  latter  constitut- 
ing its  suspensory  ligament.  The  crystalline  lens  is  a  double  convex  lens, 
the  convexity  of  the  anterior  surface  being  greater  than  that  of  the 
posterior  one,  the  antero-posterior  diameter,  ith  of  an  inch,  is,  however, 
a  little  less  than  that  of  the  lateral  one,  -3rd  of  an  inch.  With  advance 
in  age  the  convexities  diminish,  the  lens  becomes  harder  and  inelastic, 
which  accounts  for  the  gradual  diminution  in  the  power  of  accommo- 
dating the  eye  to  distances.  If  the  lens  be  examined  with  a  low  mag- 
nifying power,  there  will  be  observed  on  each  of  its  surfaces  a  star-like 
body,  nine  or  sixteen  rays  of  which  extend  from  the  centre  to  within 
about  two-thirds  of  the  periphery.  The  body  of  the  stars  and  their 
rays  are  not  of  a  fibrous  character,  like  the  rest  of  the  lens,  but  consist 
of  a  homogeneous  substance,  which  extends  between  the  fibres.  The 
latter  are  flattened,  six-sided  prisms,  from  the  jgVo"^1  to  tne  2TU¥tD  °f 
an  inch  broad,  and  from  the  tt  o~oTtu  to  ^ie  gTcTo^h  °f  an  mcn  thick. 
Their  flat  surfaces  are  parallel  with  the  surface  of  the  lens,  and  their 
direction  is  from  the  centre,  and  from  the  rays  of  one  star  to  the 
periphery,  where  they  turn  and  pass  toward  those  of  the  other.  Chem- 
ically, the  lens  is  composed  of  a  nitrogenized  substance,  called  crystal- 


782  THE    EYE    AND    VISION. 

line,  combined  with  inorganic  salts.  The  crystalline  lens  is  enclosed 
within  a  very  thin,  transparent,  elastic  membrane,  the  capsule,  which 
is  lined  anteriorly  with  a  layer  of  delicate  nucleated  cells. 

The  Aqueous  Humor. 

The  aqueous  humor  (Fig.  4.r>2,  13),  the  remaining  of  the  refracting 
media  of  the  eye,  is  a  colorless,  transparent,  almost  watery  fluid,  filling  the 
anterior  chamber  of  the  eye — that  is,  the  space  between  the  cornea  in  front 
and  the  iris  and  crystalline  lens  behind,  and  the  posterior  chamber,  or 
the  space  between  the  posterior  surface  of  the  iris  and  the  lens,  sup- 
posing that  such  a  place  exists,  which  is  very  doubtful,  and  in  any  case 
must  be  very  small.  That  the  aqueous  humor  is  secreted  possibly  by 
the  bloodvessels  of  the  iris  and  ciliary  processes,  or  the  internal  layer  of 
the  cornea,  is  shown  by  the  rapidity  with  which  it  is  reproduced  after  it 
has  been  evacuated,  as  in  surgical  operations  performed  upon  the  eye. 


CHAPTER     XLIX 


PHYSIOLOGICAL    OPTICS. 

Refraction   and   Accommodation. 

From  the  necessarily  brief  description  just  given  of  the  eye,  it  is 
apparent  that  it  resembles  essentially  in  its  structure  the  camera 
of  the  photographer,  its  refractive  media  being  comparable  to  the 
lens,  the  iris  to  the  diaphragm,  the  choroid  to  the  internal  black- 
ened surface,  the  retina  to  the  sensitive  plate,  the  image  of  the  external 
object  being  brought  to  a  focus  on  the  retina  or  sensitive  plate  respec- 
tively through  the  refraction  undergone  by  the  rays  of  light.  In 
order,  however,  to  understand  the  manner  in  which  the  rays  of  light 
are  brought  to  a  focus  on  the  retina  by  the  cornea,  crystalline  lens,  etc., 
it  will  be  necessary  to  describe  briefly  the  phenomena  of  refraction  in 
general,  and  the  course  that  rays  of  light  take  in  passing  through 
refractive  media.     Suppose  that  W  W  (Fig.  461)  represent  a  mass  of 


water,  and  CA  the  direction  of  the  beam  of  light  passing  through 
the  atmosphere  L  L,  it  will  be  observed  that  as  the  ray  of  light  passes 
through  the  water  it  is  bent  toward  the  perpendicular  A  F,  but  that  as 
it  passes  out  of  the  water  into  the  air  again  it  is  bent  away  from  the 
perpendicular.  Let  now  the  line  C A,  representing  the  direction  of 
the  incident  beam,  be  connected  with  the  perpendicular  B  F  by  the 
line  U  E,  and  the  line  representing  the  refracted  beam  A  H,  be  con- 
nected with  the  perpendicular  by  the  parallel  line  Gil,  and  it  will  be 
seen  that  the  line  6r  11  is  three-fourths  as  long  as  the  line  I)E\  and 


781  PHYSIOLOGICAL    OPTICS. 

further,  that  this  ratio  of  4  to  3,  equal  to  1.33  (more  accurately  1.336), 
will  be  invariably  the  same  whatever  the  angle  may  be  that  the  inci- 
dent beam  C  A  makes  with  the  surface  of  the  water  IK,  except  it  be  a 
right  angle,  the  beam  then  passing  directly  through  the  water  without 
being  refracted  at  all. 

If,  however,  with  A  as  a  centre,  and  a  radius  A  D,  a  circle  be 
described,  the  line  D  E  becoming  then  trigonometrically  the  sine  of  the 
angle  D  A  31,  and  the  line  Gr  II  the  sine  of  the  angle  HA  N,  the  law 
according  to  which  light  is  refracted  as  it  passes  from  air  through 
water,  may  be  expressed  by  saying  that  the  ratio  of  the  sines  of  the 
angles  of  incidence  and  of  refraction  is  equal  to  4  to  3,  equal  to  1.33,  a 
constant  for  the  particular  substance  water,  or,  briefly,  that  the  index  of 
refraction  of  water  is  1.33.  That  is  to  say,  if  the  line  BE  is  4  inches 
in  length,  then  H  Gr  will  be  3  inches,  and  so  on,  in  the  same  ratio. 
If  now,  for  water,  crown  glass  be  substituted,  it  will  be  found  that  the 
sine  of  the  angle  of  incidence  D  E  is  to  the  sine  of  the  angle  of  refrac- 
tion H  Gr  not  as  4  is  to  3,  as  in  the  case  of  air  and  water,  but  as  3  to 
2 — that  is,  the  index  of  refraction  for  the  particular  substance  crown 
glass  is  3  to  2,  equal  to  1.5.  Bearing  in  mind  then,  that  as  the  beam 
of  light  passes  from  the  air  through  the  glass  it  is  bent  toward  the 
perpendicular,  but  away  from  it  as  it  passes  out  of  the  glass,  and  that 
by  the  index  of  refraction  is  meant  the  ratio  of  the  sines  of  the  angles 
of  incidence  and  refraction,  there  will  be  no  difficulty  in  comprehend- 
ing the  manner  in  which  the  direction  of  a  beam  of  light  is  altered  in 
passing  through  biconvex  and   biconcave  lenses.      Let    0  (Fig.  462), 

Fig.  462. 


for  example,  represent  a  biconvex  lens  of  crown  glass  in  which  the 
radii  of  curvature  are  nearly  equal — that  is  to  say,  the  two  surfaces 
or  curves  of  the  lens  are  about  equally  distant  from  the  centres  of 
the  circles  of  which  these  curves  form  parts,  and  that  B  E,  O  Gr  be 
two  luminous  rays  parallel  with  the  principal  axis  A  D  passing  through 
the  optical  centre  0  of  the  lens,  which  fall  upon  the  lens  at  the 
points  E  and  Gr,  respectively.  Then,  according  to  the  law  just  enun- 
ciated, the  ray  B  E  being  first  bent  toward  the  perpendicular,  and  then 
awray  from  the  perpendicular,  and  the  ray  C G-  being  in  the  same 
manner  bent  first  toward  and  then  away  from  the  perpendicular,  and 
the  ray  A  0  being  in  the  direction  of  the  optical  axis,  and  consequently 
passing  through  the  lens  perpendicularly,  and,  therefore,  unrefracted, 


REFRACTION    AND    ACCOMMODATION.  785 

it  follows  that  the  three  rays,  and  all  others  parallel  with  them,  will  meet  at 
a  point  F,  known  as  the  principal  focus,  and  situated  in  the  principal  axis 
of  the  lens  at  a  distance  from  the  latter  {F  H)  which  will  be  determined 
presently,  and  known  as  the  principal  focal  distance.  The  eifect  of  a 
biconvex  lens  is  then  to  bring  parallel  rays  of  light  to  a  focus  on  the 
side  of  the  lens  opposite  to  the  source  of  light,  the  amount  of  converg- 
ence depending  upon  the  radius  of  curvature  to  the  lens  and  its  index 
of  refraction,  which  in  this  particular  case,  as  we  have  seen,  is  1.5. 
The  converse  of  this  is  also  true,  since  if  the  source  of  light  be  at  the 
principal  focus  F,  then  the  divergent  rays  after  leaving  the  lens  will 
be  brought  parallel  with  each  other,  and  with  the  principal  axis. 
Such  being  the  action  of  a  biconvex  lens,  it  will  be  seen  from  a  com- 
parison of  Fig.  462  with  Fig.  463,  that  the  action  of  a  biconcave  lens 

Fig.  463 


is  exactly  the  opposite  of  a  biconvex  one,  since  the  rays  of  light  (B  E, 
C  Gr,  Fig.  463),  after  being  bent  toward  their  respective  perpendicu- 
lars and  then  away  from  them,  according  to  the  law  of  refraction,  will 
diverge  from  the  principal  axis  A  D,  instead  of  converging  toward  it, 
and  the  rays  of  light  B  E,  C  Gr,  and  all  others  parallel  with  them, 
diverged  as  K L,  M  N,  instead  of  being  brought  to  a  focus.  The  con- 
verse of  this  is  also  true,  since  it  will  be  observed  that  the  converging 
rays  L  K,  N M  are  brought  parallel  with  each  other  on  the  side  of  the 
lens  opposite  that  where  the  light  is  now  supposed  to  be. 

Let  us  now  consider  the  case  in  which  the  luminous  object  L  is 
beyond  the  principal  focus  F  (Fig.  464),  but  so  near  that  all  the  inci- 
dent rays  L  E,  L  F  form  a  divergent  cone,  then,  according  to  the  law 
of  refraction,  the  rays,  after  leaving  the  lens,  will  be  found  to  come  to 
a  focus  at  I,  and  the  converse  of  this  will  be  found  to  be  true,  since,  if 
the  luminous  object  be  placed  at  I,  the  focus  will  then  be  at  L,  hence  I 
and  L  are  conjugate  foci.  Further,  it  will  be  found  by  experimenta- 
tion, or  by  calculation,  that  if  the  distance  between  the  luminous 
object  L  (Fig.  464)  and  the  lens  be  twice  the  focal  distance — that  is, 
twice  H F equals  HI — then  the  focus  I  will  be  situated  on  the  other 
side  of  the  lens  at  the  same  distance,  or  twice  H  F,  as  at  the  point  A, 
on  the  axis  A  D ;  if  the  distance  between  the  lens  and  the  luminous 

50 


786 


PHYSIOLOGICAL    OPTICS. 


object  be  less  than  twice  the  focal  distance,  the  focus  I  will  be  situated 
beyond  the  point  v4,  and  if  more  than  twice  the  focal  distance,  as  at  L, 
then  the  focus  will  be  situated  within  the  point  A,  as  at  I — that  is, 
between  the  point  A  and  the  lens.     After  what  lias  just  been  said,  with 


Fig   464. 


A  Z. 


reference  to  the  manner  in  which  the  rays  of  light  are  brought  to  a  focus 
by  biconvex  lenses,  the  position  of  the  locus,  etc.,  it  will  be  readily  seen 
from  Fig.  465  how  the  image  of  an  object,  as  of  an  illuminated  arrow, 
for  example,  is  formed  if  a  biconvex  lens  be  placed  between  the  latter 
and  a  screen.  It  will  be  observed,  however,  that  the  part  of  the  arrow 
at  a  being  brought  to  a  focus  at  x,  that  at  b  at//,  that  the  image  of  the 
arrow  is  necessarily  reversed,  and  that  if  the  luminous  object  approaches 
the  lens  its  image  recedes,  and  becomes  larger,  and  if  it  recedes  from 
the  lens  its  image  approaches,  and  becomes  smaller,  and  that  if  the 
luminous  object  be  situated  at  twice  the  focal  distance  from  the  lens,  its 
image  will  be  of  the  same  size,  and  situated  at  the  same  distance  from 
the  lens.     The  distance  at  which  the  image  is  formed  behind  the  lens 

can  be  readily  calculated  by  the   following  formula:    -  =  _ —  --,  in 
J  J  G  b        j-        I 

which,  in  the  distance  of  the  image,  /  the  local  distance  of  the  lens,  and 

I  the  distance  of  the  luminous  object;  thus,  for  example,  suppose  that/ 

equals  6  cm.,  I  equals  24  cm.,  then  —  =      —       = - 


cm. — that  is  to 


FiQ.  465. 


Fig.  466. 


say,  the  image  will  be  situated  8  cm.  behind  the  lens.     It  need  hardly 
be  added,  that  in  the  absence  of  a  lens,  the  rays  of  light  will  follow  the 


REFRACTION    AND    ACCOMMODATION 


'87 


paths  indicated  in  Fig.  466,  and  as  the  light  from  a  will  meet  at  4 
that  from  b,  at  I  that  from  a,  no  image  of  the  arrow  will  be  formed  upon 
the  screen.  Having  considered  now  the  properties  of  lenses,  let  us 
?pply  what  has  been  established  of  the  same  to  the  elucidation  of  vision, 
and  show  how  the  rays  of  light,  passing  successively  through  the  cornea, 
aqueous  humor,  crystalline  lens,  and  vitreous  humor  are  finally  brought 
to  a  focus  on  the  retina. 

In  considering  the  paths  of  the  rays  of  light  through  the  refractive 
media  of  the  eye  physicists  make  use  of  a  normal  schematic  eye,  a 
standard  eye,  so  to  speak,  in  which  certain  cardinal  points  have  been 
established,  and  by  which  the  rays  of  light  through  the  eye  can  be 
readily  constructed,  the  focus  determined,  and  the  size  of  the  image  esti- 
mated. Let  us  endeavor,  then,  to  explain  what  is  understood  by  the 
cardinal  points,  the  use  made  of  them  in  elucidating  vision,  and  how 
they  are  determined.  Let  M,  M2  be  two  refractive  media  separated 
from   each  other  by  a  spherical   surface  B  C  (Fig.  467),  constituting 

Fig.  467. 


what  is  known  optically  as  a  simple  collecting  system,  and  N  the  centre 
of  curvature — that  is,  the  centre  of  a  circle,  of  which  B  C  forms  a  part. 
All  the  radii  drawn  from  the  centre  N  to  B  C,  such  as  N  B,  N  x,  N  y, 
being  perpendicular  rays  of  light  falling  in  the  direction  of  the  radii, 
must  pass  unrefracted  through  N  as  L  D,  I1  d1,  for  example,  and  are 
called,  therefore,  lines  of  direction,  while  N.  the  point  of  intersection  of 
all  such  lines,  is  called  the  nodal  point.  The  line  0  A,  connecting  N, 
the  centre  of  curvature,  with  the  vertex  I,  and  prolonged  in  both  direc- 
tions, is  known  as  the  optic  axis,  the  plane  H  E,  perpendicular  to  the 
optic  axis  at  I,  being  called  the  principal  plane,  and  the  point  I,  within 
the  latter,  the  principal  point.  Such  being  presupposed,  it  can  be 
shown  that  all  rays  parallel  with  each  other,  and  with  the  optic  axis 
and  the  medium  M,  such  as  f  H,  p  E,  falling  upon  B  C,  come  to  a 
focus  at  F2  in  the  second  medium,  called  the  second  principal  focus, 
or  second  focal  point,  the  plane  S  F2  P,  perpendicular  to  the  optic  axis 
0  A,  at  this  point,  being  the  second  focal  plane.  Of  course,  the  con- 
verse of  the  above  is  true — that  is,  rays  diverging  from  F2,  such  as 


788  PHYSIOLOGICAL    OPTICS. 

F2  I),  F2  C,  pass  into  the  first  medium  parallel  with  each  other,  and 
with  the  optic  axis.  Further,  it  will  be  seen  from  an  inspection  of  Fig. 
507,  that  rays  which  are  parallel  to  each  other  in  the  first  medium,  but 
not  parallel  with  the  optic  axis,  such  as  Q  T,  U  Z,  come  to  a  focus  in 
the  second  medium  in  the  point  D  of  the  second  focal  plane,  where  the 
non-refracted  directive  ray  L  D  meets  the  latter,  and  that  rays  diverg- 
ing from  1>  pass  through  the  first  medium  parallel  with  each  other,  but 
not  parallel  with  the  optic  axis.  It  is  also  evident  that  all  rays,  which, 
in  the  second  medium  are  parallel  with  each  other,  and  with  the  optic 
axis,  such  as  S  B,  P  C,  come  to  a  focus  (F1)  in  the  first  medium,  called 
the  first  focal  point,  or  first  principal  focus,  the  plane  of  F1  p,  perpen- 
dicular to  the  optic  axis  at  this  point,  being  known  as  the  first  focal 
plane.  Of  course,  the  converse  of  the  above  is  true,  viz.,  that  rays 
diverging  from  F1  pass  through  the  second  medium  parallel  with  each 
other  and  with  the  optic  axis. 

Finally  it  follows  that  the  radius  of  the  spherical  surface  N  I 
is  equal  to  the  difference  of  the  distance  of  the  focal  points  F '  F " 
from  the  principal  point  I — that  is,  that  NI=F2  I — F'L  Such 
being  admitted,  it  will  be  seen  that  an  incident  ray  (Q  T)  comes  to 
a  focus  in  the  second  focal  plane  in  the  point  D,  where  the  non- 
refracted  directive  ray  L  D  meets  the  latter,  and  that  the  reversed 
image  of  an  external  object,  situated  in  the  first  medium  like  the  arrow 

^p  is  formed  in  the  second  medium  at  the  point  J,  where  the  prolonged 

ray  B  Fz  meets  the  non-refracted  directive  ray  Y  d'.  Now  did  the  eye 
consist  simply  of  two  refractive  media,  separated  by  a  spherical  surface, 
as  in  the  simple  collecting  system  just  described,  the  construction  of  the 
refracted  ray  and  of  the  image  of  the  object,  would  be  essentially  the 
same  and  equally  simple.  Inasmuch,  however,  as  the  eye  consists  of 
four  refractive  media,  cornea,  aqueous  humor,  crystalline  lens,  and 
vitreous  humor,  the  cornea  and  aqueous  humor  constituting  a  concavo- 
convex  lens,  the  crystalline  a  biconvex  lens,  and  the  vitreous  humor  a 
concavo-convex  lens,  to  apply  to  the  eye  what  has  just  been  established 
would  involve  proceeding  from  medium  to  medium,  which  would  be 
a  tedious  operation.  If,  however,  the  several  media  are  centred,  that 
is,  if  they  have  the  same  optic  axis,  which  is  pretty  nearly  the  case  in 
the  eye,  then  as  shown  by  Gauss,1  the  refractive  indices  of  such  a 
system  may  he  represented  by  two  equally  strong  refractive  surfaces  at  a 
certain  distance,  the  rays  falling  upon  the  first  system  not  being  refracted, 
but  projected,  so  to  speak,  parallel  with  themselves  to  the  second  sur- 
face as  at  x  x',  y  y' ',  refraction  taking  place  at  the  latter  just  as  if 
that  surface  alone  was  present,  the  only  data  required  in  determining 
the  above,  being  the  refractive  indices  of  the  media,  the  radii  of  the  re- 
fractive surfaces,  and  the  distances  of  the  latter  from  each  other,  which, 
as  we  will  show  presently,  can  be  experimentally  determined.  Let  Ml, 
M2,  M3,  and  M*  (Fig.  468)  be  four  media  for  example,  such  as  the  air, 
aqueous  humor,  crystalline  lens,  and  vitreous  humor ;  B  C  a  spherical 
surface  like  the  cornea,  separating  the  air  from  the  aqueous  humor  ;  L  I 

1  Dioptrische  Untersuchungen  Abhand.     Giittiugon  Gesells.,  1841. 


REFRACTION    AND    ACCOMMODATION, 


'89 


the  anterior  surface  of  a  biconvex  lens  like  the  crystalline  lens,  a 
spherical  surface  separating  the  aqueous  humor  from  the  substance  of 
the  lens  ;  and  Vv  the  posterior  surface  of  the  lens,  also  a  spherical  sur- 
face, reversely    disposed,    however,  with  reference  to  the  cornea   and 


Fig.  468. 


anterior  surface  of  the  lens,  and  separating  the  substance  of  the  lens 
from  that  of  the  vitreous  humor.  Such  being  the  relation  of  the 
refractive  media,  and  the  spherical  surfaces  separating  them,  the  cardinal 
points  of  such  a  system,  six  in  number,  as  deduced  from  the  radii  of  cur- 
vature, indices  of  refraction,  etc.,  determined  experimentally  are  as  fol- 
lows :  two  focal  points  (F'  F'*),  two  principal  points  (P  P'),  two  nodal 
points  (NN').  Inasmuch  as  the  properties  of  the  two  foci  F'  F2,  as  regards 
the  rays  of  light  diverging  from  or  converging  toward  them  respectively, 
and  of  the  anterior  and  posterior  focal  planes  f  p,  S  P,  are  essentially 
the  same  as  already  described  and  represented  in  Fig.  507,  it  will  not 
be  necessary  to  consider  them  again  in  detail  in  this  connection.  As 
regards  the  principal  points  P  P'  being  in  a  transparent  medium,  their 
relation  is  such  that  a  luminous  point  in  the  medium,  appearing  to  an 
observer  on  the  left  to  be  owing  to  the  refraction  at  _P,  to  one  on  the 
right  would  appear  to  be  at  P' .  That  is  to  say,  P  Pf,  being  conjugate 
foci  like  LI  (Fig.  464),  rays  of  light  passing  through  one  point  will 
pass  through  the  other  also  ;  P  P'  being  the  principal  points,  HE  and 
H'  E'  will  be  principal  planes,  and  each  point  of  the  one  plane  having 
a  conjugate  focus  in  the  other,  a  ray  of  light  passing  through  a  point 
on  one  plane  will  pass  through  a  corresponding  point  on  the  other  at 
the  same  distance  from  the  axis,  and  on  the  same  side,  the  distance 
F'  P  being  the  anterior  focal  length,  and  the  distance  F2  P'  the  posterior 
focal  length.  In  fact,  either  plane  may  be  regarded  as  the  image,  the 
other  being  the  object.  It  will  be  observed  that  the  nodal  points  2V2V7 
are  so  disposed  that  if  the  incident  ray  a  N  were  prolonged,  it 
would  emerge  parallel  with  the  emergent  ray  N'  a',  and  vice  versa.  In 
a  simple  lens,  however,  the  optical  centre  being  the  only  point  through 
which  a  ray  may  pass  and  emerge  parallel  to  its  original  direction,  and 
all  straight  lines  other  than  the  principal  axis  passing  through  the 
optical  centre  being  secondary  axes,  it  follows  that  rays  passing  through 
the  nodal  points  N  Nf  may  be  regarded  as  secondary  axes,  and  that 
these  points  represent  the  optical  centres  of  the  surfaces  to  which  P  P' 


(90  PHYSIOLOGICAL    OPTICS. 

respectively  belong.  Such  being  the  position  of  the  cardinal  points  in 
the  system  of  refractive  media  and  spherical  surfaces  represented  in 
Fig.  468,  let  a  b  be  an  object,  an  illuminated  arrow  for  example,  from 
which  rays  pass  through  the  above;  its  image  will  be  formed  at  b'  a'. 
That  this  must  be  the  case,  can  be  at  once  shown  by  construction,  for 
the  ray  af,  after  cutting  the  two  principal  planes  r  rr,  and  passing 
through  the  posterior  focal  points  F2,  will  meet  the  line  A;/  a',  emerging 
parallel  from  the  lens  parallel  with  a  iV,  passing  into  the  latter  at  the 
point  a',  the  same  point  where  the  ray  a  F'  after  passing  through  the 
anterior  focal  point  and  cutting  the  principal  planes  in  y  y'  meets  N'  a'. 
In  precisely  the  same  manner  it  can  be  shown  by  construction  that  the 
point  b  of  the  arrow  will  be  brought  to  a  focus  at  bf.  It  need  hardly 
be  observed  that  the  ima^e  of  the  arrow  will  be  of  course  reversed. 
Let  us  suppose  now  that  the  index  of  refraction  for  air  being  taken  as 
unity,  that  with  Listing1  the  index  of  refraction  for  the  aqueous  and 
vitreous  humors  has  been  determined  to  be  equal  to  1.3379  (^pf-)-,  that 
of  the  crystalline  lens  to  be  1.4545  (fy),  the  radius  of  curvature  of 
cornea  8  mm.  (^8-  of  an  inch),  the  radius  of  curvature  of  the  anterior  sur- 
face of  the  crystalline  lens  10  mm.,  that  of  the  posterior  surface  6  mm., 
the  distance  of  the  anterior  face  of  the  cornea  from  the  anterior  surface 
of  the  crystalline  lens  to  be  equal  to  4  mm.,  the  distance  from  the  an- 
terior surface  of  the  lens  to  the  posterior  surface,  or  the  thickness  of  the 
lens,  4  mm.,  then  by  means  of  the  appropriate  formulae,  developed 
through  the  relations  existing  between  the  radii  of  curvature,  the 
indices  of  refraction,  etc.,  and  the  six  cardinal  points,  the  exact  position 
of  the  latter  in  the  human  eye  can  be  shown  to  be  as  follows: 

The  anterior  principal  focus  12.8326  mm.  in  front  of  the  cornea,  the 
posterior  principal  focus  22.6470  mm.,  the  anterior  principal  point 
2.1746  mm.,  the  posterior  principal  point  2.5724  mm.,  the  first  nodal 
point  7.2420  mm.,  the  second  nodal  point  7.6398  mm.  behind  the  cornea. 
The  distance  between  the  anterior  principal  focus  and  the  anterior  prin- 
cipal point — that  is,  the  anterior  focal  length  being  then  15.0072  mm. 
=  12.3326  +  2.1746,  and  the  distance  between  the  posterior  principal 
focus  and  the  posterior  principal  point. — that  is,  the  posterior  focal  length 
being  20.0746  mm.  =  22.6470  —  2.5724,  and  the  distance  between  the 
two  principal  points  0.3978  mm.,  and  the  nodal  points  0.3978  mm.  The 
two  nodal  points  or  principal  points  separated  by  only  a  distance  of  0  39 
mm.  (about  the  -g-g-of  an  inch)  may  be  regarded  practically  as  coinciding, 
and  we  may  assume,  therefore,  for  the  sake  of  simplicity,  without  intro- 
ducing any  very  sensible  error  in  the  construction,  that  there  is  but  one 
nodal  or  principal  point,  and  therefore  but  one  refractive  surface  for  all 
the  media  of  the  eye.  The  eye  so  simplified,  and  constituting  the  so- 
called  reduced  eye  of  Listing,  enables  us  to  determine  very  readily  the 
position  and  size  of  the  inverted  image  of  an  external  object  formed 
upon  the  retina.  Thus,  for  example,  let  A  B  (Fig.  469)  represent  an 
object  placed  vertically  in  front  of  the  eye,  then  A  D,  B  C,  being  rays 
of  direction  and  passing  directly  through  the  nodal  point  K;  unrefracted 
rays  from  A  after  refraction,  will  come  to  a  focus  on  D,  rays  from  B  to 

1  Dioptrik  des  Auges.     Wagner,  Physiologie,  Band  iv.  S.  451. 


REFRACTION    AND    ACCOMMODATION. 


791 


a  focus  at  C,  intermediate  rays  at  some  intermediate  point  (G).  The  rays 
of  light  taking  this  course  through  the  media  of  the  eye,  the  inverted 
image  of  the  external  object  will  be  found  on  the  retina  at  D  C.  Further, 
since  in  simple  lenses  the  size  of  the  image  is  to  the  size  of  the  object  as 


Fig.  4C9. 


the  distance  of  the  image  from  the  lens  is  to  the  distance  of  the  object 
from  the  lens,  or,  as  in  the  case  of  the  crystalline  lens  which  we  are 
now  considering,  as  the  distance  of  the  image  from  the  nodal  point  g  k 
is  to  the  distance  of  the  object  from  the  nodal  point  M  k,  it  follows 
that  the  size  of  the  image 

_  size  of  the  object  X  distance  of  image  from  nodal  point 
distance  of  object  from  nodal  point. 

The  distance  of  the  image  from  the  nodal  point  being,  however,  the 
posterior  focal  distance  may  be  regarded  as  equal  to  the  distance  of  the 
retina  from  the  cornea  (P'),  minus  the  distance  of  the  nodal  point 
from  the  cornea  (R),  the  distance  of  the  object  from  the  nodal  point 
being  equal  to  the  distance  of  the  object  from  the  cornea  (P),  plus  the 
distance  of  the  cornea  from  the  nodal  point  (R);  such  being  admitted, 
the  formula  for  the  size  of  the  image  may  be  conveniently  expressed  as 
follows : 


I  = 


P+  R 


Supposing  that  the  object  0  be  1000  mm.  high,  P'  =  22.6470  mm.,  R 
—  7.4  mm.,  P  =  15.2396  metres,  then 

j_  1000  X  15.247 
15.2396  +  7.4 ' 

That  is  to  say,  that  the  image  of  an  object  1000  mm.  (39.3  in.)  in 
height  seen  at  a  distance  of  15.2396  metres  (50  feet)  is  1  mm.  (yg-th  of 
an  inch)  in  height,  or  a  thousand  times  smaller.  It  will  be  observed 
also  from  Fig.  469  that  the  visual  angle  A  k  B — that  is,  the  angle 
under  which  A  B  is  seen — being  the  same  as  the  angle  under  which  the 
objects  x  y,  r  s,  are  seen,  that  the  image  of  all  three  objects  formed  on 
the  retina  must  be  the  same,  and  that,  therefore,  the  apparent  size  of  all 
three  objects,  though  diifering  in  size,  will  be  the  same  also.     It  is  also 


792 


PHYSIOLOGICAL    OPTICS. 


Fig.  470. 


obvious  that  the  size  of  the  visual  angle  depends  on  the  size  of  the  object 
and  distance  of  the  latter  from  the  eye.  From  the  fact  of  the  smaller 
the  visual  angle  under  which  distinct  vision  is  possible  the  more  acute 
the  vision,  the  latter  is  evidently  inversely  as  the  size  of  the  visual  angle. 
The  measure  of  the  acuteness  of  vision  in  general  use  among  physiolo- 
gists and  ophthalmic  surgeons,  based  upon  this  principle  is  a  series  of 
letters,  C  CB,  the  thickness  of  which  is  one-fifth  of  their  height,  and 
made  of  such  a  size  that  at  a  distance  of  20  feet  they  subtend  an  angle 
of  5  minutes,  the  acuteness  of  vision  being  expressed  by  the  ratio  of  the 
distance  at  which  such  letters  are  still  distinctly  recognized  to  the  dis- 
tance D,  at  which  they  subtend  an  angle  of  5  minutes — that  is  to  say 

Y  =  -^-     Suppose,  for  example,  that  the  person  whose  vision  is  being 

tested  can  recognize  a  letter  at  ten  feet,  then  his   acuteness  of  vision 

will  be  V  =  77  =  ^j  =  ~?p  tnat  °f  one  whose  vision  is  perfect — that 

d       20 
is   in  whom  V  =  77  =-^=1.    Practically,  the  smallest  visual  angle 

permitting  distinct  vision  is  about  60  seconds,  and  corresponding,  as  it 
does  to  a  retinal  image  of  about  0.004  mm.,  it  will  just  about  cover  one 
of  the  cones  of  the  retina.  Two  points  seen 
under  such  a  small  visual  angle  would  therefore 
appear  as  one.  It  has  already  been  mentioned 
that  the  cardinal  points,  by  means  of  which  we 
follow  the  rays  of  light  as  they  pass  through  the 
media  of  the  eye  and  determine  the  position  and 
size  of  the  retinal  image,  are  deduced  from  the 
indices  of  refraction  of  the  aqueous  and  vitreous 
humors,  lens,  radius  of  curvature  of  cornea,  etc., 
experimentally  determined.  Inasmuch  as  the 
methods  by  which  the  indices  of  refraction  of  the 
media  of  the  eye  are  determined,  are  essentially 
the  same  as  in  the  case  of  water  or  glass,  and 
represented  in  Fig.  465,  it  need  not  in  this 
connection  be  described  again.  The  radius  of 
curvature  of  the  cornea  and  crystalline,  how- 
ever, being  deduced  by  formuhe  from  the  size 
of  their  reflected  images,  and  the  latter  being 
measured  by  the  ophthalmometer,  the  method 
of  determination  merits  at  least  a  brief  descrip- 
tion. The  principle  upon  which  the  oph- 
thalmometer, invented  by  Helmholtz,1  is  con- 
structed is,  that  if  an  image  of  an  object  be  viewed 
through  two  piano-parallel  glass  plates  (Fig. 
470)  the  image,  through  refraction,  will  appear 
double,  and  that  if  the  plates  be  so  approximated 
that  the  inner  edges  of  the  two  images  are  brought  in  contact,  then  the 
distance  between  the  outer  edges  of  the  two  images  will  be  twice  the  size 


Object   viewed  through  two 
glass  plates. 


1  Optique  Physiologique  Traduite,  by  Juval  et  Klein,  p.  11.     Paris,  18G7. 


REFRACTION    AND    ACCOMMODATION.  793 

of  the  single  image.     To  measure  the  size  of  an  image  by  the  ophthal- 
mometer, it  is  only  necessary,  then,  to  determine  the  lateral  displace- 

Fig.  471. 


M=d} 


// 


A 


b 


9 

Schema  of  ophthalmometer. 


ment  of  the  images,  which  is  accomplished  by  observing  the  angle 
made  by  the  glass  plates  P  P,  with  the  axis  X  of  the  telescope  (Fig. 
471),  through  which  the  image  is  viewed,  and  substituting  the  value  of 
the  angle  so  obtained  in  the  formula 

T  _  or  sin  (a  —  B) 


2T 


cos  B 


in  which  L  =  the  lateral  displacement,  T=  the  thickness  of  the  glass 
plates,  a  =  the  angle  of  incidence,  B  =  the  angle  of  refraction. 

The  manner  in  which  the  above  formula  is  developed,  will  become 
clear  from  a  consideration  of  the  relation  of  the  parts  involved,  as 
represented  in  Fig.  472,  in  which,  for  simplicity,  A  B  C  D  is  one  of 


To  illustrate  the  measurement  of  the  lateral  displacement,  ab. 

the  plates  of  glass  placed  in  front  of  the  objective  of  the  telescope, 
and  a  c  the  incident  ray  emanating  from  the  image  viewed,  whose 
size  is  to  be  determined.  Such  being  the  case,  the  ray  a  c,  according 
to  the  law  of  retraction,  will  be  bent  (c  i)  toward  the  perpendicular  n  k, 
as  it  passes  through  the  glass  and  away  from  the  perpendicular,  as  i  Z, 
and  parallel  with  a c  as  it  emerges  from  the  glass,  and  the  angle  a  en 
will  be  equal  to  the  angle  lim,  parallel  rays  falling  upon  parallel  sur- 


794  PHYSIOLOGICAL    OPTICS. 

faces.  Now  since  the  angle  of  incidence  acn  or  a  bears  such  a  rela- 
tion to  the  angle  of  refraction  ick  or  B,  that =  index  of   refrac- 

sin  B 

tion  =  1.65  in  case  of  flint-glass,  it  folknvs  that  sin  a  =  1.6  (sin  B),  or,  sin 

B  = — — — that  is,  when  we  learn  the   value  of  a  by   obervation,  we 
1.6  J 

can  find  the  value  of  B  by  trigonometric  tables.  The  relation  of  the 
angle  of  incidence  being  to  that  of  refraction,  such  as  just  described, 
the  point  a,  to  the  eye  of  an  observer  at  I,  would  appear  to  be  at  b,  the 
glass  plate  effecting,  therefore,  a  lateral  displacement  of  the  point  a, 
to  an  extent  a  b,  which  is  measured  by  determining  the  equal  dis- 
tances ef.  The  latter  being  equal  to  the  hypothenuse  into  the  sine  of 
the  opposite  angle — that  is,  cf=ci  sin  cif,  it  follows  that  if  Ave 
can  determine  c  i  and  sin  c  if,  we  will  obtain  cf  or  its  equal  a  b,  the 
lateral  displacement,  or  that  which  we  desire  to  determine.  Since 
the  base  he  is  equal  to  the  hypothenuse  ci  into  the  cosine  of  the 
adjacent  angle   ick    or  B — that  is,  that   kc  =  ci   cos  B,  it  follows 

KG 

thatc^= ~,  and  as    kc  is   equal   to  the   thickness   of  the  glass 

cos  B  1  8 

plates,  which  is  known,  we  may  call  it   T  and    say  that  ci= . 

Further,  the  angle  cif  is  equal  to  the  angle  hif  less  the  angle  hie, 
but  h  if  is  equal  to  the  angle  of  incidence  n  c  a  or  a,  in  that  their 
sides  are  parallel,  and  the  angle  hie  is  equal  to  the  angle  of  refraction 
ick  or  B,  in  that  they  are  alternate  angles,  therefore  cif '=  hif — 
hie,  or  sin  cif  —  sin  (a — B).  Substituting  these  values  of  ci  and  sin 
c if  in  the  formula  ke  =  ci  sin   c  if  we   obtain   k  c  or  a  b  =  T  sin 

— -i.     Inasmuch,  however,  as   there  are   two  plates  in  the  ophthal- 
cos  B 

mometer,  the  complete  formula  will  be 

,         T        277sin  (a  —  B) 

ab  or  L  =  ^ ', 

cos  B 

that  is  to  say,  the  lateral  displacement  will  be  equal  to  twice  the 
thickness  of  the  glass  multiplied  by  the  difference  between  the  sine  of 
the  angle  of  incidence  and  the  angle  of  refraction  divided  by  the 
cosine  of  the  latter.  Suppose,  for  example,  that  the  thickness  of  the 
glass  plate  be  0.325  mm.  the  index  of  refraction  of  the  flint  glass 
plate  1.65,  the  angle  of  incidence  or  a  =  6°,  as  observed  by  the 
ophthalmometer,  the  angle  of  refraction  5  =  3°  48',  as  learned  from 
the  value  of  the  angle  a  by  trigonometric  tables,  then  the  lateral  dis- 
placement will  be 

Z^2X0.325siD'6°-3°48/) 
cos  3°  48/ 

and  using  logarithms  L  =  0.025  mm. 

In  using  the  ophthalmometer  the  intrument  should  be  placed  in  the 
dark  chamber  that  is  in  a  room  with  blackened  walls,  from  which  all 
sunlight  can  be  excluded,  and  at  a  distance  of  ten  feet  from  the  eye 


REFRACTION    AND    ACCOMMODATION 


'95 


under  examination,  and  on  a  level  with  it.  A  lighted  candle  being 
placed  on  the  right-  or  left-hand  side  of  the  eye  to  be  examined,  on 
the  left  side  for  the  left  eye,  on  the  right  side  for  the  right  eye,  as  near 
as  possible,  and  a  screen  intervening  to  protect  the  eye  from  the  glare, 
by  means  of  three  small  rectangular  mirrors  fixed  by  universal  joints 
to  a  graduated  wooden  rod  the  light  from  the  candle  is  reflected  upon 
the  eye.  The  vernier  of  each  scale  of  the  ophthalmometer  further 
being  at  zero,  and  the  instrument  focussed,  the  observer  on  looking 
through  the  telescope  at  the  eye  under  observation,  will  then  see  three 
minute  specks  of  light  upon  the  cornea,  thus,  a  a  a-  If  now,  however, 
the  rotating  screws  be  turned,  which  has  the  effect  of  placing  the  plates 
of  glass  obliquely,  six  minute  specks  of  light  will  be  seen  on  the  cornea, 
thus,  a  a  a  a  a  a  ab  c  representing  one-half  of  the  amount  of  dis- 
placement in  the  one  direction,  def,  one-half  the  amount  in  the  other 
direction — that  is  to  say,  the  three  original  images  have  been  dis- 
placed through  a  distance  equal  to  that  between  the  two  extreme 
images.  Observing  now  the  angle  through  which  the  plates  have  been 
moved,  of  the  angle  of  incidence  =  a,  and  substituting  the  same  in  the 
formula  just  developed,  the  size  of  the  corneal  image  due  to  the  reflec- 
tion of  the  light  of  the  candle  from  the  three  mirrors  will  be  determined. 
In  using  the  ophthalmometer,  it  is  not  absolutely  necessary  to  make  use 
of  the  three  mirrors  just  described,  since  as  originally  used,  the  object 
thrown  upon  the  cornea  was  the  distance  between  three  candle  flames 
placed  beside  the  experimenter,  two  on  his  right  hand,  and  one  on 
his  left.  In  order  to  avoid  any  calculations,  Donders1  suggests  that  a 
scale  be  prepared,  in  which  each  degree  or  fraction  of  a  degree  corre- 
sponds to  a  certain  size  in  millimetres,  the  size  of  the  corneal  image 
being  then  determined   by  simply  referring  to   the  scale.     It  will  be 


Fig.  473. 


<r 

X4 

tt              \                 ^^^ 

J? 

\J^^ 

// 

£ 

■^/\\ 

// 

/c                            ^"\ 

s 

To  illustrate  relation  of  size  of  object,  to  size  of  virtual  image. 

remembered  that  the  object  of  determining  the  corneal  imao-e,  as  well 
as  that  of  the  image  of  the  lens,  also  accomplished  by  the  ophthal- 
mometer, though  in  a  slightly  modified  manner,  was  to  determine  the 
radius  of  curvature  of  the  cornea,  etc.  Now  from  an  inspection  of  Fig. 
473,  it  is  evident  that  the  size  of  the  object  A  B  is  to  that  of  its  virtual 
image  a  b — (that  is,  the  image  formed  through  the   prolongation  of  the 


1  Accomodation  and  Refraction  of  the  Eye,  trans,  by  Moore,  p.  19.     London,  1864. 


796 


PHYSIOLOGICAL    OPTICS. 


rays),  as  the  distance  H  G  of  the  object  from  the  cornea  CC,  is  to  the 

distance  F  Gr,  or  half  the  radius  R — that  is,  A  B  :  ah  : :  H Gr  :      M 

2 

or 


iB=abXHG   Qr  R 
AB 


2(abXB'G) 
AB 


Let  us  suppose  that  the  size  of  the  corneal  image  a  b  has  been  deter- 
mined by  the  ophthalmometer  to  be  equal  to  1  mm.,  to  obtain  R  it 
only  remains,  then,  to  determine  the  value  of  H  Gr  and  A  B.  This  is 
done  directly  by  measuring  the  distance  between  the  upper  and  lower 
reflecting  mirrors,  which  gives  the  size  of  the  object  A  B,  and  measuring 
the  distance  from  the  cornea  to  the  centre  of  the  rod  holding  the  mirrors 
and  doubling  the  distance,  since  the  light  passes  from  the  eye  to  the 
mirror,  and  thence  back  to  the  eye  again,  which  gives  the  distance  of 
the  object  from  the  cornea.  Suppose  that  the  size  of  the  object  A  B 
should  be  1000  mm.,  and  the  distance  H  Gr  3800  mm.,  then 


E 


2(1  X  3800) 
1000 


mm.  =  7.6  mm. 


— that  is,  the  radius  of  curvature  in  such  an  eye  would  be  7.6  mm., 
which  differs  but  little  from  the  radius  of  curvature  of  the  short-sighted, 
or  myopic  eye,  when  at  rest. 

The  index  of  refraction  of  the  aqueous  and  vitreous  humors,  of  the 
crystalline  lens,  the  radius  of  curvature  of  the  cornea  and  crystalline 
lens  being  determined  in  the  manner  just  described,  we  are  enabled, 
by  means  of  formulae,  as  already  mentioned,  to  fix  then  the  six  cardinal 
points,  by  means  of  which,  as  has  been  shown,  the  paths  of  the  rays 
of  light  through  the  media  of  the  eye  can  be  constructed,  and  the 
position  and  size  of  the  image  of  the  external  object  can  be  determined. 
While  it  is  true  that  rays  of  light  falling  upon  a  refracting  surface  are 

Fig.  474. 


Diagram  illustrating  aberration  of  sphericity.     (McKeniirkk.) 

brought  to  a  focus  in  essentially  the  manner  we  have  described  in 
treating  of  such  surfaces,  it  must  be  mentioned  in  this  connection  that 
of  rays  impinging  upon  a  refractive  surface,  the  peripheral  ones  being 
more  refracted  than  the  central  ones  are  not  brought  to  exactly  the 
same  focus  as  that  of  the  latter,  there  being,  in  fact,  many  foci,  and  the 


REFRACTION    AND    ACCOMMODATION. 


797 


image  of  the  object  consequently  blurred  and  ill-defined.  This  con- 
dition, known  as  the  aberration  of  sphericity  (Fig.  474),  and  corrected 
in  the  making  of  lenses  for  microscopes,  etc.,  by  appropriate  means, 
obtains  also  in  the  eye,  though  not  to  any  marked  extent,  on  account 
of  the  following  circumstances  :  1st,  that  the  lateral  most  refracted  rays 
are  cut  off  by  the  iris,  the  latter  acting  precisely  like  the  diaphragm  of 
optical  instruments ;  2d,  that  the  curvature  of  the  cornea  being  ellip- 
soidal the  lateral  rays  are  less  deviated  than  if  the  curvature  was  spher- 
ical ;  3d,  that  the  anterior  and  posterior  surfaces  of  the  crystalline  lens 
are  so  disposed  that  the  one  corrects,  to  a  certain  extent,  the  action  of 
the  other ;  4th,  from  the  fact  that  the  refractive  power  of  the  lens, 
diminishing  from  the  centre  to  the  circumference,  the  lateral  rays  are 
but  little  refracted.  Inasmuch  as  a  refracting  medium  does  not  act 
equally  upon  the  different  colored  rays  of  which  white  light  is  composed, 
a  ray  of  light  in  passing  through  a  biconvex  lens,  for  example,  is  not 
only  bent,  but  decomposed  into  the  colors  of  the  spectrum  (Fig.  475), 

Fig.  475. 


Decomposition  of  white  light  by  prism. 


the  condition  so  produced,  that  of  chromatic  aberration,  giving  rise  to 
the  formation  of  a  colored  image,  white  at  the  centre,  but  surrounded 
at  the  borders  by  a  circle  of  colors,  like  those  of  the  rainbow.  In  the 
construction  of  optical  instruments  the  chromatic  aberration,  or  aberra- 
tion of  refrangibility,  is  corrected  by  combining  lenses  having  a  different 
dispersive  power,  as  when  a  convex  lens  of  crown  glass  is  combined 
with  a  concave  lens  of  flint  glass,  so,  in  the  case  of  the  eye,  the  chro- 
matic aberration  is,  to  a  considerable  extent,  corrected  through  the 
crystalline  lens,  being  composed  of  various  layers  of  different  consistence, 
and  of  different  refractive  power.  As  a  general  rule,  indeed,  we  are 
unaware  that  our  eyes  are  not  achromatic,  like  the  lenses  of  microscopes 
and  telescopes,  but,  under  certain  circumstances,  our  attention  is  very 
forcibly  called  to  the  fact.  Thus,  if,  after  looking  at  the  cross  hairs  of 
an  astronomical  glass  by  a  red  light,  we  try  to  see  them  with  another 
colored  light,  violet,  for  example,  the  eye  must  be  changed,  the  eye, 
when  adapted  to  see  with  a  red  light,  not  being  able  to  see  by  the 
violet.  Again,  if  we  look  at  a  candle-flame  through  cobalt  blue  glass, 
which  transmits  only  the  red  and  blue  rays,  the  flame  may  appear  blue 
surrounded  by  violet,  or  vice  versa,  according  as  the  eye  has  been  accom- 


798 


PHYSIOLOGICAL    OPTICS, 


modated  for  different  distances.  It  may  be  also  mentioned  that  red 
surfaces  always  appear  nearer  than  violet  ones,  since  the  eye,  having 
to  be  accommodated  more  for  the  red  than  for  the  violet  one,  imagines 
the  former  surfaces  to  be  nearer  than  the  latter.  In  addition  to  the 
aberration  of  sphericity  and  of  refrangibility,  more  or  less  present  in 
the  eye,  from  the  fact  of  the  focal  length  of  the  vertical  meridian  of  the 
cornea  being  sharper  than  the  horizontal  median  rays  of  light  emanating 
from  a  point,  do  not  converge  to  one.  The  condition  so  caused,  and 
constituting  astigmatism,  is  a  defect  from  which  few  eyes,  if  any,  are 
free.  That  the  eyes  are  astigmatic  one  can  readily  convince  himself 
by  simply  looking  (Fig.  476)  at  two  threads  crossing  each  other  at  right 

Fio.  476. 


Diagram  illustrating  astigmatism.     Lower  figures  illustrate  appearance  of  rays,  eye  being  at  G  H  I, 
respectively.    (McKendrick.) 


angles  in  the  same  plane,  or  at  two  lines  drawn  in  ink  on  a  sheet  of 
white  paper  disposed  in  a  similar  manner,  when  it  will  be  observed  at 
the  point  of  distinct  vision  that  it  is  impossible  to  see  both  threads,  or 
lines  with  equal  distinctness  at  the  same  time ;  that  to  see  the  hori- 
zontal line  distinctly,  for  example,  the  paper  must  be  brought  near  the 
eye,  and  removed  from  it,  to  see  the  vertical  line. 

While  the  detailed  consideration  of  the  subject  of  astigmatism  belongs 
rather  to  the  ophthalmologist  than  physiologist,  it  may  be  incidentally 
mentioned  that  the  astigmatism  of  the  cornea  is,  to  a  certain  extent, 
naturally  corrected  by  that  of  the  lens,  since  the  focal  length  of  the 
vertical  meridian  differs  from  that  of  the  horizontal,  but  in  the  reverse 
sense  from  that  of  the  cornea.  The  actual  degree  of  astigmatism  present 
is  measured  by  the  difference  in  the  refraction  of  the  two  chief  meridians. 
Thus,  if  Fx  =  the  greater  focal  length,  and  F~  =  the  smaller,  then  the 

astigmatism  will    be  As  =  —  —  — .    which  can  be   corrected   by  the 

F1     F'2 

use  of  a  cylindrical  glass,  the  curvature  of  which  is  such  that  if  added 


REFRACTION    AND    ACCOMMODATION. 


■99 


to  that  of  the  horizontal  meridian,  will  make  its  focal  length  equal  to 
that  of  the  vertical  one.  The  defects  of  the  eye  due  to  aberration  of 
sphericity  and  refrangibility,  or  astigmatism,  are  so  slight,  usually,  as  not 
to  attract  attention;  near-sightedness  and  far-sightedness  are,  however, 
unfortunately  so  common,  and  interfere  to  such  an  extent  with  vision, 
as  to  necessitate  the  wearing  of  glasses.  The  cause  of  myopia  and 
hypermetropia,  and  their  treatment  constituting,  like  astigmatism,  one 
of  the  most  important  subjects  of  ophthalmology,  do  not  demand  in  this 
connection  special  consideration.  As  still  further  illustrating,  however, 
the  manner  in  which  the  rays  of  light  are  brought  to  a  focus  in  the  eye, 
and  serving  in  a  measure  also  to  elucidate  the  manner  in  which  the  eye 
is  accommodated  for  different  distances,  a  brief  description  of  these 
abnormal  conditions  may  not  appear  superfluous.  Let  us  suppose,  for 
example,  that  either  through  elongation  of  the  whole  eye  or  through  the 
greater  converging  power  of  the  lens  (Fig-  477,  2)  that  rays  of  light 

Fig.  477. 


Hypermetropic  eye  and  myopic  eye  (far-sighted  and  near-sighted  eye).  1.  Hypermetropic  eye.  The 
luminous  rays  arriving  from  an  infinite  distance  (parallels)  produce  an  ocular  cone,  the  summit  of  which 
falls  beyond  the  retina  (at  A),  either  because  the  cone  is  too  long  (lack  of  converging  power  in  the  media 
of  the  eye),  or  because  the  retina  is  too  far  forward  (the  eye  being  too  short).  2.  Myopic  eye.  The 
luminous  rays  from  an  infinite  distance  (parallels)  produce  an  ocular  cone,  the  summit  of  which  falls  in 
front  of  the  retina  (at  B),  either  because  this  cone  is  too  short  (excess  of  converging  power  in  the  media), 
or  because  the  retina  is  placed  too  far  back  (the  eye  being  too  long).  Donders's  researches  seem  to  show 
that  short-sightedness  is  owing  to  this  latter  cause,  as  is  well  shown  in  the  figure  (the  ocular  globe  being 
greatly  elongated  from  back  to  front).     (liuss.) 


from  an  object  are  brought  to  a  focus,  not  on  the  retina  but  in  front  of 
it,  with  the  effect  that  two  blurred  indistinct  images  instead  of  one  are 
seen.  Obviously,  in  order  to  see  distinctly  under  such  circumstances, 
the  object  must  be  brought  close  to  the  eye  so  that  the  rays  of  light  may 
be  brought  to  a  focus  on  the  retina,  hence  the  eye  is  said  to  be  short- 
sighted or  myopic.  Evidently,  however,  if  a  concave  lens  (C)  be  placed 
between  the  myopic  eye  and  the  object,  the  rays  of  light  will  be  made 
to  diverge  to  such  an  extent  that  they  will  come  to  a  focus  on  the  retina, 

the  formula  made  use  of  bein<T  as  follows  : — ,    in    which 

f~d        If 


800 


PHYSIOLOGICAL    OPTICS, 


f  =  the  focal  distance  of  the  concave  glass  needed,  d  =  the  distance,  8 
inches,  say,  at  which  the  object  is  held  for  the  short-sighted  eye,  D  = 

•  111 

the  normal  distance,  usually  taken  as  10  inches,  then    —  —  —  —  — 

j  8         10 

_ — that  is  to  say,  40  inches  is  the  focal  distance  of  the  concave 

—  40  Ji 

glass  needed.  On  the  other  hand,  let  Fig.  477,  1,  represent  an  eye  in 
which  either  the  whole  eye  is  too  short  or  the  lens  not  sufficiently  con- 
vex ;  then  the  rays  of  light  will  come  to  a  focus  behind  the  retina, 
two  blurred  objects  being  seen.  In  order  to  see  the  object  distinctly, 
the  latter  must  be  removed  to  a  distance  from  the  eye,  hence  the  eye  is 
said  to  be  far-sighted  or  hypermetropic.  Such  being  the  case,  obviously 
if  a  convex  lens  (C)  be  placed  between  the  hypermetropic  eye  and  the 
object,  then  the  rays  of  light  will  be  made  to  converge  and  come  to  a 
focus  on  the  retina,  the  formula  made  use  of  to  obtain  the  glass  needed 

being  as  follows:    —  —  — — ,  in  which  /=  the  focal  distance  of 

°  /         1)       a 

the  convex  glass,  D  =  the  distance  (10  inches)  at  which  the  object  would 

be  held  for  distinct  vision  in  the  normal  eye,  d  =  the  distance  for 

the  longsighted   eye  which,  let  us   say,  for  example,  is  30  inches,  then 

1  1         1         2         1      +,    ,    . 

—  —  -— that    is 

/  "  "  10      30  —  30  —  15 

to  say,  the  focal  length  of  the  con- 
vex glass  needed  is  15  inches.1  A 
very  ready  and  ingenious  method  for 
determining  whether  an  eye  is  emme- 
tropic— that  is,  normal,  myopic,  or 
hypermetropic,  is  that  suggested  and 
made  use  of  by  my  colleague,  Prof. 
William  Thomson,2  which  consists  in 
placing  a  piece  of  colored  glass  (g), 
red,  for  example,  over  one  of  the 
openings  in  the  card  used  in  Scheiner's 
experiment,  as  represented  in  Fig. 
478.  Supposing  the  eye  to  be  emme- 
tropic, it  is  evident  that  the  colored 
red  ray  and  white  ray  falling  upon 
the  retina  at  the  same  spot,  but  one 
image,  a  red  one,  will  be  observed. 
If  the  eye  be  myopic,  however — that  is,  the  retina  is  too  far  back, 
then  through  the  crossing  of  the  rays  of  light  two  images  will  be  seen,  a 
red  one  below  and  a  white  one  above.  On  the  other  hand,  if  the  eye 
he  hypermetropic  the  images  will  be  seen,  but  the  red  one  will  be  above 
the  white  one  below. 


Fra.  478. 


Scheiner's  experiment,  with  Thomson's 
modification.  A.  Source  of  light.  E.  Position 
■of  retina  in  regard  to  the  focus  C  of  the  rays 
■entering  through  two  apertures  in  a  card,  one 
of  which  is  covered  with  a  colored  glass  g  in 
an  emmetropic  eye.  H.  Position  of  the  retina 
m  n  in  a  hypermetropic  eye.  M.  Position  of 
retina  p  q  in  a  myopic  eye. 


1  In  explaining  to  an  audience  the  manner  in  which  astigmatism,  myopia,  and  hypermetropia,  are  pro- 
duced the  author  has  found  the  artificial  eye  of  Kuline,  as  made  by  Jung,  of  Heidelberg,  a  very  useful 
adjunct, 

-  American  Journal  of  the  Medical  Sciences,  Aj  ril,  1870. 


ACCOMMODATION.  801 


Accommodation. 


In  considering  the  manner  in  which  the  rays  of  light  are  refracted  aa 
they  pass  through  the  media  of  the  eye,  and  the  image  of  an  external 
object  formed  upon  the  retina,  we  have  supposed  heretofore  that  both 
the  eye  and  the  object  were  at  rest.  Every  one  is  familiar  with  the 
fact,  however,  that,  notwithstanding  that  an  object  may  approach  or 
recede  from  the  eye  in  either  case,  at  least  within  certain  limits,  it  is 
clearly  seen,  as  in  the  first,  or  intermediate  position.  Such  being  the 
case,  evidently  then  the  eye  must  undergo  some  change,  otherwise,  as 
the  object  approached  the  eye,  the  focus  would  recede  from  the  retina, 
being  formed  behind  it,  and  as  the  object  receded  from  the  eye  the 
focus  would  recede  from  the  retina  in  the  opposite  direction,  being 
formed  in  front  of  it.  Thus,  let  us  suppose  that  the  object  being  at  A 
B  (Fig.  469),  and  its  image  at  d  c,  that  the  object  is  moved  to  H,  its 
focus  would  then  be  formed  behind  the  retina  at  H',  and  the  condition 
of  the  eye  would  be  hypermetropic,  two  objects  being  seen,  as  in  the 
case  of  Scheiner's  experiments  just  described,  unless  simultaneously  with 
the  movement  of  the  object  toward  the  eye  some  change  was  induced 
in  the  latter,  by  which  the  focus  was  kept  upon  the  retina  at  d  c.  On 
the  other  hand,  if  the  object  be  moved  to  M.  then  the  focus  would  be 
formed  in  front  of  the  retina,  as  at  M7,  and  the  condition  of  the  eye 
would  be  myopic,  two  objects  being  seen,  unless  simultaneously  with 
the  movement  of  the  object  from  the  eye,  by  some  change  in  the  latter, 
the  focus  was  kept  upon  the  retina  at  d  c.  The  change  undergone  by 
the  eve.  and  by  which  the  image  of  the  object  is  kept  upon  the  retina, 
whether  the  object  approaches  or  recedes  from  the  eye,  is  known  as  the 
power  of  accommodation,  and  is  without  doubt  due  to  a  change  in  the 
shape  of  the  lens ;  the  latter  becoming  more  convex  as  the  object 
approaches  the  eye,  less  so  as  the  object  recedes  from  it ;  the  lens 
becoming  more  convex  as  the  object  approaches  the  eye,  the  effect  of 
the  greater  converging  power  of  the  lens,  wdiich  would  otherwise  bring 
the  focus  forward  toward  M7,  is  neutralized,  so  to  speak,  by  the  move- 
ment of  the  object  towTard  the  eye,  which  would  otherwise  remove  the 
focus  backward  from  the  retina  toward  H,  the  focus,  therefore,  remains 
in  the  same  position,  d  c.  On  the  other  hand,  the  lens  elongating, 
becoming  less  convex  as  the  object  recedes  from  the  eye,  the  effect 
of  the  greater  diverging  power  of  the  lens,  which  would  otherwise 
send  the  focus  backward  from  the  retina  toward  H,  is  neutralized  by 
the  receding  of  the  object  from  the  eye,  the  effect  of  which  would  other- 
wise be  to  draw  forward  the  focus  from  the  retina  to  M';  the  focus, 
therefore,  remains  at  the  same  place  on  the  retina,  d  c. 

Before  considering  the  means  by  whbh  this  change  in  the  shape  of 
the  lens  is  effected,  and  through  which  the  eye  accommodates  itself  to 
different  distances,  let  us  first  show  how  it  can  be  experimentally 
demonstrated  that  such  a  change  in  the  shape  of  the  lens,  as  that  just 
described,  does  actually  occur  during  accommodation.  With  that  object 
let  a  person,  wdiose  eye  is  to  be  examined,  be  requested  to  look  at  some 
distant  object,  and  while  doing  so  let  the  light  from  the  flame  of  a  candle 
(B,  Fig.  47  {J )  fall  upon  the  eye  (CO)  at  about  the  angle  represented  in 

■M 


802 


PHYSIOLOGICAL    OPTICS. 


the  figure  ;  if  the  eye  of  the  observer  be  situated  at  E  three  images  will 
be  seen  ;  the  first  (a)  an  erect  virtual  image,  like  that  represented  in 
Fig.  480,  due  to  the  reflection  of  the  light  from  the  cornea  (b)  to  the 
eye  of  the  observer  at  E\  the  second  (b)  also  a  virtual  erect  image  due  to 


Fig.  479. 


Change  in  the  form  of  the  lens  during  accommodation. 

the  reflection  of  the  light  from  the  anterior  surface  of  the  crystalline 
lens ;  the  third  (c)  a  real  reversed  image,  like  that  represented  in  Fig. 
480.     The  three  images  being  observed,  let  now  the  individual,  whose 


Fig.  480. 


Fig.  482. 


ale 

Reflected  images  in  the  eye.      (Dalton.) 


Real  reversed  image  of  concave  mirror. 


Phako-coj  e  of  Helmholtz.     (McKbndrick.) 


eye  is  being  examined,  look  at  a  near  object,  and  at  once  the  observer 
at  E  will  notice  that,  while  the  position  of  the  images  (Fig.  480)  a  and 
c,  due  to  the  reflection  of  the  light  of  the  candle  B  from  the  cornea  and 
posterior  surface  of  the  lens,  remains  unchanged,  that  of  the  image  6, 


ACCOMMODATION.  803 

due  to  the  reflection  of  the  light  from  the  anterior  surface  of  the  lens  is 
very  much  changed,  it  being  now  much  closer  to  a,  and  also  that  it  is 
smaller  than  when  the  individual,  whose  eye  is  being  observed,  looked 
at  a  distant  object,  which  can  only  be  accounted  for  on  the  supposition 
that  the  anterior  surface  of  the  lens  increases  in  convexity,  the  light 
falling  upon  I  instead  of  a  (Fig.  479).  In  performing  this  experiment 
the  phakoscope  of  Helmholtz  will  be  found  a  useful  instrument.  It  con- 
sists (Fig.  482)  essentially  of  a  black  triangular  box  with  four  openings  : 
the  first  opening  in  the  base  of  the  triangle  supports  a  needle  point, 
which  constitutes  the  near  object ;  the  second  opening,  directly  opposite 
to  the  first,  receives  the  eye  to  be  observed;  while  of  the  two  remaining 
lateral  openings,  one  containing  prisms  transmits  the  light,  the  other 
receives  the  eye  of  the  observer.  In  using  the  phakoscope  the  indi- 
vidual looks  first  through  the  window  at  a  distant  object,  and  then  at 
the  middle  point.  It  having  been  shown,  then,  that  the  lens  becomes 
more  convex — accommodates  itself  to  see  near  objects — it  only  remains 
now  to  account  for  this  change  in  the  shape  of  the  anterior  surface  of 
the  lens.  It  will  be  remembered,  in  speaking  of  the  action  of  the 
ciliary  muscle,  it  was  mentioned  that,  owing  to  its  disposition  with  refer- 
ence to  the  sclerotic  and  choroid,  that  in  contracting  it  would  draw  the 
choroid  forward,  thereby  relaxing  the  suspensory  ligament  of  the  lens, 
the  effect  of  which  would  be  that  the  lens,  owing  to  its  elasticity,  would 
change  its  shape. 

It  would  appear,  therefore,  that  the  change  in  the  convexity  of  the 
lens,  through  which  the  eye  accommodates  itself  to  see  near  objects, 
is  brought  about  by  the  contraction  of  the  ciliary  muscle.  If  such  be 
the  case,  of  which  there  can  be  but  little  doubt,  the  sense  of  effort  which 
we  experience  in  looking  at  near  objects  must  arise  from  the  contraction 
of  the  ciliary  muscle.  Accommodation  can  only  take  place  within  a 
certain  range,  marked  variation  being  observed  however  in  this  respect 
according  to  individual  peculiarities.  As  a  rule,  objects  situated  at  a 
distance  from  the  eye  of  6.5  metres  (20  feet)  or  beyond  to  infinity,  the 
punctum  remotum  or  far  point  to  be  seen,  do  not  necessitate  accommo- 
dation, the  parallel  rays  of  light  coming  to  a  focus  on  the  retina.  The 
nearer  however  the  object  approaches  within  this  limit,  the  eye,  the  more 
the  accommodating  power  is  exercised  until  a  point  is  reached  about  12 
cm.  (5  inches)  from  the  eye,  the  punctum  proximum  or  near  point,  which, 
if  exceeded  by  the  object,  cannot  be  compensated  by  any  further  change 
in  the  shape  of  the  lens.  The  accommodation  being  then  strained  to 
its  uttermost  if  the  object  comes  still  nearer  the  eye.  the  rays  of  light 
will  not  be  focussed  upon  the  retina.  The  range  of  accommodation  of 
the  eye  for  distance  lies  then  between  these  two  limits,  that  of  the 
punctum  remotum  and  punctum  proximum.  The  power  of  accommoda- 
tion of  the  eye  can  be  measured  by  the  converging  power  of  a  lens, 
which  gives  distinct  vision  of  an  object  placed  at  the  punctum  proximum 
without  necessitating  any  accommodation  in  the  eye — that  is,  of  a  lens 
which  brings  the  diverging  rays  of  light  from  the  punctum  proximum  to 
a  focus  on  the  retina,  just  as  if  they  had  come  parallel  from  the 
punctum  remotum.  for  which  accommodation  is  not  required  in  the 
normal  eye.      Indeed,  that   is  exactly  the  effect  of  the  change  in  the 


804  PHYSIOLOGICAL    OPTICS. 

shape  of  the  crystalline  lens  in  accommodation,  viz.,  that  of  retaining 
on  the  retina  the  focus  of  the  rays  of  light  diverging  from  the  near 
point  just  as  if  they  came  parallel  from  the  far  point.     The  focal  length 

Pig.  483. 


P*<^ 


Condition  of  refraction  in  the  normal  passiue  eye  during  accommodation. 

of  such  a  lens  is  obtained  from  the  formula  -=  — —     (1),  in  which 

J         Jr  I  > 

f  =  the  focal  length  of  the  lens,  P  =  the  distance  of  the  punctum 
proximum  (12  cm.  =  4.8  inches),  R  =  that  of  the  punctum  remotum, 

which  in  the  normal  eye  equals  infinity,  therefore  -  =  -—  cm.,  that  is 

to  say,  12  cm.  is  the  focal  distance  of  the  convex  lens,  representing 
the  power  of  accommodation.  As  the  elasticity  of  the  lens  diminishes 
as  a  result  of  a^e  and  as  further  it  becomes  more  flattened,  the  lens 
gradually  loses  the  power  of  changing  its  shape,  of  becoming  more 
convex  as  an  object  approaches  the  eye,  and  consequently  the  punctum 
proximum  recedes  further  and  further  from  the  latter.  The  diminution 
in  the  ran^e  of  accommodation  so  produced  is  known  as  presbyopia, 
which,  it  will  be  observed,  is  an  anomaly  of  accommodation,  differ- 
ing therefore  from  myopia  and  hypermetropia,  which  are  anomalies  of 
refraction.  While  the  treatment  of  presbyopia  belongs  rather  to  the 
ophthalmologist  than  to  the  physiologist,  it  may  be  mentioned  that  it 
can  be  corrected  by  placing  a  lens  before  the  eye,  such  as  would  give 
the  rays  the  direction  they  would  have  if  they  came  from  the  normal 
punctum  proximum — the  focal  length  of  the  lens  required  being  obtained 

from  the  formula  —  =  —  —    ,  in  which/  =  the  focal  length,  P  =  the 

f       P       p 
normal  punctum  proximum,  and  p  =  the  punctum  proximum  of  the 

presbyopic  eye.    Suppose  the  latter  to  be  30  cm.  (12  inches),  then  -  = 

111 

L — _z_= ,  that  is,  the  lens  required  must  have  a  focal  length  of 

12      30      20'  l 

20  cm.  (8  inches).  In  concluding  the  subject  of  refraction  and  accom- 
modation, it  may  not  appear  superfluous  if  a  brief  account  of  the  ophthal- 
moscope invented  by  Helmholtz  be  offered,  by  which  the  fundus  of  the 


ACCOMMODATION. 


805 


normal  and  diseased  eye  is  examined,  and  through  which,  in  the  hands 
of  Donders,  Graefe,  and  others,  ophthalmic  medicine  was  revolutionized. 
The  interior  of  the  eye  under  ordinary  circumstances  appears  dark, 
since  the  observer  being  between  the  eye  to  be  observed  and  the  source 
of  light  intercepts  the  very  rays  whose  reflection  from  the  interior  of 
the  eye  would  form  the  image  that  it  is  desired  to  see.  Further,  the 
diverging  rays  from  the  interior  of  the  eye  converging  as  they  pass 
through  its  media,  are  brought  to  a  conjugate  focus  outside  of  the  eye, 
which,  to  be  seen,  would  have  to  be  viewed  by  the  observing  eye  at  a 
distance  equal  to  that  of  distinct  vision — that  is,  so  far  from  the  observed 
eye,  that  little  or  nothing  could  be  distinguished.  If,  however,  the 
interior  of  the  eye  be  illuminated  by  light  reflected  from  a  concave 
mirror  the  centre  of  which  is  perforated,  and  through  and  behind  which 
the  observer  can  view  the  e}Te,  then  the  conjugate  focus  formed  as  just 
described  by  the  rays  reflected  from  the  interior  of  the  eye,  can  be  more 
or  less  distinctly  seen.  The  image  of  the  retina,  entrance  of  the  optic 
nerve,  etc.,  as  viewed  by  such  a  mirror  as  that  just  described,  and  con- 
stituting the  original  ophthalmoscope,  become,  however,  much  more  dis- 
tinct, if  -in  addition  to  the  mirror  the  observed  eye  be  viewed  through  a 
lens.  Suppose  that  the  lens  used  be  a  concave  one,  then  rays  of  light 
emanating  from  a   point   of  the  retina  (A,  Fig.  484)  (the  illuminating 


The  ophthalmoscope  with  erect  image. 

rays  from  the  mirror  (M)  being  omitted  in  the  figure  for  simplicity), 
which  would  be  brought  to  a  focus  at  B,  the  image  being  then  real, 
magnified,  and  inverted  by  the  action  of  the  interposed  diverging  lens, 
whose  focal  distance  is  P  B,  are  brought  to  a  focus  at  D,  the  image  being 
virtual,  magnified  but  erect;  that  is,  the  rays  which  come  to  the 
observer's  eye  from  the  retina  (A)  appear  through  the  action  of  the  lens 
to  come  from  D.  On  the  other  hand,  suppose  that  the  lens  used  be  a 
convex  one,  then  (Fig.  485),  the  rays  from  the  retina  (A)  which  would 

Fio.  485. 


The  ophthalmoscope  with  inverted  image. 


otherwise  come  to  a  focus  at  B  through  the  still  greater  converging  effect 
of  the  lens,  will  come  to  a  focus  at  <1,  the  image  formed  being  real  and 
inverted,  and,  while  larger  than  its  object  («)  on  the  retina,  is  smaller 
than  the  image  formed  when  the  concave  lens  is  used. 


CHAPTER    L. 

BINOCULAR  VISION.     SENSATION  AND  PERCEPTION  OF  SIGHT. 
PROTECTIVE  APPENDAGES  OF  THE  EYE. 


In  describing  the  manner  in  which  vision  is  effected  we  have  hitherto 
supposed  it  as  being  accomplished  by  a  single  eye ;  it  remains  for  us 
now  to  consider  how  both  eyes  act  in  viewing  objects,  or  binocular 
vision.  It  might  be  naturally  suppposed  from  seeing  an  object  single, 
when  viewed  with  one  eye,  that  it  would  appear  double  when  viewed 
with  both  eyes.  A  little  observation  will,  however,  make  it  clear  that 
with  one  eye  we  see  but  one  side,  so  to  speak,  of  an  object,  the  right 
side,  for  example,  Avith  the  right  eye,  the  left  side  with  the  left  eye, 
and  that  in  order  to  obtain  a  perception  of  the  entire  object  we  must 
see  the  two  sides  of  the  object  simultaneously.  Thus,  for  example, 
when  we  look  at  a  truncated  pyramid  (Fig.   486,   B)   placed  in  the 

Fig.  486. 


\ 

/ 

\ 

/ 

N 

B 

^ 

\ 

/ 

\ 

/ 

V 

a 


Illustrating  the  principle  of  the  stereoscope  and  binocular  vision. 

middle  line  before  us,  the  image  falling  upon  the  right  eye  is  such 
as  represented  at  R,  that  upon  the  left  eye  at  L,  the  perception  of 
the  form  of  B  is  the  projection,  being  only  obtained  when  the  object 
is  viewed  by  both  eyes  simultaneously.  When  two  dissimilar  images, 
one  of  the  one  eye,  and  the  other  of  the  other,  thus  fused  into  one  per- 
ception, the  inference  by  the  mind  is  that  the  object  giving  rise  to  the 
images  is  solid.  Such,  indeed,  is  the  principle  of  the  stereoscope,  in 
which  two  slightly  dissimilar  pictures,  such  as  would  correspond  to 
the  images  of  two  objects  as  seen  by  each  eye  respectively,  are  by 
means  of  mirrors  or  prisms  cast  upon  the  retina  so  as  to  give  rise 
to  a  single  perception,  that  of  solidity,  or  of  three  dimensions,  though 
each  picture  has  a  surface  of  but  two  dimensions.  In  order,  however, 
that  the  two  retinal  images  shall  be  fused  into  the  one  mental  per- 
ception, it  is  essential  that  the  two  images  shall  fall  on  corresponding 
points  of  the  retina,  at  a  a',  b  b',  c  c'  (Fig.  487),  otherwise  there  will  be 
double  vision — hence,  in  viewing  an  object  with  both  eyes  the  latter 
are  converged,  the  angle  made  by  the  axes  of  the  two  eyes  being 
large  if  the    object  is   near,  and  small  if  the  latter  be  distant.       It 


BINOCULAR    VISION. 


<"7 


will  be  observed  further,  from  an  inspection  of  Fig.  487,  that  since 
ab  =  a'  V,  that  the  angle  1  =  1  and  the  angle  1'  =  1',  and  that  since 
the  angle  2  =  2  the  angle  3  =  3,  and  that  since  be  =  b'  c',  that  the 
angle  4  =  4,  5  =  3.     But  it  follows  from   the  angles  3  3  and  5  being 


Fig.  487. 


Diagram  to  illustrate  theory  of  corresponding 
retinal  point.     (HcKendrick.) 


Diagram  to  illustrate  the  horopter. 
(McKendrick.) 


equal,  that  a",  b",  c",  cannot  lie  in  a  straight  line,  it  being  the 
property  of  a  circle  only  that  triangles  erected  on  the  same  chord 
and  reaching  the  periphery,  have  at  the  latter  equal  angles.  The  line 
joining  the  points  a"  b"  c"  must  therefore  be  a  circle1  (Fig.  488),  of 
which  the  chord  is  equal  to  the  distance  between  the  points  of  decussa- 
tion (K K)  of  the  rays  of  light  in  the  eye.  Such  a  circle  is  known  as 
the  horopter,  and  all  objects  not  lying  in  it  are  seen  double,  their 
images  falling  upon  corresponding  points  of  the  retina.  Standing  up- 
right and  looking  at  the  distant  horizon,  the  horopter  would  be  approxi- 
mately for  normal  long-sighted  persons,  a  plane  drawn  through  the  feet 
— that  is  to  say,  the  ground  on  which  they  stand. 

The  eyeball  nearly  filling  the  cavity  of  the  orbit,  and  resting  poste- 
riorly upon  a  bed  or  cushion  of  adipose  tissue,  is  moved  by  six  muscles, 
the  recti  superior  and  inferior,  externus  and  internus,  and  the  obliqui 
superior  and  inferior.  The  effect  of  these  muscles  when  acting  sepa- 
rately is  quite  apparent  from  their  origin  and  insertion.  The  four 
recti  in  the  order  named,  arising  from  the  apex  of  the  orbit  around  the 
margin  of  the  optic  foramen,  pass  straight  forward,  piercing  the  capsule  of 
Tenon  or  the  fibrous  membrane  surrounding  the  sclerotic,  to  be  inserted 
into  the  latter  tunic  at  about  the  third  or  fourth  of  an  inch  behind  the 
margin  of  the  cornea,  move  the  eye  upward,  downward,  outward,  and 
inward.  The  superior  oblique  muscle,  arising  from  the  optic  foramen, 
proceeds  toward  the  internal  angle  of  the  orbit  and  terminates  in  a 
round  tendon,  which,  passing  through  a  fibro-cartilaginous  ring  or 
pulley,  is  thence  reflected  backward  and  outward  to  be  inserted  into 
the   sclerotic  between   the   superior  and   external   recti    muscles.     Its 


1  Mull.r  :  Physiology,  trans,  by  Bftly,  vol.  ii.  p.  1177.     London,  1842. 


808 


BINOCULAR    VISION 


action  is  to  rotate  the  eyeball  downward  and  outward.  The  inferior 
oblique  muscle  arising  from  the  orbital  plate  of  the  superior  maxillary 
bone  close  to  the  external  border  of  the  lachrymal  groove  passes  out- 
ward  and  backward  between  the  inferior  rectus  and  the  floor  of  the 
orbit  to  be  inserted  into  the  external  and  posterior  part  of  the  sclerotic. 
Its  action  is  to  rotate  the  eyeball  upward  and  outward.  It  can  be 
shown,  however,  theoretically,  as  well  as  by  actual  observation,  that 
the  six  muscles  whose  actions  have  just  been  described  may  be  regarded 
as  consisting  of  three  pairs,  each  of  which  rotates  the  eye  round  a  par- 
ticular axis.  Thus  the  recti  superior  and  inferior  rotate  the  eye  up 
and  round  a  horizontal  axis  directed  from  the  upper  end  of  the  nose 
to  the  temple;  the  obliqui  superior  and  inferior  obliquely  round  a  hori- 
zontal axis  directed  from  the  centre  of  the  eyeball  to  the  occiput;  the 
recti  internus  and  externus  from  side  to  side  round  a  vertical  axis  passing 
through  the  centre  of  rotation  of  the  eyeball  situated  a  little  behind 
the  centre  of  the  optic  axis,  parallel  to  the  median  plane  of  the  head, 
the  latter  being  vertical.  The  different  muscular  actions  just  described 
may  be  briefly  summarized  in  tabular  form,  as  follows  : 


Table  LXXXI. — Action  of  Ocular  Muscles. 


Number  of  muscles  acting.  Direction. 

f  Inward, 


One 
Two 


Three 


(  Outward, 
Upward, 


Downward, 
Inward  and  upward, 

Inward  and  downward, 

Outward  and  upward, 

Outward  and  downward, 


Muscles  acting. 

J   Internal  rectus. 
{   External  rectus, 
f   Superior  rectus, 
j   Interior  oblique. 
j   Inferior  rectus. 
|   Superior  oblique, 
f  Internal  rectus. 

!  Superior  rectus. 
Interior  oblique. 
Internal  rectus. 
Inferior  rectus. 
|   Superior  oblique. 
(    External  rectus. 
Superior  rectus. 
(   Interior  oblique. 
(  External  rectus. 
■I   Interior  rectus. 
(  Superior  oblique. 


It  will  be  observed,  from  what  has  just  been  said  of  the  action  of  the 
ocular  muscles,  and  as  seen  from  a  glance  at  Table  LXXXI.,  that  even 
in  viewing  an  object  with  a  single  eye,  that  a  considerable  amount  of 
muscular  coordination  must  take  place,  since  when  the  eye  is  moved  in 
any  other  than  the  vertical  or  horizontal  meridian  three  muscles  at 
least  must  be  stimulated,  relatively  to  the  amount  of  inclination  of  the 
visual  axis  needed.  Such  being  the  case  in  single  vision,  necessarily, 
then,  the  amount  of  muscular  coordination  required  in  binocular  vision 
must  be  much  greater.  If  the  eyes  of  any  person  be  observed,  it  will 
be  noticed  that  the  two  eyes  move  alike,  when  the  right  eye  moves  to 
the  right  so  does  the  left,  and  to  the  same  extent  if  the  object  looked  at 
be  distant,  if  the  right  eye  looks  up  so  does  the  left,  and  so  in  every 
other  direction.    Briefly,  then,  the  eyes  move  in  such  a  manner  that  the 


SENSATION    OF    SIGHT.  809 

images  of  an  object  always  fall  upon  corresponding  points  of  the  retina, 
the  essential  condition,  as  we  have  seen,  for  the  production  of  single 
vision,  the  movements  of  the  two  eyes  ceasing  to  agree  with  each  other 
only  when  the  power  of  coordination  is  lost,  through  disease  or  by  alco- 
holic or  other  poisoning.  By  movements  of  the  eyes  apart,  however, 
from  those  of  the  head,  the  extent  of  the  field  of  vision  may  amount  to 
as  much  as  200  in  the  horizontal  and  2U0  in  the  vertical  meridian, 
that  of  a  single  eye  being  about  145  for  the  horizontal  and  100  for  the 
vertical  meridian. 

Sensation  of  Sight. 

Rea-ardincr  the  sensation  of  siodit  as  due  to  the  stimulation  of  the  retina 
by  light,  observation  teaches,  as  might  be  supposed,  that  the  intensity 
and  duration  of  the  sensation  will  vary  according  to  the  strength  of  the 
luminous  vibrations,  and  the  length  of  time  during  which  the  latter 
continue  to  fall  upon  the  retina.  That  the  intensity  of  the  sensation 
varies  with  that  of  the  luminous  object  is  a  matter  of  daily  experience, 
a  wax  candle,  for  example,  appearing  brighter  than  a  rushlight.  With 
a  little  experimentation  it  becomes  soon  apparent,  however,  that  the 
ration  of  the  sensation  to  the  stimulus  is  not  a  simple  one,  since  while 
the  sensations  increase  as  the  luminosity  of  the  object  increases,  the 
sensations  increase  less  and  less,  until  finally  there  is  no  appreciable 
increase  of  sensation  however  much  the  luminosity  may  be  increased — 
that  is  to  say,  when  a  light  reaches  a  given  brightness  it  appears  so 
bright  to  us  that  we  cannot  tell  when  it  becomes  anv  brighter.  It  is 
much  easier,  therefore,  to  distinguish  the  difference  between  two  feeble 
lights  than  the  same  difference  between  two  bright  lights — in  fact,  if  the 
latter  be  very  bright  it  becomes  then  impossible.  Thus,  for  example, 
while  there  is  no  difficultv  in  distinguishing  between  the  light  of  a 
candle  and  that  of  a  rushlight,  it  would  be  impossible  to  distinguish 
such  A  difference  between  the  light  of  two  suns,  supposing  the  light  of 
the  one  to  be  in  excess  of  that  of  the  other  in  the  same  ratio  as  that  of 
the  candle  over  that  of  the  rushlight,  just  as  an  addition  of  half  an 
ounce  to  twenty  pounds  will  not  be  appreciated  by  the  sense  of  weight. 
Further,  it  will  be  found  that  if  we  let  the  shadows  of  two  rushlights, 
for  example,  fall  upon  white  paper  and  then  move  one  of  the  lights  away 
until  the  shadow  ceases  to  be  visible,  that  in  performing  the  same  ex- 
periment with  two  wax  candles  the  candle  will  have  to  be  moved  through 
the  same  distance  as  that  of  the  rushlight  before  its  shadow  ceases  to  be 
seen,  the  smallest  difference  in  light  in  both  cases  appreciable  being  in- 
variably about  the  y-J-jjth  °f  *ne  total  luminosity  made  use  of.  In  this 
connection  it  may  be  appropriately  mentioned  as  elsewhere,  that  whether 
the  sensation  be  that  of  sight  due  to  the  stimulus  of  light  or  of  hearing, 
due  to  sound  or  of  temperature,  due  to  heat  or  of  touch,  due  to  muscular 
effort  or  to  weight,  thai  the  smallest  difference  of  appreciable  sensation 
is  invariably  a  constant  fractional  portion  of  the  total  force,  the  cause  of 
the  sensation  made  use  of,  differing,  however,  for  the  various  sensations. 
Thus,  for  example,  suppose  that  the  eyes  being  bandaged  and  the  hand 
extended  and  supported,  successive  weights,  as  a  drachm,  ounce,  and 
pound  be  placed  upon  it,  it  will  be  found,  whatever  be  the  weight  origin- 


810  SENSATION     OF    SIGHT. 

ally  placed  upon  the  hand,  that  in  order  to  appreciate  a  distinct  difference, 
one-third  of  the  weight  will  be  required  to  be  added  or  taken  away.  In  the 
case  of  muscular  effort,  however,  only  the  j -<j~g-th  of  the  original  weight 
would  have  to  be  added  or  subtracted  to  make  an  appreciable  difference 
in  the  sensation  ;  thus  a  weight  of  6  grains,  added  to  100  grains,  would 
make  a  perceptible  difference.  In  both  the  case  of  the  sense  of  tem- 
perature or  of  sound  the  difference  required,  however,  is  the  same  as 
that  of  weight — that  is  to  say,  a  difference  of  one-third  of  the  total  heat 
or  sound  giving  rise  to  the  initial  sensation,  added  or  subtracted,  would 
be  appreciated.  It  might  naturally  be  supposed  that  vibrations  such  as 
those  of  light  and  sound,  etc.,  in  acting  upon  the  terminal  fibres  of  the 
optic  and  acoustic  nerves,  etc.,  might  impress  the  latter  so  slightly  as 
to  give  rise  to  no  sensation  whatever,  and  that  if  the  strength  of  the 
stimulus  be  gradually  increased,  a  very  feeble  excitation  would  be  ex- 
perienced, which  might  be  called  the  lower  limit  or  minimum  of  excita- 
tion. Such,  indeed,  has  been  shown  experimentally  to  be  the  case,  the 
minimum  of  excitation  being  in  the  case  of  the  sensation  of  touch  a 
pressure  of  0.002  gramme  to  0.03  gramme,  in  that  of  temperature  J 
of  a  degree  Cent.,  the  skin  being  at  a  temperature  of  about  18.4°  C,  in 
that  of  muscular  effort  shortening  to  the  extent  of  0.044  mm.  of  the 
internal  rectus  of  the  eye,  in  that  of  sound  a  ball  of  pith  1  milligramme 
in  weight  falling  through  1  mm.  upon  a  glass  plate,  heard  at  a  distance 
of  91  mm.  from  the  ear,  in  that  of  light  an  intensity  of  about  300  times 
less  bright  than  that  of  the  full  moon. 

From  what  has  been  said  with  reference  to  sensory  impressions  it 
appears  to  have  been  well  established :  1st,  that  there  is  a  minimum  of 
excitation — that  is,  the  smallest  possible  excitation  capable  of  producing 
a  sensation ;  2d,  a  maximum  of  excitation,  over  and  above  which  no 
increase  in  the  stimulus  will  give  rise  to  any  further  increase  in  the 
sensation ;  3d,  that  there  is  a  constant  proportion  or  ratio  between  the 
intensity  of  the  excitant  and  the  intensity  of  the  sensation ;  4th".  that 
the  intensity  of  the  sensation  does  not  increase  proportionally  to  that  of 
the  stimulus  or  excitation.  It  is  evident,  therefore,  that  we  have  the 
means  of  measuring  indirectly  sensations,  however  impossible  that  might 
appear  to  be  at  first  sight,  since  the  excitation  of  any  nerve  giving  rise 
to  the  sensation,  being  due  to  an  external  stimulus,  can  be,  through  the 
latter,  arbitrarily  varied,  and  therefore  quantitatively  determined.  Fur- 
ther, the  experimental  determination  of  the  constant  proportional,  and 
the  minimum  excitation,  furnishes  the  data  by  which  the  law  expressing 
the  general  relation  of  sensation  to  excitation  can  be  graphically  inves- 
tigated and  established.  Suppose,  for  example,  that  the  sensation 
under  consideration  be  one  of  pressure,  let  the  horizontal  line  o  x,  or 
the  abscissa  (Fig.  489),  be  divided  into  equal  parts,  1,  2,  3,  4,  to  repre- 
sent increments  of  sensation,  the  zero  corresponding  to  the  minimum 
of  sensation,  the  vertical  lines,  or  the  ordinate  0«,  1ft,  2c,  3d,  4e,  the 
increments  of  stimulus,  0«  corresponding  to  the  minimum  stimulus, 
say  one-fiftieth  of  a  gramme,  each  ordinate  being  equal  to  the  preceding- 
one  plus  a  third  of  the  same,  according  to  the  determination  of  the 
constant  proportional  in  the  case  of  weight ;  it  is  evident  that  the 
difference  of  length  between   the  line  0a  and  the  lines  16,  2c,  2>d,  4e, 


SENSATION    OF    SIGHT. 


811 


indicates  the  weights  that  must  be  used,  in  order  that  the  perceptible 
difference  in  sensation  should  be  doubled,  tripled,  quadrupled,  quin- 
tupled ;  and  which,  if  the  sensations  be  as  1,  2,  3,  4,  the  weights,  or  their 
representation,  the  ordinates  will  be  found  to  be  as  10, 100,  1000, 10,000 
— that  is  to  say,  the  sensation  varies,  not  as  the  stimulus,  but  as  the 

Fig.  489. 


Graphic  illustration  that  sensation  is  proportional  to  logarithm  of  stimulus. 

logarithm1  of  the  stimulus,  the  numbers  1,  2,  3,  4,  being  the  logarithms, 
respectively,  of  10,  100,  1000,  10,000.  To  those  familiar  with  the  lan- 
guage of  the  calculus  the  above  law,  that  of  the  sensation  varying  with 
the  logarithm  of  the  stimulus,  or  the  Weber-Fechner  law  of  sensation, 
may  be  briefly  described  as  follows :  Let  s.  a  sensation,  be  a  function 

of  a  stimulus  x,  then  ds  =  K — -  (1),  ds  being  the  smallest  appreciable 

x 

increment  of  sensation  due  to  dx,  the  corresponding  increment  of  the 

stimulus  x,  and  K  a  constant.     Integrating  (1)  we  obtain  s  =  K  log. 

x  -f-  c,  which  becomes  0  =  K  log.  x'  -J-  c  if  x  be  diminished  to  x',  at 

which  the  sensation  ceases — that  is,  c  =  —  K  log.  x\  and  s  =  K  log. 

©  O 

x  —  K  log.  x',  or  s  =  K  log 

x' 

Returning  from  this  little  necessary  digression  to  the  sensation  of 

sight,  it  is  evident  that  the  duration  of  the  sensation  is  longer  than  that 

©  © 

of  the  stimulus,  the  sensation  of  sight  and  the  stimulus  of  light  being 

©  _©  © 

comparable,  in  this  respect,  to  a  muscular  contraction,  as  induced  by  a 
single  induction  shock.  It  is  for  this  reason  that  if  two  flashes  of  light 
follow  each  other  sufficiently  quickly  within  the  one-tenth  of  a  second 
for  a  faint  light,  and  the  one-thirtieth  of  a  second  for  a  strong  one,  the 
two  sensations  arising  are  fused  into  one.  Hence,  the  fact  of  a  lumi- 
nous point  moving  rapidly  around  in  a  circle  giving  rise  to  the  sensation 
of  a  continuous  circle  of  light,  which  reminds  one  of  the  production  of 
muscular  tetanus.  That  the  duration  of  the  stimulus  of  light  necessary 
to  give  rise  to  the  sensation  of  sight  must  be  very  short,  is  shown  from 
the  fact  of  the  electric  spark  being  seen,  though  the  latter  is  known  to 

1  A  logarithm  of  a  number  is  the  exponent  of  the  power  to  which  it  is  necessary  t"  raise  a  fixed 
number  to  produce  the  given  number.  Suppose  the  fixed  number  to  be  10,  the  given  number  IO0  or 
1000,  then  2  and  3  will  be  the  logarithms  of  100  and  1000  respectively,  since  lo-  =  100,  103  —  pjiin. 


812  SENSATION    OF    SIGHT. 

last   but  the  vr , ,,  </,, ,th  of  a  second.      When  a  large  portion  of  the 

retina  is  affected  by  light  the  total  sensation  experienced  is  greater  in 
amount  than  when  a  small  portion  is  so  affected,  a  large  piece  of  white 
paper,  for  example,  affecting  our  consciousness  more  than  a  small  piece. 
If,  however,  the  surfaces  of  the  papers  be  equally  and  uniformly  illumi- 
nated, the  small  piece  will  appear  as  bright,  or  white,  as  the  large  one, 
the  intensity  being  the  same  in  both  cases,  Further,  as  might  be 
expected,  if  the  images  of  the  two  papers  be  situated  upon  the  retina  at 
sufficient  distances  apart,  the  two  sensations  will  be  distinct,  the  relative 
intensity  of  the  same  depending  upon  the  brightness  of  the  objects, 
while,  if  the  images  are  so  close  to  each  other  that  the  sensation  fuses 
into  one,  then  the  total  sensation  experienced  will  be  greater  than  that 
due  to  either  one  of  the  images,  though  not  equal  to  the  sum  of  the 
single  sensations.  As  a  general  rule,  the  best  eyes  fail  to  distinguish 
two  parallel  white  streaks  when  the  distance  separating  them,  as  meas- 
ured from  the  middle  of  each,  subtends  an  angle  of  less  than  73 
seconds,  though  some  individuals  can  distinguish  objects  so  close  to  each 
other  that  the  distance  separating  them  does  not  subtend  an  angle  of 
more  than  50  seconds.  Now,  as  the  retinal  image  corresponding  to  an 
angle  of  73  seconds  would  measure  in  the  schematic  eye  about  the  5.36 
of  a  micromillimetre  (the  -^ihroth  °f  an  incn),  and  that  corresponding 
to  an  angle  of  50  seconds,  about  the  3.65  of  a  micromillimetre,  and  as 
the  average  diameter  of  a  retinal  cone  measures  at  its  widest  part  about 
3  micromillimetres,  it  is  evident  that  the  visual  sensory  area  has  a  cor- 
responding physical  basis  in  the  retinal  anatomical  area,  which  renders 
it  highly  probable  that  there  is  still  another  corresponding  cerebral  or 
perceptive  area. 

It  has  already  been  mentioned  that,  owing  to  the  unequal  refrangi- 
bility  of  different  kinds  of  light,  that  white  light  in  passing  through 
a  prism  is  not  only  refracted,  but  is  decomposed  into  the  seven 
kinds  of  light  of  which  white  light  is  composed,  viz.,  violet,  indigo, 
blue,  green,  yellow,  orange,  and  red,  or  the  colors  of  the  spectrum. 
In  considering,  however,  the  manner  in  which  we  become  conscious 
of  the  different  colors  of  which  the  spectrum  is  composed,  or  of  any 
colors  or  color,  we  must  disabuse  ourselves  at  once  of  the  idea  that  what 
we  call  color  exists  outside  of  our  own  consciousness  objectively  as  such, 
since  what  we  call  color  in  ourselves  subjectively,  can  be  shown  experi- 
mentally to  be  due  objectively  to  a  vibration,  an  oscillatory  movement,  a 
wave  of  a  definite  length  passing  into  the  eye  at  a  certain  velocity,  all 
kinds  of  light  being  so  propagated.  In  fact,  color  objectively  is  to  the 
eye  what  we  shall  see  pitch  in  the  case  of  sound  is  to  the  ear,  the  latter 
depending  solely  upon  the  number  of  vibrations  striking  the  ear  in  a 
second.  In  other  words,  a  wave  of  a  certain  length,  propagated  at 
a  definite  rate,  in  falling  upon  the  retina  gives  rise  in  us  to  a  sensa- 
tion of  a  particular  color.  Thus,  the  color  red  is  due  to  the  impinging 
upon  the  retina  of  a  wave  about  the  39^00  of  an  inch  in  length, 
travelling  at  such  a  velocity  that  about  474,439,680,000,000  such 
waves  enter  the  eye  in  a  second ;  the  color  violet  to  a  wave  about  the 
_1_  of  an  inch,  about  690,000,000,000,000  such  waves  entering  the 
eye  in  a  second,  the  waves  giving  rise  to  the  violet  color  being  shorter 
than  those  to  which  the  red  color  is  due,  but  following  each   other  into 


SENSATION    OF    SIGHT.  813 

the  eye  more  rapidly  than  the  latter,  the  waves  to  which  the  other  colors 
of  the  spectrum  are  due  with  reference  to  their  length  and  velocity, 
lying  between  the  extremes  just  mentioned.  The  sensation  of  color 
.depending  then  upon  the  successive  impulses  imparted  to  the  fibres  of 
the  optic  nerve  by  waves  of  different  length  travelling  at  different 
velocities,  it  is  obvious  that  it  would  be  useless  to  look  into  the  external 
world  for  any  attribute  or  quality  that  would  correspond  objectively  to 
what  we  call  in  ourselves  the  sensation  of  color.  In  other  words,  the 
color  red  or  violet  of  an  object  is  in  ourselves,  not  in  the  object  looking 
red,  because  the  wave  giving  rise  to  red  is  reflected  from  the  object  into 
our  eyes,  the  remaining  waves  being  absorbed  by  the  object;  similarly 
surrounding  objects  look  red  when  viewed  through  a  red  glass,  the  wave 
giving  rise  to  red  being  alone  transmitted  through  the  glass  to  our  eve 
the  remaining  Avaves  being  absorbed  by  the  glass,  and  so  with  all 
other  colors.  Our  knowledge  of  color  depending  then  upon  the  im- 
pression made  upon  the  sensorium  by  the  waves  of  light,  can  never 
be  absolute,  but  only  relative.  In  other  words  we  can  never  know 
the  light  in  itself  by  the  thing  itself,  or  the  "ding  an  sich  "  as  Kant1 
expressed  it,  but  only  by  just  so  much  as  the  light  or  thing  affects 
our  consciousness.  The  extent  to  which  sensation  is  dependent  upon 
the  susceptibility  of  the  organism  of  being  impressed  by  the  external 
world,  is  shown  by  the  fact,  that  notwithstanding  the  solar  spec- 
trum extends  beyond  the  violet  in  one  direction,  and  beyond  the  red 
in  another,  the  eye  under  ordinary  circumstances  is  unconscious  of 
the  existence  of  these  extremes,  being  so  organized  as  not  to  be 
affected  by  the  ultra  violet  or  chemical  rays,  or  the  ultra  red  or  heat 
rays.  Our  knowledge  being  due  to  sensations  arising  from  impres- 
sions made  by  the  environment  upon  the  organism,  cannot  then  be 
innate,  but  must  have  been  ultimately  derived  from  experience,  and 
therefore  relative  as  held  by  Locke.2  After  what  has  just  been  said,  it 
is  evident  that  no  physical  or  chemical  changes  in  the  retina  will  account 
for  our  sensation  of  color,  since  the  cause  of  the  latter  lies  not  in  the 
retina,  which  is  simply  an  intermediate  organ,  correlating  the  physical 
with  the  psychical,  but  in  that  part  of  the  cerebrum  wrhere  the  still 
physical  vibration  gives  rise  to  sensation.  Indeed,  the  cause  of  the 
sensation  of  color,  as  might  be  premised  from  the  present  imperfect 
state  of  physiological  psychology,  is  not  yet  understood,  although  a 
great  number  of  interesting  observations  have  been  made  with  refer- 
ence to  the  effect  of  fusing  colors  of  complementary  colors,  of  which 
a  brief  account  at  least  in  this  connection  must  be  given. 

Though  we  have  spoken  of  the  solar  spectrum  consisting  of  seven 
colors,  as  a  matter  of  fact,  it  is  made  up  not  only  of  such,  but  also  of  a 
great  number  of  intermediate  tints  as  well.  External  nature  presents 
the  same  tints,  and  also  a  number  of  others  like  those  of  purple,  brown, 
gray,  etc.,  which  however,  are  not  present  in  any  part  of  the  spectrum. 
While  such  tints  are  apparently  due  to  distinct  simple  sensations,  it  can 
be  shown  experimentally  that  in  reality  they  are  compouud  ones,  being 
obtainable  by  the  fusion  of  two  or  more  color  sensations.      Thus,  purple 

1  Critique  of  Pure  Benson,  trans,  by  Max  Muller.    Second  Part,  p  39.    London,  1881. 
-  Of  Human  Understanding,  Locke's  Works,  char/,  ii.  vol.  i.     Loudon,  1S83. 


M  1 


SENSATION    OF    SIGHT. 


"which,  as  just  mentioned,  is  not  present  in  the  spectrum,  may  be  readily 
produced  by  the  fusion  of  red  and  blue,  as,  for  example,  by  so  placing  a 
red  and  blue  wafer  and  a  glass  (Fig.  490)  that  the  light  will  be  reflected 
from  the  red  wafer  (D)  in  the  same  direction  as  that  coming  from  the 
blue  wafer  (B).  In  the  same  way  the  various  tints  of  nature  may  be 
obtained  by  fusing  different  colors,  sensations  with  that  of  white  or  black, 
different  kinds  of  brown  resulting  from  mixtures  of  yellow,  red,  white. 


Fig.  400. 


Fig.  401. 


r^ 


l~~^n 


Lambert's  method  of  studying  combinations 
of  colors. 


Rotating  disk  of  Sir  Isaac  Newton  for  mixing- 
colors. 


and  black,  grays  from  white  and  black,  as  can  be  shown  by  making  use 
of  a  rotating  disk,  on  the  surface  of  which  colored  sectors  are  painted, 
the  resulting  color  being  white  for  example,  in  that  of  the  instance 
represented  in  Fig.  491.  Experimenting  in  this  way,  it  can  be  shown 
that  the  quality  of  a  color  depends  on  the  wave  length  of  its  constituent 
waves  and  on  the  relative  amount  of  colored  and  white  light  falling 
upon  the  retina  in  a  given  time,  a  color  being  saturated  when  unmixed 
with  white  light,  as  in  the  case  of  the  colors  of  the  spectrnm. 

As  regards  the  fusion  of  colors,  it  is  evident  from  what  has  been  said 
of  the  subject  of  color,  that  in  mixing  red  and  yellow  to  produce  an 
orange,  for  example,  undistinguishable  from  the  orange  of  the  spectrum, 
that  the  sensation  of  orange  cannot  be  due  to  the  uniting  of  the  red  and 
yelloAv  waves  differing  in  length  from  each  other  to  form  an  orange  wave 
differing  in  length  from  either,  but  that  it  is  the  mixture  of  the  sensation 
of  red  and  yellow  that  gives  rise  to  the  sensation  of  orange.  In  other 
words,  the  mixture  is  psychical  not  physical.  It  is  an  interesting  fact, 
that  certain  colors,  when  mixed  together  in  pairs  in  certain  definite 
proportions,  give  rise  to  the  sensation  of  white,  as,  for  example,  red  and 
blue-green,  orange  and  blue,  yellow  and  indigo-blue,  green-yellow  and 
violet ;  such  colors  are  said  to  be  complementary  colors,  since  given  the 
color  of  one  of  the  pairs,  say  red,  all  that  is  necessary  or  complementary 
to  produce  white  is  the  other  color  of  the  pair,  or  green.  It  can  be  also 
experimentally  shown,  by  means  of  the  rotating  disk,  that  the  mixture 
in  proper  proportions  of  any  three  distinct  colors  of  the  spectrum  arbi- 
trarily selected  but  sufficiently  far  apart,  as,  for  example,  red,  green,  and 
violet,  will  produce  white,  and  that  by  the  further  addition  of  white  the 


SENSATION    OF    SIGHT, 


815 


sensations  of  all  the  other  colors  can  be  obtained.  In  order  to  avoid 
any  misunderstanding  as  regards  the  production  of  the  sensation  of 
white,  it  should  be  mentioned  that  the  mixture  of  red,  green,  and  violet 
pigments,  unless  they  are  perfectly  pure,  will  not  produce  white;  a 
mixture  of  pigments  being  totally  different  from  a  mixture  of  sensations 
of  colors,  since  the  color  produced  by  the  mixing  of  pigments  is  due  to 
the  light  which  has  escaped  absorption  by  the  same  rather  than  the  color 
due  to  a  mixture  of  the  colors.  For  example,  the  sensations  of  indigo 
and  yellow,  when  mixed,  give  rise  to  the  sensation  of  white,  the  sensa- 
tion due  to  the  mixing  of  indigo  and  yellow  pigments  is,  however,  green, 
the  indigo  absorbing  the  red  of  the  yellow  and  the  yellow  absorbing  the 
blue  of  the  indigo,  green  only  being  left  for  both  to  reflect.  Facts  like 
those  just  mentioned  with  reference  to  the  fusion  of  colors,  their  comple- 
mentary relation,  the  composition  of  white  light,  etc.,  led  the  celebrated 
Young,1  in  the  beginning  of  this  century,  and  Helmholtz,2  in  recent 
times,  to  advocate  the  view  that  all  of  our  sensations  of  color  are  com- 
pounds of  three  primary  color  sensations,  red,  green,  and  violet,  and 
that  waves  of  different  lengths  give  rise  to  all  three  of  these  sensations 
according   to   their  particular  length — that  is  to  say  (Fig.   492),   the 

Fig.  492. 


xt  0         TT  fin  SI.  V 

Diagram  of  three  primary  color  sensations.  1  is  the  so-called  "red,"  2  "  green,"  and  3  "violet"  pri- 
mary color  sensation,  i?,  0,  Y,  etc  ,  represent  the  red,  orange,  yellow,  etc.,  color  of  the  spectrum,  and 
the  diagram  shows,  by  the  height  of  the  curve  in  each  case,  to  what  extent  the  several  primary  color 
sensations  are  respectively  excited  by  vibrations  of  different  wave-lengths.     I  Foster.) 

orange  wave  gives  rise  to  much  of  the  first  sensation,  or  red,  less  of  the 
second  or  green,  and  to  little  of  the  third  or  violet;  on  the  other  hand. 
that  the  blue  wave  gives  rise  to  little  of  the  red  sensation,  to  more  of 
the  green,  and  to  much  of  the  violet,  etc.  The  anatomical  basis  for  the 
above  is  the  assumption  that  three  kinds  of  nerve  fibres  exist  in  the 
retina,  the  excitation  of  which  gives  rise  respectively  to  the  sensations  of 
red,  green,  and  violet — homogeneous  light — all  three  of  these  so-called 
fundamental  sensations,  but  with  different  intensities  according  to  the 
length  of  the  wave:  long  waves  exciting  most  powerfully  the  fibres  whose 
stimulation  give  rise  to  the  sensation  of  red.  medium  waves  those  causing 
the  sensation  of  green,  short  waves  those  causing  the  sensation  of  violet. 
Accepting  provisionally  the  Soung-Helmholtz  theory  of  color  sensation, 
it  serves  to  explain  some  of  the  phenomena  of  color-blindness,  after-images, 


1  Lectures  on  Natural  Philosophy.     London,  1807J 


-  Op.  cif„  p.  382. 


816  SENSATION    OF    SIGHT. 

etc.  While  almost  all  individuals  are  aide  to  appreciate  differences  of 
color,  there  are  some,  and  the  number  is  far  greater  than  usually  sup- 
posed, who  are  unaffected  by  certain  colors,  the  most  common  delect 
being  an  insensibility  to  red,  blindness  to  green  and  violet  being  rare. 
Thus,  for  example,  in  Daltonism  or  blindness  to  red,  so  called  on  account 
of  its  having  been  observed  in  the  celebrated  Dalton,  the  red  end  of  the 
spectrum  appears  dark,  a  red  gown  lying  on  a  green  grass  plot,  a  red 
cherry  among  green  leaves,  are  distinguished,  not  by  their  color  but  by 
their  form,  the  color  of  the  gown  or  the  fruit  appearing  to  such  an  eye 
not  red  but  green  like  that  of  the  grass  or  leaves.  Remembering  that 
green  is  the  complementary  color  to  red,  and  supposing  that  in  a  dal- 
tonic  eye  the  fibres  whose  stimulation  in  an  ordinary  eye  would  give  rise 
to  the  color  of  red,  are  either  absent,  diseased,  or  paralyzed,  the  phe- 
nomenon just  referred  to  can  be  accounted  for.  Similarly  if  after  a  red 
patch  has  been  looked  at  steadily  for  some  time  until  the  eye  becomes 
fatigued,  a  white  surface  be  looked  at,  a  green  patch  will  be  seen  instead 
of  the  red  one,  the  green  fibres  of  the  retina,  so  to  speak,  being  fresh, 
are  susceptible  of  being  excited  by  the  green  color  (or  wave  giving  rise 
to  it)  of  the  white  light  reflected  from  the  paper,  the  red  fibres  being, 
howrever,  exhausted,  are  no  longer  susceptible  of  being  excited  by  the 
red  color  (or  the  wave  giving  rise  to  it)  of  the  Avhite  light.  In  the  same 
manner  many  other  negative  after-images  can  be  explained,  so  called  as 
contrasted  with  positive  after-images  which  are  simply  due  to  a  sensa- 
tion, being  continued  even  after  the  object  giving  rise  to  it  has  been 
removed  from  the  field  of  vision.  Thus,  for  example,  if  the  eye  be 
directed  momentarily  to  the  sun  the  image  of  the  latter  will  be  present 
for  some  time  after,  or  if  a  window  be  looked  at  for  an  instant  on  early 
waking  and  the  eye  then  closed,  an  image  of  the  same  with  its  bright 
panes  and  darker  sashes  will  persist  for  some  time.  While  the  Young- 
Helmholtz  theory  of  color  sensation  is  accepted  by  many  physiologists, 
another  theory  has  been  advanced  by  Aubert1  and  Hering2  among  others, 
the  latter  of  whom  maintain  that  the  primary  color  sensations  are  white, 
black,  red,  yellow,  green,  and  blue,  and  that  these  different  sensations 
are  due  to  the  changes  in  the  so-called  visual  substance  of  the  visual 
apparatus,  the  changes  giving  rise  to  the  sensations  of  black,  green,  and 
blue  being  processes  of  a  constructive-assimilating  kind,  those  giving 
rise  to  the  sensations  of  white,  red,  and  yellow,  of  a  destructive-assimi- 
lating kind.  If  Hering's  view  be  accepted,  then  black  and  white, 
green  and  red,  blue  and  yellow,  far  from  being  complementary,  must  be 
regarded  as  antagonistic  to  each  other,  and  the  visual  substance  assumed 
to  be  always  undergoing  changes,  never  in  a  state  of  rest.  The  limits 
of  this  work  will  not  permit  of  further  illustration  or  discussion  of  the 
relative  merits  of  the  Helmholtz  and  Hering  theories  of  the  sensations 
of  color ;  it  may  be  pointed  out,  however,  once  more,  that  whether  the 
one  or  the  other  theory  be  accepted,  we  are  not  a  wdiit  nearer  the 
explanation  of  the  sensation  of  color,  since  the  transformation  of  the 
ultimate  physical  vibration  or  wave  into  the  psychical  color  sensation 
takes  place  not  in  the  retina  but  in  the  cerebrum. 

i  Physiologie  der  Netzhaut,  18G6.  '-'  Wien.  Sitzbeiicbt,  lxvi.  (1872),  lviii.,  l.\i.\  ,  lxx. 


perception  of  sight.  817 

Perception  of  Sight. 

It  has  already  been  mentioned  that  as  the  apparent  size  of  an  object 
depends  upon  the  visual  angle,  if  two  objects,  though  of  different  size, 
subtend  with  the  eye  equal  angles — that  is,  if  their  visual  angles 
are  the  same — the  apparent  size  of  the  objects  will  be  the  same.  The 
real  size  of  an  object  is  therefore  not  determined  by  the  sense  of  sight, 
the  latter  only  giving  rise  to  the  sensation  of  its  apparent  size.  The 
estimate  of  the  real  size  of  an  object  is  really  an  inference  based  upon 
its  apparent  size,  but  modified  by  the  knowledge  of  its  distance  from 
the  eye.  In  other  words,  it  is  not  a  simple  sensation,  but  a  judgment 
based  upon  the  sensations  of  touch,  as  well  as  those  of  sight.  Know- 
ing the  distance  of  an  object  from  us,  we  infer  from  its  apparent  size 
its  real  size:  and  conversely,  knowing  the  size  of  the  object,  we  infer  its 
distance.  Thus  if  the  image  of  some  well-known  object,  a  man,  for 
example,  appear  in  our  field  of  vision,  and  Ave  know  how  far  off  the 
man  is,  we  infer  his  size  from  that  of  our  retinal  image;  and,  con- 
versely, knowing  the  size  of  the  man,  if  his  retinal  image  be  very  small, 
Ave  infer  that  the  man  is  very  far  off.  That  our  estimate  of  the  size 
of  an  object  is  dependent  upon  the  knowledge  of  its  distance  from  us, 
is  shown  from  the  fact  that  if  Ave  have  no  means  of  even  approxi- 
mately estimating  the  latter,  it  is  impossible  to  obtain  any  idea  of  its 
size.  Thus  the  sun,  though  about  four  hundred  times  the  distance  of 
the  moon,  is  apparently  of  the  same  size  as  the  latter,  but  Ave  infer 
from  that  very  reason  that  the  one  body  is  larger  than  the  other ;  did 
Ave  not  knoAV,  hoAvever,  their  relative  distance  from  the  earth,  it  Avould 
be  impossible  to  say  which  of  the  two,  the  sun  or  the  moon,  A\Tas  the 
larger  body.  Our  estimate  of  the  distance  of  objects  is  not  only  based 
upon  their  size,  but  largely  upon  the  presence  of  surrounding  and 
intermediate  objects,  it  being  difficult  to  estimate  the  distance  of  an 
object  entirely  isolated,  as  in  looking  at  a  single  distant  object  at  sea. 
The  muscular  sensations  arising  through  the  contraction  of  the  ocular 
muscles  in  converging  the  visual  axis  for  near  objects,  and  diverging 
the  same  for  distant  ones,  aid  us  very  much  in  forming  a  correct  judg- 
ment as  to  the  distance  of  objects.  As  Avith  our  estimate  of  the 
distance  of  objects,  so  with  that  of  the  idea  of  solidity,  Avhich  is 
essentially  an  estimate  of  the  distance  of  the  different  parts  of  an 
object,  the  idea  being  a  judgment,  a  mental  combination  of  the  tAvo 
dissimilar  pictures  formed  upon  the  retina,  the  image  of  the  object  as 
viewed  by  the  right  eye  being,  as  already  mentioned,  different  from 
that  as  viewed  by  the  left  eye,  the  resultant  image  being  seen  in  relief, 
and  giving  rise  to  the  idea  of  solidity.  The  fact  that  Ave  see  objects 
erect,  though  their  images  are  reversed  upon  the  retina,  as  already 
mentioned,  is  due  to  the  fact  of  the  sensation  of  the  image  derived  from 
the  sense  of  sight  being  modified  by  the  sensation  of  the  object  derived 
from  the  sense  of  touch.  The  mind  associating  images  situated  at 
the  upper  and  inner  part  of  the  retina  Avith  the  objects  giving  rise  to 
them  but  situated  beloAv  and  to  the  outer  side  of  the  eye,  and  images 
at  the  upper  and  outer  part  of  the  retina  with  objects  situated  below 
and  to  the  inner  side  of  the  eye,  and  projecting  outAvard,  the  images 

52 


818  PERCEPTION    OF    SIGHT. 

or  the  luminous  sensation  back  to  the  objects  giving  rise  to  them, 
finally  perceives  the  objects  erect.  In  the  same  way,  but  conversely, 
when  a  phosphene  or  luminous  image  is  created  by  pressing,  say  on 
the  outer  or  lower  side  of  the  eyeball,  the  image  appears  to  lie  above 
and  to  the  inner  side  of  the  eye.  Indeed,  the  association  of  the  sense 
of  sight  with  that  of  touch  in  obtaining  the  ideas  of  the  size,  distance, 
solidity,  position  of  objects,  etc.,  is  so  intimate,  that  were  our  knowl- 
edge of  the  same  derived  through  the  sense  of  sight  alone,  it  would  be 
of  the  most  inexact  and  unreliable  character.  That  such  is  the  fact, 
has  been  shown  by  cases  like  those  of  the  youth  reported  by  Chesel- 
den,1  who  for  some  time  after  the  sense  of  sight  was  given  him,  he 
having  been  born  blind,  saw  everything  flat,  as  in  a  picture,  and  sup- 
posed that  objects  when  seen,  touched  his  eyes,  as  objects  when  felt, 
touched  his  fingers.  The  newly  acquired  sense  of  sight  at  first  rather 
hindered  him  in  finding  his  way  about  the  house,  which  he  could  do 
perfectly  well  by  the  sense  of  touch  alone.  The  fact  that  the  youth 
could  not  tell  of  his  two  pets  which  was  the  cat,  and  which  was  the 
dog,  by  the  sense  of  sight  alone,  though  he  could  at  once  distinguish 
them  by  feeling  them,  led  him  one  day  to  feel  the  cat  and  at  once  look 
at  her,  and  then  setting  her  down,  said,  "  So  puss,  1  shall  know  you, 
another  time."  What  has  just  been  said  renders  it  very  probable,  as 
held  by  Locke,2  that  a  person  born  blind,  on  suddenly  obtaining  his 
sight,  would  be  unable  by  sight  alone  to  distinguish  a  cube  from  a 
sphere — that  is,  to  be  able  to  say  which  was  the  sphere,  which  the 
cube,  for  though  he  knows  how  the  sphere  or  the  cube  affects  his 
touch,  he  has  not  learned  by  experience,  as  yet,  that  if  the  cube, 
etc.,  affects  his  touch  so  and  so,  it  will  affect  his  sight  so  and  so,  and 
enable  him  by  sight  alone  to  distinguish  it  from  the  sphere.  Since 
our  perception  of  external  objects  is  elaborated  out  of  the  sensations 
that  the  retinal  images  give  rise  to,  it  might  be  supposed  that  the 
perception  would  invariably  correspond  to  the  sensation,  just  as  the 
latter  would  correspond  to  the  retinal  image  causing  it.     As  a  matter 

Fig.  493.  Fig.  494. 


EH 


Illustration  of  irradiation.     (McKf.ndrick.)  Illusions  of  size. 

of  fact,  however,  such  is  not  invariably  the  case,  discrepancies  arising 
between  the  retinal  image  and  the  perception,  some  of  cerebral,  others 
of  retinal  origin,  the  effect  of  which  is  so  to  modify  the  perception 
that  the  usually  reliable  judgment  as  to  the  size,  distance,  etc.,  of 
objects  is  perverted.  Thus,  for  example,  the  white  square  (Fig.  493) 
on  the  black  ground  appears  larger,  and  the  black  square  on  the  white 
ground  smaller,  than  it  really  is,  the  over-lapping  of  the  white  light  in 

i  Phil.  Trans.,  17i*,  p.  477.  2  Op.  cit.,  Book  II.  chap.  ix.  p.  256. 


PROTECTIVE    APPENDAGES,  ETC.,  OF    THE    EYE.        819 


either  case,  or  the  irradiation,  being  due,  as  it  were,  to  retinal  or 
cerebral  fibres  other  than  those  directly  stimulated  by  the  light  being- 
thrown  into  sympathetic  vibration.  If  a  white  strip  be  placed  between 
two  black  ones,  the  inner  edges  of  the  former — that  is,  the  edges 
nearest  the  black  will  appear  by  contrast  whiter  than  the  median 
portions.  In  the  same  manner,  the  centre  of  a  white  cross  placed 
upon  a  black  background,  will  often  appear  shaded,  as  compared  with 
the  remaining  parts.  The  judgment  may  also  be  at  fault  with  reference 
to  size,  as  in  Fig.  494,  when  though  the  distance  A  B  is  equal  to  the 
distance  B  C,  the  former  appears  to  be  the  greater;  or  with  reference 
to  direction,   as  in  the   case   of  Zoellner's  (Fig.  495)   lines,  which,  if 

Fig.  495. 


s  '  c  \  < 


Zoellner's  figure,  showing  au  illusion  of  direction.     (MoKendrick.) 

looked  at  obliquely,  will  give  the  impression  that  the  vertical  lines, 
though  parallel,  converge  or  diverge,  and  the  oblique  lines,  though 
continuous  across  them,  are  not  exactly  opposed  to  each  other.  That 
the  above  effect  is  due  to  an  error  of  judgment,  is  shown  by  the  fact 
that  by  an  effort  it  may  be  controlled,  the  lines  being  then  seen  as 
they  really  are.  If  two  equal  squares  be  marked,  one  with  vertical, 
and  the  other  with  horizontal,  alternate  dark  and  light  bands,  the 
former  will  appear  broader,  and  the  latter  higher  than  it  really  is. 
Short  persons  should  therefore  wear  dresses  horizontally  striped  if  they 
wish  to  increase  their  apparent  height,  and  stout  persons  avoid  wearing 
longitudinally  striped  ones.  Many  other  such  examples  might  be 
given,  but  the  above  will  suffice  to  illustrate  the  errors  of  judgment  that 
the  sense  of  sight  alone  may  lead  one  into. 

Protective  Appendages,   etc.,  of  the  Eye. 

The  eyeball,  with  its  muscles,  etc.,  is  protected  by  the  bony  orbit, 
the  outer  wall  of  which  is  stronger  than  the  inner  one,  the  eye  being 


820        PROTECTIVE    APPENDAGES,  ETC.,  OF    THE    EYE. 

more  exposed  to  injury  from  the  outer  than  the  inner  side;  the 
inner  wall  of  the  orbit  projecting,  however,  considerably  beyond  the 
outer  wall,  the  extent  of  vision  is  far  greater  in  the  outward  than  in 
the  inner  direction.  The  upper  semi-circumference  of  the  orbit  and 
the  superciliary  ridge  is  provided  with  short,  stiff  hairs,  the  eye- 
brows, which  serve  to  protect  the  eyelids  from  the  perspiration  of 
the  forehead,  and  to  shade  the  eye  from  excessive  light.  The  eyelids 
consist  of  folds  of  very  thin  integument  lined  by  mucous  membrane, 
the  conjunctiva,  the  subcutaneous  connective  tissue  being  thin,  loose, 
and  free  from  fat,  and  containing  small  papillae,  and  sudoriferous 
glands.  The  eyelashes,  the  short,  stiff  curved  hairs  projecting  from 
the  borders  of  the  lids  in  two  or  more  rows,  serve  to  protect  the  eye 
from  dust,  and,  to  a  certain  extent,  also,  to  shade  it.  The  palpebral 
cartilages,  extending  from  the  edges  of  the  lids,  which  they  support,  to 
the  margin  of  the  orbit,  are  small,  elongated,  semilunar  plates,  attached 
internally  by  the  tendo-palpebrarum  to  the  lachrymal  groove,  externally 
by  the  external  tarsal  ligament  to  the  malar  bone,  and  supported  by 
the  palpebral  ligament.  On  the  posterior  surface  of  the  tarsal  car- 
tilages, lying  just  beneath  the  conjunctiva,  are  found  the  Meibomian 
glands,  which,  in  structure,  are  modified  sebaceous  glands,  whose  secre- 
tion, an  oily  fluid,  in  smearing  the  edges  of  the  eyelids,  prevents  the  over- 
flow of  the  tears.  The  eyelids  serve  to  protect  the  eyeball, their  move- 
ments constituting,  respectively,  the  opening  and  closing  of  the  eye,  the 
act  of  winking  favoring  the  passage  of  tears  over  the  globe  and  through 
the  lachrymal  canals  into  the  nasal  sac;  and  hence,  when'the  orbicu- 
laris palpebrarum  is  paralyzed,  by  the  contraction  of  which  muscle  the 
eye  is  closed,  the  teai's  do  not,  as  readily  as  usual,  pass  into  the  nose. 
The  eye  is  principally  opened  by  the  raising  of  the  upper  eyelid  through 
the  contraction  of  the  levator  palpebrarum,  though  it  is  also  opened 
through  the  elevation  of  the  upper  and  depression  of  the  lower  eyelids, 
respectively,  through  the  action  of  the  plain  muscular  fibres  existing  in 
both  eyelids,  and  which  are  innervated  by  the  sympathetic,  the  orbicu- 
laris palpebrarum  being  supplied,  as  has  already  been  mentioned,  by 
the  facial  and  the  levator  palpebne  by  the  third  nerve. 

The  eyes  are  usually  kept  open,  almost  involuntarily,  though  we  can 
close  or  open  them  at  will ;  the  action  of  the  orbicularis  muscle  is,  how- 
ever, to  such  an  extent  of  a  reflex  character,  that  if  the  globe  of  the  eye 
be  touched  or  irritated,  or  if  the  impression  of  light  produces  pain,  it  is 
then  impossible  to  keep  the  eye  open.  It  has  already  been  mentioned 
that  the  inner  surface  of  the  upper  and  lower  eyelids  is  lined  by  a 
mucous  membrane,  the  conjunctiva.  The  conjunctiva,  continuous  with 
the  membrane  lining  the  puncta  lachrymalis,  and  the  lachrymal  ducts, 
is  reflected  forward  from  the  inner  periphery  of  the  lids  over  the  eye- 
ball, that  lining  the  lids  being  called  the  palpebral,  that  covering  the 
eyeball  the  ocular  conjunctiva;  the  latter  differing,  further,  in  its  scle- 
rotic and  corneal  portions.  At  the  point  where  the  membrane  is  reflected 
upon  the  globe  it  presents  a  superior  and  inferior  fold,  the  former  con- 
taining numerous  glandular  follicles  and  minute  lachrymal  glands.  At 
the  inner  canthus  there  is  a  vertical  fold,  the  so-called  plica  semilunaris, 
which,  morphologically,  corresponds  to  the  inner  and  third  eyelid,  or 


PROTECTIVE    APPENDAGES,    ETC.,    OF    THE    EYE.        821 

the  nictitating  membrane  present  in  many  of  the  lower  animals,  as  in 
sharks,  birds,  and  some  mammals.  The  canicula  lachrymalis,  the  red- 
dish spongy  elevation  situated  at  the  inner  portion  of  the  plica  just 
mentioned,  consists  of  a  collection  of  follicular  glands  with  a  few  deli- 
cate hairs  on  its  surface.  The  eye  is  kept  continually  moist  by  a  thin, 
watery  fluid  secreted  by  the  lachrymal  gland,  which,  after  being  spread 
over  the  globe  by  the  movement  of  the  lids  and  of  the  eyeball,  passes 
into  the  lachrymal  apparatus,  any  overflow  upon  the  cheek,  constituting 
the  tears,  being  prevented  ordinarily  by  the  secreting  of  the  Meibomian 
glands.  The  lachrymal  gland,  about  the  size  of  an  almond,  ovoid  in 
form,  and  of  a  racemose  type  of  structure,  is  situated  at  the  upper  and 
outer  portion  of  the  orbit.  It  presents  six  to  eight  ducts,  five  or  six  of 
which  open  above,  and  two  or  three  below  the  outer  canthus  of  the  eye. 
The  tears  consist  largely  of  water,  which  amounts  to  over  90  per  cent., 
the  remaining  elements  being  made  up  of  small  quantities  of  epithelium, 
albumen,  sodium  chloride,  alkaline  and  earthy  phosphates,  mucus,  and 
fat.  The  actual  amount  of  the  lachrymal  secretion  has  not  been  deter- 
mined. Every  one  is  familiar  with  the  fact  that  the  secretion  of  tears 
is  very  much  increased  by  emotion  ;  hypersecretion  may  be  also  readily 
induced  through  reflex  action  by  irritation  of  the  conjunctiva,  nasal 
mucous  membrane,  muscular  effort,  laughing,  coughing,  and  sneezing, 
the  efferent  nerves  involved  being  the  lachrymal  and  orbital  branches  of 
the  fifth  nerve,  branches  of  the  cervical  sympathetic ;  the  afferent 
nerves  varying  according  to  the  exciting  cause.  The  lachrymal  appa- 
ratus, through  which  the  tears  usually  flow  into  the  nose,  begins  by 
two  little  points  or  orifices,  the  puncta  lachrymalis,  which  leads  into  the 
upper  and  lower  lachrymal  canals,  the  latter  surrounding  the  canicula 
lachrymalis.  Just  beyond  the  canicula  the  canals  unite  and  pass  then 
into  the  lachrymal  sac  or  the  upper  dilated  portion  of  the  nasal  duct. 
The  duct  being  about  half  an  inch  in  length,  fibrous  in  structure,  and 
lined  with  ciliated  epithelium,  empties  into  the  inferior  meatus  of  the 
nose.  Reflux  of  the  tears  from  the  nose  to  the  eye  is  prevented  by  the 
folds  of  mucous  membrane  present  in  the  lachrymal  canals,  and  at  the 
opening  of  the  duct  into  the  nose,  acting  as  valves,  the  latter  one  acting, 
in  this  respect,  much  more  effectually  than  the  former. 


CHAPTER   LI. 

PHYSIOLOGICAL  ACOUSTICS. 

Just  as  we  have  seen  that  in  order  to  understand  how  vision  is 
accomplished,  some  knowledge  of  optics  is  absolutely  essential,  so  for 
the  comprehension  of  the  manner  in  which  the  voice  is  produced  and 
sound  is  heard,  a  knowledge  of  acoustics  is  equally  indispensable. 
Similarly  as  in  the  case  of  vision,  attention  was  continually  being  called 
to  the  distinction  between  the  sensation  of  sight  and  the  waves  of  light 
giving  rise  to  it,  so  in  case  of  sound,  the  sensation  of  hearing  must  be 
distinguished  from  the  waves  of  sound  giving  rise  to  it,  for  what  consti- 

o  Oct 

tutes  in  us  subjectively  hearing,  is  out  of  us  objectively  vibration.  Our 
knowledge  of  sound  must  be  then  like  that  of  light,  etc.,  of  all  knowl- 
edge only  relative,  depending  upon  the  vibrations,  and  the  extent  of  the 
susceptibility  of  the  auditory  apparatus  being  impressed  by  the  same. 
Let  us  consider  first  then,  how  sound  is  produced  in  general,  and  more 
especially  by  the  larynx,  and  then  turn  to  the  consideration  of  how  it 
is  appreciated  by  the  brain  through  the  ear  and  auditory  nerve.  The 
sensation  of  sound,  or  more  properly  of  musical  sound  as  contrasted 
with  mere  noise,  is  due,  as  we  shall  see  presently,  to  the  periodic  rhythmic 
vibratory  wave-like  oscillation  of  the  sounding  or  sonorous  body,  being 
transmitted  by  an  elastic  medium,  usually  the  air,  to  the  ear,  noise  being 
due  to  the  oscillations  being  transmitted  in  an  unperiodic,  irregular 
manner.  The  drawing  of  the  bow  across  the  strings  of  a  violin  gives 
rise  in  us  to  what  we  call  music,  the  shaking  of  a  box  containing  nails, 
chisels,  files,  etc.,  to  noise,  the  auditory  nerve  being  affected  in  the  one 
case  by  oscillations  following  each  other  in  a  regular,  orderly  sequence, 
and  in  the  other  by  irregular,  disorderly  oscillations  following  each  other 
in  no  sequence  at  all.  The  effect  of  noise  upon  the  ear  has  often  been 
compared  to  that  of  flickering  light  upon  the  eye,  the  painful  experi- 
ence in  both  cases  being  due  to  the  sudden,  abrupt,  and  irregular  stimu- 
lation of  the  auditory  and  optic  nerves  respectively.  Nevertheless,  the 
difference  between  noise  and  sound  is  not  an  absolute  one,  being  rather 
one  of  degree  than  of  kind,  as  shown  by  the  noise  due  to  the  rattling 
of  a  carriage  over  stones,  becoming  a  musical  sound  as  soon  as  the  oscil- 
lations become  rhythmical  and  regular  in  character.  Let  us  endeavor 
to  explain  now  by  a  few  simple  illustrations,  what  is  meant  by  periodical 
rhythmical  vibrations,  to  which  the  sensation  of  sound  has  just  been 
said  to  be  due.  Let  us  suppose,  for  example,  that  a  number  of  persons 
are  standing  in  a  row,  one  behind  the  other,  each  individual's  hands 
resting  against  the  back  of  the  one  in  front  of  him,  and  that  the  indi- 
vidual at  the  one  end  of  the  row  be  suddenly  pushed  from  behind,  for- 
ward against  the  individual  standing  in  front  of  him,  the  latter  in  turn 
will  be  pushed  against  the  individual  standing  in  front  of  him,  and  so 


PROPAGATION    OF    SOUND    IN    AIR. 


823 


through  the  whole  row  until  the  last  individual  will  be  pushed  forward. 
Further,  let  us  suppose  that  the  push  be  not  very  violent,  and  that  the 
individual  at  the  one  end  of  the  row  first  pushed  forward  regains  his 
erect  position,  and  then  the  second  regains  his,  and  so  on  through  the 
Whole  row  until  the  last  man  at  the  other  end  of  the  row  regains  his 
position,  it  is  evident  that  though  each  individual  person  may  have 
swayed  to  and  fro,  oscillated  pendulum-like  through  a  very  small  frac- 
tional part  of  the  distance  through  which  the  push  has  passed,  the  push 
itself  or  the  wave  may  have  been  transmitted  through  a  long  row  of 
individuals,  a  hundred  or  more.  Conceive  the  first  individual  body,  the 
last  individual  of  the  row,  to  be  the  tympanic  membrane  of  the  ear,  the 
intermediate  individuals  of  the  row,  laminae  of  air  or  of  any  other  elastic 
medium,  and  we  can  readily  picture  to  ourselves  what  is  taking  place  in 
the  air,  as  the  wave  giving  rise  to  the  sensation  of  sound  passes  from 
the  sounding  body  to  the  ear.  The  conditions  being  strictly  analogous 
in  both  cases,  each  lamina  of  air  being  pushed  forward  against  its 
neighbor,  through  the  elasticity  of  the  air,  after  giving  up  its  motion  to 
the  next  lamina  will  recoil  again,  and  just  as  in  the  case  of  the  indi- 
viduals in  the  row,  the  more  rapid  the  to  and  fro  motion  of  the  laminse 
of  the  air,  the  greater  the  velocity  of  the  push  transmitted  through  the 
row  and  of  the  sound  wave  through  the  air.  On  account  of  the  im- 
portance of  thoroughly  understanding  the  manner  in  which  the  sound 
is  propagated  in  air,  let  us  consider  a  little  more  particularly  the  case 
in  which  it  is  propagated,  through  a  tube  of  indefinite  length.  Let 
A  B  (Fig.  496)  be  a  tube  filled  with  air,  the  temperature   and  pressure 

Fig.  496. 


H 

G 

F 

E          D 

C 

B 

i 
i 

P 

!  A 

To  illustrate  propagation  of  sound  in  air. 


being  constant,  and  let  us  suppose  that  P  be  a  piston,  oscillating  rapidly 
from  C  to  D,  then  as  the  piston  passes  from  C  to  D,  it  condenses  the 
air  in  the  tube,  the  condensation,  however,  not  extending  at  once 
throughout  the  whole  tube,  but  on  account  of  the  great  compressibility 
of  the  air  only  to  the  extent  D  E.  As  the  piston,  however,  then  passes 
from  D  back  to  C,  the  air  in  contact  with  its  posterior  face  expands  and 
becomes  rarefied,  and  by  the  time  that  the  piston  reaches  C,  the  air  has 
become  rarefied  to  an  extent  (E  D)  exactly  equal,  but  opposite  in  direction 
to  that  of  the  previous  condensation  (D  E).  Supposing  the  tube  A  B 
to  be  divided  into  equal  parts  (D  E,  E  F,  F  C,  G  H),  etc.,  it  is  also 
evident  that  by  the  time  the  condensation  beginning,  at  say  E,  reaches 
F  due  to  the  forward  movement  of  the  piston  from  C  D,  condensing 
D  E,  that  the  rarefaction  beginning  at  E  due  to  the  backward  motion 
of  the  piston  from  D  to  C  will  reach  D,  and  that  the  forward  condensa- 
tion E  F  and  backward  rarefaction  E  D  are  equal  and  opposite  in 
direction.      The   condensed  and  rarefied  laminae  of  air  (E  F,  E  D)  so 


824  PHYSIOLOGICAL    ACOUSTICS. 

produced  during  the  forward  and  backward  movements  of  the  piston, 
constitute  a  wave,  a  vibration,  an  undulation,  just  as  the  to  and  fro 
motion  of  a  pendulum  constitutes  a  vibration,  the  length  of  the 
sonorous  wave  or  vibration  being  the  distance  traversed  by  the  sound 
during  the  complete  vibration,  or  to  and  fro  movement  of  the  vibrating 
body  causing  it.  In  France,  however,  a  vibration  is  considered  as 
being  either  the  to  or  fro  movement,  not  both,  that  is  to  say,  each  Eng- 
lish vibration  is  equal  to  two  French  ones.  By  a  vibration  we  shall 
always  mean  the  double  vibration  equal  to  two  single  French  ones. 
That  is  to  say,  as  the  piston  passes  from  C  to  D,  the  sound  travels 
from  D  to  E,  and  as  the  piston  passes  back  from  D  to  C,  the  sound  passes 
on  from  E  to  F.  It  need  hardly  be  added,  that  the  length  of  the 
undulations  will  be  less  in  proportion  to  the  rapidity  with  which  they 
follow  each  other,  and  that  though  the  to  and  fro  movements  of  the  in- 
dividual particles  of  the  air  giving  rise  to  the  condensations  and  rare- 
factions may  be  very  slight,  and  the  undulations  long  or  short,  few  or 
many  in  a  given  time,  the  sound  wave  itself  may  be  transmitted  to  a 
great  distance. 

Such  being  the  manner  in  which  a  sound-wave  is  propagated  in  a 
cylindrical  tube,  there  will  be  no  difficulty  in  comprehending  how  sound- 
waves are  propagated  in  an  uninclosed  medium,  if  we  only  conceive 
each  molecule  of  the  vibrating  body  as  acting  as  the  piston  in  the  tube, 
a  series  of  waves  alternately  condensed  and  rarefied  being  then  generated 
around  each  centre  of  vibration,  the  sound  radiating  in  all  directions, 
like  the  waves  of  water  spreading  out  upon  the  surface  from  some  point 
of  disturbance — the  intensity  of  the  same  gradually,  therefore,  in  both 
instances  diminishing.  That  sounding  bodies  are  actually  vibrating  can 
be  readily  demonstrated.  In  the  case  of  strings  it  is  a  mere  matter  of 
observation,  the  vibrations  being  so  apparent  as  to  be  visible  to  the 
naked  eye.  It  will  be  remembered,  also,  that  we  made  use  of  the  traces 
due  to  the  vibration  of  a  reed  or  tuning-fork  to  determine  small  intervals 
of  time,  and,  indeed,  by  such  graphic  methods  we  are  accustomed  to  test 
the  accuracy  of  our  standard  tuning-forks.  Apart,  also,  from  the  thrill 
experienced  when  a  sounding  bell  is  touched,  its  vibrations  are  made 
visible  indirectly  at  least  by  the  brisk  to-and-fro  movement  of  pith  balls 
placed  in  contact  with  it.  The  vibrations  of  a  sounding  glass  plate  can 
also  be  rendered  visible,  as  first  shown  by  the  celebrated  Chladni1  by 
sprinkling  sand  upon  its  surface,  the  sand  only  remaining  at  rest  upon 
the  part  of  the  plate  not  in  vibration,  and  disposing  itself  in  character- 
istic lines  according  to  the  shape  of  the  plate  and  the  character  of  the 
sound.  It  has  already  been  mentioned  that  the  vibrations  of  sonorous 
bodies  can  only  give  rise  to  the  sensation  of  sound  in  us  by  the  inter- 
vention of  an  elastic  medium  interposed  between  the  ear  and  the 
vibrating  body,  and  vibrating  with  the  latter.  While  this  medium  is 
usually  the  air,  the  waves  of  sound  are  also  transmitted  through  gases, 
vaporous  liquids,  and  solids.  A  diver  at  the  bottom  of  the  water  can 
hear  the  sound  of  voices  on  the  bank ;  the  scratching  of  a  pen  at  one 
end  of  a  piece  of  wood  is  heard  at  the  other  end  ;  while  the  earth  con- 

1  Die  Akustik,  S.  xvi, 


INTENSITY    OF    SOUND.  825 

ducts  sound  so  well  that  if  at  night  the  ear  be  placed  upon  the  ground, 
the  steps  of  horses,  or  other  sounds  or  noise  can  be  heard  at  a  great 
distance  off.  That  the  waves  of  sound  are  not  propagated  in  vacuo,  as 
first  shown  by  Hawksbee,1  can  be  very  easily  demonstrated  by  means  of 
the  apparatus  constructed  by  Queen  &  Co.,  for  the  author,  which 
consists  of  an  air-pump  and  receiver  standing  upon  wadding,  and 
a  bell,  the  hammer  of  which  is  made  to  strike  by  clock-work  set 
going  by  the  raising  of  a  detent  passing  through  the  top  of  the  receiver. 
The  bell,  etc.,  having  been  placed  within  the  receiver,  the  air  from 
the  latter  exhausted  by  the  pump,  and  the  hammer  made  to  strike,  no 
appreciable  sound  will  be  heard  until  the  air  is  allowed  to  pass  into 
the  receiver.  By  allowing  hydrogen  gas,  which  is  fourteen  times  lighter 
than  air,  to  pass  into  the  receiver,  and  by  which  the  air  is  rendered  very 
much  more  attenuated,  such  a  perfect  vacuum  is  obtained  that  not  the 
slightest  sound  is  heard,  even  though  the  ear  be  placed  against  the  bell 
itself.  The  experiment  just  described  is  not  only  a  very  striking  one, 
as  proving  that  sound  is  not  transmitted  in  vacuo,  or  a  very  attenuated 
atmosphere,  but  it  illustrates  the  difference  between  the  cause  of  sound 
and  the  sensation  of  sound,  since,  though  the  hammer  may  be  seen 
striking  the  bell  and  causing  it  to  vibrate,  no  sound  is  heard  as  long  as 
the  vacuum  is  maintained,  there  being  no  intermediate  medium  to 
transmit  the  vibrations  of  the  bell  to  the  ear.  Sounds,  however  pro- 
duced, whether  by  strings,  reeds,  tuning-forks,  bells,  plates,  etc.,  are 
distinguished  by  their  intensity,  pitch,  and  quality,  and  as  these  differ- 
ences in  the  character  of  sounds  must  be  thoroughly  appreciated  in  order 
to  understand  how  the  voice  is  produced,  and  sounds  are  heard,  let  us 
endeavor,  therefore,  to  explain  them  now  a  little  in  detail. 

Intensity  of  Sound. 

By  the  intensity  of  sound  is  meant  the  loudness  of  sound.  We  hear 
one  sound  louder  than  others  because  the  particles  of  air  set  in  motion 
by  the  sounding  body  strike  the  tympanic  membrane  of  the  ear  harder 
in  the  one  case  than  another.  Just  as  the  force  with  which  a  ball  strikes 
a  target  can  be  shown  on  mechanical  principles  to  be  proportional  to  its 
weight  and  the  square  of  the  velocity  with  which  it  is  moving,  so  the 
force  with  which  the  air  particles  strike  the  tympanic  membrane  can  be 
shown  to  be  proportional  to  the  square  of  the  maximum  velocity  with 
which  it  is  moving.  The  intensity  of  a  sound  depends,  however,  on  the 
density  of  the  air  in  which  the  sound  is  generated,  and  not  on  that  of 
the  air  in  which  it  is  heard.  Thus,  while  a  cannon  fired  in  a  valley 
may  be  heard  at  the  top  of  a  high  mountain  above,  the  same  cannon 
fired  at  the  top  of  the  mountain  will  not  be  heard  in  the  valley  below, 
the  sound  generated  in  the  dense  air  of  the  valley  being  loudeV  than  that 
generated  in  the  rare  air  on  the  top  of  the  mountain.  The  intensity  of 
the  sound  is  also  proportional  to  the  square  of  the  amplitude  of  the 
vibration,  the  amplitude  being  the  width  of  swing,  the  distance  through 
which  the  air  particle  moves  to  and  fro  when  the  sound-wave  passes  it. 

That  such  is  the  case  can  be  readily  shown  by  means  of  vibrating 

i  Phil.  Trans.,  vol.  xxiv   p.  Knit. 


826  PHYSIOLOGICAL    ACOUSTICS. 

cords;  for  if  the  latter  are  long,  the  oscillations  being  visible  to  the  eye, 
it  will  be  seen  that  the  sound  becomes  feebler  in  proportion  as  the  ampli- 
tude of  the  oscillation  decreases.  The  intensity  of  sound  is  modified  by 
the  distance  of  the  sonorous  body  from  the  ear,  varying  inversely  as  the 
square  of  the  distance ;  that  is  to  say,  for  example,  the  intensity  of  the 
sound  of  a  bell,  situated  at  a  distance  of  20  yards  from  the  ear,  would 
be  only  one-fourth  of  the  intensity  of  the  same  bell  if  situated  at  10 
yards  from  the  ear,  or  half  the  distance ;  or,  what  is  the  same  thing, 
the  intensity  of  four  bells,  situated  at  a  distance  of  20  yards,  is  the 
same  as  that  of  one  bell  situated  at  a  distance  of  10  yards  from  the  ear, 
supposing,  of  course,  that  the  bells  are  all  of  the  same  size,  and  other 
conditions  equal.  That  the  intensity  of  the  sound  must  diminish  in  the 
above  ratio — that  is,  as  the  square  of  the  distance — will  become  evident 
when  it  is  borne  in  mind  that,  as  the  spherical  waves  of  sound  radiate 
outward  from  the  centre  of  disturbance  toward  the  periphery,  the  mass 
of  air  set  in  motion  must  be  continually  augmented  as  the  squares  of  the 
distance  from  the  centre,  the  areas  of  circles  being  to  each  other  as  the 
squares  of  their  radii.  The  matter  affected  increasing  then  as  the 
square  of  the  distance,  the  intensity  of  the  sound  must  diminish  in  the 
same  ratio.  If,  however,  the  wave  of  sound  be  propagated  in  a  tube, 
lateral  diffusion  being  prevented,  as  in  Fig.  496,  then  the  sound  can  be 
transmitted  through  great  distances  with  very  little  diminution  in 
intensity  ;  thus  Biot  found  that  a  person  whispering  at  one  end  of  one  of 
the  empty  water-pipes  of  Paris,  a  tube  3120  feet  in  length,  could  be  heard 
at  the  other  end,  and  that  the  firing  of  a  pistol  at  one  end  of  the  tube  put 
out  a  lighted  candle  at  the  other.  The  intensity  of  sound  is  modified  by 
the  condition  of  the  atmosphere,  sound  being  better  propagated  in  calm 
than  in  windy  weather ;  in  the  latter  case,  however,  sound  is  better 
heard  when  transmitted  in  the  direction  of  the  wind  than  in  the  opposite 
direction.  Finally,  the  intensity  of  sound  is  very  much  increased  by 
the  proximity  of  a  sonorous  body.  Hence,  the  association  of  sounding- 
boxes  with  strings,  as  in  the  case  of  the  violin,  guitar,  etc.,  the  increase 
in  the  loudness  of  the  sound  being  then  due  to  the  fact  that  the  box  and 
air  within  it  vibrate  in  unison  with  the  strings  as  we  shall  endeavor 
presently  to  explain.  The  distance  at  which  sounds  are  heard, 
depending  upon  their  intensity,  may  be  very  great ;  thus,  it  is  said  that 
the  report  of  the  volcano  at  St.  Vincent  was  heard  at  Demerara,  300 
miles  off,  and  the  firing  at  Waterloo  at  Dover.1 

Pitch  of  Sound. 

Sounds  are  distinguished,  as  already  mentioned,  not  only  by  their 
intensity  or  loudness,  but  by  their  pitch  or  height.  The  pitch  of  a 
sound  can  be  shown  to  depend  upon  the  number  of  vibrations  made  by 
a  sounding  body  in  a  given  time — a  second,  for  example — sounds  of  low 
pitch  being  due  to  the  aerial  vibrations  impinging  upon  the  tympanic 
membrane  following  each  other  slowly,  those  of  high  pitch  to  the  aerial 
vibrations  following  each  other  rapidly.     Thus,  for  example,  the'  pitch 

1  Ganot :  Physics,  trans,  by  Atkinson,  p   175.     London,  1870. 


FITCH    OF    SOUND. 


827 


of  the  sound  of  a  string  four  feet  in  length,  sufficiently  tensed,  and  of  a 
given  density  and  thickness,  vibrating  128  times  in  a  second  (Do2,Ut2, 

G2,  C  of  piano),  is  low  as  compared  with  that  of  one  two  feet    -Q. 

in  length,  vibrating  256  times  in  a  second  (Do3,Ut3,CV),  gjjy r— 

or  an  octave  above.1     In  the  same  way,  the  pitch  of  the    ^T     h£ 
sound  of  an  organ-pipe  four  feet  in  length  due  to  128  vibrations  per 
second  (Do'-'Ut2)  is  low  as  compared  with  that  of  the  sound  of  one  two 


Fig.  497. 


Fig.  499. 


Fig.  498. 


Vibration  of  string.     (Ttndall.) 

feet  in  length,  due  to  256  vibrations  per  second  (Do3Ut3)  or 
the  octave  above.  It  may  be  mentioned  in  this  connection 
that,  while  in  the  case  of  the  string  it  is  the  vibrations  of  the 
latter  (Fig.  497)  that  give  rise  to  the  aerial  vibrations  affect- 
ing the  auditory  apparatus,  in  the  case  of  the  organ-pipe  it  is  to  the  vibra- 
tions of  the  enclosed  column  of  air  that  the  aerial  vibrations  are  due,  as  the 

current  of  air  forced  by  the  bellows 
through  the  mouth  P  B  of  Fig.  498 
of  the  pipe  in  striking  against  the 
upper  1  levelled  lip  B,  produces  a 
shock,  the  air  issues  from  the  em- 
bouchure or  space  between  the  lips 
in  an  intermittent  manner,  the  pul- 
sations so  produced  in  being  trans- 
mitted to  the  air  enclosed  Avithin  the 
pipe  in  turn  set  it  into  vibration, 
which  causes  the  sound.  It  will  be 
observed,  also,  as  might  have  been 
anticipated  on  mechanical  principles, 
that  the  number  of  vibrations,  both 
in  the  case  of  the  string  and  pipe, 
are  inversely  as  the  lengths,  the 
number  of  vibrations  in  both  cases 
being  doubled  by  halving  the  lengths, 
since,  in  the  latter  case,  the  amount 
of  work  to  be  done  being  one-half,  it 
can  be  done  in  half  the  time,  or 
double  the  work  can  be  done  in  the 
same  time.  The  distinction  between 
intensity  or  loudness  and  pitch  or 
height  must  be  carefully  borne  in 
mind,  being,  as  just  shown,  due  to 
entirely  different  causes  ;  a  sound,  therefore,  may  be  a  loud  one,  and  yet 
be  low  in  pitch  ;   and,  on  the  other  hand,  a  sound  may  not  be  a  loud 


Hi- 


k 


Jidf 


Ik'lmlioltz  do 


1  If  the  5th  A  of  the  piano  he  tuned  to  vibrate  440  vibrations  per  second,  instead  of  426  times  as  as- 
sumed in  text,  then  the  middle  C  or  It*  will  vibrate  2G4  times,  and  the  lowest  C33  times  per  second. 


828 


PHYSIOLOGICAL    ACOUSTICS. 


one,  and  yet  be  high  in  pitch.  In  sounding  the  long  string  and  long- 
organ-pipe,  apart  from  the  intensity  of  the  sound,  and  from  the  pitch 
of  the  note  Do2Ut2,  128  vibrations  per  second,  the  same,  therefore,  in 
both  cases,  another  and  very  marked  difference  is  appreciable,  and  that 
by  not  especially  musical  ears,  viz.,  the  character  or  quality  of  the 
sound.     Before  considering,  however,  the  quality  of  sound,  or  that  in 


Fig.  500. 


Fig.  501. 


Siren  of  Cagniard  de  la  Tour. 


Showing  oblique  opening  in  siren 
of  Cagniard  de  la  Tour. 

which  the  sound  of  a  violin,  for  example, 
differs  from  that  of  a  piano,  and  the  sound 
of  the  latter  from  the  sound  of  the  organ- 
pipe,  or,  in  general,  that  which  distin- 
guishes the  sounds  of  different  kinds  of 
musical  instruments,  let  us  first  endeavor  to 
explain  how,  by  means  of  the  siren,  we  are 

able  to  determine  the  number  of  vibrations  to  which  the  pitch  of  a  sound 
is  due.  The  siren — so  callal  on  account  of  its  emitting  sounds  when 
under  water  in  its  original  form  as  invented  by  Cagniard  de  la  Tour — 
is  apparently  a  much  more  simple  instrument  than  that  we  shall  make 
use  of,  or  the  double  siren  of  Helmholtz  (Fig.  499).  The  principle  upon 
which  both  instruments  are  constructed  is,  however,  the  same,  since  the 
siren  of  Helmholtz  consists  of  two  Dove  sirens,  the  Dove  siren  in  turn 
differing  from  that  of  Cagniard  de  la  Tour  (Fig.  501)  in  being  provided 
with  four  series  of  orifices  instead  of  one.  Such  being  the  case,  let  us 
begin  our  description  of  a  double  siren  with  that  of  a  single  Dove  siren. 
Suppose,  for  example,  that  the  lower  Dove  siren  (Fig.  499)  be  taken  apart, 
it  will  be  seen  that  the  tube  B  leads  into  the  brass  cylinder  C,  the  top  of 
which  is  closed  by  a  brass  plate  a  b,  perforated  with  four  series  of  holes 
disposed  concentrically,  the  outermost  series  containing  16,  the  next  12, 
the  next  10,  the  next  8  orifices,  the  latter  being  opened  or  closed,  respect- 
ively, by  pressing  in  or  pulling  out  the  keys  numbered  correspondingly. 
It  will  also  be  seen  that  the  brass  disk,  receiving  in  its  centre  the  steel 
axis  x,  is  also  perforated  with  16,  12,  10,  and  8  orifices,  disposed 
concentrically  at  the  same  distance  from  the  centre,  and  with  the  same 
intervals  between  them  as  those  on  the  top  of  the  cylinder  C,  the  only 
difference  between  the  two  sets  being  that  those  passing  through  the  top 
of  the  cylinder  C,  while  oblique  in  direction  (Fig.  500),  are  oppositely 
inclined  to  those  passing  also  obliquely  through  the  brass  disk  d  e. 


PITCH    OF    SOUND.  829 

The  two  sets  of  orifices  being  so  disposed  to  each  other  if  air  be  forced 
by  a  pair  of  bellows  through  the  tube  B  into  the  cylinder  C,  the  air  will 
issue  from  the  latter  not  vertically  but  in  side  currents,  which  in  im- 
pinging against  the  sides  of  the  orifices  of  the  disk  will  drive  the  disk 
around  the  axis  x,  held  upright  by  means  of  a  steel  cap  brought  down 
on  its  upper  end.  As  the  disk  turns  around,  its  orifices,  coming 
alternately  over  the  orifice  of  the  cylinder  C  and  over  the  intervening 
spaces,  the  continuous  current  of  air  passing  through  the  cylinder  C  is 
carved  into  discontinuous  puffs,  which  at  first  follow  each  other  so 
slowly  that  they  may  be  counted.  As  the  motion  of  the  disk,  however, 
increases  the  puffs  of  air  succeed  each  other  so  rapidly  that  the  air  links 
them  together  as  continuous  musical  notes,  whose  pitch  can  then  be  at 
once  shown  to  depend  upon  the  number  of  puffs  of  air  or  vibrations, 
by  simply  increasing  or  diminishing  the  rapidity  of  the  rotation  of  the 
disk,  the  pitch  of  the  note  rising  or  falling  accordingly.  In  order, 
however,  to  determine  the  number  of  puffs  of  air  issuing  from  the  orifices 
in  a  given  time,  a  second,  for  example,  they  must  be  recorded.  This  is 
accomplished  by  providing  the  axis  x  at  its  upper  part  with  a  screw  s 
(Fig.  502)  which  works  into  a  pair  of  toothed  wheels,  the  latter  rotat- 
ing as  the  disk  and  its  axis  turn,  the  number  of  rotations  being 
indicated  by  the  hands  on  the  dial  plates  (omitted  in  Fig.  499,  but 
represented  in  Fig.  501),  the  hand  of  one  dial  plate  making  an  entire 
revolution  while  that  of  the  other  passes  over  but  one  division  of  the 
graduated  circumference.  The  process  of  recording  can  be  started  or 
stopped  by  simply  pushing  a  button,  which  throws  the  wheel-work 
just  mentioned  into  or  out  of  action.  In  order,  now,  to  show  how  by 
means  of  the  siren  we  determine  that  the  note  Do3,  Ut3  emitted  by  the 
string  or  organ-pipe  two  feet  long,  is  due  to  the  vibrations  following 
each  o+her  at  the  rate  of  256  vibrations  a  second,  Ave  force  the  air  from 
the  bellows  through  the  cylinder  C  until  the  disk  rotates  so  rapidly  that 
the  sound  produced  by  the  siren  is  in  unison  with  that  emitted  by  the 
string  or  organ-pipe  sounded  at  the  same  time.  The  sound  of  the  siren 
and  the  string  or  pipe  being  then  in  perfect  unison,  we  push  the  button 
and  so  set  o-oino;  the  recording  mechanism  and  let  the  siren,  sing  for  iust 
one  minute,  then  instantly  stopping  the  recording,  we  observe  by  the 
hands  of  the  dial  plate  the  number  of  rotations  the  disk  d  e  has  made  in 
that  time.  It  will  be  found  that  the  number  is  just  960,  dividing  this 
by  60  the  quotient,  or  16,  will  be  the  number  of  times  that  the  disk  has 
rotated  in  one  second,  but  since  16  orifices  were  open  in  one  rotation  of 
the  disk  16  puft's  of  air  issued  in  succession  from  the  siren,  and  conse- 
quently during  16  rotations  256  puffs  of  air.  As  the  note  Do3,  U3  pro- 
duced by  the  siren  Avas  due  to  the  number  of  puffs  or  vibrations  of  air, 
and  as  the  note  of  the  siren  Avas  in  unison  with  that  due  to  the  sounding 
of  the  string  or  pipe,  the  latter,  or  Do3,  must  be  also  due  to  the  same 
number  of  vibrations,  viz.,  256  vibrations  per  second.  It  will  be  remem- 
bered that  Avhile  the  outermost  series  of  orifices,  those  which  in  the 
preceding  experiment  were  supposed  to  be  open,  are  16  in  number,  the 
innermost  series  of  orifices  are  only  8  in  number.  If  the  latter  now  be 
opened  as  Avell  as  the  former  by  pushing  in  the  key  numbered  8,  then 
tAvo  sounds  will  be  simultaneously  emitted  by  the  siren,  one  of  Avhich, 


830  PHYSIOLOGICAL    ACOUSTICS. 

Do3,  is  due,  as  before,  to  the  rate  of  vibration  being  256  per  second,  the 
other  Do2  an  octave  below,  the  rate  being  just  half,  or  128  vibrations  per 
second,  the  air  issuing  from  8  orifices  during  one  rotation  of  the  disk, 
instead  of  from  16,  as  in  the  former  case.  The  innermost  and  outer- 
most series  of  orifices  being  open,  then  the  rate  of  vibration  of  the  two 
sounds  is  as  1  to  2.  From  what  has  just  been  said,  it  is  evident,  without 
further  explanation,  that  if  the  innermost  series  of  8  orifices  and  the 
next  series  to  it  of  10  orifices  be  open,  then  the  rate  of  vibration  will  be 
as  4  to  5 — that  is  to  say,  of  the  two  notes  produced  by  the  siren 
simultaneously,  if  one  be  Do2,  due  to  128  vibrations  per  second,  the 
other  note  will  be  Mi2  E2,  due  to  160  vibrations  per  second,  and  if  the 
innermost  series  of  8  orifices  and  the  third  series  from  within  outward, 
that  of  12  orifices,  be  both  open,  then  the  rate  of  vibration  of  the  two 
sounds  will  be  as  2  to  3 — that  is,  if  Do2  be  one  of  the  two  notes  heard 
simultaneously  the  other  note  will  be  Sol2  G2,  due  to  198  vibrations  per 
second.  It  follows,  therefore,  that  if  the  three  innermost  series  of  orifices, 
8,  10,  and  12,  be  open  we  will  obtain  the  major  chord  Do2  E2  G2  Do2 
Mi2  Sol2,  and  if  in  addition  at  the  same  time  the  outermost  series  of  16 
orifices  be  open  C2  E2  G2  C3,  which,  as  produced  by  the  siren,  is  quite 
musical.  The  construction  and  manner  of  using  a  single  Dove  siren 
being  now  understood,  there  will  be  no  difficulty  in  comprehending  that  of 
Helmholtz,  it  consisting,  as  already  mentioned,  of  two  clove  sirens.  It 
must  be  mentioned,  however,  that  the  outermost  series  of  orifices  in  the 
lower  of  the  two  sirens  are  18  in  number  instead  of  16,  as  in  the  single 
Dove  siren  we  have  just  described,  and  that  the  orifices  in  the  four  series  of 
the  upper  siren  are  respectively  9, 12, 15,  and  16  in  number.  If,  therefore, 
we  wish  to  obtain  by  the  double  siren  the  major  chord  C2  E2  G2  and  C3 
at  the  same  time,  the  series  of  orifices  8,  10,  and  12  must  be  opened  in 
the  lower  siren,  and  the  series  of  16  orifices  of  the  upper  siren,  the  air 
being  allowed,  of  course,  to  pass  from  the  bellows  through  both  sirens, 
the  number  of  rotations  of  the  disks  being  recorded  in  the  same 
manner  as  already  described  by  wheel-work  attached  to  the  axis  common 
to  the  two  sirens,  and  omitted  for  simplicity  in  Fig.  499.  It  will  be 
observed  that  the  double  siren  is  provided  with  resonance  boxes  the 
half  of  each  of  which  has  been  removed  in  the  figure,  which  greatly 
intensifies  the  fundamental  sound.  The  upper  siren  is  also  connected 
with  a  toothed  wheel  and  pinion  turned  by  a  handle,  by  which  we  are 
enabled  to  rotate  the  cylinder  of  the  upper  siren  as  well  as  the  disk, 
the  handle,  etc.,  being  so  disposed  that  if  it  be  turned  to  the  right  the 
orifices  in  the  cylinder  and  in  the  disk  will  then  pass  over  each  other 
more  quickly  than  if  the  cylinder  was  at  rest,  and  if  in  the  reverse 
direction  more  slowly,  the  pitch  rising  in  the  one  case,  the  puffs  succeed- 
ing each  other  then  more  rapidly,  and  falling  in  the  other,  following 
more  slowly.  The  use  of  the  dial  and  index  underneath  the  handle 
will  be  illustrated  hereafter.  It  is  needless  to  say  that  by  doubling  all 
parts  of  the  siren,  etc.,  as  done  by  Helmholtz,1  that  many  varied  com- 
binations can  be  introduced,  and  that  the  general  usefulness  of  the 
instrument  has  thereby  been  greatly  increased. 

i  On  the  Sensation  of  Tone,  transl.  by  A.  J.  Ellis,  r.  245.     London,  1875. 


UALITY    OF    SOUND. 


831 


Quality  of  Sound. 

Every  fundamental  tone,  whether  produced  by  a  string,  column  of 
air,  reed,  etc. — that  is,  a  sound  due  to  the  string,  for  example,  vibrating 
through  the  whole  of  its  length  (Fig.  497),  may  be  accompanied  by 
partial  tones  or  overtones1  due  to  the  string  vibrating  through  the  half, 
third,  fourth,  etc.,  of  its  length  (Fig.  502,  (2),  (4),  (6)),  and  since  the 
overtones,  accompanying  and  reinforcing  the  fundamental  tone,  due 
to  the  sounding  of  the  string  of  one  instrument,  are  not  the  same  as 
those  of  another,  or  if  in  part  the  same,  are  then  more  or  less  accentu- 
ated, there  arises  in  consequence  a  difference  in  the  character  of  the 
sound  as  produced  by  the  two  instruments,  very  appreciable,  even  by 
unmusical  ears,  which  is  called  their  quality.  Thus,  for  example,  the 
sound  of  the  string  of  a  violin  may  be  as  loud  as  that  of  the  piano,  or 
of  that  of  the  vibrating  column  of  air  of  the  organ-pipe,  or  of  that  of 
the  vibrating  reed  of  the  oboe,  the  pitch  of  the  particular  note  emitted 
by  the  four  instruments  may  be  the  same,  the  number  of  vibrations  per 


Fig.  -30-2. 


Fig.  503. 


^b 


■P? 


(1)       (2)     (3)     (4)      (5)      (6) 

Formation  of  nodes  and  ventral  segments.     (Ttndail.) 


(1)    (2)     (3)     (4) 

Vibrations  of  tube.    (Tvxdall.) 


second  to  which  the  note  is  due  being  equal  in  all  four  instances,  and 
yet  no  one  fails  to  appreciate  the  difference  in  the  character  or  the 
quality  of  the  sound,  the  overtones  reinforcing  the  fundamental  note 


1  By  the  1st,  2d,  and  3d  overtones,  etc  ,  will   be  meant  in  this  chapter,  tones  due  to  vibrations  whose 
rates  are  twice,  three,  or  four  times  as  rapid  as  that  of  the  fundamental  tone. 


832  PHYSIOLOGICAL    ACOUSTICS. 

being  different  in  each  instance.  Inasmuch,  however,  as  the  thorough 
understanding  of  the  conditions  upon  which  the  quality  of  sound 
depends  is  not  only  important,  but  absolutely  essential,  in  compre- 
hending the  manner  in  which  the  vowels  are  produced  by  the  larynx, 
for  example,  let  us  endeavor  to  explain  a  little  more  in  detail  how  these 
partial  vibrations,  to  which  the  overtones  are  due,  come  to  be  super- 
imposed upon  the  fundamental  one,  and  how  their  presence  can  be 
detected.  Let  c  a  (Fig.  503)  represent  a  long  India-rubber  tube  fixed  at 
the  one  end,  and  free  at  the  other.  By  taking  hold  of  the  free  end, 
stretching  the  tube  a  little,  and  properly  timing  the  impulses,  the  tube 
can  be  made  to  swing  to  and  fro,  to  vibrate  as  a  whole,  as  represented 
in  Fig.  497.  Stop  the  motion,  and  now,  by  a  jerk,  raise  a  hump  upon 
the  tube,  the  hump  will  be  observed  to  run  along  the  tube  a  b,  b  c  (Fig. 
503,  (1),  (2)),  and  having  reached  the  fixed  end  of  the  tube  c,  will  then 
run  back  again,  but  in  the  reverse  direction.  But  just  as  the  latter  c  b 
(3)  starts  at  c,  let  the  tube  be  jerked  again,  so  as  to  start  the  hump  a  b 
(3)  at  a,  then  by  the  time  that  the  foremost  part  of  the  hump  beginning 
at  c  arrives  at  b,  that  beginning  at  a  will  also  have  reached  a,  the  effect 
of  which  will  be  that  the  point  b  will  remain  at  rest.  For  the  hump  a 
b  (3)  in  moving  on  to  c  must  tend  the  point  b  to  the  right,  and  the 
hump  c  b  moving  on  to  a  must  tend  to  move  the  point  b  to  the  left,  the 
consequence  of  which  is,  that  the  point  b,  in  being  acted  upon  by  equal 
and  opposite  forces,  will  not  move  at  all.  Such  being  the  case,  the  two 
halves,  ab,  be  of  the  tube  b  c,  will  vibrate  as  if  they  were  independent 
of  each  other  (Fig.  503  (4)).  The  point  b  at  rest  is  known  as  the  node, 
the  vibrating  parts  a  b,  b  c  as  the  ventral  segments,  twice  the  length  of 
a  ventral  segment  constitutes  a  wave,  the  latter  being  made  up  by  both 
the  hump  and  the  depression  following  the  same.  By  experimenting  a 
little,  it  will  be  soon  found  that  the  tube  a  c  (Fig.  502)  can  be  so  swung 
as  to  form  two  nodes  with  three  ventral  segments  (4),  or  three  nodes  with 
four  ventral  segments  (Fig.  502,  (6)),  and  so  on,  the  tube  vibrating  in 
thirds,  fourths,  etc.,  of  its  lengths,  and  a  little  reflection  will  make  it  clear 
that  the  cause  of  the  formation  of  the  nodes,  or  points  of  rest,  and  of  the 
string  in  consequence  vibrating  in  its  aliquot  parts,  is  precisely  the  same 
as  that  just  given  in  the  case  of  the  formation  of  one  node  and  two  ven- 
tral segments.  Let  us  now  modify  the  preceding  experiment  slightly 
by  encircling  the  tube  a  c  at  its  centre  (Fig.  502,  (1))  with  the  thumb 
and  forefinger  of  one  hand,  and  taking  hold  of  the  middle  of  the  lower 
half  of  the  tube  a  b  with  the  other  hand,  pull  it  aside.  It  will  be  ob- 
served that  one  node  is  formed,  and  two  ventral  or  vibrating  segments 
(2),  the  upper  half  of  the  tube  vibrating  as  well  as  the  lower.  Experi- 
menting in  this  way,  but  encircling,  however,  the  tube  at  one-third  (3) 
or  one-fourth  (5)  of  its  length,  and  pulling  the  lower  third  (3)  or  lower 
fourth  (5)  of  the  tube  away  by  seizing  them,  respectively,  at  their  cen- 
tres, the  tubes  will  be  oscillated,  so  that  tAvo  nodes  with  three  ventral 
segments  (4),  or  three  nodes  with  four  ventral  segments  (6),  will  be 
formed,  as  the  case  may  be,  the  vibrations  of  the  string  through  the 
space  encircled  by  the  thumb  and  finger,  a  distance  of  one  inch,  acting 
upon  the  upper  part  of  the  tube  exactly  as  the  hand  acted  when  it 
caused  the  tube  to  swing  as  a  whole.     In  precisely  the  same  manner, 


QUALITY    OF    SOUND. 


833 


by  placing  a  feather  (Fig.  504)  upon  the  centre  of  the  stretched  violin- 
string,  just  as  we  encircled  the  tube  with  the  thumb  and  finger,  and 


Fig   504. 


Formation  of  one  node  and  two  ventral  segments.     (Tynpall.) 

drawing   a  bow  across  the  centre  of  the  half  of  the  strinor  instead  of 
pulling  it  aside  with  one  hand,  the  string  will  be  made  to  vibrate  in 

Fig.  505. 


Formation  of  two  nodes  and  three  ventral  segments.     (Tyndall.) 

halves,  as  shown  by  the  little  paper  rider  being  thrown  off.  Similarly, 
by  touching  the  string  with  a  feather  at  a  third  (Fig.  505),  or  a  fourth 
(Fig.  506)  of  its  length,  and  drawing  the  bow  across  the  centre  of  the 

Fig.  50fi. 


Formation  of  three  nodes  and  two  ventral  segments.     (Tynd  ill.) 

right  hand  third  or  fourth,  the  string  will  vibrate  in.  thirds  or  fourths, 
two  nodes  with  three  ventral  segments,  or  three  nodes  with  four  ven- 
tral segments  being  formed,  as  shown  by  the  two  or  three  red  paper  riders 
placed  upon  the  vibrating  parts  being  tossed  off,  and  the  one  or  two  blue 
ones  remaining  on  the  string  being  situated  at  the  nodes,  or  points  of 
rest  A  beautiful  way  of  demonstrating  the  presence  of  nodes  and  ven- 
tral segments,  occasionally  made  use  of  by  the  author  in  addressing  a 
large  audience,    is  to  place  a  string  connected  at    one   end  with  the 

53 


834 


PHYSIOLOGICAL    ACOUSTICS. 


prong  of  a  tuning-fork,  and  tit  the  other  with  a  peg,  by  which  it  can  be 
loosened  or  tightened  in  front  of  the  calcium  light  lantern,  an  appear- 
ance  such   as  that  represented  in    Fig.    507    being   presented ,  when 


Fig.  507. 


3<CL^J-  JiBBiMC 


&=s|j!j^^ 


Nodes  and  segments  of  a  vibratory  string  as  shown  by  lantern. 

the  fork  is  sounded,  according  to  the  extent  to  which  the  string  is 
tensed.  While  the  string  may  vibrate  as  a  whole,  or  in  halves,  thirds, 
fourths,  fifths,  etc.,  separately,  as  we  have  just  shown,  as  a  matter  of  fact, 
the  string  usually  in  vibrating  breaks  up,  so  to  speak,  into  its  aliquot 
parts,  the  superimposing  of  which  vibrations  upon  the  fundamental 
vibration  of  the  string — that  is,  of  the  vibration  due  to  the  swinging  of 
the  string,  as  a  whole,  gives  rise  to  a  resultant  vibration,  which  has 
been  shown  to  be  equal  to  the  algebraic  sum  of  all  the  vibrations,1  as 
represented  in  Fig.  508,  in  which  the  lower  curve  represents  the  com- 
pound vibration  resulting  from  the  blending  of  the  three  upper  curves, 


Fig.  508. 


F.g.  .-)09. 


Resonator  of  Helmholtz. 


representing,  respectively,  simple  vibra- 
tions, whose  ratio  is  as  1,  2,  3.  Of  course, 
it  must  not  be  supposed  that  sounds, 
simple  or  compound,  are  ^\ur  to  curves 
like  those  depicted  in  Fig.  508  ;  the  latter 
are  simply  graphic  representations  of 
waves  of  sound,  which,  as  we  have  seen, 
consist  of  condensations  and  ra refactions 
Compound  waves.  (McGregor  kobinson.)    °*  the  air-      1  hat  the  tone   due   to  the 

sounding  of  a  string  of  the  piano,  such  as 
Do2,  Ut2,  vibrating  128  times  per  second,  is  not  a  simple,  but  a  com- 
pound tone,  will  be  appreciated  by  a  trained  musician,  wdiose  sensitive 


1  Helmhultz,  op.  cit.,  p.  l:\ 


QUALITY     OF     SOUND. 

ear  enables  him  to  distinguish  some  at  least  of  the  overtones  accom- 
panying the  fundamental  tone.  Any  one.  however,  can  convince  himself 
that  such  a  tone  as  that  of  Ut2  sounded  by  the  piano,  as  elicited  by  singing 
the  corresponding  note,  is  a  compound  one.  resulting  from  the  blending 
of  the  fundamental  tone  with  overtones,  the  latter  being  due  to  the  par- 
tial vibrations  of  the  string,  as  the  former  is  to  the  oscillating  of  the  string 
as  a  whole,  by  adapting  to  his  ear  in  succession  each  one  of  the  series 
of  nine  resonators,  of  which  one  is  represented  in  Fig.  509,  devised  by 
Helmholtz.1  and  so  constructed  as  to  intensify  the  sound  of  each  par- 
ticular overtone  accompanying  the  fundamental  tone,  that  overtone 
being  then  heard  alone.  Thus,  for  example,  the  first  and  largest  reso- 
nator, marked  Ut2,  being  applied  to  the  ear.  let  the  note  Ut2  be  sounded 
due  to  128  vibrations  a  second:  the  first  overtone  or  harmonic,  or  the 
octave  above  Ut3.  256  vibrations  per  seconds,  will  be  heard,  due  to  the 
string  vibratingin  halves,  the  sound  distinctly  beard  with  the  resonator 
being  the  same  as  if  the  note  Ut   had  been  sounded. 

Applying  the  second  or  next  largest  resonator,  marked  Sol3,  to  the 
ear  and  sounding  the  Ut2  string  on  the  piano  the  second  overtone, 
the  twelfth  above  the  fundamental,  or  Sol3  G\  will  be  heard,  due  to  the 
string  vibrating  in  thirds,  the  sound  heard  being  the  same  as  if  the 
note  G"  had  been  sounded.  Adapting  in  succession  the  remaining 
resonators  gradually  diminishing  in  size,  and  marked  respectively  Ut* 
Mi4,  Sol4  Si'M  Ut5.  Re5  Mi5,  the  3d,  4th,  5th,  6th.  7th,  8th,  and  9th  over- 
tones due  to  the  string  or  harmonics  will  be  heard  vibrating  in  fourths. 
fifths,  sixths,  etc..  the  sounds  beard  with  the  resonators  being  the  saun- 
as if  the  notes  Ut4  Mi4  Sol4  Sib4  Ut5  Re5  Mi5  had  been  separately 
sounded,  or  as  expressed  in  musical  notation  as  follows.  Ut2  being 
the  fundamental  tone : 


j& 


jr^r-r  r  r  ■  ^i=m 


Ut-'        Ut;  Sol  Ut*        Mr>         Sol*        Si>*        Utf  KeS        Mi? 

It  is  obvious,  therefore,  why  when  the  notes  Ut3  Sob  Ut*are  sounded  on 
a  musical  instrument  at  the  same  time  with  Ut2,  the  resulting  sound 
should  be  harmonious,  since  these  three  sounds  reinforce  respectively 
the  first,  second,  and  third  overtones  due  to  the  string  vibrating  in 
halves,  thirds,  and  fourths  respectively.  In  the  same  way,  Mi4  Sol4 
SiL'4  Ut"1  Re°  Mi°  reinforcing  the  overtones  due  to  the  string  Ut2  vibrating 
in  fifths,  sixth-,  sevenths,  eighths,  and  ninths,  when  sounded  with  Ut2, 
will  also  give  a  harmonious  sound. 

Having  described  the  manner  in  which  partial  vibrations  are  formed, 
and  how  in  being  superimposed  upon  the  fundamental  vibration  a 
resultant  vibration  arises,  and  how  the  overtones  due  to  the  partial 
vibrations  in  being  blended  with  the  fundamental  tone  due  to  the 
fundamental  vibration  give  rise  to  a  compound  tone,  it  becomes  evident 
without  further  explanation,  that  by  means  of  the  Helmholtz  resonators 

1  Op.  cit  .  p.  68 


836 


PHYSIOLOGICAL    ACOUSTICS. 


Fig.  510. 


we  can  analyze  any  sound,  and  demonstrate  whether  it  be  a  simple  or 
compound  one,  and,  if  the  latter,  what  overtones  are  present,  and  in 
this  way  show  on  what  the  quality,  timbre,  or  klangfarbe  of  the  sound 
depends.  Thus,  for  example,  the  quality  of  the  sound  of  the  piano,  as 
compared  with  that  of  the  violin,  depends  upon  the  fact  that  in  the  case 
of  the  latter,  when  bowed,  though  the  first  six  overtones  or  harmonies 
are  present,  as  in  the  case  of  the  piano,  they  are  so  faintly  sounded  as 
to  be  overpowered  by  the  seventh,  eighth,  ninth,  and  tenth  overtones. 
The  overtones  in  the  case  of  an  open  pipe  are  not  the  same  as  in  the 
case  of  a  closed  one;  those  of  the  clarionet  differ  from  those  of  the 
oboe,  and  so  through  the  whole  range  of  orchestral  instruments. 
Inasmuch,  however,  as  in  addressing  a  large  audience,  from  the  nature 
of  the  case,  it  is  impossible  for  each  one  individually  to  make  use  of 
the  resonators  and  satisfy  himself  of  the  existence  of  overtones  upon 
which  the  quality  of  a  sound  depends ;  the  author  is  accustomed  to 
demonstrate  the  same  by  means  of  Koenig's  manometries  apparatus.1 
The  latter  (Fig.  510)  consists  of  a  frame  supporting  fourteen  resonators 

each  of  which  leads  by  a  narrow  India- 
rubber  tube  into  a  small  chamber,  com- 
pletely divided  into  two,  by  an  India- 
rubber  partition.  The  posterior  part  of 
the  chamber  is  in  communication  with  the 
resonator,  the  anterior  part  provided  with 
a  gas  jet  with  a  reservoir  containing  gas, 
led  thither  by  an  ordinary  gas  pipe.  Each 
resonator  is  connected  in  this  way  with  its 
own  gas  chamber  and  burner,  the  burners 
being  all  placed  in  a  row,  one  above  the 
other.  Opposite  the  gas  burners  is  a  long 
mirror  with  four  reflecting  sides,  at  right 
angles  to  one  another,  which  can  be 
revolved  on  an  almost  perpendicular  axis 
by  a  toothed  wheel  arrangement.  Turn- 
ing on  the  gas,  and  lighting  it  as  it  issnes 
from  the  jets  in  the  chambers  connected  with  the  resonators,  and 
revolving  the  mirror,  the  light  reflected  from  the  surfaces  of  the  latter 
appears  as  continuous  bands.  If,  however,  the  air  in  any  one  of  the 
resonators  be  thrown  into  vibration,  then  the  India-rubber  partition  of 
the  chamber  separating,  on  the  one  hand,  the  air  continuous  with  that 
of  the  resonator,  and,  on  the  other,  the  gas,  will  vibrate,  and  the  gas  and 
flame  thrown  into  agitation,  the  particular  band  of  light,  the  corre- 
sponding band  of  light,  becoming  segmented.  Let  now  a  tuning  fork 
Ut3,  vibrating  256  times  a  second,  be  sounded  in  front  of  the 
apparatus  ;  at  once  the  flame  in  connection  with  the  resonator  marked 
Ut3,  will  become  segmented,  but  the  remaining  flames  will  still  appear 
as  continuous  bands  of  light,  since  if  the  tuning  fork  be  properly 
bowed  the  sound  produced  will  be  a  pure,  simple  tone,  unaccompanied 
with  overtones.     Let  now,   however,  the  Ut3  Do3  of  the   piano,  or   an 


Manometric  apparatus.     (Kcenig.) 


1  Rudolph  Koenig,  Quelques  Experiences  d'Acoustique,  p.  73.     Paris,  1882. 


QUALITY    OF    SOUND. 


837 


open  organ  pipe  two  feet  long,  giving,  therefore,  the  same  fundamental 
note,  be  sounded,  and  immediately  some  of  the  remaining  bands  of  light 
will  become  segmented,  as  well  as  the  one  connected  with  the  resonator 
marked  U3,  since  the  air  of  the  resonators  with  which  they  are  in  con- 
nection has  been  thrown  into  vibration  by  the  particular  overtones  pre- 
sent, as,  for  example,  in  Fig.  511,  a,  b,  respectively,  representing  the 

Fig.  511. 


Fundamental  note. 


Octave  of  preceding. 

flames  due  to  the  fundamental  and  octave  above  it.  In  this  way  an 
optical  demonstration  can  be  given  of  the  fact  that  the  quality  of  the 
note  of  any  musical  instrument  depends  upon  what  particular  overtones 
or  harmonics  accompany  the  fundamental,  and,  as  we  shall  see  pres- 
ently, of  the  manner  in  which  the  vowel  sounds  are  produced  by  the 
human  voice.  As  it  is  important  that  the  manner  in  which  resonators 
reinforce  or  intensify  sounds  should  be  understood,  a  brief  account  of 
the  cause  of  resonance  in  general  may  be  as  appropriately  considered 
here  as  elsewhere. 

It  is  well  known  that  the  velocity  with  which  sound  travels  in  air 
at  the  freezing  temperature  is  1090  feet  in  a  second,  the  velocity 
increasing  about  two  feet  for  every  additional   degree  of  heat,  Centi- 


a  B 


Fig.  512. 
-2G  inches 


->c 


V 


Vibrating  of  tuning  fork.     (Tyxdall.) 


grade  (1.8°  F.).  Let  us  suppose  that  the  temperature  of  the  surround- 
ing atmosphere  be  8.5°  Cent.  (47.3°  F.),  and  that  a  tuning  fork 
vibrating  256  times  per  second  be  sounded ;  it  is  obvious  that  if,  at  the 


838 


PHYSIOLOGICAL    ACOUSTICS. 


Fig.  513. 


end  of  the  second,  the  sound  lias  reached  a  distance  of  1109  feet, 
then  each  vibration  must  have  been  52  inches  long,  since  52  by  256 
is  1109  feet,  and  as  a  vibration  or  wave  of  sound  consists,  as  we  have 
seen,  of  a  condensation  and  rarefaction,  the  condensation  and  rarefaction 
must  have  been  both  just  2b'  inches  in  length — that  is  to  say,  as  the 
prong  of  the  tuning  fork  (Fig  512)  moves  from  A  to  B,  a  distance  of 
perhaps  the  one-twentieth  of  an  inch,  it  generates  the  one-half  of  the 
sonorous  wave,  the  condensation,  the  foremost  point  of  which  readies  the 
point  C,  a  distance  of  twenty-six  inches,  at  the  some  instant  that  the 
prong  of  the  fork  reaches  B,  and  that  as  the  forward  motion  is  being 

delivered  up  to  the  air  succeeding  C — that 
is,  as  the  prong  of  the  fork  moves  back  from 
B  to  A,  the  other  half  of  the  sonorous  wave, 
is  generated,  the  rarefaction.  Such  being 
the  case,  let  the  tuning  fork  now  be  sounded 
over  a  jar  (Fig.  513),  of  which  the  column 
of  air  within,  from  top  to  bottom,  meas- 
ures just  thirteen  inches,  or  one-fourth  the 
length  of  the  vibration  or  wave  due  to  the 
sounding  of  the  fork.  It  follows  from  what 
has  just  been  said,  that  during  the  time  the 
prong  of  the  fork  moves  from  a  to  b,  the 
condensation,  the  air  which  it  produces  runs 
from  the  top  of  the  jar  to  the  bottom,  thir- 
teen inches,  and  from  the  bottom  to  the  top, 
thirteen  inches,  or  twenty-six  inches  in  all, 
the  reflected  Avave  reaching  the  prong  of 
the  fork  just  as  the  latter  reaches  b ;  and 
similarly,  that  during  the  time  the  prong  returns  to  a  from  b,  the  rare- 
faction to  which  it  gives  rise,  runs  down  from  the  top  of  the  jar  to  the 
bottom,  and  up  again,  also  a  distance  in  all,  of  twenty-six  inches. 

The  vibrations  of  the  fork  being,  therefore,  perfectly  synchronous  with 
the  vibrations  of  the  aerial  column  within  the  jar,  the  motion  will 
accumulate  in  the  latter,  and  spreading  out  into  the  room,  the  sound  will 
be  greatly  augmented  as  everyone  will  appreciate,  when  the  tuning  fork 
is  sounded  first  at  some  distance  from,  and  then  over  the  mouth  of  the 
resonating  jar.  From  what  has  just  been  said,  it  necessarily  follows 
that  if  we  sound  other  tuning  forks,  vibrating  at  different  rates,  the 
length  of  the  column  of  air  must  be  varied  accordingly  if  we  wish  to 
make  use  of  the  latter  as  a  resonator.  It  is  for  this  reason  that  the 
resonators  we  made  use  of  in  demonstrating  the  presence  of  overtones 
were  of  different  size,  and  that  the  resonators  of  Koenig's  manometric 
apparatus  are  so  constructed,  that  by  drawing  them  out  to  varying 
distances,  the  sound  that  each  resonator  will  reinforce,  will  then  be  ap- 
parent. It  was  on  account  of  its  resonating  qualities,  that  in  sounding 
the  bell  in  a  preceding  experiment,  the  latter  was  placed  near  the 
mouth  of  ajar,  by  means  of  which  the  intensity  of  the  sound  was  very 
much  increased.  The  ancients  were  well  acquainted  with  the  efficacy 
of  such  aids  in  intensifying  sound,  resonant  brass  vessels  being  placed, 
according  to  Vitruvius,  in  their  theatres  to  strengthen  the  voices  of  the 


Tuning  fork  vibrating 
with  jar. 


in   uimsou 


QUALITY    OF    SOUND.  839 

actors.  It  is  on  account  of  the  resonating  properties  of  sounding  boards, 
that  the  latter  are  associated  with  musical  instruments,  and  that  the 
stethoscope  also  has  proved  in  the  hands  of  the  clinician  such  an  aid  in 
the  diagnosis  of  disease  by  auscultation.  It  may  not  prove  uninterest- 
ing in  this  connection  to  mention  that  the  velocity  of  sound  in  air  was  ap- 
proximately deduced  by  Newton '  from  the  elasticity  and  density,  the 
velocity  being  shown  to  be  directly  proportional  to  the  square  root  of 
the  elasticity,  and  inversely  as  the  square  root  of  the  density.  The  im- 
mortal author  of  the  Principia,  however,  failed  to  take  into  considera- 
tion, as  shown  afterward  by  Laplace,2  that  the  condensation  in  giving 
rise  to  heat,  and  increasing  the  elasticity,  thereby  increases  the  velocity, 
and  that  the  discrepancy  existing  between  the  velocity  of  sound  experi- 
mentally observed,  and  as  theoretically  calculated  by  Newton,  disap- 
pears if  the  calculated  velocity  be  multiplied  by  1/1.414  or  the  square 
root  of  the  ratio  of  the  specific  heat  of  air  at  constant  volume,  to  that 
at  constant  pressure.  Thus,  if  Jri  be  equal  to  the  true  or  observed 
velocity,  J^be  equal  to  the  velocity  as  calculated  by  Newton,  or  916 
feet  per  second,  OP  the  specific  heat  of  air  at  constant  pressure,  OV 

OP 

the  specific  heat  of  air  at  constant  volume,  and  the  ratio  of = 

1  .  OV 

1.414,  then 

V  =  V  ^(JTv  or  F  =  916  x  VYXu  =  109°  feet' 

As  a  matter  of  fact,  however,  at  the  present  day  the  ratio  1.414  per 

second  is  obtained  by  the  reverse  operation — that  is,  knowing  J77  and  V, 

V'2        CP2  ■  OP 

evidently  then =  2,  from  wThich  we  obtain  the  ratio  — 

V2         O  V '  O  V 

Having  shown  that  sounds  are  produced  by  the  vibrations  of  plates, 
bells,  strings,  pipes,  reeds,  membranes,  etc.,  and  how  the  same  are  dis- 
tinguished by  their  intensity,  pitch,  and  quality,  let  us  turn  now  to  the 
consideration  of  the  larynx,  and  by  means  of  the  principles  just  estab- 
lished, endeavor  to  determine  what  kind  of  an  acoustical  instrument 
the  larynx  is  and  how  the  voice  is  produced  by  it. 

1  Philosophise  Naturalis  Principia  Mathematica,  Liber  Secunrhis  Propositio  xlix.     Londini,  1726. 

2  Mecauiqtie  Celeste,  tome  iv   p.  87.    Hull,  ties  Sciences  Sue,  Philomatiqae,  1821,  pp.  101-183.    Puisson, 
Annates  de  Chimie  et  Physique,  tuuie  xxiii.  ZM. 


CHAPTER   LI  I. 

THE  LARYNX,  AND  THE  PRODUCTION  OF  THE  VOICE 
AND  SPEECH. 


Fig.  514. 


The  larynx,  the  organ  of  the  voice,  situated  at  the  top  of  the  trachea 
and  below  the  root  of  the  tongue  and  the  hyoid  bone,  consists  of  a  frame- 
work of  cartilages,  connected  by  ligaments,  provided  with  muscles, 
bloodvessels,  and  nerves,  and  lined  with  mucous  membrane.  The 
cartilages  of  the  larynx  are  nine  in  number,  three  single  and  symme- 
trical pieces,  the  thyroid,  cricoid,  and  epiglottic,  and  three  pairs,  the 
arytenoid,  cornicula  laryngis,  and  cuneiform ;  the  last  two  pair  are,  how- 
ever, very  small.      The  thyroid  (Fig.  514),  the  largest  of  the  cartilages 

of  the  larynx,  consists  of  two  lateral 
ring-like  plates  or  alse,  continuous 
in  front,  but  diverging  behind. 
The  angular  projection  in  front,  sur- 
rounded by  a  deep  notch  much  more 
marked  in  the  male  than  in  the 
female,  and  in  some  men  more  than 
others,  is  known  as  Adam's  apple, 
while  the  blunt  processes  connected 
through  ligaments  with  the  hyoid 
bone,  into  which  the  posterior  angles 
are  prolonged,  are  called  the  supe- 
rior and  inferior  horns,  of  which  the 
superior  is  the  larger.  The  cricoid 
cartilage,  resembling  in  shape  a  seal 
ring,  is  situated  between  the  thyroid 
and  the  first  ring  of  the  trachea, 
with  the  latter  of  which  it  is  con- 
nected. While  quite  narrow  in  front, 
the  cricoid  cartilage  deepens  consid- 
erably posteriorly,  and  at  the  back 
part  of  its  upper  border,  articulates 
by  means  of  two  convex  oval  promi- 
nences with  the  arytenoid  cartilages, 
and  laterally  through  two  circular 
facets  with  the  inferior  horns  of  the 
thyroid  cartilage.  The  arytenoid  cartilages  are  two  three-sided  recurved 
pyramids,  resting  by  their  bases  upon  the  posterior  and  highest  portion 
of  the  cricoid  cartilage.  The  apex  of  each  arytenoid  cartilage  is 
usually  surmounted  by  a  yellowish  cartilaginous  nodule,  the  corniculum 
laryngis  or  cartilages  of  Santorini.  while  the  folds  of  mucous  membrane, 
extending  from  the  summit  of  the  arytenoid  cartilages  to  the  epiglottis, 


>*. 


Bird's-eye  view  ofTarynx  from  above  :  o  e  h, 
the  thyroid  cartilage,  embracing  the  rings  of  the 
cricoid,  r  u  x  h>,  and  turning  upon  the  axis,  x  z, 
which  passes  through  the  lower  horns.  N  F, 
N  F,  the  arytenoid  cartilages  connected  by  the 
arytenoideus  transversus  ;  T  v,  T  v,  the  vocal 
ligaments ;  N  x,  the  right  crico-arytenoideus 
lateralis  (the  left  being  removed) ;  v  kf,  the 
left  thyro-arytenoideus  (the  right  being  re- 
moved) ;  N  I,  N  7,  the  crico-arytenoidei  postici ;  B, 
b,  the  crico-arytenoid  ligaments.    (Carpenter.) 


THE    LARYXX. 


841 


contain  also  two  small  yellowish  cartilaginous  bodies,  the  cuneiform  car- 
tilages or  cartilages  of  Wrisberg.  The  remaining  cartilages  of  the 
larynx,  the  epiglottis  consisting  really  of  fibro- cartilage,  somewhat 
spoon-shaped  in  form,  while  free  at  its  broad  extremity,  is  attached  at 
its  narrow  end  by  a  band  of  fibro-elastic  tissue  to  the  thyroid  cartilage 
within  the  entering  angle  of  its  two  halves,  and  to  the  tongue,  hyoid 
bone,  and  arytenoid  cartilages  by  the  glosso-epiglottidean,  hyo-epiglotti- 
dean,  and    aryteno-epiglottidean  folds, 

respectively.      The  cavity  of  the  larynx  Fig.  515. 

(Fig.  515)  is  divided  by  the  glottis  or 
rima-glottidis — that  is.  the  long,  narrow 
fissure,  running  from   before  backward  ,  \# 

on  a  level  with   the  lower   part  of  the  %:'' <  ft 

arytenoid  cartilages — into  an  upper  and       18t 
lower   compartment.      The   upper  com-      12 
partinent  commencing  with  the  pharynx      -11  af  *.'; $*§ 

by  the  superior  aperture  of  the  larynx,      lsSf.'V."7 iC'Jm  i-T" '1?J 

contains  the  ventricles   and  the  upper 
or    so-called    false    vocal     cords.       The      J' 
lower    compartment    passes    inferiorly       W 
into  the  trachea  without  any  observable         ""™ 
constriction  between    them.     The   mu- 
cous membrane  lining  the  cavity  of  the  10~  V 
larynx,    continuous    with    that    of   the  J%  _ 
pharynx  and  trachea,   extending  from  V^i 
the  epiglottis  to  the  tongue  and  aryte-              8-l-S 
noid  cartilages  as  the  glosso-arytenoid 
epiglottidean   folds,  descends   from   the 
superior  aperture,   and   is    reflected   at 
each  side  outwardly  and  upwardly  as  a 
pair  of  pouches',   the   ventricles  of  the 
larynx  oval  recesses  communicating  by 
a  transverse  elliptical   orifice  with  the 

•     1 ; n    ,1         i  -11  i  Longitudinal     section    of     the    human 

interior   ot  the  larynx,   and   prolonged     ,  ,  ..  , 

J         •  1  a  larynx,  showing  the  vocal  cords,     I,  v.-n- 

Upwai'd  and  OUtward  as  the  laryngeal  tricle  of  the  larynx;  2,  superior  vocal  cord; 
pouches.       The  Upper    edge    of  the  Veil-       3,  inferior  vocal  cord :    i,  arytenoid  carti- 

tricle,  somewhat  prominent  through  the     iage  ;,5' section  of  the  i^™'1  ™**° • 6> 

_  r  p  6,    inferior   portion   of    the   cavity  of  the 

presence  Ot  Connective  tissue,  IS  known  larynx ;  7,  section  of  the  posterior  portion 
as    the    false  VOCal  Cord,    since    it    is    not       °f  tie  cricoid  cartilage;  8,  section  of  the  an- 

concerned  in  the  production  of  the  voice,     terior  portion  of  the  cricoid  ™rtilas» ;  9> 

■.       ,  ,  *  ..  -li  Bupenor  border  of  the  cricoid  cartilage ;  10, 

the  lower  edge  Corresponding  With  the  sectionofthe  thyroid  cartilage;  11,11,  su- 
Upper  border  Of   the  VOCal   membrane  Or       perior  portion  of  the  cavity  of  the  larynx: 

true  vocal  cord,  as  it  is  often  improperly     v2<  13>  ^ytmoid  eland  ; 14.  ™>  epiglottis; 

hi  j  ,i  .,  .  /»       i  ■   i         15>  17,  adipose  tissue;    IS,    section  of  the 

called,  and  upon  the  vibration  of  which  hyoidbone.19i  19)  2ll,  trachea.  (Sappbt.) 
the  production   of   the  voice    depends. 

From  the  ventricles  the  mucous  membrane  passes  downward,  lining  the 
vocal  membrane,  cricoid  cartilage,  and  finally  becomes  continuous  with 
that  of  the  trachea.  The  mucous  membrane  of  the  larynx  is  soft,  thin, 
and  pale  red,  its  epithelium  being  of  the  ciliated  columnar  form,  except 
upon  the  so-called  vocal  cords,  where  it  is  squamous   like   that  of  the 


842 


THE     LAKY NX 


pharynx  and  mouth.  While  adhering  tightly  to  the  epiglottis,  the 
vocal  membrane,  and  the  interior  of  the  cricoid  cartilage,  the  mucous 
membrane  in  other  parts  of  the  larynx  is  loosely  attached  to  the  sub- 
jacent parts  by  connective  tissue. 

The  vocal  membrane  (Fig.  516),  about  seven  lines  long  in  the  male 
and  five  in  the  female,  bounding  the  anterior  thirds  of  the  aperture  of 
the  glottis,  and  consisting  of  elastic  tissue,  may  be  regarded  as  extend- 
ing from  the  front  and  sides  of  the  upper  border  of  the  cricoid  cartilage, 
upward  to  the  bases  of  the  arytenoid  cartilages,  and  to  the  lower  part  of 
the  entering  angle  of  the  thyroid.  The  lower  portion  of  each  vocal 
membrane  is  the  strongest,  and  may  be  seen  at  the  front  of  the  larynx 
in  the  interval  between  the  thyroid  and  cricoid  cartilages.  The  lateral 
portions  are  thin  and  are  separated  by  the  thyroid  and  arytenoid  muscles 
from  the  ahe  or  wings  of  the  thyroid.  The  upper  margins  of  the  vocal 
membranes — that  is,  the  parts  corresponding  in  position  to  the  lower 
edges  of  the  ventricles,  extending  on  either  side  from  the  anterior  prom- 
inent angle  of  the  base  of  the  arytenoid  cartilages  to  the  entering  angle 
of  the  thyroid,  being  somewhat  thickened,  are  usually  described  as  the 


Fig.  516. 


Fro.  517. 


External  and  sectional  views  of  the  larynx.  A  m  B. 
The  cricoid  cartilage.  E  C  G.  The  thyroid  cartilage. 
G.  Its  upper  horn.  C.  Its  lower  horn,  where  it  is 
articulated  with  the  cricoid.  F.  The  arytenoid  carti- 
lage. E  F.  The  vocal  ligament.  A  K.  Crico-thy- 
roideus muscle.  Fern.  Thyroid-arytenoideus  muscle. 
X  e.  Crico-arytenoideus  lateralis.  «.  Transverse  sec- 
tion of  arytenoideus  transversus.  m  h.  Space  between 
thyroid  and  cricoid.  15  h.  Projection  of  axis  of  articu- 
lation of  arytenoid  with  cricoid.     (Carpenter.) 


Diagram  of  a  model  illustrating  the  action  of 
the  levers  and  muscles  of  the  larynx.  The 
stand  and  vertical  pillar  represent  the  cricoid 
and  arytenoid  cartilages,  while  the  rod  6  c, 
moving  on  a  pivot  at  c,  takes  the  place  of  the 
thyroid  cartilage ;  a  b  is  an  elastic  hand  rep- 
resenting the  vocal  ligament.  Parallel  with 
1h is  runs  a  cord  fastened  at  one  end  to  the  rod 
b  c,  and,  at  the  other,  passing  over  a  pulley  to 
weight  B.  This  represents  the  "thyro-arytenoid 
muscle.  A  cord  attached  to  the  middle  of  6  c, 
and  passing  over  a  second  pulley  to  the  weight 
A,  represents  the  crico-thyroid  muscle.  It  is 
obvious  that  when  the  bar  b  c  is  pulled  down 
to  the  position  c  </,  the  elastic  band  a  b  is  put 
on  the  stretch.     (HuxLEY.) 


"true  vocal  cords,"  as  contrasted  with  the  false  vocal  cords,  or  the  upper 
edges  of  the  ventricle.  As  a  matter  of  fact,  however,  apart  from  the 
vocal  membrane,  of  which  they  are  the  upper  thickened  edges,  no  such 


THE    LARYNX. 


813 


Fig.  518. 


organs  as  vocal  cords  exist,  either  structurally  or  functionally.  That 
the  whole  vocal  membrane  consists  of  elastic  tissue  is  readily  shown  by 
the  yellowish  color  of  the  tissue  being  distinctly  seen  through  the  over- 
lying mucous  membrane,  which  in  this  situation  is  quite  thin.  The 
essentially  membranous  character  of  the  vibrating  portion  of  the  larynx 
is  well  seen  in  the  case  of  the  elephant,  in  which  animal  the  vocal  mem- 
branes are  two  elastic  bands  almost  two  inches  in  length  and  nearly 
three-quarters  of  an  inch  in  breadth.  Inasmuch  as  the  vocal  mem- 
branes extend  from  the  arytenoid  cartilages  to  the  thyroid,  it  is  evident 
that  if  these  cartilages  approach  or  recede  from  each  other  the  vocal 
membranes  will  be  relaxed  or  tensed  accordingly,  and  that  if  the  aryte- 
noid cartilages  be  rotated  backward  or  forward  the  vocal  membranes 
will  recede  or  diverge  from  each  other,  or  will  approach  and  become 
parallel.  Such  changes  in  the  tension 
of  the  vocal  membranes  and  in  the  form 
of  the  glottis,  just  referred  to,  are,  as 
a  matter  of  fact,  brought  about  through 
the  action  of  the  intrinsic  assisted  by 
the  extrinsic  muscles  of  the  larynx  upon 
the  thyroid  and  arytenoid  cartilages. 
Thus  the  crico-thyroid  muscle  (Figs. 
516,  517)  arising  from  the  front  and 
side  of  the  cricoid  cartilage  to  be  in- 
serted in  the  lower  border  of  the  thy- 
roid in  drawing  the  latter  downward 
and  forward,  and  therefore  away  from 
the  arytenoid,  tenses  the  vocal  mem- 
brane. On  the  other  hand  the  thyro- 
arytenoid muscle  (Figs.  514,  517) 
arising  from  the  inner  surface  of  the 
thyroid  cartilage  to  be  inserted  into  the 
outer  surface  and  base  of  the  arytenoid 
cartilage,  in  drawing  the  latter  forward 
relaxes  the  vocal  membrane.  The  effect 
of  the  contraction  of  the  crico-thyroid 
muscles  in  stretching  the  vocal  mem- 
branes is  increased  by  the  simultaneous 
contracting  of  the  arytenoid,  crico- 
thyroid, postici,  and  sterno-thyroid  mus- 
cles, that  of  the  thyro-arytenoid  in  relax- 
ing the  vocal  membranes  by  the  action 
of  the  crico-thyroid  lateralis  and  thyro- 
hyoid muscles.  The  posterior  crico- 
arytenoid muscle  (Fig.  518),  so  called 
on  account  of  its  arising  from  the  posterior  surface  of  the  cricoid  carti- 
lages to  be  inserted  into  the  external  angle  of  the  base  of  the  arytenoid 
cartilage,  in  rotating  the  latter  backward  not  only  widens  the  glottis 
(Fig.  519),  but,  as  just  mentioned,  also  assists  in  tensing  the  vocal 
membrane.  The  lateral  crico-arytenoid  muscles  (Fig.  520)  lying  under 
the  wing  of  the  thyroid  cartilage,  arising  from  the  upper  lateral  border 


Larynx  from  behind  with  its  muscles;  E. 
Epiglottis,  with  the  cushion  W;  C.  (W) 
Cartil.  Wrisbergii;  C.  S.  Cartil.  sautorin- 
ianse ;  C.  c.  Cartil.  cricoidea.  Cornu  sup. 
cornu  inf.  cartilaginis  thyreoidesa  ;  M. 
car.  ir.,  Musculus  arytenoideus  transversus; 
Mm.  ar.  obi.,  Musculi  arytenoids  obliqui : 
M  or.  (iryt  p  int.  Musculus  crico-arytenoideus 
posticus;  Par*,  curt.,  Pars  cartilaginea ; 
Pare  memb  ,  pars  merubrauacea  trachse. 
(Landois.) 


844 


THE    LARYNX. 


of  the  cricoid  to  be  inserted  into  the  external  angle  of  the  base  of  the 
arytenoid  cartilage,  in  contracting  rotate  the  latter  forward  and  press 
together  their  inner  edges,  and  not  only  narrow  the  glottis  but  assist  in 
relaxing  the  vocal  membrane.      The  arytenoid  muscle,   consisting  of 


Fig.  51  y. 


Lozenge  shape  of  the  glottis,  produced  by  the  action  of  the  posterior  crico-arytenoid  muscle.     (Kuss.) 

transverse  and  oblique  fasciculi,  being  attached  to  the  posterior  concave 
surface  of  the  arytenoid  cartilages,  in  contracting  draw  the  latter  together 
and  so  narrow  the  glottis.  In  addition  to  the  muscles  just  described, 
there  are  usually  found  a  few  muscular  fibres  passing  from  the  epiglottis 
to  the  thyroid  and  arytenoid  cartilages,  known  as  the  thyro-  and  aryteno- 

Fio.  520. 


To  illustrate  action  of  crico-arytenoid  lateralis  muscle.     (Kuss  ) 

epiglottidean  muscles,  whose  functions  appear  to  be  to  depress  the  epi- 
glottis and  compress  the  laryngeal  pouches  respectively.  Such  being, 
in  brief,  the  general  structure  of  the  larynx,  it  follows,  from  what  was 


PRODUCTION    OF    THE    VOICE. 


845 


said  in  the  preceding  chapter,  that  if  the  air  expired  from  the  lungs  and 
ascending  in  the  trachea  in  passing  through  the  glottis  throws  the  elastic 
vocal  membranes  into  vibration,  a  sound,  the  voice,  will  be  produced, 
the  character  of  which  will  depend  upon  the  tension  of  the  vocal  mem- 
branes, shape  of  the  glottis,  etc.,  just  as  we  can  produce  a  sound  by 
forcing  air  by  means  of  a  bellows  through  a  glass  tube  over  the  mouth 
of  which  have  been  stretched  two  elastic  membranes.  Lest,  however, 
the  analogy  of  the  bellows  and  pipe  to  the  lungs  and  trachea  might 
suggest  the  idea  of  the  larynx  acting  as  an  organ  pipe,  or  that  the 
misnomer  vocal  cords  might  give  the  impression  that  the  larynx  acts  as 
a  stringed  instrument,  let  us  compare  the  range  of  the  voice,  on  the  one 
hand,  with  that  of  notes  as  produced  by  organ  pipes  and  strings  on  the 
other,  and  it  will  then  become  evident  that  the  larynx  does  not  act  like 
either.  The  range  of  the  human  voice  in  the  two  sexes,  and  of  the  bass 
and  tenor  voice  in  the  male  and  female,  can  be  most  conveniently 
illustrated  by  musical  notation  after  Miiller,1  as  follows : 


CONTRALTO 

64  rib.  80vib.  128  vil>.  I    1024 

do  re  mi  fa  sol  la  si  do  re  mi  fa  sol  la  si  do  re  mi  fa  sol  la  si  do  re  mi  fa  sol  la  si  do     vib. 
11      11111222     2    2     223     33333     3    444     44445 


from  which  it  will  be  seen  that  the  voice  ranges  ordinarily  from  mix 
P^5 1^  80  vibrations  per  second,  the  lowest  note  of  the  male  bass 

r,  -0- 

voice,  to  do5    Ut5  \-A^ — ^z  i  10:24  vibrations  per  second,  the  highest 

e 

note  of  the  female  soprano  or  tenor,  though  it  should  be  mentioned  that 

some  bass  voices   reach  the  fa2  FvE^ H  42.6  vibrations  per  second 

-0- 
of  the  octave  below  the  above  scale  or  even  lower,  and  some  soprano 


voices    the    soL 


=t 


m 


1536    vibrations    per    second   above  and 


even  higher.  The  human  larynx  being  capable,  therefore,  in  the  case 
of  a  man  of  emitting  ordinarily  a  note  due  to  80  vibrations  a  second, 
and  in  a  woman  of  one  due  to  1024  vibrations,  would  have  to  be  over 
five  feet  long  and  six  inches  long,  respectively,  if  it  acted  like  an  organ 

i  Physiology,  trans,  by  Baly,  vol.  ii.  p.  1030.    London,  1842. 


846  PRODUCTION    OF    THE    VOICE. 

pipe,  since  that  would  be  the  length  of  the  pipes  giving  those  notes, 
the  notes  of  an  eight  foot  pipe  and  six  inch  pipe  being  due  to  64  and 
10_'4  vibrations  a  second,  respectively.  Similarly  no  notes  as  deep  as 
those  of  the  buss  voice  can  be  produced  by  strings  as  short  as  the  vocal 
membranes,  however  the  latter  may  be  relaxed. 

Further  apart  from  the  fact  of  the  vocal  membranes  being  too  short 
to  produce  bass  notes  on  the  supposition  that  they  act  like  strings,  the 
E  string  of  the  double  bass  for  example,  vibrating  41  ]  times  per  second, 
the  ratio  of  the  vibrations  of  the  vocal  membranes  to  the  weights  ex- 
tending  them  is  not  the  same.  Thus,  for  example,  while  it  is  well 
known  that  the  vibrations  of  a  string  are  doubled  by  quadrupling  the 
extending  weights,  the  number  of  vibrations  being  proportional  to  the 
square  root  of  the  weight,  the  vibrations  of  the  vocal  membranes,  as 
shown  experimentally  by  Muller,1  are  not  so  doubled  by  quadrupling 
the  extending  weight,  the  vibrations  not  reaching  the  octave  above,  as  in 
the  case  of  a  string,  by  several  semitones.  On  the  other  hand,  it  has  been 
shown  by  Muller  that  the  vibrations  of  the  vocal  membranes  are  gov- 
erned by  the  same  law  as  that  regulating  the  vibrations  of  reeds  or 
tongues,  when  the  latter  are  associated  with  pipes.  The  latter  qualifi- 
cation must  be  borne  in  mind,  since  in  reed  instruments  like  the  accor- 
dion, concertina,  seraphine,  harmonium,  etc.,  in  which  the  reed  or 
tongue  vibrates  in  a  sort  of  frame  that  permits  of  the  air  passing  out  on 
all  sides  of  it  through  a  narrow  channel,  thereby  increasing  the  strength 
of  the  blast,  the  sound  produced  is  due  to  the  vibration  of  the  reed  or 
tongue  alone,  and  is  regulated  entirely  by  the  length  and  elasticity  of 
the  latter.  In  reed  instruments  like  the  clarionet,  bassoon,  and  oboe,  how- 
ever, in  which  the  single  or  double  reeds  are  associated  with  pipes,  the 
air  setting  the  reed  in  vibration  traverses  the  whole  length  of  the  pipe 
before  escaping  into  the  atmosphere,  and  consequently  the  sound  pro- 
duced is  due  to  the  vibrations  of  both  reed  and  pipe  combined,  and  not 
to  either  of  them  singly — the  two  sounds  accommodating  themselves  to 
each  other  in  such  a  way  that  only  one  sound  is  heard,  the  fundamental 
being  neither  always  that  of  the  reed  alone  nor  of  the  pipe  alone.  In 
the  case  of  the  clarionet,  in  which  the  reed  is  a  single  broad  tongue,  and 
in  the  oboe  and  bassoon,  in  which  the  reeds  are  double  and  somewhat 
spoon-  or  spatula-shaped,  the  different  notes  are  produced  by  closing  or 
opening  a  series  of  holes,  the  position  of  which  has  been  determined  by 
experiment.  In  the  reed  pipes  of  the  organ,  however,  in  which  the  reed 
is  inserted  into  the  pipe  through  a  plug,  each  note  has  a  separate  pipe. 
It  was  established  more  especially  by  Weber2  that  reeds  associated  with 
pipes,  as  in  the  case  of  the  voice  and  of  the  instruments  just  mentioned, 
possess  certain  well-marked  properties  by  which  they  can  be  at  once 
distinguished  from  other  musical  instruments,  such  as  organ  pipes,  flutes, 
etc.,  and  with  which,  in  the  case  of  the  voice,  they  may  be  confounded. 
Among  the  most  important  of  such  properties  may  be  mentioned,  1st, 
that  the  pitch  of  a  reed,  though  it  cannot  be  raised,  may  be  lowered  by 
joining  it  to  a  tube,  but  at  the  utmost  by  not  more  than  an  octave ; 
2d,  that  the  fundamental   note  of  the  reed  so  lowered  may  be  raised 

1  Op.  cit.,  p.  'J8">.  -  Poggeudorf :  Auuulen,  xvi.  xvii. 


PEODUCTION    OF    THE    VOICE, 


847 


again  to  its  original  pitch  by  a  lengthening  of  the  tube,  the  latter  then 
yielding  the  same  fundamental  note  as  the  reed  of  the  instrument  with- 
out the  tube,  whilst  by  a  further  lengthening  the  pitch  is  again  lowered, 
and  by  a  still  further  lengthening  raised  again,  3d,  that  the  length  of 
the  tube  necessary  to  lower  the  note  to  any  given  pitch,  depends  on  the 
relation  existing  between  the  rapidity  of  the  vibrations  of  the  tongue 
of  the  reed  and  those  of  the  column  of  air  in  the  tube,  each  taken 
separately.  Accepting  the  above  as  the  essential  conditions  which  an 
instrument  must  fulfil  in  order  to  constitute  a  reed  instrument,  Midler1 
showed  that  the  larynx,  in  fulfilling  the  same,  must  be  regarded  as  a 
reed  instrument,  the  vocal  membranes  being  comparable  to  membranous 
vibrating  tongues.  The  conclusion  just  arrived  at,  based  upon  acoustic 
principles,  that  the  larynx  is  a  reed  instrument,  is  fully  borne  out,  not 
only  by  the  fact  that  in  several  instances  persons  rendered  voiceless  by 
the  loss  of  their  larynx,  have  been  enabled  to  speak,  so  as  to  be  perfectly 
heard  through  the  introduction  into  the  trachea  of  a  tube  containing  a 
reed,  but  also  by  observing  directly  the  larynx  during  phonation  with 
the  laryngoscope.  Among  the  first  to  investigate  the  larynx  in  this 
way  was  Manuel  Garcia,2  so  distinguished  as  a  singing  teacher, 
whose  experiments  were  made  principally  with  the  view  of  determining 
the  scientific  principles  upon  which  the  teaching  of  singing  should  be 
based,  and  which,  up  to  that  time,  had  been  taught  by  purely  empirical 
methods.  The  difficulty  of  observing  the  vocal  membranes  during 
phonation  on  account  of  the  epiglottis  hiding  so  much  of  their  anterior 
portions,  especially  in  the  production  of  high  notes,  is  a  familiar  fact  to- 


Fig.  521. 


A,  the  glottis  during  the  emision  uf  a  high  note  in  singing.     B,  an  easy  or  quiet  inhalation  of  air. 

those  in  the  habit  of  using  the  laryngoscope.  The  perfect  control, 
however,  nossessed  by  Garcia  over  his  own  vocal  organs,  together  with 
the  skill  with  which  he  examined  them  in  his  own  person,  enabled  him 
finally  to  determine  very  satisfactorily  the  changes  actually  undergone 

1  Op.  cit.,  pp.  985,  999,  1023.  -  Pr  c.  of  Royal  Society  Lond  ,  1856,  vol.  vii.  p   399. 


848  PRODUCTION    OF    THE    VOICE. 

by  the  glottis  and  vocal  membranes  during  singing,  the  accuracy  of  the 
observations,  models  of  scientific  research,  being  fully  confirmed  by  later 
observers.  The  changes  in  the  glottis  during  ordinary  breathing  (Fig. 
521,  A  A')  having  been  already  described,  it  will  be  only  necessary  in 
this  connection  to  recall  the  fact,  that  during  inspiration  the  glottis, 
through  the  action  of  the  crico-arytenoidei  postici  muscles,  is  widely 
dilated,  and  that  during  expiration,  the  larynx  appearing  to  be  passive, 
the  air  is  gently  forced  out  through  the  glottis  by  the  expiratory  move- 
ments of  the  chest.  Garcia  having  first  noticed  the  movements  of  the 
larynx  during  his  ordinary  breathing,  observed  next  that  just  at  the 
moment  of  making  a  vocal  effort,  his  glottis  underwent  an  entire  change, 
the  arytenoid  cartilages  being  so  approximated  that  the  vocal  cords 
were  brought  parallel  to  each  other  (the  distance  separating  them,  it  may 
be  here  mentioned,  not  exceeding  the  one-twelfth  of  an  inch),  the  glottis 
then  appearing  as  a  narrow  slit  (Fig.  521,  B  Br).  The  glottis  being  thus 
prepared,  so  to  speak,  for  the  emission  of  a  note  through  the  action  of 
the  expiratory  muscles,  air  is  forced  through  the  slit  or  chink,  the  effect 
of  which  is  that  the  vocal  membranes  are  thrown  into  vibration,  the 
particular  note  emitted  being  due  essentially  to  the  length  and  tension 
of  the  latter.     Thus,  according  to  Garcia,  in  the  production  of  the  bass 


=t 


notes  rK±? — ^- 


the  glottis  is  agitated  by  large  and  loose  vibra- 


tions throughout  its  entire  extent,  the  lips  comprehending  in  their 
length  the  anterior  apophyses  of  the  arytenoid  cartilages  and  the  vocal 
cords. 

As  the  pitch  of  the  sound  rises  through  the  gradual  apposition  of  the 
apophyses  the  length  of  the  glottis  is  encroached  upon,  and  with  the 


emission  of  the  sounds  Fpszz      =zd  the  apophyses  touch  each  other 


throughout  their  whole  extent,  their  summits  being  solidly  fixed  one 
against  the  other  at  the  notes  Efifc |~~~F~       With  the  production  of 


the  notes  pffiy      ~1 |j  >  an(^  so  on  uPwal'd  to  the  end  of  the  register, 


the  vibrations  are  due  to  the  vocal  membranes  alone,  the  length  of  the 
glottis  diminishing,  and  the  cavity  of  the  larynx  becoming  very  small 
as  the  pitch  of  the  voice  continues  rising.  These  changes  undergone 
by  the  glottis  in  the  shape  and  size  and  in  the  length  and  tension  of  the 
vocal  membranes  in  the  production  of  low  and  high  notes  by  the  larynx, 
as  observed  by  Garcia  and  subsequent  investigators,  become  intelligible 
when  it  is  remembered,  as  shown  in  the  last  chapter,  that  the  pitch  of 


PRODUCTION     OF    THE    VOICE.  849 

the  note — that  is,  the  number  of  vibrations  per  second — rises  as  the  length 
of  the  string,  pipe,  or  membrane  diminishes,  or  the  tension  increases,  the 
change  in  the  shape  of  the  glottis  and  of  the  tension  of  the  vocal  mem- 
branes being  accomplished  by  the  action  of  the  muscles,  as  already 
explained.  Thus,  men  have  deeper  voices  than  boys  and  women,  their 
larynx  being  larger,  and  their  vocal  membranes  longer.  That  the  aper- 
ture of  the  glottis  is  narrowed  during  the  production  of  sounds  any  one 
can  convince  himself  by  comparing  the  time  of  an  ordinary  expiration 
with  that  required  for  the  passage  of  the  same  quantity  of  air  during  a 
vocal  effort,  and  that  the  size  of  the  aperture  varies  with  the  pitch  of 
the  note,  from  the  fact  of  there  being  a  far  less  passage  of  air  during 
the  production  of  a  low  note  than  in  that  of  a  high  one.  That  the 
production  of  low  and  high  notes  is  due  to  variations  in  the  tension  of 
the  vocal  membranes,  as  brought  about  by  the  action  of  the  thyroary- 
tenoid and  crico-thyroid  muscles,  is  made  evident  during  the  passage 
of  the  voice  from  one  extreme  of  the  scale  to  the  other  by  the  move- 
ment of  the  thyroid  on  the  cricoid  cartilage,  which  is  quite  apparent  if 
the  tip  of  the  finger  be  placed  over  the  crico-thyroid  ligament.  As 
illustrating  the  nicety  and  precision  with  which  the  tension  of  the  vocal 
membranes  is  regulated  by  muscular  contraction,  let  us  suppose,  with 
Midler,1  that  the  average  length  of  the  vocal  membrane  in  man  during 
repose  is  about  y^g-th  of  an  inch,  and  during  the  greatest  tension  y^g-th, 
the  difference  being,  therefore,  yg°<j-th,  or  the  ^-th  of  an  inch,  and  that 
in  the  female  the  corresponding  extremes  are  about  -yyo*^1  an^  iVo^1' 
the  difference  being  ^yg-th,  or  the  ^-th  of  an  inch,  and  that  the  natural 
compass  of  the  voice  is  about  two  octaves,  or  twenty-four  semitones. 
Such  being  the  case,  as  any  cultivated  voice  can  sing  ten  intervals 
between  the  twenty-four  semitones,  such  a  voice  can  produce  240  sounds, 
necessitating,  however,  over  240  different  states  of  tension.  Inasmuch, 
however,  as  the  available  length  of  vocal  membrane  to  be  tensed  is  only 
the  4th  and  the  -|-th  of  an  inch  in  the  sexes,  it  follows  that  in  the  pro- 
duction of  each  of  the  240  sounds  the  vocal  membrane  must  be  dimin- 
ished voluntarily  by  the  yjVo^1  an^  tne  T92~o^  0I>  an  ^ncn  m  ^ne  case 
of  the  male  and  female  singer,  respectively,  and  by  considerably  less  in 
the  case  of  such  phenomenal  voices  as  those  of  Bastardella,  Catalani, 
Cruvelli.  and  Patti,  for  example,  with  a  compass  of  three  octaves,  and 
even  more.  The  remarkable  distinctness  with  which  certain  voices 
could  be  heard,  like  those  of  the  celebrated  basso,  Lablache,  and  the  late 
Madame  Parepa  Rosa,  clearly  above  the  sounds  of  a  large  chorus  and 
orchestra,  is  due  rather  to  the  absolute  accuracy  with  Avhich  the  tension 
of  the  vocal  membranes  could  be  regulated  by  those  great  singers,  to  the 
purity  of  their  tones  rather  than  to  the  mere  loudness  or  intensity.  It 
should  be  mentioned,  however,  that  the  singers  just  referred  to  were  of 
magnificent  physique,  as  might  have  been  expected,  the  power  of  the 
voice  being  due  to  the  force  with  which  the  air  is  expelled  from  the  lungs. 
As  the  action  of  the  diaphragm  and  abdominal  muscles  has  already  been 
considered,  it  will  be  only  necessary  in  this  connection  to  recall  what 
has  already  been  said,  that  the  inspiratory  and  expiratory  acts  can  be 

■  Op   cit.,  vol.  ii.  p.  1018. 

;.4 


850  PRODUCTION    OF    THE    VOICE. 

so  nicely  balanced  by  a  skilful  singer  as  to  enable  him  to  produce  the 
most  delicate  tones.  It  need  hardly  be  added  that  while  sounds  may 
be  uttered,  and  even  words  spoken  during  inspiration,  that  the  true 
and  natural  voice,  and,  as  we  shall  see  presently,  articulate  speech  are 
only  produced  during  expiration.  While,  in  childhood,  the  general 
character  of  the  voice  is  the  same  in  both  sexes,  in  the  adult  condi- 
tion the  male  voice  differs  very  much  from  that  of  the  female,  the 
difference  becoming  marked  at  the  age  of  puberty.  If  castration  be 
performed,  therefore,  the  contralto,  or  soprano,  voice  of  the  boy  will  be 
retained  through  life,  and  such  a  voice  being  susceptible  of  considerable 
cultivation  advantage  was  cruelly  taken  of  the  fact  at  one  time  to  fill 
choirs  with  desirable  voices.  After  the  age  of  puberty,  however,  the 
quality  of  the  female  voice  remains  the  same,  except  in  gaining  strength 
and  extending  its  compass.  At  this  period,  in  the  case  of  the  male, 
however,  the  wdiole  character  of  the  voice  changes  through  the  develop- 
ment of  the  larynx.  While  the  intensity  of  the  voice  in  both  sexes 
depends  upon  the  force  with  which  the  air  is  expelled  through  the 
larynx,  and  the  range  or  pitch,  bass,  tenor,  contralto,  and  soprano,  upon 
the  length  and  tendon  of  the  vocal  membranes,  the  quality  of  any  par- 
ticular individual  voice,  male  or  female,  depends  upon  the  shape,  size, 
and  general  make  of  the  larynx,  and  on  the  character  of  the  auxiliary 
resonating  cavities.  In  concluding  our  account  of  the  production  of  the 
voice,  a  brief  description,  at  least,  of  the  influence  exerted  by  the  acces- 
sory vocal  organs,  viz.,  the  trachea,  ventricles,  superior  vocal  cords, 
epiglottis,  pharynx,  nasal  cavities,  and  mouth,  should  be  offered.  The 
trachea  not  only  serves  to  conduct  air  to  the  larynx,  but  through  the 
vibration  of  its  own  column  of  air  reinforces  the  sound  produced  by 
the  larynx,  the  vibration  being  perfectly  appreciable  if  the  finger  be 
placed  upon  the  trachea  during  a  powerful  vocal  effort.  The  ventricles 
probably,  also,  intensify  the  sound,  the  homologous  parts  being  enor- 
mously developed  in  monkeys  and  apes  possessing  very  loud  voices, 
such  as  the  South  American  howler  (Mycetes),  the  chimpanzee,  and 
gorilla. 

That  the  superior  or  false  vocal  cords  and  the  epiglottis  are  not 
essential  to  the  production  of  the  voice,  can  be  shown  by  experiments 
like  those  of  Longet,1  in  which  the  above  parts  were  removed  in  animals 
without  the  voice  being  materially  affected,  and  in  man  those  cases  in 
which  the  epiglottis  had  been  lost  through  wounds  or  disease.  The 
pharynx,  mouth,  and  nasal  fossce,  acting  as  resonating  cavities,  modify, 
however,  very  considerably  the  sounds  produced  by  the  vocal  mem- 
branes. Indeed,  in  the  production  of  the  natural  voice  their  resonance 
is  essential.  Thus,  Avhile  in  the  production  of  low  notes  the  velum 
palati  is  fixed,  and  the  bucco-pharyngeal  and  naso-pharyngeal  cavities 
reinforce  the  laryngeal  sounds,  in  the  passage  upward  to  the  higher 
notes  these  cavities  are  reduced  in  size,  the  isthmus  contracting  until, 
with  the  emission  of  the  highest  notes,  the  nasal  fossfe  is  shut  off  entirely, 
and  the  mouth  and  pharynx  alone  resound,  the  tongue  at  the  same  time 
beino-  drawn  back  into  the  mouth  with  its  base  projecting  upward  and 

1  Physiologie,  tome  ii.  p.  728.     Paris,  18G9. 


SPEECH.  851 

the  tip  downward,  the  capacity  of  the  resounding  cavity  is  still  further 
diminished.  Such  being  the  mechanism  by  which  the  chest  tones  or 
chest  register  are  produced,  it  is  only  necessary  to  add,  that  if  the  velum 
palati  be  thrown  forward  instead  of  backward,  thereby  cutting  off  the 
mouth  from  the  pharynx,  the  resonance  being  then  due  to  the  naso- 
pharyngeal cavity,  that  we  pass  from  the  chest  register  into  that  of  the 
head  tones  or  head  register.1  According  to  the  late  Madame  Seiler,2 
however,  the  head  tones  are  due  to  the  vocal  membranes  being  firmly 
approximated  posteriorly,  an  oval  opening  being  left  Avith  vibrating  edges 
involving  only  one-half  or  one-third  of  the  vocal  membranes,  which 
gradually  contracts  as  the  pitch  of  the  tone  rises.  As  in  the  case  of 
the  head  register,  so  in  that  of  the  falsetto  or  middle  register  of  the 
female,  a  difference  of  opinion  still  prevails  as  to  the  exact  manner  of 
its  production.  Thus,  while,  according  to  Fournie,3  the  falsetto  is  due 
to  the  tongue  being  pressed  strongly  backward  and  the  epiglottis  forced 
over  the  larynx;  according  to  Seiler,4  it  is  due  to  the  thin,  fine  edges  of 
the  vocal  membranes  alone  vibrating.  While  the  distinction  between 
the  chest,  falsetto,  and  head  registers  so  far  as  pitch  is  concerned,  is  not 
an  absolute  one,  and  while  we  find  that  every  voice  possesses  all  three 
registers,  nevertheless  the  chest  register  almost  characterizes  male  voices 
and  the  contralto  of  the  female,  the  falsetto  being  the  most  natural 
voice  of  the  soprano,  though  the  latter  voice  is  capable  of  chest  tones, 
while  the  head  voice  is  particularly  well  developed  in  tenors  and  in  the 
female  voice.  The  falsetto  is  but  little  cultivated  at  the  present  day  by 
tenors,  and  even  when  it  or  either  of  the  other  two  registers  is  partic- 
ularly well  developed  the  singer  should  endeavor  to  pass  as  insensibly  as 
possible  from  one  register  to  another,  to  give  the  impression  that  his 
voice  possessed  but  one. 

Speech. 

While  the  position  of  man  as  the  head  of  the  animal  kindom  depends 
upon  the  development  of  his  intelligence,  there  can  be  no  question 
that  his  superiority  over  all  other  animals  is,  to  a  great  extent, 
due  to  his  being  able  to  convey  his  ideas  to  others  by  expression,  or 
articulate  speech.  Speech  is  voice  modulated  by  the  throat,  nose, 
tongue,  and  lips.  Voice  may,  therefore,  exist  without  speech,  and  if 
the  production  of  the  voice  be  restricted  to  the  vibrations  of  the  vocal 
membranes,  it  may  be  said  that  speech  can  exist  without  voice,  since, 
in  whispering,  the  vibrations  of  the  muscular  walls  of  the  lips  replace 
those  of  the  vocal  membranes,  a  whisper  being,  in  fact,  a  very  low 
whistle.  Articulate  sounds  are  usually  divided  by  orthoepists  into 
vowels  and  consonants  :  vowels  being  continuous  sounds  due  to  the 
voice  alone,  but  modified  by  the  form  of  the  aperture  through  which 
they  pass  out;  consonants,  interrupted  sounds  due  to  the  interruption, 
more  or  less,  of  the  voice,  and  sounded  with  vowels.  This  classifica- 
tion is  not,  however,  a  very  natural  one,  since  the  sound  of  the 
English  i,  being  a  diphthongal  sound,  cannot  be  prolonged  like  a  true 

1   FonrniS  :   Physiologic  de  la  voix  et  de  la  parole,  p.  421.     Paiis.  18(50. 

-   The  Voire  in  Singilig,  p.  56.     Pkila.,  1808.  3  Op.  cit.,  p.  4C3.  *  Op.  fit  ,  p.  56. 


852  SPEECH. 

vowel  (a,  o),  while  certain  consonants  (1,  r,  f)  can  be  pronounced 
without  the  current  of  air  being  interrupted.  The  vowel  sounds,  by 
which  we  mean  u,  o,  a,  e,  are  due  to  the  reinforcing  of  the  overtones 
of  the  fundamental  tone  of  the  larynx  by  the  cavity  of  the  mouth,  the 
changes  in  the  shape  of  which  give  rise  to  so  many  resonantors,  each 
of  which  is  adapted  to  the  reinforcing  of  the  particular  overtone  to 
which,  together  with  the  fundamental  tone,  the  particular  vowel  is  due. 
The  presence  of  overtones  coexisting  with  the  fundamental  tone  of 
the  larynx  in  the  emission  of  vowel  souuds,  and  the  determination  of 
what  particular  overtone  accompanies  the  fundamental  tone  in  the 
production  of  any  particular  vowel,  can  be  shown  by  the  Kcenig  mano- 
metric  apparatus  described  in  the  last  chapter.  Thus  the  vowel  sound 
u  is  due  to  the  fundamental  tone  being  emitted  strong,  the  cavity  of 
the  mouth  being  made  as  deep  as  possible,  by  keeping  the  tongue  down 
at  the  bottom,  and  pushing  the  lips  out,  the  mouth  then  reinforcing 
the  fundamental  tone  of  the  larynx,  and  tuned,  according  to  Kamig1 
and  the  experiments  of  the  author,  to  the  pitch  of  the  note  Sib;2  (Fig- 
522),  due  to  224   vibrations  per  second.     The   sound  o  is  due  to  the 

Fig.  522. 


r 


Vowels,  OU        0  A  E  I 

Tones,  Sfy    s,^8       Sfe      g^      ^ 

No.  of  Vibs.,  224,     448,        896,      1702,      3584. 
Pitch  of  vowels.     (KffiNiG.) 

fundamental  note  of  the  larynx  being  present,  but  especially  its 
first  octave  above  being  emitted  also,  and  very  strong,  the  cavity 
of  the  mouth  being  enlarged  through  the  retraction  of  the  lips  so 
as  to  reinforce  the  octave,  and  tuned  to  the  pitch  of  the  note  Si^3, 
due  to  448  vibrations  per  second.  The  sound  a,  like  the  preceding 
two  vowels,  is  due  to  the  presence  of  the  fundamental  tone  of  the  larynx, 
but  differs  from  o  in  that  the  fundamental  is  accompanied  by  the 
double  octave  above,  the  orifice  of  the  mouth  being  so  widened 
that  the  cavity  of  the  mouth  is  tuned  to  the  pitch  of  the  note  Sfc4 
due  to  896  vibrations  per  second.  In  the  production  of  the  sound 
e  the  cavity  of  the  mouth  is  still  more  retracted,  reinforcing  the 
third  octave  above  the  fundamental,  the  cavity  of  the  mouth  being 
tuned  to  the  pitch  of  the  note  Si^j  due  to  1792  vibrations  per 
second.  As  the  four  vowels  u,  o,  a,  e,  can  be  produced  during  one 
continuous  expiration,  during  which  the  fundamental  and  overtones 
generated  by  the  vocal  membranes  remain  the  same,  by  simply 
changing  the  shape  of  the  mouth,  it  is  evident  that  the  production 
of   each  individual  vowel  will    depend,    as    already    mentioned,    upon 

iQuolques:    Experiences  d'Acoustique,  p.  65.     Paris,  1SS2. 


SPEECH.  853 

which  particular  octave  or  overtone  is  reinforced  by  the  cavity  of  the 
mouth,  the  pitch  of  the  latter  depending  upon  its  shape,  and  that  the 
shape  of  the  mouth  remaining  unchanged,  the  corresponding  vowel 
will  be  emitted  as  long  as  the  expiration  blast  lasts.  Now  while  the 
vowel  i  agrees  with  the  four  vowels  just  mentioned  in  being  due  to 
the  reinforcement  of  an  overtone,  the  fourth  octave  accompanying  the 
fundamental  by  the  cavity  of  the  mouth,  which  in  this  instance  is 
tuned  to  the  pitch  of  the  note  S;^6,  due  to  3584  vibrations  per  second, 
an  octave  higher  than  in  the  case  of  the  vowel  e,  it  differs  from  the 
true  vowels  in  that,  the  cavity  of  the  mouth  remaining  the  same,  if  the 
expiratory  blast  be  prolonged,  it  does  not  remain  i,  but  becomes  e. 
The  vowels  are  the  only  real  vocal  sounds,  it  being  only  on  a  vowel 
that  a  note  can  be  said  or  sung.  Speech,  however,  is  made  up  not 
only  of  vowels,  but  of  consonants — that  is,  of  sounds  that  are  sounded 
in  conjunction  with  a  vowel.  While  the  distinction  between  vowels 
and  consonants,  as  already  mentioned,  is  not  an  absolute  one,  it  may  be 
said  that  while  vowels  are  due  to  the  vibrations  of  the  vocal  membranes 
being  modified  by  the  mouth,  consonants  are  due  to  the  expiratory 
blast  being  interrupted  in  various  ways  in  its  course  through  the 
throat  and  mouth ;  the  vibrations  of  the  vocal  membranes,  when  essen- 
tia.1,  being 'rather  secondary  in  character.  Consonants  may  be  divided 
according  to  their  manner  of  production,  into  two  kinds,  explosive 
and  continuous,  the  sound  of  the  explosive  consonants  being  due  to  the 
sudden  establishment  or  removal  of  a  particular  interruption,  that  of 
the  continuous  consonant  to  the  air  rushing  continuously  through  some 
constriction,  for  example,  explosive  consonants  are  the  labials  p,  b, 
dentals  t,  d,  and  gutturals  k,  g,  p,  t,  and  k,  being  uttered  without 
the  voice,  b,  d,  and  g  (hard)  with  the  voice — that  is,  are  accompanied 
by  a  vowel  sound.  In  uttering  p,  the  lips  are  first  closed,  then  the 
expiratory  blast  suddenly  opening  them,  the  sound  is  produced.  Simi- 
larly the  sudden  interruption  of  the  contact  of  the  tip  of  the  tongue 
with  the  hard  palate,  and  of  the  root  of  the  tongue  with  the  soft  palate 
gives  rise  respectively  to  the  sounds  t  and  k.  The  continuous  con- 
sonants are  subdivided  into  aspirates,  resonants,  and  vibratory. 

The  aspirates  include  the  labials  f,  v,  the  dentals  s,  1,  sh,  th 
(hard),  z,  zh,  th  (soft),  and  the  gutturals  ch,  gh.  Like  the  explosive 
consonants,  some  of  the  aspirates  are  uttered  without  the  voice,  as  f, 
s,  1,  sh,  c,  h;  some  with  the  voice,  as  v,  z,  zh,  th,  ch.  The  reso- 
•nants  include  the  sounds  m,  n,  ng,  and  the  vibratory  the  sound  r. 
common  and  guttural.  Of  the  aspirates,  f  and  s  are  formed  through 
the  lips  and  teeth  being  brought  nearly  in  contact  respectively  ;  th 
through  the  placing  of  the  tongue  between  the  two  partially  open  rows 
of  teeth ;  1  when  the  tip  of  the  tongue  is  placed  against  the  hard  palate, 
and  the  air  escapes  at  the  sides  ;  sh  through  the  dorsal  surface  of  the 
tongue  being  raised  toward  the  palati,  the  passage-way  between  the  two 
being  thereby  narrowed  ;  ch  and  gh  through  the  approximation  of  the 
root  of  the  tongue  to  the  soft  palate.  In  the  production  of  all  of  the 
resonants  the  vocal  membranes  vibrate  and  the  nasal  chambers  resonate, 
the  closing  of  the  lips  in  particular  giving  rise  to  m,  the  contact  of  the 
tongue  with  the  hard  palate  to  n,  and  the  approximation  of  the  root  of 


854  SPEECH. 

the  tongue  to  the  soft  palate  to  ng.  The  vibratory  consonants  include 
the  various  forms  of  the  sound  r,  so  called  on  account  of  being  pro- 
duced by  the  vibration  of  the  constricted  portion  of  the  vocal  passage; 
thus,  the  common  r  is  due  to  the  vibrations  of  the  point  of  the  tongue 
elevated  against  the  hard  palate ;  the  guttural  r  to  vibrations  of  the 
uvula  or  other  parts  of  the  walls  of  the  pharynx.  The  tongue,  while 
an  organ  of  speech,  is  not  essential,  since  after  its  loss  the  faculty  of 
speech  more  or  less  perfect  remains.  Finally,  while  the  consonant  e  is 
a  breathed  aspirate,  it  differs  from  all  other  letters  in  being  formed  in 
the  larynx  itself,  the  glottis  being  narrowed  enough  to  produce  a  wind- 
rush,  but  not  sufficiently  to  throw  the  vocal  membranes  into  vibration, 
c  is  redundant,  producing  the  same  effect  as  k  or  s ;  q  is  equivalent  to 
1,  being  used  only  before  the  vowel  u  ;  x  is  the  ame  as  ks  at  the  end  of 
a  syllable,  and  z  when  beginning  a  word. 

While  the  limits  of  this  work  will  not  permit  of  any  further  detailed 
consideration  of  orthoepy,  or  of  any  theory  of  the  origin  and  growth  of 
language  in  general,  or  of  that  of  the  language  in  which  this  work  is 
written  in  particular,  the  above  description  will  suffice  as  a  general 
account  of  the  production  of  articulate  speech,  a  factor  almost  as  im- 
portant as  that  of  intelligence  in  the  development  of  civilization. 


CHAPTER    LIII 


THE  STRUCTURE  OF  THE  EAR,  AND  THE  SENSATION  OF 

HEARING. 

The  organ  of  hearing  is  usually  described  as  consisting  of  three  parts, 
an  external,  middle,  and  internal  ear,  the  latter  including  the  auditory 
nerve.  For  convenience,  as  well  as  to  avoid  repetition,  the  functions  of 
the  three  parts  of  the  ear  will  be  considered  at  the  same  time  as  that  of 
the  description  of  their  structure. 

The  Structure  and  Functions  of  the  External  Ear. 

The  pinna,  auricle,  or  ear,  in  the  ordinary  sense  of  the  term — that  is, 
the  portion  projecting  from  the  head  (Fig.  523),  with  the  exception  of  the 

Fig  523. 


h 


View  of  parts  composing  the  organ  of  hearing  of  the  right  sitle.     a.  Pinna  and  lobe.     6.  Meatus  externus. 
o.  Meuibraua  tympani.     <l.  Cavity  of  tympanum,     e    Eustachian  tube. 


lower  lobular  portion  consists  of  fibro-cartilage  and  presents  certain  prom- 
inences, the  tragus  and  antitragus,  ridges  the  helix  and  antihelix,  which 
together  with  their  fossae,  adapt  it  to  receive  the  aerial  vibrations  giving 
rise  when  transmitted  to  the  auditory  nerve  to  the  sensation  of  sound. 
Owing  to  the  immobility  of  the  ear,  through  the  imperfect  development 


856  STRUCTURE    OF    THE    MIDDLE     EAR. 

of  the  attolens,  attrahens,  and  retrahens  auri,  as  well  as  its  intrinsic 
muscles,  the  external  ear  is  not  as  functionally  important  in  man  as  in 
the  case  of  the  lower  animals  for  the  appreciation  of  the  intensity  of 
sound,  since  persons  deprived  of  it  do  not  experience  any  sensihle  change 
in  their  power  of  hearing.  -That  the  external  ear  is,  however,  of  use  in 
enabling  us  to  judge  as  to  the  direction  of  sounds,  any  one  can  convince 
himself  by  filling  the  convolutions  with  wax,  or  flattening  the  ear  forcibly 
against  the  side  of  the  head,  when  it  will  he  found  impossible  to  deter- 
mine the  direction  from  which  the  sound  comes.  Such  is  also  the 
experience  of  those  persons  who  have  lost  the  external  ear  from  wounds, 
etc.  Indeed,  there  can  be  little  doubt  that  we  judge  as  to  the  origin 
and  direction  of  sounds  from  the  fact  that  the  sound  waves  do  not  im- 
pinge upon  the  ears  alike,  and  that  the  intensity  of  the  sound  is  modified 
by  the  manner  in  which  it  falls  upon  the  external  ear  and  is  reflected 
from  it.  IJence,  in  determining  whether  a  sound  proceeds  from  directly 
behind  or  in  front  of  us,  we  usually  incline  the  head  in  the  direction 
from  which  we  suppose  it  to  come.  The  aerial  vibrations  having  been 
collected  by  the  external  ear,  are  thence  transmitted  by  the  external 
auditory  meatus  from  the  concha  or  the  deep  concavity  within  the  posi- 
tion of  the  antihelix  and  subdivided  by  the  helix  to  the  tympanum. 
The  external  auditory  meatus,  about  an  inch  and  a  quarter  in  length,  is 
directed  inward  and  forward,  upward  and  downward,  and  is  narrowest 
at  its  middle  portion.  It  consists  of  two  portions,  an  interfibro-carti- 
laginous  one,  the  prolongation  of  the  auricle,  and  an  inner  osseous  one,  a 
part  of  the  temporal  bone,  both  portions  being  lined  with  skin.  The  skin 
of  the  outer  portion  is  thick  and  provided  with  numerous  hairs,  sebaceous 
and  ceruminous  glands.  The  latter,  small,  round,  brownish-yellow  bodies 
imbedded  in  the  subcutaneous  tissue,  and  giving  rise  to  the  punctured 
appearance  of  the  skin  are  modified  sudoriferous  glands,  consisting,  like 
the  latter,  of  a  narrow  tube  coiled  upon  itself  in  the  form  of  a  ball,  and 
secrete  the  cerumen  or  ear-wax.  The  latter  is  said  to  be  composed  of 
fatty  and  albuminous  matters  of  salts  of  soda  and  lime,  and  has  a  very 
bitter  taste,  a  property  which  has  been  considered  of  service  in  prevent- 
ing insects  entering  the  ear.  The  cerumen,  which  probably  consists 
of  sebaceous  matter  mixed  with  the  proper  secretion  of  the  ceruminous 
glands,  lubricates  the  meatus.  The  skin  of  the  inner  osseous  portion  of 
the  meatus  is  very  thin,  destitute  of  hairs  and  glands,  and  at  the  bottom 
of  the  meatus  is  continued  over  the  tympanic  membrane  as  its  outer 
investing  layer. 

The  Structure  of  the  Middle  Ear. 

The  middle  ear,  separated  from  the  external  ear  by  the  tympanic 
membrane,  includes  the  tympanum  or  drum  of  the  ear,  the  ear  bones, 
with  their  ligaments,  muscles,  the  mastoid  sinuses,  and  the  Eustachian 
tube.  The  tympanum,  an  irregular  cavity  in  the  interior  of  the  petrous 
portion  of  the  temporal  bone,  is  about  half  an  inch  in  height  and  breadth, 
and  perhaps  the  sixth  of  an  inch  from  without  inward,  is  closed  in  front 
by  the  tympanic  membrane,  at  the  back   by  the  wall  of  the  labyrinth, 


STRUCTURE     OF    THE    MIDDLE    EAR. 


857 


and  opens  above  and  posteriorly  into  the  sinuses  and  in  front  into  the 
Eustachian  tube.  The  tympanic  membrane  separating,  as  already  men- 
tioned, the  external  auditory  meatus  from  the  tympanum,  is  about  two- 
fifths  of  an  inch  in  height  and  breadth,  somewhat  funnel-shaped  in  form, 
and  is  disposed  obliquely  (Fig.  523,  c),  its  outer  depressed  surface  or 
umbo  being  directed  downward  and  forward.  The  tympanic  membrane 
is  inserted  by  the  greater  part  of  its  circumference  into  a  groove  which, 
while  in  the  adult  is  regarded  as  a  portion  of  the  temporal  bone,  is  in 
reality  the  only  part  visible  of  an  originally  entirely  separate  osseous 
ring,  the  homologue  of  the  tympanic  bone  of  the  lower  vertebrates,  but 
which  in  man,  instead  of  remaining  distinct  as  in  them,  coossifies  as 
development  advances  with  the  temporal  bone,  and  grows  outwardly  as 

a  Fig.  VJ4.  B 


Bones  of  the  tjmpanumof  the  left  side.  A.  Malleus:  1,  long  or  slender  process  ;  3,  the  hand'-:  4, 
Short  process  ;  5,  head.  B.  Incus  :  1,  body  ;  i,  short  or  posterior  process  ;  3,  the  long  process  with  the 
orbicular  process  4.  C.  Stapes:  1,  head  :  4,5,  crura;  6,  base.  D.  The  three  bones  in  their  natural  con- 
nection :  m,  malleus  ;  sc,  incus;  s,  stapes.     C*.  Base  of  the  stripe*. 

the  osseous  external  auditory  meatus,  its  morphological  significance 
being  thereby  entirely  lost  sight  of.  The  tympanic  membrane,  thin  and 
translucent,  is  composed  of  a  layer  of  fibrous  tissue,  the  membrana 
propria,  covered  externally  by  the  skin  of  the  external  auditory  meatus, 
and  internally  by  the  mucous  membrane  of  the  tympanum,  the  latter 
being  continuous  with  that  lining  the  Eustachian  tube.  The  fibrous 
layer  of  the  tympanum  consists  of  two  sets  of  fibres,  of  which  the  greater 
part  radiate  from  its  centre,  the  remaining  ones  being  concentrically 
disposed  at  the  periphery.  The  little  ear  bones  (Fig.  524),  three  in 
number,  the  malleus,  incus,  and  stapes,  are  disposed  within  the  tym- 


858  STRUCTURE    OF    THE     MIDDLE    EAR. 

panum  from  before  backward  in  the  order  named.  The  malleus,  so 
called  on  account  of  its  resemblance  to  a  hammer,  is  suspended  verti- 
cally from  the  floor  of  the  tympanum  by  a  slender  bund  of  fibres,  the 
suspensory  ligament,  which  passes  into  its  head,  the  latter  articulates 
through  an  oval  facet  covered  with  cartilage  with  the  body  of  the  incus. 
The  malleus  is  also  connected  with  the  tympanic  membrane,  its  taper- 
ing slightly  twisted  manubrium  or  handle  passing  down  into  the  fibrous 
layer  of  the  latter  as  far  as  its  centre.  From  the  neck  of  the  malleus, 
or  the  constricted  portion  below  the  head,  two  processes  are  given  off, 
one  of  which,  the  largest,  or  processus  gracilis,  projecting  at  right  angles, 
passes  into  the  Grasserian  fissure  to  be  attached  to  the  laxator  tympani 
muscle  arising  from  the  spinous  process  of  the  sphenoid  bone,  and  so 
called  on  account  of  its  relaxing  the  tympanic  membrane.  The  tensor 
muscle  tensing  the  tympanic  membrane  and  inserted  into  the  neck  of  the 
malleus,  on  the  other  hand,  arising  from  the  end  of  the  cartilage  of  the 
Eustachian  tube,  and  the  contiguous  surfaces  of  the  sphenoid  and  temporal 
bones,  passes  through  a  special  canal  of  the  latter  into  the  tympanum. 

The  incus  or  anvil,  situated  behind  and  articulated  with  the  malleus 
as  already  mentioned,  is  also  sustained  in  its  position  by  a  fibrous  band, 
its  suspensory  ligament,  its  short  backwardly  projecting  process  with 
the  posterior  part  of  the  tympanum.  The  long  process  of  the  incus 
curved  and  tapering,  descending  nearly  parallel  with  the  manubrium  or 
handle  of  the  malleus,  terminates  in  the  so-called  orbicular  process,  by 
which  it  articulates  through  cartilage  with  the  facet  on  the  head  of  the 
stapes  or  stirrup.  The  orbicular  process  is  in  reality  a  distinct  bone, 
being  separable  from  the  incus  even  at  birth  ;  soon  after,  however,  it 
becomes  so  ossified  with  the  latter  as  to  be  undistinguishable  from  it. 
The  stapes  or  stirrup,  situated  inwardly  between  the  incus  and  the 
foramen  ovale  of  the  vestibule,  is  disposed  at  right  angles  to  the  long 
process  of  the  incus,  the  crura — that  is,  the  portion  joining  its  head 
and  its  base,  lying  horizontally  in  the  tympanum.  By  its  annular  liga- 
ment, the  margin  of  the  base  of  the  stapes  is  connected  with  the  border 
of  the  foramen  ovale  of  the  vestibule,  the  pressure  of  the  base  of  the 
stapes  against  the  oval  window  or  the  perilymph  back  of  it  being  regu- 
lated by  the  stapedius  muscle,  which  arising  within  the  hollow  of  the 
pyramid,  or  the  conical  eminence  projecting  from  the  back  part  of  the 
tympanum,  is  inserted  into  the  head  of  the  stirrup.  The  mastoid 
sinuses,  so  called  from  being  situated  in  the  interior  of  the  mastoid  por- 
tion of  the  temporal  bone,  are  irregular  cavities  lined  with  mucous 
membrane,  which  communicate  by  a  large  orifice  with  the  upper 
and  back  part  of  the  tympanum.  The  Eustachian  tube  (Fig.  523,  e) 
about  an  inch  and  a  half  long  and  somewhat  trumpet-shaped  in  form, 
extends  from  the  front  part  of  the  tympartum  obliquely  downward, 
forward,  and  inward,  terminating  by  an  oval  orifice  in  the  pharynx  on  a 
level  with  the  turbinated  bone  at  the  back  of  the  posterior  nasal  orifice. 
The  Eustachian  tube  consists  of  two  portions,  an  upper  osseous  portion 
situated  in  the  petrous  portion  of  the  temporal  bone  and  opening  into 
the  tympanum,  and  a  lower  fibro-cartilaginous  portion  opening  into  the 
pharynx,  the  two  portions  being  united  within  the  angle  between  the 
squamous  and  petrous  portions  of  the  temporal  bone.     It  is  lined  with 


FUNCTIONS    OF    THE     MIDDLE    EAR.  859 

mucous  membrane  provided  with  ciliated  epithelium,  continuous  on  the 
one  hand  with  that  of  the  tympanum,  and  on  the  other  with  that  of  the 
pharynx.  The  existence  of  such  a  tube  as  that  just  described,  putting  the 
cavities  of  the  middle  ear  in  communication  with  that  of  the  pharynx, 
as  well  as  the  presence  of  a  chain  of  bones  connecting  the  membrana 
tympani  with  the  oval  window  of  the  vestibule,  will  become  intelligible 
when  the  development  of  the  ear  is  considered. 

Functions  of  the  Middle  Ear. 

Such  being  in  general  the  structure  and  relations  of  the  tympanic 
membrane,  ear  bones,  Eustachian  tube,  etc.,  if  the  aerial  vibrations 
collected  and  transmitted  by  the  auricle  to  the  external  auditory  meatus 
throw  the  tympanic  membrane  into  vibration,  the  vibrations  of  the 
latter  will  in  turn  be  transmitted  by  the  ear  bones  through  the  inter- 
mediation of  the  vestibule,  etc.,  to  the  terminal  filaments  of  the  audi- 
tory nerve,  and  so  give  rise  to  the  sensation  of  sound.  The  importance 
of  the  membrana  tympani  in  audition  is  shown  by  the  fact  that  the 
acuteness  of  hearing  is  always  more  or  less  affected  in  those  cases  in 
which  the  membrane  is  thickened,  perforated,  or  destroyed,  and  that 
relief  is  obtained  by  the  wearing  of  an  artificial  membrane  if  the  latter 
can  be  tolerated.  This  becomes  perfectly  intelligible  when  it  is  remem- 
bered, as  shown  by  Miiller,1  that  while  aerial  vibrations  are  communi- 
cated to  solid  bodies  like  the  ear  bones  only  with  difficulty  and  with 
considerable  diminution  in  their  intensity,  they  are  communicated  very 
readily  to  the  same,  a  tense  membrane  like  the  tympanic  membrane 
intervening,  the  fact  of  the  membrane  being  fixed  at  the  periphery,  and 
having  air  on  both  sides  of  it  being  also  most  favorable  conditions. 
That  membranes  of  as  small  extent  as  that  of  the  membrana  tympani 
when  stretched  are  readily  thrown  into  vibration,  can  be  shown  by 
experiments  like  those  of  Savart2  in  which  sand  strewed  over  their 
surface  was  cast  off,  on  sonorous  vibrations  being  excited  in  their 
vicinity.  It  is  a  well-known  fact,  that  membranes  vibrate  more  power- 
fully, more  intensely,  when  relaxed  than  when  tensed,  hence  the  sensi- 
tiveness to  all  sounds  experienced  in  facial  palsy,  which  is  due  to 
the  want  of  innervation  of  the  tensor  tympanic  muscle  by  the  filaments 
of  the  paralyzed  facial  supplying  it.  It  is  also  worthy  of  mention  in 
this  connection,  that  the  vibrations  of  the  membrana  tympani  are  more 
intense  in  proportion  as  the  latter  approaches  a  vertical  position,  as 
accounting  to  some  extent  for  the  appreciation  of  sounds  by  musicians, 
in  some  of  whom  the  tympanic  membrane  is  almost  vertically  disposed, 
whereas  in  persons  with  but  little  ear  for  music,  the  membrane  is  very 
oblique  in  position.  It  has  already  been  explained,  that  sounds  not 
only  differ  in  their  loudness  or  intensity,  but  in  their  pitch  or  number 
of  vibrations  per  second  as  well,  and  since  we  hear  sounds  of  different 
pitch,  it  is  obvious,  therefore,  that  there  must  be  some  means  of  tuning — 
that  is.  of  tightening  or  relaxing  the  tympanic  membrane,  so  that  the 
vibrations  of  the  latter  shall  be  the  same  per  second  as  those  to  which 

i  Physiology,  vol.  ii.  p.  1248. 

-  Journal  de  Physiologic,  tuine  iv.  p.  203.     Paris,  1824. 


8(H)  FUNCTIONS    OF    THE    MIDDLE    EAR. 

the  particular  note  or  notes  heard  are  due.  That  is  to  say,  every  sonor- 
ous aerial  wave — that  is,  a  condensation  and  a  rarefaction, — bending 
the  tympanic  membrane  once  in  and  once  out,  the  rate  of  vibration  of 
the  membrane  must  be  the  same  as  that  of  the  vibration  of  the  sonorous 
body  causing  it,  if  the  particular  sound  due  to  the  latter  is  to  be  heard. 
That  the  membrana  tympani  is  relaxed  for  sounds  of  low  pitch  and 
tensed  for  those  of  high  pitch,  is  shown  by  the  insensibility  to  low  tones, 
and  marked  appreciation  to  high  ones,  being  proportional  to  the  extent 
to  which  the  membrane  is  tensed.  Thus,  if  the  mouth  and  nose  being 
closed,  we  attempt  to  breathe  forcibly  by  expanding  the  chest,  the  air 
within  the  tympanum  becoming  rarefied,  the  tympanic  membrane  will 
be  forced  in  by  the  external  air  and  rendered  more  tense,  the  effect  of 
which  is  that,  as  Dr.  Wollaston1  showed,  we  become  deaf  to  low  sounds. 
A  similar  deafness  to  sounds  of  low  pitch  is  also  produced,  the  nose  and 
mouth  being  stopped  when  a  strong  effort  is  made  to  expire,  the 
increased  tension  of  the  membrane  being  due,  however,  in  this  instance 
to  the  air  being  forced  into  the  tympanum  through  the  Eustachian  tube 
instead  of  being  sucked  out  of  it  and  the  membrane  being  pushed  out- 
wardly. A  sudden  concussion  may  produce  temporary  deafness  in 
either  of  the  above  ways — that  is,  by  forcing  air  either  into  or  out  of 
the  tympanum. 

It  is  evident,  from  the  facts  just  mentioned,  that  the  function  of  the 
Eustachian  tube  is  the  maintaining  of  equilibrium  between  the  air 
within  the  tympanum  and  the  air  without.  Hence  if  the  tube  be 
closed,  which  is  usually  the  case,  according  as  the  external  air  becomes 
denser,  as  in  descending  in  a  diving-glass,  or,  rarer,  as  in  making  high 
mountain  ascents,  the  tympanic  membrane  will  be  pushed  in  or  out  in 
either  case,  will  be  rendered  more  tense  and  pain  and  deafness  experienced, 
both  of  which  can,  however,  he  usually  relieved  by  the  act  of  swal- 
lowing, which,  in  opening  the  Eustachian  tube,  reestablishes  the  equi- 
librium between  the  internal  and  external  pressure.  It  may  be  men- 
tioned, in  this  connection,  that  the  Eustachian  tube  is  opened  by  the 
contraction  of  the  tensor  palati,  levator  palati,  and  the  palato-pharyn- 
geus  muscles ;  the  tensor  palati,  in  drawing  the  hook  of  the  cartilage 
outward,  and  the  levator  palati,  in  drawing  the  end  of  the  cartilage 
upward  and  inward,  enlarge  and  widen  its  pharyngeal  orifice,  the  palato- 
pharyngeus  fixing  the  cartilage.  With  the  relaxing  of  the  muscles  just 
mentioned,  through  the  elasticity  of  the  cartilage,  the  tube  then  closes 
again  almost  entirely,  a  narrow  chink  alone  remaining.  Since,  while 
the  Eustachian  tube  is  open,  the  cavity  of  the  tympanum  is  in  commu- 
nication with  that  of  the  pharynx,  it  follows  that  if  we  swallow  several 
times  in  succession,  the  nose  and  mouth  being  closed,  that  the  air  will 
be  gradually  drawn  from  the  tympanic  cavity,  the  membrane  being  ren- 
dered tense  by  the  external  atmospheric  pressure,  as  in  the  case  just 
mentioned,  in  which  forced  inspiratory  efforts  were  made,  and  an  insen- 
sibility to  low  sounds  experienced.  That  the  tympanic  membrane  is 
tensed  for  high  sounds  is  shown  by  the  fact  that  in  certain  individuals,2 

i  riiilos.  Trans.  Lond  ,  1820,  p.  306. 

2  Blake  :  Trans  of  the  Amer.  Otolugical  Soc,  vol.  v.  p.  77.     Boston,  1872. 


FUNCTIONS    OF    THE    MIDDLE    EAR.  861 

-whose  ordinary  limit  of  appreciation  -was  of  sounds  due  to  fifteen  hun- 
dred vibrations  per  second  by  voluntary  contraction  of  the  tensor  tym- 
pani  muscle,  this  -was  increased,  so  that  sounds  could  be  heard  due  to 
2500  vibrations  per  seconds.  There  can  be  little  doubt,  then,  that 
the  membrana  tympani  is  relaxed  or  tensed,  according  as  the  sonorous 
vibrations  are  low  or  high  in  pitch,  and  that  the  variations  in  the 
tension  of  the  membrane  arc  regulated  by  the  action  of  the  laxator  and 
tensor  tympani  muscles.  While  there  is  a  great  difference  in  indi- 
viduals, as  regards  the  appreciation  of  sounds,  some  persons  being 
insensible  to  the  hum  of  insects,  the  chirrup  of  the  sparrow,  the  squeak 
of  the  bat ;  others  to  the  high  sounds  of  small  organ-pipes,  or  even  the 
highest  notes  of  the  piano;  there  is  a  limit,  nevertheless,  to  audibility 
in  all,  the  tympanic  membrane  failing  to  link  together  into  a  continuous 
tone  vibrations  succeeding  each  other  less  rapidly  than  16  a  second,  or 
more  so  than  38.000  a  second.  In  the  former  case,  Ave  are  conscious 
only  of  separate  shocks;  in  the  latter,  Ave  are  unconscious  of  sound  alto- 
gether. The  range  of  audibility  lying  within  the  above  limits  embraces, 
therefore,  about  11  octaves;  of  which  about  two-thirds,  or  7  octaves 
only,  are,  however,  made  use  of  in  music.  It  is  true,  that  we  obtain 
from  the  loAvest  C  of  the  piano  the  note  due  to  32  vibrations  per  second, 
and  from  the  lowest  A  of  the  new  grand  piano  are  due  to  27  vibra- 
tions per  second,  and  from  a  closed  organ-pipe  16  feet  long,  or  an 
open  one  32  feet  long,  the  loAvest  C,  due  to  16  vibrations  per  second, 
but  the  latter  sound,  and  that  of  the  lowest  C  or  A  of  the  piano,  are 
so  unmusical,  so  dull  and  groaning  in  character,  that  they  are  but  little 
used.  The  deepest  tone  made  use  of  in  orchestral  music  being  that  due 
to  the  E  string  of  the  double  bass,  giving  41|  vibrations,  the  highest 
that  of  the  D  of  the  piccolo  flute,  due  to  4752  vibrations  per  seconds ; 
it  may  be  said  that  practically  the  range  of  musical  sounds  is  confined 
between  40  and  4000  vibrations  per  second,  the  highest  C  of  the  piano 
reaching  4224  vibrations  per  second — that  is,  in  round  numbers,  as 
just  said,  about  7  octaves.  Even  Avithin  such  limits  the  immense 
number  and  kind  of  sonorous  Avaves  that  fall  upon  the  tympanic  mem- 
brane Avhile  listening  to  a  grand  opera  as  given  by  the  leading  artists, 
together  with  full  choral  and  grand  orchestral  accompaniment,  must 
impress  one  with  the  remarkable  acoustic  properties  of  the  membrana 
tympani,  so  small  and  delicate,  and  yet  so  susceptible  to  such  an 
immense  number  and  variety  of  sounds.  But  little  imagination  is 
required  to  picture  to  one's  self,  during  the  performance  of  an  opera, 
the  sonorous  Avaves  floAving  across  the  auditorium,  and  breaking  upon 
the  drum  of  the  ear  like  those  of  the  ocean  upon  some  weather-beaten 
rock  or  beach,  the  long  waves,  from  35  to  12  feet  in  length  proceeding 
from  the  deep  bass  instruments  and  voices  of  the  bassos  like  billows 
from  the  distant  sea,  the  short  ones  from  30.3  inches  in  length,  like 
ripples  or  white  caps,  from  the  violins,  flutes,  and  voices  of  the  tenors 
and  sopranos,  with  intermediate  ones  of  different  lengths,  and  yet  all 
following  each  other  in  such  orderly  mathematical  sequence  that,  amidst 
such  a  variety  of  sounds,  Ave  are  conscious  of  nothing  but  melodious  and 
harmonious  tones.  From  the  fact  of  our  being  able  to  appreciate  the 
latter,  it  is  obvious  that  the  tympanic  membrane  is  susceptible  of  being 


862  FUNCTIONS    OF    THE    MIDDLE    EAR. 

impressed  by  simultaneous  as  well  as  by  successive  sounds,  and  while 
the  limits  of  this  work  do  not  permit  of  any  consideration  of  harmony, 
discord,  of  cords,  of  consonant  intervals,  or  those  that  give  the  ear  a 
sense  of  relief,  or  dissonant  ones  that  must  be  resolved,  etc.,  it  seems 
proper  to  point  out  and  illustrate  the  fact  that  the  vibrations  to  which 
harmonious  sounds  are  due  are  in  a  definite  ratio  to  each  other,  and, 
that,  whatever  the  cause  may  be,  sounds  are  harmonious  in  proportion 
as  the  ratio  between  the  number  of  the  vibrations  giving  rise  to  them 
is  a  simple  one. 

The  simplest  ratio  being  one  to  one,  two  sounds,  as  produced  by  the 
siren,  for  example,  will  be  in  perfect  union,  if  the  pitch  of  both  be  the 
same.  The  next  simplest  ratio  being  1  to  2,  a  harmonious  sound  will 
remain,  if  with  the  fundamental  its  first  overtone  above,  or  octave,  be 
at  the  same  time  given — that  is,  if  with  Ut3  C3  256  vibrations  per 
second,  Ut4,  C4  512  vibrations  per  second  be  also  sounded.  The  waves, 
never  interfering  with  each  other,  will  give  rise  to  no  discord,  and  the 
two  sounds  blended  into  one  may  be  continued  indefinitely.  Proceed- 
ing in  the  same  manner,  according  to  the  simplicity  of  the  ratio,  the 
next  in  order  will  be  that  of  2  to  3,  or  C  to  G — that  is,  with  Ut3  C3 
256  vibrations  per  second,  So?  G3  384  vibrations  per  second  may  be 
sounded ;  for  there  being  for  every  two  waves  of  C  three  waves  of  G, 
there  will  be  a  coincidence  for  every  second  wave  of  C  and  every  third 
wave  of  G.  The  next  ratio  being  that  of  3  to  4,  or  C  and  F,  C3  and  F3 
Fa3,  341.3  vibrations  per  second,  may  be  sounded  together.  Although 
we  have  already  shown  by  the  siren  that  the  sounding  of  the  notes  C  E 
G,  together,  give  rise  to  the  harmonious  major  chord,  nevertheless, 
according  to  the  law  that  the  smaller  the  ratio  of  vibration  between  dif- 
ferent sounds  the  more  perfect  the  harmony,  the  combination  of  C  with 
E — that  is,  in  the  ratio  of  4  to  5,  or,  as  in  the  above,  of  256  to  320 — is 
a  less  pleasing  one  than  that  of  C  to  F,  in  which  the  ratio  is  3  to  4.  It 
is  the  want  of  harmony  of  F  with  G  that  excludes  it  from  the  cord 
C  E  G  C;  the  cord  C  F  A  C  is,  however,  a  harmonious  one.  Continuing 
the  next  ratio,  that  of  6  to  5,  or  of  C  to  E  flat,  a  minor  third,  consist- 
ently with  its  ratio,  being  less  simple  than  that  obtaining  in  the  major 
third,  is  a  less  harmonious  one.  Finally,  as  illustrating  a  step  further 
the  law  just  enumerated,  it  may  be  mentioned,  though  well  known,  that 
the  interval  corresponding  to  a  tone  in  which  the  vibrations  giving  rise 
to  the  two  notes  C3  D3,  for  example,  are  in  the  ratio  8  to  9,  256  to  288 
is  a  dissonant  one,  and  that  the  interval  of  a  semitone  C  to  D  flat,  in 
which  the  ratio  is  15  to  16,  is  a  very  sharp,  grating,  and  dissonant  one. 
About  five  hundred  years  before  our  era1  it  was  shown  by  Pythagoras 
that  if  a  stretched  string  was  so  divided  into  two  parts  that  one  was  twice 
the  length  of  the  other,  and  the  two  parts  of  the  string  sounded  simulta- 
neously, that  the  note  emitted  by  the  short  part  was  the  octave  emitted 
by  the  long  one.  Continuing  to  experiment,  this  celebrated  philosopher 
next  showed  that  if  the  string  be  divided  in  the  ratio  of  2  to  3  then 
the  interval  between  the  notes  emitted  would  be  that  of  a  fifth;  and 
further,  that,  according  to  the  ratio  in  which  the  string  was  divided,  the 

1  Montucla  :  Hist,  des  Mathematiques,  Paris,  An.  vii.  tome  i.  p.  114. 


1st. 

2d. 

3d. 

«h. 

5th. 

Gth. 

7th. 

8th. 

c 

D 

E 

F 

G 

A 

B 

C 

1 

256 

8 

288 

4 

320 

3 
4 

341 

i 
384 

.3  " 

426 

8 

480 

i 

512 

FUNCTIONS    OF    THE     MIDDLE    EAE.  863 

remaining  more  or  less  consonant  intervals  would  be  heard  (Table 
LXXXIL),  the  harmony  of  the  two  sounds  being-  proportional  to  the 
simplicity  of  the  ratio  of  the  two  parts  into  which  the  string  was  divided. 

Table  LXXXIL 

1st. 

Note  .... 
Lengths  of  the  string, 
Number  of  vibrations, 

This  important  law,  the  first  step  made  in  the  physical  explanation  of 
musical  intervals,  Pythagoras,  however,  did  not  account  for,  it  remaining 
for  later  investigators  to  show  that  the  vibrations  of  strings  are  inversely 
proportional  to  their  lengths.  It  has  just  been  mentioned  that  while 
the  combination  of  a  fundamental  tone  with  its  octave,  for  example,  is 
a  consonant,  pleasing  one,  giving  rise  to  no  discord,  that  of  the  interval 
of  a  tone,  or  of  a  semitone,  is  a  dissonant,  disagreeable,  discordant  one. 
It  remains  for  us  now,  therefore,  to  determine,  if  possible,  the  physical 
cause  of  discord.  It  will  be  remembered  that  in  the  double  siren  of 
Helmholtz  there  are  two  series  of  12  orifices,  each  common  to  both 
sirens ;  such  being  the  case,  if  both  these  series  of  orifices  are  opened 
and  air  forced  through  the  instrument,  the  two  sounds  produced  will  be 
in  unison,  and  will  continue  so,  since  the  pitch  of  both  will  be  the  same 
however  low  or  high  the  sound  may  be.  In  describing  the  double  siren 
attention  was  also  called  to  the  fact  that,  by  turning  the  handle  of  the 
upper  siren  the  orifices  of  the  wind  chest  will  either  meet  or  retreat 
from  those  of  its  retreating  disk,  the  pitch  of  the  upper  siren  rising  or 
falling  accordingly.  But  the  relation  of  the  rotation  of  the  handle  to 
that  of  the  upper  wind  chest  is  such  that  if  the  handle  be  turned  through 
45  degrees  the  wind  chest  turns  through  15  degrees,  or  through  the  ^jth 
of  its  circumference,  which  causes  the  orifices  of  the  upper  wind  chest  to 
be  closed  at  exactly  the  same  moment  that  the  12  orifices  of  the  lower 
wind  chest  are  opened,  and  vice  versa,  the  effect  of  which  is  that  the 
intervals  between  the  puffs  of  the  lower  siren — that  is,  the  rarefactions 
of  its  sonorous  waves — will  be  filled  up  by  the  puffs  or  condensations  of 
the  waves  of  the  upper  one.  But  if  the  condensation  of  the  one  set  of 
sonorous  waves  coincides  with  the  rarefactions  of  the  other,  set  there  will 
be  neither  condensation  nor  rarefaction,  upon  which  all  sound  depends, 
the  fundamental  sounds  of  the  siren  will  be  extinguished  through  the 
interference  of  the  two  sounds,  as  it  is  called,  and  absolute  silence  would 
result  were  it  not  for  the  presence  of  the  overtones  of  the  siren.  Ro- 
tating, however,  the  wind  chest  through  30  degrees,  or  the  y^th  of  its 
circumference,  by  turning  the  handle  through  90  degrees,  the  puffs  or 
condensations  of  the  sonorous  waves  of  the  lower  siren  will  coincide  with 
those  of  the  upper  one,  reinforcing  the  latter;  and  as  this  latter  takes  place 
once  for  each  90  degrees,  there  will  be  4  of  these  reinforcings,  or  beats, 
as  they  are  called,  for  every  360  degrees,  or  for  one  rotation  of  the  handle. 

The  change  in  the  pitch  of  the  sound  emitted  by  the  upper  siren 
induced  by  the  rotating  of  the  handle,  the  pitch  of  the  sound  emitted 
by   the  lower  siren   remaining  the  same,  gives  rise  then  to  beats  of 


864  FUNCTIONS    OF     THE    MIDDLE    EAR. 

which  there  will  be  four  for  every  one  rotation  of  the  handle.  For  a 
time,  however,  there  may  be  heard  twelve  or  eight  beats;  when  such  is 
the  case,  it  is  due  to  the  strength  of  the  second  or  first  overtone  being 
sufficient  to  overpower  the  fundamental,  which  vibrating  three  times 
and  twice  as  rapidly  as  the  fundamental,  will,  of  course,  give  rise  to 
three  times,  or  twice  as  many  beats.  It  is  through  the  presence  of 
these  overtones  that,  though  the  tone  of  the  fundamental  may  swell  or 
sink  as  the  handle  is  turned,  sound  is  still  heard,  even  though  the 
handle  reach  the  position  at  which  the  fundamental  sound  through 
interference  is  extinguished.  Beats  can  be  readily  produced  by  tuning 
forks  which  are  especially  suited  for  this  purpose,  no  overtones  being 
generated  if  the  forks  be  properly  toned.  Let  us  suppose,  for  example, 
that  of  two  standard  tuning  forks  Ut3,  each  giving  256  vibrations  per 
second,  and  whose  sounds  are  therefore  in  unison,  one  of  which  be 
weighted  just  sufficiently  to  cause  it  to  vibrate  a  little  more  slowly 
than  the  other,  say  255  times.  The  two  sounds  then  emitted  will 
no  longer  flow  on  continuously  in  unison,  there  being  now  alternate 
diminutions  and  reinforcements  of  the  sound  or  beats,  and  in  this 
particular  case  one  beat  per  second,  which,  it  will  be  observed,  is  exactly 
the  difference  between  the  tAvo  rates  of  vibration  of  the  two  forks,  256 
and  255.  A  moment's  reflection  will  make  it  clear  why  the  beats  should 
occur,  and  at  such  a  rate.  Since  the  one  fork  vibrates  256  times  in  a 
second,  and  the  other  255  times,  it  is  evident  that  at  the  end  of  the 
second  the  wave  of  the  latter  fork  will  be  one  vibration  behind  that  of 
the  former,  and  at  the  end  of  the  half  second  a  half  a  wave  behind, 
the  one  fork  having  made  128  vibrations,  the  other  127|,  but  at  that 
moment  the  condensation  of  the  one  wave  coinciding  with  the  rarefac- 
tion of  the  other,  the  sounds  will  be  extinguished  through  their  com- 
plete  interference  with  each  other.  From  the  half  of  the  second 
onward,  however,  until  the  end  of  the  second,  the  condensations  rein- 
force each  other  more  and  more,  until  at  the  end  of  the  256th  vibra- 
tion of  the  one  fork,  and  the  255th  of  the  other  condensation  coincides 
with  condensation,  and  rarefaction  with  refraction,  the  full  effect  of 
both  sounds  being  then  experienced.  Similarly,  from  the  half  second 
where  the  interference  is  complete  backward  to  the  beginning  of  the 
second,  condensation  coincides  more  and  more  with  condensation,  rare- 
faction with  rarefaction,  until  at  the  beginning  of  the  second,  of  course, 
as  at  the  end,  the  coincidence  is  complete.  Suppose,  however,  that  the 
two  forks  vibrate  240  and  234  times  a  second,  then  at  the  end  of  the 
first  £th  of  a  second,  one  fork  will  have  generated  40  sonorous  waves, 
the  other  39,  the  one  wave  being  one  vibration  ahead  of  the  other, 
and  therefore,  at  the  end  of  the  y^th  of  a  second  half,  a  vibration 
ahead.  This  instant  being,  however,  that  at  which  interference  is  com- 
plete, during  which  the  sound  is  extinguished,  the  time  elapsing  on  the 
one  hand  between  it,  or  the  yV^n  °^*  ^ne  seconcl,  ar*d  the  beginning  of 
the  second,  and  on  the  other  to  the  end  of  the  Jth  of  the  second,  will 
be  characterized,  as  in  the  preceding  case,  by  a  gradual  diminution, 
followed  by  a  gradual  augmentation  of  the  sound  or  one  beat ;  but  as 
this  is  repeated  in  this  case  six  times  during  the  second,  there  will  be 
six  beats,  which,  it  will  be  observed,  is  exactly  the  difference  between 


FUNCTIONS    OF    THE    MIDDLE    EAR.  865 

the  two  rates  of  the  forks,  240  and  234.  Experimenting  this  way 
with  forks,  pipes,  etc.,  it  can  be  proved  that  the  number  of  beats  per 
second  is  always  ecpual  to  the  difference  between  the  rates  of  vibration 
of  the  two  sounds  to  whose  interference  they  are  due.  Now  it  has 
been  shown  by  Helmholtz  that  if  the  beats  per  second  succeed  each 
other  less  rapidly  than  33  per  second,  the  sound  is  not  disagree- 
able, but  if  at  that  rate,  the  dissonance  becomes  then  absolutely 
intolerable.  As  the  number  of  beats  per  second,  however,  increases, 
the  dissonance  diminishes,  and  when  the  beats  have  reached  the  rate  of 
132  a  second,  they  disappear  and  discord  vanishes.  Beats  are  there- 
fore the  cause  of  dissonance  or  discord,  and  intervals  free  from  them 
will  be  harmonious.  Thus  the  fundamental,  due,  for  example,  to  256 
vibrations  per  second,  when  continued  with  its  octave  due  to  512  vibra- 
tions is  a  harmonious  one,  free  from  beats,  since  the  difference  in  the 
rate  of  vibration,  or  256,  is  too  high  to  admit  of  them.  The  interval 
of  the  fifth  C  and  G  is  still  harmonious,  the  difference  in  the  rate  of 
vibration,  384 — 256=128,  being  also  too  high.  On  the  other  hand,  the 
interval  of  the  fourth  C  and  F  due  to  341  and  256  vibrations  per 
second,  respectively,  is  somewhat  dissonant,  the  difference  between 
the  rates  of  vibration  being  59,  admitting,  therefore,  of  that  number 
of  beats  below  the  limits  at  which  discord  vanishes ;  and  the  interval 
of  C  and  E  more  dissonant  still,  the  difference  in  their  rates  of 
vibration  being  64,  the  notes  being  due  to  256  and  320  vibrations  per 
second,  respectively.  It  should  be  mentioned  in  this  connection,  in 
order  to  avoid  any  misconception,  that  the  phenomenon  of  beats  is  of  an 
entirely  different  nature  from  that  of  the  resultant  tones  discovered  by 
Sorge,  Sartini,  and  Helmholtz.  That  resultant  tones  should  ever  have 
been  considered  as  identical  with  beats,  is  not  so  strange,  since  the 
rate  of  vibration  of  the  first  difference  tone,  or  the  loudest  resultant 
tones  like  that  of  beats,  is  equal  to  the  difference  in  the  rates  of  vibra- 
tions of  the  two  primary  sounds  producing  them,  which  led  the 
celebrated  Young  to  regard  resultant  tones  as  due  to  the  linking 
together  of  rapidly  recurring  beats.  Resultant  tones  are,  however, 
produced  in  a  totally  different  manner  from  beats,  being  due  to  the 
continuation  of  the  secondaiy  waves  generated  when  the  vibrations 
giving  rise  to  the  two  sounds  producing  them  are  so  intense  as  to  exceed 
the  ordinary  law  of  the  superposition  of  vibrations.  That  a  resultant 
tone  is  not  made  up  of  beats,  is  shown  by  the  fact  that  while  a  resultant 
tone  due  to  thirty-three  vibrations  per  second  is  smooth,  consonant, 
musical  beats  succeeding  each  other  at  that  rate,  as  already  mentioned, 
are  most  dissonant. 

In  concluding  this  necessary  digression  upon  the  nature  of  musical 
intervals,  discords,  beats,  resultant  tones,  etc.,  it  must  be  observed  that 
whether  they  are  caused  in  the  manner  indicated,  or  however  they  may 
be  accounted  for  physically,  hereafter,  in  any  case,  no  explanation  what- 
ever is  offered  why  one  rate  of  vibration  should  affect  us  agreeably,  and 
another  rate  disagreeably — that  is,  if  sounds  are  harmonious  through  the 
absence  of  discords,  why  should  the  presence  of  the  latter  give  rise  in 
us  to  a  sense  of  discomfort,  dissonance'.''  Nor  have  we  any  reason  to 
hope,  judging  from  the  past,  that  the  study  of  mere  acoustics  will  ever 


866  STRUCTURE    OF    THE    INTERNAL    EAR. 

throw  any  light  upon  our  sensations  of  tone  subjectively,  or  contribute 
to  the  progress  of  music  objectively.  Indeed,  it  appears  to  be  generally- 
forgotten  by  the  cultivators  of  harmony,  that  the  best  music  was  com- 
posed when  acoustics  was  in  its  infancy,  to  this  day,  the  best  illustration 
of  theoretical  harmony  being  taken  from  theAvorks  of  Mozart,  Handel, 
Haydn,  and  that  according  to  one  of  the  latest  and  highest  authorities1 
the  science  of  sound  has  "  not  added  one  cord  or  progression  that  was  not 
known  to  Bach."  Remarkable  as  are  the  properties  of  the  tympanic 
membrane,  and  essential  as  it  is  undoubtedly  in  normal  hearing,  when 
it  is  remembered  that  it,  together  with  the  remaining  part  of  the  middle 
as  well  as  the  external  ear,  is  only  the  intermediate  means  by  which 
the  terminal  filaments  of  the  auditory  nerve  are  excited,  it  becomes 
intelligible  why  after  the  rupture  or  even  absence  of  both  membranes, 
hearing,  though  impaired,  and  appreciation  of  musical  sounds  are  still 
possible.  The  innumerable  and  different  kind  of  sonorous  waves  im- 
pinging upon  the  tympanic  membrane  and  throwing  it  into  vibration  to 
be  appreciated  in  consciousness  as  sounds,  must  be  thence  conducted  to 
the  vestibule  of  the  internal  ear.  This  is  accomplished  by  the  chain  of 
ear  bones  stretching  across  the  tympanum  from  the  tympanic  membrane 
to  the  foramen  ovale  of  the  vestibule.  The  ear  bones,  while  three  in 
number,  in  point  of  fact  may  be  regarded  physiologically  as  being 
equivalent  to  one  long  bone,  vibrating  to  and  fro  with  the  tympanic 
membrane.  That  such  is  the  case  is  not  only  shown  by  the  manner  in 
which  the  bones  are  articulated  with  each  other,  but  from  the  fact  that 
in  the  lower  vertebrates  the  homologue  of  the  stapes  is  a  long  rod-like 
bone,  passing  from  the  tympanic  membrane  to  the  vestibule,  the  homo- 
logue of  the  incus  and  malleus  not  being  situated  within  the  tympanum, 
but  outside  of  it,  entering  into  the  formation  of  the  lower  jaw.  That 
the  stapes  is  pressed  against  the  liquid  of  the  vestibule  by  the  move- 
ment of  the  tympanic  membrane  and  ear  bones  can  be  shown  experiment- 
ally, as  by  Helmholtz,  by  fitting  a  slender  glass  tube  into  the  semicircular 
canal  and  filling  the  vestibule  and  part  of  the  tube  with  water,  when, 
through  the  forcing  of  the  tympanic  membrane  inward,  the  water  will 
be  seen  to  rise  nearly  the  ^ij-th  °f  an  incn-  On  the  other  hand,  the 
risk  of  tearing  away  the  stapes  from  its  attachment  to  the  foramen  ovale 
during  the  outward  movement  of  the  tympanic  membrane  is  avoided 
through  the  cog-like  joint  between  the  malleus  and  the  incus  being 
loosened,  no  very  great  traction  being  then  exerted  upon  the  stapes.  The 
movement  upon  the  tympanic  membrane  and  ear  bones  can  be  graphi- 
cally studied,  and  recorded,  as  by  Koenig,2  by  attaching  a  style  to  the 
incus  or  malleus,  the  tympanic  membrane  being  thrown  into  vibration 
by  two  organ  pipes,  and  the  sound  of  the  latter  reinforced  by  a  resonator. 

Structure  of  the  Internal  Ear. 

The  internal  ear  includes  the  labyrinth  and  the  auditory  nerve.  The 
labyrinth,  so-called  on  account  of  its  highly  complex  structure,  consists 
of  the  vestibule,  semicircular  canals,  and  cochlea.     Though  these  parts 

l  nnjrli  A.  Clarke  :  narmony  mi  the  induction  Method,     Phil.,  1880. 
"  Quelques  :  Exiieriem.es  d'Acouatique,  p.  2d.     Paris,  1882. 


STRUCTUEE    OF    THE    INTERNAL    EAR.  867 

are  imbedded  in  the  petrous  portion  of  the  temporal  bone,  their  osseous 
walls  are  independent  of  the  bony  structure  of  the  latter.  This  is  well 
seen  at  birth,  when  the  whole  labyrinth  can  be  readily  excavated  from 

Fig.  525. 


1,  _', 3.  Turns  of  cochlea.     4.  Fenestra  rotunda.     5.  Fenestra  ovalis.     8,  9,  10.  Posterior  semicircular  canal. 
11.  Superior  semicircular  canal.     12.  External  or  horizontal  semiciicular  canal. 

the  surrounding  loose  osseous  substance.  The  vestibule,  situated 
between  the  tympanum  and  the  internal  auditory  meatus,  is  a  somewhat 
oval-shaped  cavity  about  the  Ath  of  an  inch  in  diameter,  passing  postero- 
externally  into  the  semicircular  canals,  and  antero-internally  into  the 
cochlea,  and  communicating  with  the  tympanum  by  the  foramen  ovale. 
The  semicircular  canals,  so  called  on  account  of  their  form,  are  three  in 
number  and  are  named  from  their  position  superior,  posterior,  and 
inferior,  or  external,  the  two  former  being  disposed  vertically,  the  latter 
horizontally,  Each  semicircular  canal  expands  at  one  extremity  into  a 
bottle-like  dilatation,  the  ampulla,  which  communicates  with  the  vesti- 
bule. Of  the  undilated  extremities  two  unite,  and  then  with  the 
remaining  one  also  open  into  the  vestibule.  The  three  semicircular 
canals  thus  communicate  with  the  vestibule  by  five  orifices.  The  vesti- 
bule, semicircular  canals,  and  cochlea  as  well,  are  lined  throughout 
with  a  thin  periosteal  membrane,  which  in  passing  over  the  foramen 
ovale  and  foramen  rotundum  thereby  close  these  orifices.  Within  the 
cavity  of  this  membrane  is  found  a  serous-like  fluid,  the  liquor  cotemnii 
or  perilymph  of  Breschet,  an  appropriate  name  on  account  of  its  sur- 
rounding the  membranous  labyrinth  also  containing  a  similar  fluid,  the 
endolymph  of  Breschet  or  liquor  of  Scarpa.  The  membranous  laby- 
rinth, so  called  on  account  of  its  membranous  structure,  and  receiving 
the  terminal  filaments  of  the  internal  auditory  nerve,  floats  in  the  peri- 
lymph within  the  bony  labyrinth,  with  the  walls  of  which  it  is  more  or 
less  connected  by  delicate  fibrous  bands.  The  membranous  labyrinth, 
like  the  osseous,  consists  of  three  parts,  vestibule,  semicircular  canals. 


868 


STRUCTURE  OF  THE  INTERNAL  EAR. 


Fig.  526. 


Membranous  labyrinth.  Cs.  Semicircular 
canals.  U.  Utriculus.  S.  Sacculus.  A.  Aque- 
duct of  vestibule.  Or.  Ductus  reuniens.  Co. 
Cochlea. 


and  cochlea.     The  membranous  vestibule  (Fig.  526),  however,  is  com- 
posed of   two  distinct  sacs  or  pouches,  the  utriculus  (U)  and  sacculus 

(S),  the  former  of  which,  the  larger, 
occupies  the  hemi-elliptical  fossa  of 
the  bony  vestibule,  and  gives  off 
three  membranous  semicircular 
canals,  the  latter,  the  smaller,  the 
hemispherical  fossa  and  gives  off 
through  a  narrow  duct  the  mem- 
branous cochlea. 

The  saccuMs  and  utriculus,  while 
not  communicating  directly,  do  so 
indirectly  through  the  membranous 
aqueduct  (A)  of  the  vestibule,  the 
latter  being  formed  through  union  of 
the  small  ducts  proceeding  from  the  sacculus  and  utriculus,  respectively. 
Adhering  to  the  inner  surface  of  both  the  utriculus  and  sacculus,  may  be 
seen  white,  discoidal  masses,  consisting  of  minute  crystalline  particles  of 
calcium  carbonate,  the  so-called  otoliths  or  otocoma.  The  membranous, 
semicircular  canals,  about  one-third  of  the  diameter  of  the  osseous  ones,  in 
the  perilymph  of  which  they  float,  resemble  the  latter  in  form  and  general 
disposition,  being  three  in  number,  disposed  superiorly,  vertically,  and 
horizontally,  expanding  into  ampullae,  and  communicating  with  the 
membranous  vestibule  by  five  orifices.  The  membranous  vestibule  and 
semicircular  canals,  consisting  of  three  layers,  an  outer  fibrous,  an  inner 
epithelial,  and  an  intermediate  membrana  propria,  receive,  as  already 
mentioned,  the  terminal  filaments  of  the  vestibular  branch  of  the  internal 
auditory  nerve.  The  latter  divides  at  the  bottom  of  the  internal  audi- 
tory meatus  into  three  branches,  the  first  of  which,  passing  through  the 
pyramidal  eminence  of  the  bony  vestibule  at  the  superior  cribriform  spot, 
is  distributed  to  the  utriculus  and  ampullae  of  the  superior  and  inferior 
or  horizontal  semicircular  canals;  the  second  passing  through  the  hemi- 
spherical fossa  at  the  middle  cribriform  spot,  is  distributed  to  the  sacculus ; 
and  the  third  through  the  ampulla  of  the  bony  posterior  semicircular 
canal  at  the  inferior  cribriform  spot,  to  the  ampulla  of  the  membranous 
posterior  semicircular  canal.  Just  in  those  situations  where  the  nerve 
fibres  penetrate  the  membranous  vestibule  (macula  acustica)  and  the 
membranous  semicircular  canals  (crista  acustica),  their  outer  or  fibrous 
layer  is  intimately  associated  through  connective  tissue  with  the  bony 
wall  of  the  vestibule  and  canals,  the  perilymph  being  here  absent.  The 
ultimate  nerve  fibres  having  passed  through  the  membranous  vestibule 
and  canals,  finally  terminate  in  what  may  be  called  the  auditory  epithe- 
lium, which  appears  to  consist  essentially  of  columnar  cells  inter- 
mixed with  spindle-shaped  ones  supporting  long,  firm  bristles,  the 
auditory  hairs  (Fig.  527),  which  penetrate  into  the  soft  otolith  mass 
supporting  the  otoliths  and  the  endolymph.  Up  to  the  present  moment, 
in  order  to  prevent  confusion,  we  have  purposely  avoided  mentioning, 
except  incidentally,  the  bony  or  membranous  cochlea,  and  yet  it  will  be 
found  that  the  cochlea,  though,  at  first  sight,  resembling  but  little  a 
semicircular  canal,  consists,  like  the  latter,  of  a  bony  tube  enclosing  and 
attached  to  a  membranous  one,  the  latter  floating  in  perilymph  and  con- 


STRUCTURE    OF    THE    INTERNAL    EAR. 


869 


taining  endolymph.  For  simplicity  sake,  let  us,  in  considering  the 
structure  of  the  cochlea,  begin  by  disabusing  our  minds  of  it  being  a 
coiled  tube,  and  regard  it  as  a  straight  one,  as  it  is  throughout  its  whole 


Fig.  527. 


Diagram  of  the  auditory  epithelium,  and  the  mode  of  termination  of  the  nerves  of  the  ampulla;. 
6.  Spindle-shaped  cells,  each  supporting  an  auditory  hair  (8).  7.  Basal  supporting  cells.  3,4.  Nerve 
fibre  passing   through  the  tunica  propria  to  join  the  plexus  in  the  epithelium.     (M.  Schultze.) 


Fig.  528. 


Section  through  one  of  the  roils  of  the  cochlea,  diagrammatic  Mag.  3n.  ST.  Scala tympani.  SV. 
Scala  vetitibuli  C  C.^Canalis  cochleae.  1.  Membrane  of  Reissner  forming  its  vestibular  wall.  «.  Limlms 
laminae  spiralis.  6.  Sulcus  spiralis.  3.  Cochlear  nerve,  mc.  Membrana  tectoria.  mb.  Meuibrana  basilaris. 
d  e.  Rods  of  Corti.     4.  Ligamentum  spirale. 


870  STRUCTURE    OF    THE    INTERNAL    EAR. 

length  in  birds,  and  at  its  commencement  in  man  ;  and  further,  let  us 
begin  our  description  of  its  structure  by  supposing  that  we  are  viewing 
the  cochlea  at  its  commencement  in  transverse  section,  as  obtained  by 
dividing  the  vestibule  along  the  line  passing  over  9  (Fig.  525),  and  look- 
ing at  the  cochlear  portion  of  the  section  endwise,  as  represented  in 
Fig.  528.  Looking  at  the  cochlea  from  such  a  point  of  view,  it  will  be 
seen  to  consist  of  a  bony  tube,  divided  by  a  septum  partly  bony  (lamina 
ossea),  partly  membranous,  into  an  outer  and  inner  space,  the  latter 
communicating  through  the  foramen  rotundum  with  the  tympanum, 
and  called,  therefore,  the  scala  tympani  ;  the  former  continuous  with 
the  bony  cavity  of  the  vestibule,  and  communicating,  therefore,  indi- 
rectly through  the  foramen  ovale  with  the  tympanum,  and  called  the 
scala  vestibuli.  This  may  be  at  once  shown  by  readjusting  the  cochlear 
portion  of  the  section  that  we  have  just  been  considering  to  the 
remaining  portion  of  the  bony  labyrinth,  and  passing  bristles  through 
the  foramen  rotundum  and  ovale,  supposing  the  membrane  passing 
across  this  opening  and  the  stapes  be  removed.  Conceiving,  however, 
that  the  cochlea  be  a  straight  tube,  and  supposing  it  to  be  divided  longi- 
tudinally, it  will  be  found  that  the  bony,  membranous  partition  (Fig. 
529)  is  absent  at  the  end  of  the  cochlea  (helicotrema),  the  end  opposite 
to  the  vestibule,  the  consequence  of  which  is  that  the  bristles  just  passed 
through  the  foramen  ovale  from  the  tympanum,  if  continued  onward, 
after  traversing  the  scala  vestibuli,  will  pass  at  the  end  of  the  cochlea 
into  the  scala  tympani,  and  thence,  through  the  foramen  rotundum, 
reach  the  tympanum.  Such  being  the  relations  of  the  scala  vestibuli 
and  scala  tympani  to  each  other  and  to  the  vestibule   on  the  one  hand, 

Fig.  529. 


Diagrammatic  view  of  the  relative  position  of  the  parts  of  the  ear.  EM.  External  meatus,  Ty  M.  Tym- 
panic memlirane.  "Vij.  Tympanum.  M.  Malleus.  I.  Incus.  S.  Stapes  R.  Round  window.  0.  Oval  window 
S  G.  Semicircular  canal.  U.  Utriculus.  S.  Sacculus.  V.  Vestibule.  SV.  Scala  vestibula.  ST.  Scala 
tympani.     MC  Membranous  cochlea.    L  S.  Lamina  ossea.    Em.  Eustachian  tube.    A  N.  Auditory  nerve. 

and  to  the  tympanum  on  the  other,  on  the  supposition  that  the  cochlea 
is  a  straight  tube,  it  is  obvious  that  if  the  latter  be  turned  two  and  a  half 
times  upon  itself  around  an  axis  or  modiolus  from  right  to  left  in  the 
right  ear,  and  the  reverse  in  the  left,  the  apex  being  situated  downward, 


STRUCTURE    OF    THE     INTERNAL    EAR 


871 


Fig.  530. 


forward,  and  outward,  that  the  above  relations  will  not  in  any  way  be 
essentially  changed.  From  an  inspection  of  Fig.  528,  representing 
the  cochlea  in  transverse  section,  it  will  be  observed,  however,  that  the 
membranous  portion  of  the  septum  dividing  the  interior  of  the  cochlea 
into  the  scala  vestibuli  and  scala  tympani,  and  attached  to  the  osseous 
wall  by  the  ligamentum  spirali,  consists  of  two  layers,  a  basilar  mem- 
brane, and  a  tectonal  membrane,  a  space  intervening  between  the  two, 
and  that  just  at  the  point  where  the  tectonal  membrane  is  attached  to 
the  osseous  lamina,  which  in  the  coiled  tube  is,  of  course,  spirally  dis- 
posed, a  third  membrane,  the  membrane  of  Reissner,  passes  obliquely 
across  to  the  outer  osseous  wall. 

As  a  matter  of  fact,  however,  in  nature,  at  both  ends  of  the  cochlea, 
through  the  space  intervening  between  the  basilar  and  Reissner  mem- 
branes, being  covered  in  by  membrane,  the  vestibular  scala  is  separated 
from  the  tympanic  scala  by  a  membranous  tube  which  is  given  oif  by 
the  membranous  sacculus  (Fig.  529)  through  the  ductus  reuniens  n,  just 
as  the  membranous  semicircular  canals  are  given  off  by  the  utriculus, 
the  other  end  of  the  membranous  coch- 
lear tube  being  attached  by  its  pointed 
blind  extremity  to  the  wall  of  the  cupola, 
the  latter  partly  bounding  the  helico- 
trema.  And  just  as  the  membranous 
semicircular  canal,  filled  with  endolymph 
and  floating  in  perilymph,  is  attached  to 
the  wall  of  the  bony  semicircular  canal, 
so  is  the  membranous  cochlea,  filled  with 
endolymph  and  floating  in  perilymph, 
attached  to  the  wall  of  the  bony  cochlea, 
the  membranous  cochlea,  however,  being 
spirally  disposed  like  the  bony  cochlea  enclosing  it  (Fig.  530).  The 
membranous  cochlea  differs,  however,  from  the  membranous  semicircular 
canal,  not  only  in  being  coiled  upon  itself,  but  in  the  highly  complex 
character  of  the  structures  lying  in  the  space  intervening  between  the 
basilar  and  tectonal  membranes,  known  as  the  rods  of  Corti,  which 
receive  the  terminal  filaments  of  the  cochlear  branch  of  the  internal 
auditory  nerve. 

The  rods  of  Corti  are  stiff,  rod-like  bodies,  disposed  in  two  sets,  an 
inner  set  and  an  outer  set ;  the  inner  numbering  about  6000,  the 
outer  about  4500.  The  inner  rods  being  inclined  outwardly,  and  the 
outer  rods  inwardly,  the  two  sets  of  rods  meet  at  their  heads,  the  space 
between  the  rods — that  is,  between  the  latter  and  the  basilar  membrane — 
being  known  as  the  canal  of  Corti.  The  inner  rods  support  on  their 
inner  surface  one  row  of  epithelial  cells,  the  inner  hair  cells,  so  called, 
on  account  of  their  terminating  in  short,  stiff  hairs;  the  outer  rods  on 
their  outer  surface  three  or  four  rows  of  similar  cells,  though  somewhat 
more  elongated  than  the  outer  hair  cells.  The  hairs  of  the  latter  pass 
through  ring-like  structures,  the  reticulum,  attached  to  the  heads  of  the 
outer  rods.  Both  the  outer  and  outer  hair  cells,  in  all  probability, 
receive,  directly  or  indirectly,  the  terminal  filaments  of  the  cochlear 
nerve  (Fig.  53i).  The  latter,  after  passing  through  the  foramina  of  the 
spiral  tract  at  the  bottom  of  the  internal  auditory  meatus,  ascend  through 


Diagrammatic  view  of  the  osseous  coch- 
lea laid  open.  1.  Modiolus  or  central  pillar. 
2.  Placed  on  three  turns  of  the  lamina  spir- 
alis. 3.  Scala  tympaui.  4.  Scala  vestibuli. 


ri 


STRUCTURE    OF    THE    INTERNAL    EAR. 


Fid.  Wl. 


or-  yuLtSiil^HI 


sp.  I. 


h.i.\h 


i.r. 

n     I 


l.r. 


e.r.  v\i 

f  ' 


1  ii 


Semi-diagrammatic  view  of  part  of  the  basilar  mem- 
brane and  tunnel  of  Corti  of  tho  rabbit,  from  above  and 
the  side.  Much  magnified.  I.  Limbus.  Or.  Extremity 
or  crest  of  limbus  with  teeth-like  projections,  b,  b. 
Basilar  membrane,  p.  Perforations  for  transmission  of 
nerve  fibres  N,  which  are  represented  at  the  lower  part 
of  the  figure,  but  omitted  for  the  sake  of  clearness  in 
the  upper,  i,  r.  Fifteen  of  the  inner  rods  of  Corti.  h,  i. 
Their  flattened  heads  seen  from  above,  e,  r.  Isine  outer 
rods  of  Corti.  /;,  c.  Their  heads,  with  the  phalangeal 
processes  extending  outward  from  them  and  forming 
with  the  two  rows  of  phalanges,  the  lamina  reticularis. 
(,  r.  The  fibres  of  the  outer  rods  are  seen  to  be  continued 
into  the  striation  of  the  basilar  membrane,  through 
which  the  connective  tissue  fibres  and  nuclei  of  the 
undermost  laver  are  seen.  Portions  of  a  few  of  the  basilar 
processes  of  the  outer  hair-cells  remain  attached  to  the 
membrane.     (Quain  and  Sharpey.) 


the  axis  of  the  cochlea,  and  thence 
traversing  the  lamina  ossea 
spiralis  perforate  the  basilar 
membrane,  and  so  reach,  by  in- 
termediate filaments,  the  hair 
cells,  bearing  in  mind  that  the 
base  of  the  stapes  is  adherent 
to  the  periosteum  lining  the  ves- 
tibule and  covering  the  fora- 
men ovale;  it  is  evident  that 
the  vibrations  of  the  tympanic 
membrane,  in  being  transmitted 
through  the  ear  bones  to  the 
perilymph  filling  the  bony  laby- 
rinth, will  throw  into  vibration 
the  endolymph  filling  the  mem- 
branous labyrinth  and  the  hairs 
projecting  into  it,  and  conse- 
quently the  auditory  nerve,  re- 
garding, as  we  do,  the  hairs  as  the 
terminal  filaments  of  the  vesti- 
bular and  cochlear  nerves,  into 
which  the  auditory  nerve  divides 
in  the  meatus,  whence  the  vibra- 
tions, in  being  further  transmit- 
ted to  the  temporo-sphenoidal 
convolutions  of  the  cerebrum, 
give  rise  to  the  sensation  and 
perception  of  the  sound.  With 
reference  to  the  function  of  the 
membrane  covering  the  foramen 
rotundum,  the  membrana  sec- 
ondaria,  which  consists  on  the 
tympanic  side  of  the  mucous 
membrane,  and  on  the  cochlear 
of  the  periosteal  layer  lining  the 
scala  tympani  of  the  cochlea ; 
while  nothing  is  positively 
known,  in  all  probability  it  is 
pushed  outward,  as  the  stapes 
is  pushed  inward,  which  would 
obviously  be  of  advantage  in 
absorbing  some,  at  least,  of 
the  superfluous  sonorous  wave 
motion.  Such  being,  in  general, 
the  disposition  and  relation  of 
the  parts  of  which  the  internal 
ear  is  composed,  and  the  man- 
ner in  which  the  auditory  nerve 
is   distributed   to   it,    is  thrown 


STRUCTURE     OF    THE     INTERNAL    EAR.  873 

into  vibration,  it  is  to  be  expected  that  such  a  complexity  of  structure  is 
correlated  with  a  corresponding  differentiation  in  function.  As  a  matter 
of  fact,  however,  nothing  has  been  definitely  established  as  regards  the 
specific  functions  of  the  vestibule,  semicircular  canals,  and  cochlea, 
which  is  clue,  no  doubt,  to  any  exnerimental  investigation  being  so  diffi- 
cult on  account  of  the  nature  of  the  case,  and  from  the  pathological  and 
clinical  data  on  the  subject  being  so  meagre  and  unreliable  in  character. 
In  the  absence  of  such  evidence  the  facts  of  comparative  anatomy  alone 
remain  as  a  means  of  elucidating  the  functions  of  the  internal  ear.  It 
is  well  known  to  anatomists  that  the  organ  of  hearing  exists  in  the 
lower  animals  in  a  very  rudimentary  condition  ;  thus,  in  certain  of  the 
Crustacea,  for  example,  the  ear  consists  of  an  invagination  of  the  skin, 
a  cutaneous  pit  lined  with  hairs,  situated  in  the  basal  joint  of  the 
internal  antennae,  which  may  remain  open,  and  contain  particles  of 
sand,  or  may  be  closed  and  enclose  calcareous  otoliths.  A  similar 
vesicle,  lined  with  ciliated  epithelium,  and  containing  otoliths,  is  also 
found  in  the  mollusca  situated  upon  the  infra-oesophageal  portion  of  the 
nervous  collar  surrounding  the  alimentary  canal.  On  the  supposition 
that  the  vesicle  just  described  as  occurring  in  the  Crustacea  and  mol- 
lusca, and  even  in  lower  forms  of  life,  as  in  the  annelida,  hydrozoa,  etc., 
is  a  rudimentary  organ  of  hearing,  its  functions  must  be  limited  almost 
entirely  to  the  appreciation  of  the  intensity  or  loudness  of  sounds — at 
least  it  is  difficult  to  conceive  of  animals  relatively  so  lowly  organized 
being  affected  to  any  very  great  extent  by  difference  in  pitch  and 
quality.  If  such  is  the  case,  and  it  be  admitted  that  this  vesicle,  or 
otocyst  of  the  lower  animals,  is  the  homologue  of  the  vestibule  of  the 
higher,  which  the  study  of  the  development  leads  us  to  suppose,  then 
it  follows  that  the  function  of  the  vestibule  in  man  is  the  appreciation 
of  the  intensity  of  sound.  In  passing  from  the  invertebrata  to  the 
vertebrata,  and  more  particularly  to  the  fishes,  we  find,  with  the  excep- 
tion of  the  amphioxus,  in  which  the  ear  is  absent  altogether,  that  the 
organ  of  hearing  becomes  more  complex  as  we  ascend  through  the  suc- 
cessive forms  of  piscine  life.  Thus,  in  the  myxine,  the  ear  consists  of  a 
vestibule  with  one  semicircular  canal;  in  the  lamprey  of  a  vestibule 
with  twTo  semicircular  canals;  and  in  the  teliosts  of  three  with  a  rudi- 
mentary cochlea  as  well.  Now,  while  it  is  evident  that  it  would  be  of 
advantage  to  fishes  to  be  able,  not  only  to  distinguish  loud  from  low 
sounds,  but  also  the  direction  from  which  the  sounds  proceed,  the 
appreciation  of  melodious  and  harmonious  ones  would  be  of  no  use.  and 
since  the  homology  of  the  semicircular  canals  of  the  lower  vertebrates 
with  those  of  the  higher  ones  is  undoubted,  in  all  probability  our  appre- 
ciation of  the  direction  and  distance  of  sounds,  which  is  very  much  a 
matter  of  education,  is  connected  in  some  way  with  these  structures,  ex- 
periments, and  pathological  facts,  already  referred,  to  prove  conclusively 
that  injury  of  the  semicircular  canals  involves  disorders  of  equilibrium. 
To  what  extent  the  latter  are  due  to  the  hearing  being  impaired,  and  how 
much  to  the  transmission  of  the  afferent  impressions  to  the  cerebellum 
being  interfered  with,  upon  which  the  maintenance  of  equilibrium  partly 
depends,  is  difficult,  if  not  impossible,  to  determine  exactly.  By  a 
method  of  exclusion,  then,  the  inference  is  rather  forced  upon  us,  that 


874  STRUCTURE    OF    THE    INTERNAL    EAR. 

our  sensation  of  tone  depends,  in  some  way,  upon  the  cochlea,  the  struc- 
ture of  which  undoubtedly  suggests  that  its  function  is  rather  concerned 
with  the  appreciation  of  the  quality  of  sound,  a  sort  of  universal  reso- 
nator, than  with  that  of  pitch  or  intensity.  Regarding  the  rods  of 
Corti,  and  the  hair  cells  lying  upon  them,  as  so  many  piano  keys  and 
strings  appropriately  tuned,  it  is  obvious  that  it  would  analyze  sounds, 
like  our  series  of  resonators.  The  objection  to  the  above  ingenious 
view  of  Helmholtz,  that  the  cochlea  in  birds  is  very  rudimentary,  is 
not  a  necessarily  fatal  one,  since,  though  many  birds  can  sine,  it  does 
not  follow  that  their  sensations  and  ideas  of  melody  and  harmony  should 
be  as  developed  as  that  of  man  ;  on  the  contrary,  in  the  absence  of  a 
complex  brain  it  is  difficult  to  comprehend  how  they  should  have  any 
considerable  appreciation  of  musical  sound.  In  conclusion,  it  must  not 
be  forgotten  that  whatever  function,  if  any,  be  assigned  to  the  different 
parts  of  the  internal  ear,  that  the  cause  of  the  sensation  of  sound,  like 
that  of  color,  lies  in  the  brain,  and  in  its  subjective  aspect  is  as  little 
understood  in  the  one  case  as  the  other. 


CHAPTER    LIT. 


MUSCULAR  CONTRACTILITY. 


In  considering  the  subject  of  nervous  irritability,  it  will  be  remem- 
bered that  the  contraction  of  a  muscle  following  stimulation  of  the 
nerve  supplying  it,  was  taken  as  an  indication  and  measure  of  the 
changes  occurring  in  the  latter.  The  changes  undergone  by  the  muscle 
itself,  however,  during  its  contraction  remain  still  to  be  described. 
Muscles  are  of  two  kinds,  striped  and  unstriped,  of  which  the  former 
will  be  first  studied.  Striped  muscles,  such  as  the  skeletal  muscles, 
heart,  diaphragm,  etc.,  consist  of  fasciculi  or  bundles  of  fibres  separated 
by  connective  tissue,  the  latter  being  prolonged  from  the  outer  envelope 
or  perimysium  covering  the  muscle.  Each  muscular  fibre  is  a  more  or 
less  cylindrical  tube  from  3  to  4  cm.  (1.2  to  1.6  of  an  inch)  in  length, 
T^th  of  a  mm.  (y-J- 


and  between  ^th  and 


0th  and  g-^oth  of  an  inch)  in 


Fig.  532. 


i  £     f*    ■  i  i 

l  /  /     '    «  ' 


A.  Portion  of  a  medium-sized  human  muscular  fibre  (magnified  nearly  800  diameters).  B,  separated 
bundles  of  fibrils,  equally  magnified  ;  a,  a,  larger,  aud  b,  b,  smaller  collections  ;  c,  still  smaller ;  <l,  'I,  the 
smallest  which  could  be  detached.     (Kirkes.) 

diameter,  and  consists  of  three  parts,  the  sarcolemma  or  sheath,  the 
sarcous  substance,  and  the  nuclei  or  muscle  corpuscles.  The  sarco- 
lemma is  the  elastic,  transparent,  structureless,  and  colorless  sheath  enclos- 
ing the  sarcous  substance.     The  latter  being  marked  transversely  by 


876  MUSCULAR    CONTRACTILITY. 

alternating  light  and  dark  bands,  is  said  to  be  transversely  striate.  If 
fresh  muscular  fibre  be  examined  in  its  own  juice,  not  only  the  light  and 
dark  bands  just  referred  to  will  be  seen,  but  it  will  be  observed  (Fig. 
•");'>_')  that  the  light  band  is  divided  into  two  by  what  looks  like  a  line, 
but  which  seems  to  be  in  reality  the  edge  of  the  membrane,  running 
transversely  across  the  fibre  and  attached  all  around  to  the  sarcolemma, 
through  which  each  fibre  is  divided  into  a  series  of  compartments 
placed  end  to  end.  It  is  within  these  compartments  that  the  sarcous 
substance  is  situated.  The  latter  consists  of  a  broad,  dim,  doubly 
refracting  (anisotropous)  contractile  disk,  both  ends  of  which  are  capped 
by  a  layer  of  clear,  homogeneous,  refracting  (isotropous)  soft  or  fluid 
substance.  The  nuclei  or  muscle  corpuscles  lie  immediately  under  the 
sarcolemma,  their  long  axis  being  in  the  long  axis  of  the  fibre,  and  in 
all  probability  generate  the  sarcous  substance.  As  already  mentioned, 
muscles  being  active  organs  are  well  supplied  with  blood,  and  with  sen- 
sory as  well  as  motor  nerves ;  the  sensibility  of  muscles  is  relatively, 
however,  but  slight.  The  second  variety  of  muscle,  the  non-striped  or 
smooth,  occurring  among  other  situations  in  the  alimentary  canal, 
arteries,  ureter,  etc.,  consists  of  fusiform  or  spindle-shaped  cells  with 
tapering  ends,  varying  in  length  from  45  to  230  mic.  mm.  (-g^th  to 
Y^-g-th  inch)  in  breadth,  from  4  to  10  mic.  mm.  (-goVg-tli  to  2 5\ 0 th 
inch).  Within  each  cell  may  be  seen  after  the  addition  of  acetic  acid, 
a  solid,  oval,  elongated  nucleus,  containing  one  or  more  nucleoli,  in 
which  the  motor  nerves  derived  from  the  sympathetic  and  consisting  of 
both  medullated  and  non-medullated  fibres,  appear  to  terminate.  Non- 
striped  muscle,  while  freely  supplied  with  blood,  is  not,  however,  so  vas- 
cular as  the  striped  variety.  Striped  muscle  or  ordinary  flesh  is  either 
neutral  or  slightly  alkaline  in  reaction,  and  consists  chemically  by 
weight,  of  three-fourths  water  and  one-fourth  nitrogenous,  non-nitro- 
genous matters,  and  salts.  Of  the  nitrogenous  matters  the  most  impor- 
tant is  the  coagulable  substance  that  becomes  in  dead  rigid  muscle 
myosin,  though  albuminates,  creatin,  xanthin,  hypoxanthin,  taurin, 
inosic  and  uric  acids  are  also  present.  Among  the  non-nitrogenous 
matters  may  be  mentioned  para  or  sarco,  lactic  acid,  mosete  or  muscle 
sugar,  glycogen,  dextrine,  and  glucose.  Of  the  salts,  the  principal 
ones  are  the  alkaline  phosphates  and  sulphates,  potassium  and  sodium 
chloride.  But  little  is  known  of  the  chemical  composition  of  unstriated 
muscular  tissue,  beyond  the  fact  of  it  consisting  of  water,  nitrogenous 
and  non-nitrogenous  bodies. 

Let  us  turn  now  to  the  consideration  of  the  physical  and  chemical 
changes  undergone  by  the  muscle  during  its  contraction.  Many  of  the 
most  striking  phenomena  of  muscular  contraction  as  well  as  the  method 
of  observing  and  recording  the  same,  have  already  been  incidentally 
demonstrated  in  considering  nervous  irritability.  It  will  be  remem- 
bered, that  by  attaching  a  lever  to  a  muscle  and  connecting  the  pen  of 
the  same  with  the  recording  cylinder  or  the  plate  of  the  pendulum 
myograph,  that  we  obtained  a  trace  (Fig.  533),  that  of  the  muscle 
curve,  and  that  by  means  of  suitable  chronographic  apparatus  we 
determine  the  latent  period,  the  time  intervening  between  the  beginning, 
the  maximum,  and  the  end  of  the  contraction,  the  curve  of  tetanus,  etc. 


MUSCULAR    CONTRACTILITY 


877 


Further,  by  means  of  the  galvanometer  and  differential  rheotome,  it 
was  shown  that  during  a  period  of  rest,  the  nerve  exhibited  an 
electrical  current,  but  that  during  its  excitement  the  electrical  cur- 
rent disappeared,  and  the  nerve  current  appeared,  the  rate  of  disap- 
pearance of  the  one  being  the  same  as  that  of  the  appearance  of  the 
other.     It  will  only  be  necessary,  therefore,  in  this  connection,  after 

Fi(i.  533. 


a  h 


I0(T'  27F»  ?~5'  °»  a  second. 

A  muscle-curve  obtained  by  means  of  the  pendulum  myograph.  To  be  read  from  left  to  right,  a  indi- 
cates the  moment  at  which  the  induction-shock  is  sent  into  the  nerve,  b  the  commencement,  c  the  maxi- 
mum, and  d  the  close  of  the  contraction.  The  two  smaller  curves  succeeding  the  larger  one  are  due  to 
oscillations  of  the  lever.  Below  the  muscle-curve  is  the  curve  drawn  by  a  tuuing-foi  k  making  ISO  double 
vibrations  a  second,  each  complete  curve  representing  therefore  T|-^t"  of  a  secoutl-  lf  will  be  observed 
that  the  plate  of  the  myograph  was  travelling  mure  rapidly  toward  the  close  than  at  the  beginning  of  the 
contraction,  as  shown  by  the  greater  length  of  the  vibration-curves.     (Foster.) 

recalling  what  has  already  been  said,  to  repeat  that  there  is  a  negative 
variation  of  the  electrical  current  of  muscle  during  the  activity  of  the 
latter,  and  to  add  that  this  negativity,  as  shown  by  Bernstein,1  travel- 
ling at  the  rate  of  8  metres  (9.8  feet)  a  second,  with  an  average  length 
of  10  millimetres,  is  immediately  followed  by  or  transmitted  into  a 
visible  contraction  wave,  the  muscle  impulse  travelling  at  its  heels  at 
about  the  same  rate,  but  with  a  wave  length  of  from  200  to  400  milli- 
metres, which  causes  the  muscular  fibre  as  it  passes  over  it  to  swell 
and  shorten.  If  a  portion  of  living  irritable  muscle  of  an  insect,  that 
of  Telephorus,  for  example,  be  viewed  under  the  microscope,  the  con- 
traction waves  observed  passing  along  the  fibres  may  be  fixed  by  appro- 
priate treatment  with  osmic  acid,  and  so  compared  with  the  remaining 
portion  of  the  fibre  at  rest.  By  such  method  of  investigation,  it  has 
been  shown,  that  while  the  dark  and  light  bands  so  characteristic  of 
striated  muscle  at  rest  are  still  observable  in  the  muscle  when  con- 
tracted, the  relation  of  the  two  is  reversed,  that  is  to  say,  the  dark  band 
in  the  contracted  muscle  corresponds  t<>  the  light  band  in  the  quiet  one, 
and  vice  versa,  the  distinction  between  light  and  dark  bands  not  being 
observable,  however,  during  the  intermediate  stage  between  rest  and 
contraction.  While  there  is  still  some  difference  of  opinion  as  to  the 
interpretation  of  all  of  the  appearances  of  such  a  preparation,  the  same 


i  Untersuchungen,  S.  58.     Heidelberg,  1871. 


8/8  MUSCULAR    CONTRACTILITY. 

makes  very  evident  the  swelling  and  shortening  of  the  fibres,  which  is 
brought  out  even  better  if  the  object  be  viewed  by  polarized  light. 

In  describing  the  induction  apparatus  of  Du  Bois-Reymond,  it  will 
be  remembered  that  the  secondary  coil  can  be  removed  as  desired  from 
the  primary  and  the  strength  of  the  stimulus  thrown  into  the  nerve  or 
muscle  in  this  way  varied.  Beginning  with  a  very  weak  stimulus  and 
gradually  increasing  the  same,  the  corresponding  contraction  will  be  found 
to  increase,  at  first  rapidly  then  more  slowly  until  a  maximum  is  reached, 
then  to  diminish  until  contraction  finally  ceases  through  the  muscle 
being  fatigued  from  repeated  stimulation.  If  the  distance  through  which 
the  secondary  coil  be  slid  along  be  laid  down  as  the  abscissa  line  and 
the  extent  of  contraction  as  the  ordinates,  the  curve  obtained  will  be  the 
graphic  representation  of  the  contraction  considered  as  a  function  of  the 
stimulus.  It  should  be  mentioned,  in  this  connection,  that  while  muscles 
in  the  body,  where  they  are  on  the  stretch  after  contraction,  return  at 
once  to  their  initial  length,  out  of  the  body  fail  to  do  so  either  as  com- 
pletely or  as  quickly,  the  rapidity  and  extent  of  the  return  appearing 
to  depend  upon  the  nutrition  of  the  muscle.  Suppose  that  instead  of 
varying  the  electrical  stimulus,  as  in  the  case  just  mentioned,  we  main- 
tain it  as  constant  as  possible,  but  that  we  place  in  the  little  scale  pan 
suspended  from  the  lever  attached  to  the  muscle  successively  10,  20, 
30,  40,  and  50  grammes — that  is,  we  gradually  increase  the  weight  the 
muscle  has  to  lift  to  increase  the  resistance  that  it  has  to  overcome. 
Contrary  to  what  might  naturally  be  expected,  the  resistance  offered  to 
the  contraction,  for  a  time  at  least,  increases  the  contraction,  then  with 
a  continued  increase  of  weight,  the  contraction  having  reached  a  maxi- 
mum, gradually  diminishes  until  finally  it  ceases  altogether.  If  the 
weio"hts  be  regarded  as  the  abscissas  and  the  extent  of  contraction  as  the 
ordinates,  then  the  curve  obtained  will  represent  the  contraction  regarded 
as  a  function  of  the  resistance.  It  will  be  observed,  in  experimenting 
with  weights,  that  a  stretched  muscle  reaches  quickly  its  initial  length 
after  the  extending  cause  has  been  removed,  the  elasticity  not  being 
very  great  but  perfect.  Contrary,  however,  to  what  might  have  been 
expected,  the  extensibility  is  not  diminished  during  contraction  but 
increased,  so  that  the  muscle  has  to  overcome  the  resistance  due  to  its 
extensibility  before  it  can  raise  any  weight.  Thus,  suppose  that  a 
muscle  be  extended  a  given  extent  by  a  weight  of  say  40  grammes 
during  rest,  and  then  that  it  be  unloaded  and  throAvn  into  a  state  of 
tetanus  and  then  again  loaded  with  the  same  weight,  the  extension  in 
the  latter  case  will  be  greater  than  in  the  former.  It  will  also  be 
learned,  by  experimenting  with  gradually  increasing  weights,  that  finally 
the  elongation  of  the  muscle  due  to  its  elasticity  is  exactly  compensated 
by  the  shortening  due  to  its  contraction,  such  a  contraction  of  static 
equilibrium  being  reached  in  the  case  of  the  frog,  the  transverse  section 
being  one  square  centimetre  and  the  weight  692  grammes,  and  in  man, 
the  muscles  being  those  of  the  calf  of  the  leg,  and  the  weight  8  kilo- 
grammes (17. (>  lbs.). 

The  work  done  by  a  muscle,  like  all  work,  is  estimated  by  the  height 
through  which  a  weight  is  raised.  Thus,  if  5  grammes  (77.1  grains)  are 
raised  27  millimetres  (1.08  inch)  by  the  muscle  of  a  frog,  then  27  x  5, 


MUSCULAR    CONTRACTILITY.  879 

135  grammes  millimetres  (83  grain  inch)  work  is  done  by  such  a  muscle. 
By  gradually  increasing  the  weights  and  noting  the  heights  through 
which  they  are  raised,  it  will  be  found  that  the  work  done  gradually 
increases  as  the  weight  increases  until  a  maximum  is  reached,  after 
which  there  is  a  gradual  diminution  until  the  muscle,  as  in  the  former 
instances,  ceases  to  contract.  The  fatigue  experienced  by  muscle  during 
prolonged  contraction,  which  sooner  or  later  brings  the  latter  to  an 
end,  appears  to  be  due  to  the  accumulation  of  the  waste  effete  products 
incidental  to  its  activity.  Within  certain  limits  such  matters  are  elimi- 
nated as  rapidly  as  formed  and  new  materials  for  the  repair  of  the  muscle 
are  at  the  same  time  supplied.  If,  however,  the  contractions  follow 
each  other  very  rapidly,  sufficient  time  is  not  allowed  for  the  accom- 
plishing of  these  processes,  and  the  equilibrium  between  disassimilation 
and  assimilation  is  no  longer  maintained.  While  the  cohesion  and  irri- 
tability of  muscle  are  diminished  by  fatigue,  the  elasticity  is  but  little,  if 
at  all,  affected.  The  latent  period  is,  however,  lengthened.  During 
fatigue  the  extent  of  contraction  is  smaller  and  the  latter  lasts  longer 
than  when  the  muscle  is  fresh,  the  return  to  the  initial  length  is  also 
slower.  As  might  be  expected,  a  muscle  is  fatigued  much  sooner  when 
it  does  work  than  when  it  simply  contracts  without  doing  work.  If  a 
stethoscope  or  myophone  be  applied  over  a  powerfully  contracting 
muscle,  the  biceps,  for  example,  a  deep,  low  tone  will  be  heard,  the 
pitch  of  which  is  about  40  vibrations  a  second,  and  which  is,  without 
doubt,  due  to  the  successive  shortenings  which  make  up  a  muscular 
contraction,  the  latter  caused,  in  all  probability,  by  40  nervous  impulses 
being  transmitted  to  the  nerve  centres  along  the  motor  nerves  to  the 
muscle.  We  say  that  the  pitch  of  this  muscular  sound  or  tone  is  40 
vibrations  per  second  and  caused  by  40  nervous  impulses,  because  that 
is  the  note  actually  heard,  and  because  we  can  produce  such  a  note 
experimentally  out  of  the  body  by  stimulating  the  nerve  that  number  of 
times,  or  a  note  due  to  80  vibrations  per  second  by  stimulating  the 
nerve  that  number  of  times. 

It  should  be  mentioned,  however,  that  according  to  most  physiolo- 
gists, the  muscular  sound  heard  when  the  biceps  contracts,  while  due  to 
40  vibrations  per  second,  is  really  the  first  overtone  or  first  octave 
above  the  fundamental,  the  latter  being  due  to  20  vibrations  per 
second.  If  such  be  the  case,  then  the  muscle  contracts  only  20  times 
a  second,  the  pitch  of  the  muscular  sound  produced  is  20  vibrations  a 
second,  and  the  nerve  is  stimulated  20  times  a  second.  Whether  the 
muscular  sound  heard  be  the  fundamental  note  or  the  octave  above,  in 
either  case,  however,  the  mechanism  of  its  production  is  the  same — 
that  is,  due  to  muscular  vibration.  It  will  be  remembered  that  in 
accounting  for  the  first  sound  of  the  heart,  muscular  contraction  was 
assigned  as  one  of  the  causes,  and  while  there  is  no  doubt  that  it  is  an 
element  in  the  production  of  the  first  sound,  it  must  be  admitted  that 
it  is  difficut  to  understand  how  the  contraction  of  the  heart,  if  a  simple 
one,  can  give  rise  to  a  muscular  sound,  which  we  have  just  seen  is  pro- 
duced by  numerous  contractions.  Facts  of  this  kind,  as  well  as  pecu- 
liarities in  the  muscular  structure  of  the  heart  itself,  lead  one  to  suppose 
that  possibly  the  contraction  of  the  heart  during  its  ventricular  systole 


880  MUSCULAR    CONTRACTILITY. 

is  rather  of  a  tetanic  than  simple  character,  as  is  usually  supposed. 
The  muscle  sound  or  muscle  tone  due  to  successive  muscular  contrac- 
tions must  not  be  confounded  with  what  is  unfortunately  called  mus- 
cular tonus  or  muscular  tonicity,  hy  which  is  meant  the  state  of 
tension  due  to  the  muscles  in  the  living  body  being  more  or  less 
stretched  between  their  attachments.  Such  being  the  case,  when  a 
muscle  is  divided  transversely  it  contracts,  the  two  parts  receding 
from  each  other.  The  sphincter  muscles,  however,  do  not  appear  to 
be  stretched  during  repose,  but  only  when  they  are  dilated.  On 
the  other  hand,  by  the  term  muscular  tone,  as  understood  more 
especially  by  neurologists,  is  meant  the  firmness  or  tone  of  muscle  due 
to  continued  nervous  excitement  emanating  from  the  spinal  cord.  By 
some  physiologists,  however,  it  is  denied  that  the  spinal  cord  exerts 
any  such  tonic  influence  upon  the  muscles,  and  yet  it  is  well  known 
that  a  decapitated  frog  will  remain  in  a  sitting  posture  as  long  as  the 
spinal  cord  is  intact,  but  that  with  its  removal  the  limbs  fall  apart. 
Further,  the  limbs  of  a  decapitated  turtle,  and,  to  a  certain  extent,  those 
of  a  decapitated  rabbit,  also  retain  their  firmness,  tone,  but  with  the 
removal  of  the  spinal  cord  become  lax,  flaccid.  Such  facts  are  incom- 
prehensible, unless  it  be  supposed  that  the  muscles  are  maintained  firm, 
elastic,  resilient,  through  the  influence  of  the  spinal  cord.  As  the 
influence  exerted  by  heat,  blood  supply,  etc.,  upon  the  activity  of  the 
muscle  is  essentially  the  same  in  the  case  of  muscle  as  in  that  of  nerve, 
it  will  not  be  necessary  to  dwell  further  upon  the  same  in  this  connec- 
tion. If  living  contractile  frog's  muscle,  freed  as  much  as  possible 
from  blood,  be  frozen  and  then  minced  and  rubbed  up  in  a  mortar  with 
four  times  its  weight  of  snow  containing  1  per  cent,  of  sodium  chloride, 
a  mixture  will  be  obtained,  which  at  about  0°  Cent.,  can  be  filtered. 
The  filtrate  so  obtained,  or  muscle  plasma,  at  first  fluid  becomes  at 
ordinary  temperature,  jelly-like,  and  then  separates  into  a  clot  and 
serum,  the  action  which  before  coagulation  was  neutral,  or  slightly  alka- 
line, now  being  distinctly  acid.  The  serum  contains  albumen  and 
extractives ;  the  clot  consists  of  myosin,  a  substance  intermediate  in 
character  between  fibrin  and  globulin.  It  will  be  observed,  as  in  the 
case  of  the  fibrin  of  the  blood,  that  myosin  does  not  exist  as  such  in 
living  contractile  muscle,  but  that  it  is  developed  during  the  coagula- 
tion of  the  same  out  of  some  preexisting  albuminous  element  or 
elements.  The  myosin  so  developed  from  living  muscle  does  not  differ 
at  all  from  the  myosin  obtained  by  appropriate  chemical  manipulation 
from  dead  muscle.  Indeed,  the  passage  of  a  muscle  into  the  condition 
of  rigor  mortis,  characterized  by  loss  of  its  irritability,  softness,  trans- 
lucency,  extensibility,  and  elasticity  may  be  regarded  as  being  essen- 
tially due  to  the  coagulation  of  its  muscle  plasma,  to  the  development 
of  myosin  out  of  its  preexisting  albuminous  elements.  Since  living 
muscle  during  its  contraction  becomes  distinctly  acid  from  having  been 
previously  faintly  alkaline  or  neutral  from  a  considerable  amount  of 
carbonic  and  lactic,  or  sarcolactic  acid  being  set  free,  as  in  the  con- 
dition of  rigor  mortis,  from  the  fact  of  the  muscle,  as  in  the  latter 
distinction,  becoming  rigid,  it  might,  at  first  thought,  be  supposed  that 
the  changes  occuring  during  the  contraction  of  the   living  muscle  are 


MUSCULAR    CONTRACTILITY, 


881 


essentially  the  same  as  those  occurring  in  rigor  mortis,  due  to  the 
oxidation  of  some  complex  albuminous  material  elaborated  and  stored 
up  in  the  muscle  during  its  periods  of  repose.  That  the  phenomenon 
of  muscular  contraction  is  not,  however,  identical  with  that  of  rigor 
mortis,  is  shown  by  the  important  fact  that  during  muscular  contraction 
no  myosin  is  developed,  upon  the  formation  of  which  the  phenomenon 
of  rigor  mortis  depends,  and  that  during  contraction  the  extensibility 
of  the  muscle  is  increased,  instead  of  being  diminished,  and  that  it  does 
not  lose  its  translucency. 

But  little  is  positively  known  as  to  the  physical  and  chemical  changes 
undergone  by  unstriated  muscular  fibre  during  death  or  contraction  ; 
from  what  has  been  established,  however,  we  are  led  to  believe  that  the 
processes  going  on  in  unstriated  muscle  fibre  differ  in  degree  rather  than 
in  kind  from  those  just  described  as  occurring  in  striated  muscle.  While 
the  limits  of  this  work  do  not  permit  of  any  discussion  of  general  mus- 
cular movements  which  would  involve  a  detailed  description  of  the 
muscles  and  joints  and  the  consideration  of  animal  mechanics,  a  brief 
account  of  how  ordinary  movements  are  performed  does  not  appear  in- 
appropriate in  concluding  this  chapter.  The  greater  part  of  the  skeletal 
muscles  may  be  regarded  as  so  many  sources  of  power  for  moving  the 
bones  viewed  as  levers.  The  levers  are  of  three  kinds  or  orders  according 
to  the  relative  position  of  the  power,  the  weight  to  be  moved,  and  the  axis 
of  motion  or  fulcrum.     In  a  lever  of  the  first  kind,  as  in  Fig.  534,  A,  the 


Illustration  of  lever  of  first  order.     (Kikkes.) 

power  (P)  is  at  one  end,  the  weight  (W)  at  the  other,  and  the  fulcrum  (F) 
in  the  middle.  As  a  familiar  example  of  the  first  kind  of  lever,  occurring 
in  the  human  body,  may  be  mentioned  the  raising  of  the  body  from  the 
stooping  posture  by  the  action  of  the  hamstring  muscles  attached  to  the 
tuberosity  of  the  ischium  (Fig.  534,  B).  In  a  lever  of  the  second  kind 
(Fig.  535,  A),  the  power  is  at  one  end,  the  fulcrum  at  the  other,  and  the 
weight  in  the  middle.  The  depression  of  the  lower  jaw  in  the  opening 
of  the  mouth  is  an  illustration  of  a  lever  of  the  second  kind  (Fig.  535,  B), 

56 


882 


MUSCULAR    CONTRACTILITY. 


in  which  the  tension  of  the  muscles  elevating  the  jaw  represents  the 
weight.  In  a  lever  of  the  third  kind  (Fig.  536,  A),  while  the  fulcrum 
and  weight  are  at  either  end,  the  power  is  in  the  middle.  The  flexing 
of  the  forearm  by  the  action  of  the  biceps  muscle  (Fig.  536,  B)  is  an 


\ 


Elastic  I  Band 


Fig.  535. 
w 


Illustration  of  lever  of  second  order.     (Eibkkb  ) 


instance  of  this  form  of  lever  in  the  body.     The  different  movements  of 
the  foot  offer  an  illustration  of  all  three  kinds  of  levers:  of  the  first  kind 


Fig.  -536. 


Illustration  of  lever  of  third  order.     (Kirkes.) 


when  the  foot  is  raised  and  the  toe  tapped  upon  the  ground,  the  ankle- 
joint  being  the  fulcrum  (Fig.  537,  I) ;   of  the  second  when  the  body  is 

Fid.  537. 


i  ii  in 

Illustration  "1  levers  of  all  three  orders. 
W.  Weight  of  resistance.     F.  Fulcrum.     P.  Power.     (Huxley.) 

raised  upon  the  toes,  the  ground  being  the  fulcrum  (Fig.  537,  II) ;  of  the 
third  kind,  when  one  dances  a  weight  up  and  down  by  moving  only  the 
foot,  the  fulcrum  being  the  ankle-joint  (Fig.  537,  III).  As  a  general 
rule,  in  the  human  body,  the  power  is  so  disposed  with  reference  to  the 
fulcrum,  that  while  a  greater  range  of  motion  is  acquired  the  power  is 
diminished.     Thus,  in  the  case  of  the  action  of  the  biceps,  it  is  evident 


MUSCULAR    CONTRACTILITY. 


883 


that  a  great  amount  of  force  must  be  put  forth  to  move  the  forearm,  but 
that  a  considerable  range  of  movement  is  obtained  through  a  relatively 
slight  shortening  of  the  muscular  fibres.  In  the  act  of  standing,  as 
accomplished  by  muscular  action,  the  body  is  in  a  vertical  position  of 
equilibrium,  a  line  drawn  from  the  centre  of  gravity  of  the  body  falling 
within  the  feet  placed  upon  the  ground.  .The  head  being  firmly  fixed 
upon  the  vertebral  column  by  the  cervical  muscles  pulling  from  the 
latter  upon  the  occiput,  and  the  vertebral  column  itself  being  fixed  by 
the  longissimus  dorsi  and  quadratus  lumborum  muscles.  In  the  sitting 
position,  the  head  and  trunk  together  constituting  an  immovable  column, 
are  supported  upon  the  tubera  ischii.  In  the  forward  posture  the  line  of 
gravity  passes  in  front,  in  the  backward  posture  behind,  and  during  the 
erect  posture  between  the  tubera  ischii.  In  walking,  the  two  legs  act 
alternately,  the  one  leg,  the  active  or  supporting  leg,  carrying  the  trunk, 
the  other  leg  being  inactive  or  passive.  The  act  of  walking,  for  con- 
venience of  description,  may  be  considered  as  made  up  of  two  acts.  Act 
1st  (Fig.  538) :  the  active  leg  being  vertical  and  slightly  flexed  at  the 

Fig.  538. 


Phases  of  walking.  The  thick  lines  represent  the  active,  the  thin  the  passive  leg.  7).  The  hip-joint. 
k,  a.  Knee.  f,b.  AukU*.  c,  d.  Heel,  m,  e.  Ball  of  the  tarso-meta tarsal  joints,  z,  g.  Point  of  great  toe. 
(Landois.) 

knee,  alone  supports  the  centre  of  gravity  of  the  body,  the  passive  leg 
touching  the  ground  with  the  tip  of  the  great  toe  (2)  only.  At  this 
moment  the  position  of  the  leg  corresponds  to  a  right-angle  triangle 
in  which  the  active  leg  and  ground  represent  the  two  sides,  the  passive 
leg  the  hypothenuse.  Act  2d  :  the  active  leg  being  inclined,  moves 
forward  to  an  oblique  position,  the  trunk  moves  forward,  the  active  le«- 
being  at  at  the  same  time  lengthened  that  the  trunk  may  remain  at  the 
same  height.  The  latter  is  accomplished  by  extension  of  the  knee 
(•"'..  4,  5),  and  the  lifting  of  the  heel  from  the  ground  (4,  5),  until  the 
foot  finally  rests  upon  the  ground  by  the  point  of  the  great  toe.  As 
the  active  leg  is  extended  and  moves  forward  the  tips  of  the  toes  of  the 
passive  leg  leave  the  ground  (3),  and  being  slightly  flexed  at  the  knee- 
joint  perform  a  pendulum-like  movement  (4,  5),  the  passive  foot  passing 
as  far  in  front  of  the  active  leg  as  it  was  previously  behind  it.  The 
foot  being  then  placed  flat  upon  the  ground,  the  centre  of  gravity  is 


884  MUSCULAR    CONTRACTILITY. 

transferred  to  what  now  becomes  the  active  leg,  the  latter  being  slightly 
flexed  at  the  knee  and  placed  vertically.  The  first  act  is  then  repeated, 
and  so  on.  It  will  be  observed  that  during  walking  the  trunk  leans 
toward  the  active  leg  and  inclines  somewhat  forward,  the  effect  of  which 
is  to  overcome  resistance  of  the  air,  and  that  it  slightly  rotates  on  the 
head  of  the  active  lemur.  Running  differs  from  rapid  walking  in  that 
at  a  particular  moment,  both  legs  not  touching  the  ground,  the  body  is 
raised  in  the  air,  the  necessary  impetus  being  given  to  the  body  by  the 
forcible  extension  of  the  active  leg. 


CHAPTER    LV. 

REPRODUCTION. 

Spontaneous  Generation.     Fissiparous,  Gemmiparous,  and 
Sexual  Generation. 

At  an  immensely  remote  period  the  earth  must  have  been  entirely 
destitute  of  life,  at  least  the  physical  conditions  of  the  azoic  period  of 
geologists,  and  the  aeons  preceding  it  were  such  as  to  make  the  exist- 
ence of  life,  as  Ave  are  acquainted  with  it,  impossible.  "Whether  the 
nebular  hypothesis  of  the  earth  having  been  cast  off  from  the  sun  be 
accepted  or  not,  there  can  be  no  doubt  that  at  an  inconceivably  dis- 
tant period  the  earth  was  in  a  fluid  or  semi-fluid  molten  condition,  and 
its  temperature  so  high  as  to  render  life  impossible,  or  even  to  admit  of 
the  union  of  the  chemical  elements  composing  it,  the  latter  existing 
then  separately,  as  they  do  in  all  probability  now,  in  the  sun,  as  shown 
by  spectral  analysis.  The  basalts,  porphyries,  and  lavas  entering  into 
the  formation  of  the  igneous  rocks,  the  volcanic  action  constantly  going 
on  at  the  present  day  in  many  parts  of  the  world,  the  seismic  disturb- 
ances, the  high  temperature  of  mines,  etc.,  not  only  prove  that  origi- 
nally the  world  was  but  little  else  than  a  ball  of  fire,  but  also  that  the  fire, 
far  from  being  extinguished,  is  only  now  restricted  to  the  inner  subter- 
raneous regions  lying  under  the  crust  of  the  earth.  If  speculation  be 
admitted,  we  can  conceive  how  with  the  loss  of  heat  and  the  lowering 
of  the  temperature  through  the  combination  of  hydrogen  and  oxygen 
that  water  was  formed,  and  that  gradually  through  the  combination  of 
the  chemical  elements  the  binary  and  ternary  salts  entering  into  the 
formation  of  the  rocks  constituting  the  crust  of  the  earth  were  next 
produced,  and,  finally,  the  physical  conditions  being  suitable,  that  the 
combination  of  carbon,  hydrogen,  oxygen,  nitrogen,  and  phosphorus 
or  sulphur  atoms,  resulted  in  the  development  of  protoplasm,  or  the 
simplest  kind  of  life.  It  is  true  that  the  idea  of  life  being  generated 
spontaneously,  as  just  supposed,  is  repugnant  to  all  that  we  know  of 
life  as  reproduced  at  the  pi'esent  day,  there  being  no  evidence  Avhatever 
that  life  now  is  ever  generated  otherwise  than  from  preexisting  life, 
solitary  tapeworms,  maggots,  etc.,  often  cited  by  the  uneducated  as 
instances  of  animals  spontaneously  generated,  offering  no  exception  to 
the  rule,  being  in  reality  reproduced,  like  all  life,  by  preexisting  animal 
life.  That  the  first  life  appearing  upon  the  face  of  the  earth  was 
nevertheless  spontaneously  generated,  developed  independently  of  pre- 
existing life  must  be  admitted,  since  there  was  no  antecedent  life 
during  the  azoic  period  to  give  rise  to  it.  As  to  the  conceivability  or 
inconceivability  of  how  spontaneous  generation  was  brought  about,  of 
how   protoplasm,  with   its   remarkable  properties,   was  ever  developed 


886  REPRODUCTION. 

through  the  combination  of  chemical  elements  possessing  different 
properties,  it  may  be  said  that  it  is  just  as  difficult  to  comprehend 
how  the  combination  of  acid  and  base  will  give  rise  to  a  salt  exhibiting 
properties  possessed  by  neither,  or  how  two  gases  like  oxygen  and 
hydrogen  in  combination  produce  a  liquid,  water,  different  from  either. 
In  either  case  we  must  suppose  that  the  properties  of  the  substance 
formed,  however  remarkable,  are  the  sum  of  the  properties  of  the 
elements  entering  into  combination  and  giving  rise  to  the  substance, 
whatever  is  true  of  the  inorganic  in  this  reaped  being  true  of  the 
organic  as  well,  the  question  in  either  case  being  one  of  the  redis- 
tribution of  matter  and  force  only.  Admitting  that  life  originated 
spontaneously,  there  is  little  reason,  however,  to  hope  that  the  physical 
conditions  which  obtained  when  life  first  appeared  upon  the  face  of  the 
earth  can  ever  be  realized  experimentally  so  as  to  enable  one  to  gen- 
erate life  de  novo.  Still  it  must  not  be  forgotten  that  what  appears 
impossible,  inconceivable,  to  one  age,  becomes  perfectly  so  to  a  suc- 
ceeding one.  Life  having  once  appeared  upon  the  face  of  the  earth, 
however  produced,  there  is  no  reason  to  suppose  that  it  has  ever  been 
entirely  absent,  since  catastrophies,  such  as  volcanic  eruptions,  earth- 
quakes, floods,  climatic  changes,  etc.,  which  are  so  destructive  to 
life,  are  relatively  local  in  action.  Further,  the  first  life,  out  of  which 
all  life  has  since  been  gradually  developed  through  inheritance  and 
variation,  must  have  been  of  the  simplest  kind ;  indeed,  so  simple  as  to 
make  it  difficult,  if  not  impossible,  to  say  whether  such  life  should  be 
regarded  as  animal  or  vegetable,  its  characters  being  intermediate 
between,  and  partaking  of  the  nature  of  both  plants  and  animals. 
The  latter,  judging  from  their  remains  as  presented  in  the  Cambrian 
and  Silurian  rocks,  or  such  as  immediately  overlie  the  azoic  strata, 
were  also  at  first  of  a  simple  kind.  Thus  among  the  plants  and 
animals  living  in  these  early  ages  of  the  primary  period  of  geologists 
may  be  mentioned  seaweeds,  jelly  fish,  coral-making  polyps,  crinoids, 
brachiopods,  various  kinds  of  mollusca,  trilobites,  etc.  Passing  on 
through  the  later  ages  of  the  primary  period,  the  life  becomes  more 
varied  and  complex;  fishes,  ganoids,  and  sharks,  and  land  plants,  pine- 
like lepidodendrons,  and  ferns  making  their  appearance  during  the 
Devonian  age,  or  that  of  the  sandstone,  and  reptiles  in  the  carboniferous 
age,  or  that  of  the  coal  period,  remarkable  also  for  the  richness  of  its 
cryptogamous  plants.  As  the  ages  rolled  on,  during  which  the  Jura 
rocks  Avere  deposited  in  Switzerland,  the  chalk  cliffs  in  England,  the 
marls  in  New  Jersey,  phanerogamous  or  flowering  plants,  palms  and 
trees  like  those  of  our  own  forests,  oaks,  dogwoods,  poplars,  beeches, 
appeared,  while  among  the  animals  that  lived  during  these  ages  may 
be  mentioned  fishes  resembling  those  of  the  present  day  ;  gigantic 
reptiles,  birds,  and  probably  a  few  marsupial  mammals. 

During  the  tertiary  period  that  followed,  the  flowering  plants  and 
trees  then  flourishing  resembled  closely  those  of  the  forests  of  the  present 
day,  the  invertebrate  forms  of  life  differed  but  little  from  those  existing 
now,  the  fishes  and  reptiles  were  similar  to  those  found  in  our  rivers, 
oceans,  and  forests ;  while  herbivorous  animals,  resembling  the  taper, 
peccary,  camel,  deer,  horse,  rhinoceros,  and  elephant,  roamed  in  herds 


FISSION  —  G  EM  MAT  ION. 


887 


over  the  continents,  hippopotami  wallowed  in  the  streams  ;  while  beasts 
of  prey  were  also  numerous,  being  represented  by  animals  closely  allied 
to  the  lion,  tiger,  hyena,  dog,  and  panther,  of  the  present  day.  During 
.  the  close  of  the  tertiary,  or,  rather,  of  the  post-tertiary  period,  the 
general  aspect  of  the  world  differed  but  little  from  that  presented  by  it 
now,  man  appears  but  in  a  condition  of  development,  probably  far 
lower  than  that  of  the  lowest  existing  savage,  and  the  process  of  civili- 
zation begins. 

The  idea  of  repi'oduction  is  usually  associated  with  that  of  the  differ- 
ence of  sex;  the  production  of  offspring  naturally  suggesting  the  idea 
of  two  parents.  Many  plants  and  animals,  however,  are  reproduced 
entirely  independent  of  sexual  intercourse,  by  what  is  known  as  fission 
or  gemmation ;  and  as  many  of  the  structures  of  the  body  are  devel- 
oped by  these  processes,  it  is  essential  that  they  should  be  at  least  briefly 
illustrated.  By  the  process  of  fission  is  meant  the  division  of  the  single 
parent  organism  into  two  or  more  parts,  each  of  which  will  become  a 
new  being,  similar  in  form,  inheriting  the  properties  of  the  parent. 
Reproduction  by  the  process  of  fission  may  be  observed  in  many  of  the 
lower  cryptogamous  plants,  and  among  animals  in  the  infusoria,  anne- 
lida,  etc.,  illustrations  of  which  have  been  given.  What  interests  us  in 
this  connection,  however,  as  regards  fission  is,  that  the  segmentation  of 
the  vitellus  of  the  egg,  the  development  of  the  embryonic  blood  cor- 
puscles (Fig.  539),  the  proliferation  of  the  cells  constituting  morbid 
growths,  etc.,  are  accomplished  by  this  process.  On  the  other  hand, 
by  gemmation  is  understood  the  reproduction  of  the  new  being  by  a 
process  of  budding,  as  seen   in   ordinary  flowering  plants,  and  among 


Fig.  539. 


Fig.  540. 


Division  of  Mood  cells  in  embryo  of  stag. 
(Frey.) 

animals  in  the  hydra,  actinia,  etc., 
each  bud  becoming  a  new  animal. 
In  certain  cases  of  gem  mi  parous 
reproduction,  however,  the  buds, 
instead  of  bei  ng  cast  off  as  produced, 
remain  attached  to  the  parent 
stock,  and  so  give  rise  to  a  colony, 
as  in  the  hydroids  (Fig.  540),  each  member  of  which  is  in  communica- 
tion, directly  or  indirectly,  with  each  other.      Such  a  mode  of  reproduc- 


Hydroid  colony.      Eudendrium  ramosum. 
(Gkgexbaub.) 


REPRODUCTION. 


tion  in  the  human  body  is  seen  in  the  development  of  a  racemose  gland 
(Fig.  541)  through  the  division  and  subdivision  of  a  simple  follicular 


Diagrammatic  view  of  development  of  glands. 

gland.  The  reproduction  of  man  and  most  animals,  however,  is  accom- 
plished by  the  union  of  a  spermatozoon  and  an  ovum,  specialized 
products  of  the  male  and  female  generative  apparatus  respectively, 
which,  while  elaborated  by  a  process  of  fission,  or  gemmation,  unlike 
the  products  of  the  latter,  must  fuse  together  in  order  to  give  rise  to  a 
new  being,  neither  spermatozoon  nor  ovum,  by  themselves,  being  capable 
of  further  development.  Further,  it  will  be  observed  that  since,  in  the 
production  of  a  new  being  by  sexual  generation,  the  union  of  the  sper- 
matozoon and  ovum  is  indispensable,  the  qualities  of  the  parents  must 
be  transmitted  to  their  offspring.  The  female  generative  organs,  situ- 
ated partly  within  and  partly  without  the  pelvis,  consist  of  the  uterus, 
Fallopian  tubes,  vagina,  ovaries,  the  external  and  internal  labia,  cli- 
toris, etc.     The  uterus  (Fig.   542),    or  womb,  is  a  pyriform,   hollow 

Fig.  542. 


Sketch  of  the  uterus  and  its  appendages.  1.  Uterus,  with  its  peritoneal  covering  partially  retained. 
2.  Its  fundus.  3.  Its  neck,  with  the  forepart  of  the  attachment  of  the  vagina  removed.  4.  Mouth  of 
the  uterus.  5.  Interior  of  the  vagina.  C.  Broad  ligament,  removed  on  the  opposite  side.  7.  Position  of 
the  ovary  behind  the  broad  ligament.  8  Round  ligament.  9.  Oviduct,  or  Fallopian  tube.  10.  Its  fim- 
briated fxtromity.  11.  Ovary.  12.  Ovarian  ligament.  13.  Process  connecting  the  fimbriated  extremity 
with  the  ovary.     14.  Cut  border  of  the  broad  ligament.     (Wilson.) 

muscular  organ,  lying,  in  the  unimpregnated  condition,  within  the 
pelvis,  between  the  rectum  and  the  bladder,  and  maintained  in  position 
by  its  attachment  to  the  vagina  by  the  recto-  and  vesico-uterine  peri- 
toneal folds,  and  the  round  and  broad  ligaments,  its  upper  broad 
extremity  is  known  as  the  fundus,  or  base,  the  narrow  extremity  the 
cervix,  or  neck,  and  the  intervening  portion  as  the  corpus,  or  body. 
The  uterus  is  about  two  and  a  half  inches  in  length,  two  inches  in 
breadth,  and  one  inch  in  thickness. 


STRUCTURE    OF    UTERUS.  889 

The  walls  of  the  uterus  consisting  of  unstriated  muscular  tissue  being 
about  one  half  an  inch  in  thickness,  the  cavity  of  the  latter  is  but  a 
narrow  space.  That  of  this  body  is  lined  with  a  thin,  soft,  smooth,  and 
ciliated  mucous  membrane  of  a  pale  red  color,  containing  numerous 
tubular  glands  adhering  closely  to  the.  underlying  muscular  tissue,  their 
being  no  intermediate  fibrous  or  submucous  tissue,  which  becomes 
continuous  with  the  mucous  membrane  of  the  Fallopian  tubes  and  that 
of  the  neck  of  the  uterus.  The  mucous  membrane  of  the  latter  is  of 
the  squamous  character,  thicker  and  less  soft  than  that  of  the  body  of 
the  uterus,  its  glands  being  of  the  simple  follicular  kind  and  secretin-' 
a  tenacious  mucus,  the  latter  in  an  inspissated  condition,  giving  rise  to 
the  so-called  ovula  Nabothi.  The  uterine  mucus,  both  of  the  fundus 
and  cervix,  is  alkaline  in  reaction.  The  Fallopian  tubes,  or  the  horns 
of  the  uterus,  are  trumpet-shaped  tubes  about  four  inches  in  length,  ex- 
tending from  the  fundus  outwardly  above  and  beyond  the  ovary.  The 
outer  free  extremity  opening  into  the  abdominal  cavity  expands  into  a 
funnel-shaped  orifice  the  pavilion,  the  margin  of  which  being  fringed 
with  a  number  of  irregular  processes,  gives  rise  to  its  name  of  fim- 
briated extremity.  One  of  the  largest  of  these  fringed  processes, 
doubled  so  as  to  include  a  furrow,  extends  along  the  edge  of  the  broad 
ligament  to  be  attached  to  the  ovary.  The  Fallopian  tube  is  lined  with 
ciliated  mucous  membrane,  continuous  through  its  interim  or  uterine 
orifice  with  that  of  the  cavity  of  the  fundus,  and  disposed  in  a  longi- 
tudinal manner  or  as  narrow  folds.  The  tube  itself  consists  of  fibrous 
intermixed  with  unstriated  muscular  tissue,  loosely  invested  by  peri- 
toneum. The  small  sac,  often  absent,  attached  by  a  long  pedicle  close 
to  the  fimbriated  extremity,  is  the  remains  of  the  duct  of  Miiller  of  the 
embryo,  as  we  shall  see  presently.  The  vagina  is  a  cylindrical  canal 
about  four  inches  in  length  and  an  inch  and  a  quarter  in  breadth 
(in  the  virgin  adult),  extending  from  the  uterus,  the  neck  of  which 
projects  into  it  to  the  vulva.  The  vagina  consists  of  three  coats,  an  outer 
fibro-elastic,  a  middle  unstriated  muscular,  and  an  inner  mucous;  the 
epithelium  of  the  latter  is  of  the  squamous  kind,  and  is  provided  with 
numerous  minute  conical  papillae.  In  the  virgin  condition,  the  lower 
orifice  or  entrance  of  the  vagina  is  constricted  by  a  crescentic  or  zone- 
like fold  of  the  lining  of  the  membrane,  the  so-called  hymen.  The 
latter  is  usually  obliterated  by  sexual  intercourse,  childbirth,  etc. ;  in 
some  instances,  however,  it  is  so  strong  that  even  impregnation  may 
occur  without  its  being  ruptured.  Its  presence  cannot,  therefore,  be 
taken  as  an  evidence  of  virginity,  or  its  absence  of  the  contrary.  The 
inner  surface  of  the  anterior  and  posterior  walls  of  the  vagina  is 
roughened  by  folds,  the  wart-like  eminences  into  which  they  are  divided 
more  particularly  at  the  entrance  of  the  vagina  being  known  as  the 
carunculpe  myrtiformes.  While,  as  just  mentioned,  the  uterine  mucus  is 
alkaline  in  reaction,  that  of  the  vagina  is  decidedly  acid.  The  two 
ovaries  are  compressed  ovoid  bodies,  situated  behind  the  broad  ligament 
and  enclosed  by  a  pouch  of  the  latter  about  an  inch  from  the  uterus, 
to  which  they  are  attached  by  the  ovarian  ligament.  The  ovary  con- 
sists of  a  reddish  spongy  fibrous  stroma,  enclosed  in  a  dense  fibrous 
tunic,  the  tunica  albuginea.     Within  the  stroma  of  the  ovary  are  found 


8'M) 


REPRODUCTION. 


numerous  (several  thousand)  vesicular-like  bodies,  varying  from  a  micro- 
scopical size  to  the  fourth  of  an  inch  in  diameter,  the  Graafian  follicles 
or  vesicles,  so-called  after  Regnerus  de  Graaf  their  discoverer.1  These 
vesicles  (Fig.  543),  which  are  especially  abundant  at  the  peripheral  por- 


Fig.  543. 


Graafian  follicle.     (II.tcckei.. 


tion  of  the  stroma  of  the  ovary,  consist  of  an  outer  fibro-vascular  layer 
or  tunic,  a  middle  basement  membrane  or  membrana  propria,  and  an 
inner  layer  of  polyhedral  granular  epithelial  cells,  the  membrana  granu- 
losa. At  the  side  of  the  Graafian  follicle  lying  next  the  surface  of  the 
ovary,  the  cells  of  the  membrana  granulosa  are  heaped  up,  constitut- 
ing the  discus  proligerus,  within  which  is  found  the  ovum  or  egg, 
only  discovered  as  recently  as  1827  by  Von  Baer.3  The  remaining 
portion  of  the  Graafian  follicle — that  is,  the  part  not  occupied  by  the 
discus  proligerus  with  the  enclosed  egg — is  filled  with  a  serous  liquid 
containing  granules,  nuclei  cells  apparently  detached  from  the  membrana 
granulosa.  The  ovum  or  egg  as  just  discharged  from  the  follicle,  has 
usually  adhering  to  it  the  cells  of  the  discus  proligerus  and  shreds  of 
epithelium;  the  latter  being  removed,  the  egg  can  then  be  seen  with  the 
naked  eye  on  a  perfectly  clean  piece  of  glass  as  a  very  minute  speck, 
averaging  in  length  the  T|o-th  of  an  inch  Q-th  millimetre)  in  diameter. 
Under  the  microscope  the  ovum  or  egg  (Fig.  544)  appears  as  a  spheroidal 
body,  exhibiting  the  characters  of  an  organic  cell  as  already  described. 
Thus,  it  consists  of  a  cell  Avail,  an  elastic  vitellus  membrane,  the  zona 
pellucida,  measuring  about  YsVo'th  °^  an  ^ncn  (TFS"tn  °f  a  millimetre)  in 
diameter,  and  which,  while  apparently  a  clear  pellucid  membrane,  is  in 


1  I)e  Mulierum  Orsanis  Generation]  inservientibus  Tractatus  Novus,  p.  177.     Lus*d.  Batav.,  1672. 
-  De  Ovi  mammalium  ot  hominis  geueri,  Lipsiate,  1827.     Ueber  Entvvicklungs  Geschicbte  der  Tbiere, 
Kbnigsberg,  1828. 


HUMAN    OVUM. 


891 


reality  striated,   the  strife   being  probably  canals   through  which   the 
spermatozoa  pass  into  the  egg. 

Fig.  544. 


The  human  ovum.     (Hjeckel. ) 

The  cell  contents,  yelk  or  vitellus,  enclosed  within  the  zona  pellucida, 
consist  of  a  soft  or  semifluid  protoplasmic  matter,  containing  granules 
and  oil  globules,  among  which  may  clearly  be  seen  a  nucleus  and  nucle- 
olus. The  nucleus,  or  germinal  vesicle,  as  it  is  called,  in  the  ovum  dis- 
covered in  mammals  by  Coste,1  in  1834,  usually  situated  near  the  surface 
of  the  egg,  is  a  clear,  spheroidal  vesicle,  and  measures  about  the  -3-5-oth 
of  an  inch  (-^V^  of  a  millimetre),  containing  granular  fluid,  and  the 
nucleolus,  macula,  or  the  germinal  spot.  The  latter,  discovered  by 
Wagner,2  in  1835,  measures  about  the  ^^^th  of  an  inch  (^th  of  a 
millimetre,  in  diameter.  It  is  a  fact  of  profound  significance  that  the 
human  ovum,  or  first  cell,  from  which  all  the  cells  composing  the 
body  are  developed,  should  be  practically  undistinguishable,  morphologi- 
cally at  least,  from  the  ova  of  the  remaining  monodelphous  mammalia: 
and  further,  that  the  first  or  transitory  egg-stage  through  which  man 
passes  should  be  permanently  retained  as  such  through  life  in  many  of 
the  lower  plants  or  animals,  such  beings  never  passing  beyond  this  uni- 
cellular stage.  Further,  the  very  lowest  forms,  as  well  as  the  highest 
forms  of  life,  including  man,  begin  in  exactly  the  same  way  as  masses  of 
protoplasm;  the  immature  human  ovum,  like  an  immature  ova,  being  a 
mass  of  protoplasm  and  the  zona  pellucida  a  secondary  formation. 
The  ova  are  developed  from   the  germinal   epithelium   (Fig.    545),  a 

1  Recherches  sur  la  generation  des  Mammiteres  par  Delpech  et  Coste,  Paris,  1834. 
-  Mttller:  Arehiv,  18:i5.     ProdromuB  historic  generationis,  Lips.,  183G. 


892 


K  EP  KOIHCTION. 


covering  of  the  primitive  ovary.  Through  the  inward  growth  of  this 
epithelium  into  the  substance  of  the  ovary,  cords  of  cells  (b  d)  are 
formed,  which  become  divided  into  compartments  through  the  encroach- 
ment of  the  fibrous  stroma.  Of  the  cells  within  these  compartments  the 
largest  beeome  ova  :  the  smallest,  the  cells  of  the  membrana  granulosa 


Vertical  section  through  the  ovary  of  a  newborn  female.     (Waldeyer.) 


of  the  Graafian  follicle  (e/),  the  wall  of  which  is  continuous  with  the 
stroma.  As  development  advances,  fluid  accumulates  between  the 
growing  cells,  the  follicle  assumes  the  shape  of  a  vesicle,  the  egg  lying 
eventually  to  its  inner  wall.  With  the  ripening  or  maturation  of  the 
ovum,  the  Graafian  follicle  comes  to  the  surface  of  the  ovary,  the  wall  of 
which  as  well  as  that  of  the  follicle  becoming  at  the  same  time  thinner 
and  thinner,  until,  finally,  they  are  ruptured,  and  so  permit  of  the 
escape  of  the  egg.  From  the  fact  of  the  egg  or  embryo  being  found  in 
the  Fallopian  tube  or  uterus,  instead  of  in  the  abdominal  cavity,  except 
in  the  unusual  case  of  abdominal  pregnancy,  it  is  evident  that  the  Fal- 
lopian tube  must  be  so  disposed  with  reference  to  the  Graafian  follicle 
that  at  the  moment  of  its  rupture  a  temporary  passage-way  is  usually 
formed  from  one  to  the  other.  As  a  matter  of  fact,  it  is  not  positively 
known  how  the  egg  passes  from  the  Graafian  follicle  to  the  Fallopian 
tube.  It  may  be  supposed,  however,  that  the  fimbriated  extremity 
affixes  itself  to  the  ovary  at  the  moment  of  rupture  of  the  follicle,  or 
that  the  egg,  dropping  into  the  furrow  of  the  long  fimbriated  process 
situated  at  the  edge  of  the  broad  ligament  and  attached  to  the  ovary,  is 
transferred  by  ciliary  action  into  the  orifice  of  the  tube,  and  thence  by 
the  same  kind  of  action  through  the  Fallopian  tube  into  the  uterus. 
The  egg  having  arrived  in  the  cavity  of  the  latter,  if  not  in  the  mean- 
time impregnated,  sooner  or  later  decomposes  and  disappears.  Before 
describing,  however,  the  manner  in  which  the  ovum  is  impregnated, 


CORPUS    LUTEUM, 


893 


certain  changes  undergone  by  the  Graafian  follicle  and  the  mucous  mem- 
brane of  the  uterus,  incidental  to  the  maturation  and  escape  of  the  ovum 
from  the  follicle,  "whether  the  ovum  be  impregnated  or  not,  must  be  first 
considered. 


Corpus  Luteum  of  Menstruation  and  Pregnancy. 

It  is  impossible  to  convey  by  words  any  idea  of  the  extent  of  the 
congestion  of  the  internal  generative  apparatus  of  the  female  during  the 
period  of  the  maturation  and  escape  of  the  ovum  from  the  Graafian  follicle. 
The  author  can  only  say  that  in  making  post-mortem  examinations  of 
females  dying  while  menstruating,  he  was  impressed  with  the  fact  that 
the  bloodvessels,  arteries,  capillaries,  and  veins  were  distended  to  an 
extent  never  accomplished  by  an  artificial  injection,  however  successfully 
performed.  Such  being  the  case  (as  might  be  expected),  with  the 
rupture  of  the  Graafian  follicle,  there  being  quite  an  abundant  hemor- 
rhage, the  cavity  of  the  follicle  fills  with  blood.  The  latter  soon  coagu- 
lating, as  it  would  do  if  extravasated  elsewhere,  the  clot  remains 
enclosed  within  the  walls  of  the  follicle  (Fig.  546),  having  no  organic 
connection,  however,  with  the  latter,  but  simply 
lying  loose  in  the  cavity  of  the  follicle,  out  of 
which  it  can  be  readily  turned  by  the  handle  of  a 
scalpel.  The  clot,  which  at  this  moment  is  large, 
soft,  and  gelatinous,  soon  begins  to  contract,  and 
the  serum  exuded  being  absorbed  by  the  adjacent 
parts,  it  becomes  smaller  and  denser.  The  color- 
ing matter  of  the  clot  at  the  same  time  undergoing 
the  usual  changes  incidental  to  extravasation,  and 
being  to  a  great  extent  absorbed  with  the  serum, 
a  diminution  in  its  color  becomes  quite  perceptible. 
During  this  period,  about  two  weeks,  the  lining 
membrane  of  the  follicle,  which  at  the  moment  of 
rupture  presents  a  smooth,  transparent,  vascular 
appearance,  becomes  much  thickened  and  convo- 
luted. Through  the  continued  condensation  of 
clot  and  thickening  of  the  lining  membrane,  as 
just  described,  the  follicle  has  become  so  altered 
in  its  appearance  that  by  the  end  of  three  weeks 
it  can  be  no  longer  recognized  as  such,  and  is 
henceforth  known  as  the  corpus  luteum,  though  its  color  can  scarcely 
be  said  as  yet  to  be  distinctly  yellow.  At  this  period  the  corpus  luteum 
may  be  described  as  a  rounded  tumor,  about  four-fifths  of  an  inch 
(twenty  millimetres)  in  length,  situated  in  the  stroma  of  the  ovary,  and 
projecting  from  the  surface  of  the  latter,  the  surface  of  the  corpus  pre- 
senting a  minute  cicatrix,  the  mark  of  the  rupture  of  the  follicle. 

If  such  a  corpus  luteum  be  divided  longitudinally  (Fig.  547),  it  will 
be  found  to  consist  of  a  central  clot  and  a  convoluted  wall,  and  it  will 
be  observed  that,  while  the  clot  and  the  convoluted  wall  lie  in  contact 
with  each  other,  there  is  neither  anv  organic  connection  between  the 
convoluted  wall  and  the  clot,  on  the  one  hand,  nor  the  surrounding  ova- 


Graafian  follicle,  recently 
ruptured  during  menstrua- 
tion, and  filled  with  a  bloody 
coagulum  ;  shown  in  longi- 
tudinal section.  «.Tissue  of 
the  ovary.  6.  Membrane  of 
the  vesicle,  e.  Point  of  rup- 
ture.    (Dalton.) 


894 


REPRODUCTION 


rian  tissues,  on  the  other.  Prom  this  time  on,  the  corpus  luteum  under- 
goes a  retrograde  metamorphosis.  By  the  end  of  the  fourth  Avcek  it  is 
diminished  to  about  half  of  the  size  attained  at  the  end  of  the  third  week, 
the  central  clot  has  been,  to  a  great  extent,  absorbed,  the  convoluted 
wall  is  with  difficulty  separated  from  the  central  clot  and  the  peri- 
pheral ovarian  tissue,  and  its  color,  instead  of  having  faded,  like  that  of 
the  clot,  is  now  of  a  bright  yellow.  After  this  period  it  will  be  found 
impossible  to  separate  the  yellowish  convoluted  wall,  either  from  the 
ovarian  tissue  or  the  central  clot,  and  by  the  end  of  two  months  the 


Fro.  547. 


Fig.  548. 


') 


Human  ovary  out  opeu,  showing  a  corpus  luteum, 
divided  longitudinally,  tbree  weeks  after  menstrua- 
tion. From  a  girl,  twenty  years  of  age,  dead  of 
haemoptysis.     (Dalton.) 


Ovary,  showing  corpus  luteum,  nine  weeks 
after  menstruation.  From  a  girl  dead  of 
tubercular  meningitis.     (Dalton.) 


whole  corpus  luteum  will  be  found  to  be  reduced  to  the  condition  of  a 
greenish,  cicatrix-like  spot  (Fig.  548),  about  one-fourth  of  an  inch 
(6  millimetres)  in  diameter.  At  the  end  of  six  months  the  corpus  luteum 
has  usually  disappeared.  It  may,  however,  be  sometimes  found,  though 
in  a  very  atrophied  condition,  even  seven  or  eight  months  after  the 
rupture  of  the  follicle.  Such,  in  brief,  is  the  manner  in  which  the 
corpus  luteum  of  menstruation  is  developed  out  of  the  ruptured  Graafian 
follicle  from  which  the  ovum  has  escaped,  at  least  as  observed  by  the 
author  in  a  number  of  females  dying  from  natural  causes  or  violent 
deaths,  and  which  does  not  differ  essentially  from  the  process  so  admi- 
rably described  by  Dalton.1  As  during  pregnancy  far  more  blood 
flows  to  the  female  generative  apparatus  than  during  menstruation,  it 
might  necessarily  be  supposed  that  while  the  production  of  the  corpus 
luteum  would  be  essentially  the  same  in  both  conditions,  the  corpus 
luteum,  being  better  nourished,  would  grow  larger  and  persist  longer 
than  the  corpus  luteum  of  menstruation.  That  such  is  the  case  there 
can  be  no  doubt,  a  corpus  luteum  being  present  at  the  end  of  pregnancy 
even,  and  measuring  as  much  as  half  an  inch  in  diameter.  While 
marked  differences  exist,  therefore,  between  the  corpus  luteum  of  men- 
struation and  that  of  pregnancy,  nevertheless,  as  these  differences  are 


1  Trans,  of  the  American  Med.  Assoc,  vol.  iv.  p.  547. 
Phlla.,  1882. 


Phila.,  1851.     Thysiology,  7th  edit.,  p.  608. 


MENSTRUATION.  895 

of  degree,  and  not  of  kind,  and  since  the  corpus  luteum  of  menstrua- 
tion during  the  first  three  weeks  increases  in  size,  but  that  of  pregnancy 
after  the  first  six  months  diminishes,  it  can  be  readily  conceived  that 
at  a  particular  moment  the  corpus  luteum  of  menstruation  might  be  of 
the  same  size  as  that  of  pregnancy,  and  that  if  the  color  of  the  clot  and 
convoluted  Avail  in  the  two  were  not  well  marked,  the  two  corpora  lutea 
might  be  undistinguishable.  At  least  such  has  been  the  experience  of 
the  author,  in  comparing  numerous  corpora  lutea  of  menstruation  of 
various  ages  with  those  of  pregnancy.  Further,  that  the  presence  or 
absence  of  a  corpus  luteum  cannot  be  accepted  as  positive  evidence  of 
impregnation  having  taken  place  is  shown  by  the  fact  that,  although  in 
several  instances  during  post-mortem  examinations  a  fcetus  was  removed 
from  the  uterus  by  the  author,  not  a  trace  of  a  corpus  luteum  could  be 
found  in  either  ovary,  and,  on  the  other  hand,  in  more  than  one  instance 
a  well-developed  corpus  luteum  being  present  several  months  after  the 
last  menstruation,  there  was  not  the  slightest  reason  to  believe  that 
during  that  period  there  had  been  a  fcetus  in  the  uterus,  at  least  the 
relatives  of  the  deceased  had  no  object  in  concealing  the  fact  of  impreg- 
nation, if  such  had  really  occurred. 

Menstruation. 

Coincident  with  the  maturation  and  escape  of  the  ovum  from  the 
Graafian  follicle,  the  mucous  membrane  of  the  uterus  undergoes 
several  well-marked  changes.  Thus,  while  in  the  ordinary  conditions 
it  measures  only  about  the  one-fourteenth  of  an  inch  in  thickness,  at 
this  period  it  becomes  twice  or  even  three  times  as  thick.  It  is 
also  much  softer  and  more  loosely  attached  to  the  underlying  part 
than  ordinary,  being  somewhat  rugose  in  character.  The  glands 
are  very  much  enlarged,  and  the  surface  of  the  membrane  smeared 
with  blood.  The  latter  is  due  to  a  kind  of  fatty  degeneration  set 
up  in  the  mucous  membrane  involving  the  bloodvessels,  by  which 
the  capillaries  are  ruptured.  The  hemorrhage  so  caused  constitutes 
the  menstrual  Mow,  or  the  menses,  catamenia,  etc.,  and  appears 
monthly  in  the  healthy  female.  It  appears  to  be  pure  arterial  blood 
mixed  with  desquamated  utero-vaginal  epithelium;  the  amount  of  the 
latter  would  appear  from  the  observations  of  the  author  to  be  greater 
than  usually  supposed.  The  menstrual  blood  is  kept  from  coagulating 
by  the  vaginal  mucus.  As  might  be  expected  from  the  nature  of  the 
case,  it  is  impossible  to  say  how  much  blood  is  discharged  during  the 
menstrual  period,  for,  apart  from  the  difficulty  experienced  in  collecting 
it,  women  vary  very  much  in  respect  to  the  amount  of  blood  lost. 
From  five  to  twenty  ounces  may  be  accepted  as  an  approximative  esti- 
mate of  the  total  flow  during  the  menstrual  period.  Menstruation  is 
sometimes  regarded  as  the  effect  of  ovulation,  the  trio  being  so  inti- 
mately associated.  Since  menstruation,  hoAvever,  occurs  without  ovula- 
tion in  the  absence  of  ovaries,  and  ovulation  without  menstruation,  it  is 
evident  that  the  two  phenomena  are  not  related  as  cause  and  effect,  but 
should  be  considered  as  the  effects  of  a  common  cause,  the  general 
preparation  of  the  system  for  impregnation.  Indeed,  the  thickening 
and  shedding  of  the  mucous  membrane  of  the  uterus,  and  hemorrhage 
during  menstruation,  differ  only  in  degree,  not  in  kind,  from  the  changes 


896  REPRODUCTION. 

undergone  by  the  mucous  membrane  during  pregnancy  and  parturition. 
That  the  menstrual  flow  is  the  effect  of  a  deep-lying  cause,  the  fitting 
of  the  mucous  membrane  for  the  reception  of  the  ovum,  though  not  due 
to  the  production  of  the  latter,  is  shown  by  the  constitutional  disturb- 
ance experienced  by  the  female  when  the  menses  first  appear,  and  ever 
afterward  with  their  monthly  reappearance,  though  then  to  a  less  extent. 
The  menses  usually  appear  between  the  age  of  thirteen  and  fifteen 
years  and  much  earlier  in  warm  climates.  At  this  period,  the  age  of 
puberty,  there  is  a  general  development  of  the  body,  the  limbs  become 
fuller  and  rounder,  hair  appears  on  the  mons  veneris,  the  mammary 
glands  enlarge,  ova  maturate,  and  the  disposition  changes.  Just  before 
the  establishment  of  the  flow,  either  in  the  case  of  its  first  appearance 
or  in  after  recurring  ones,  for  about  two  days  a  feeling  of  general 
malaise  is  experienced,  particularly  a  sense  of  weight  and  fulness  in 
the  pelvic  organs,  the  vagina  mucus  is  increased  in  amount  and  becomes 
rusty  in  color,  and  gives  rise  to  the  odor  so  perceptible  in  certain 
females,  the  breasts  also  enlarge,  showing  the  sympathies  of  the  latter 
for  the  generative  organs.  With  the  establishing  of  the  flow,  the  dis- 
agreeable feelings  and  uneasiness  usually  pass  away,  and  by  the  end  of 
the  fourth  day,  though  the  time  varies,  the  flow  ceases,  and  the  mucous 
membrane  returns  to  its  normal  condition.  At  about  forty-five  years  of 
age  the  menses  become  irregular  in  their  recurrence  and  usually  cease 
altogether  at  fifty.  The  phenomenon  of  the  menses  is  not  restricted  to 
the  human  female,  as  is  often  supposed,  the  heat  or  rut  of  the  lower 
animals  being  essentially  the  same  process.  Indeed,  in  the  monkeys 
(macacus  cynocephalus),  apes,  their  is  a  discharge  of  blood  monthly,  and 
in  the  mare,  cow,  and  dog  the  same,  but  recurring  at  longer  intervals. 
It  is  a  significant  fact,  that  the  female  of  animals,  except  monkeys,  only 
receive  the  male  during  the  rutting  or  menstruating  period. 

The  Male  Generative  Apparatus. 

The  male  generative  apparatus  consists  of  the  testicles,  the  spermatic 
ducts,  the  seminal  vesicles,  prostate  and  suburethral  glands,  and  the 
penis.  The  testicles  (Fig.  549),  secreting  the  spermatic  fluid,  are  two 
glandular  bodies  suspended  by  the  spermatic  cords  within  the  scrotum. 
The  latter  is  essentially  a  musculocutaneous  pouch,  divided  into  two 
recesses  by  a  septum  for  the  reception  of  the  two  testicles.  Each  testicle 
consists  of  an  anterior  oval  portion  of  the  body  or  testes  proper,  and  a 
posterior  elongated  portion  clasping,  as  it  were,  the  former,  the  epididy- 
mis. The  upper  portion  of  the  epididymis  is  known  as  the  head  or 
globus  major,  the  lower  part  as  the  tail  or  globus  minor,  which  in 
turning  upward  upon  itself,  becomes  the  spermatic  duct.  The  testes  are 
covered  with  a  dense  white  fibrous  membrane,  the  tunica  albuginea, 
which  at  the  back  of  the  testes  forms  a  process,  the  mediastinum. 
The  latter  being  prolonged  as  fibrous  bands  to  be  inserted  into  the  inner 
surface  of  the  tunica  albuginea,  serves  as  a  sort  of  scaffolding  to  support 
the  delicate  glandular  substance  within.  The  testicle  proper,  is  made 
up  of  about  two  hundred  lobules,  each  lobule  in  turn  consisting  of  from 
one  to  six  seminiferous  tubules,  of  which  there  are  perhaps  eight  hun- 
dred in  all. 


MALE     GENERATIVE    APPARATUS. 


897 


The  seminiferous  tubules  at  the  narrow  end  of  the  lobule  assume  a 
straight  course,  being  then  known  as  the  vasa  recti.  The  latter 
entering  the  mediastinum,  constitute  together  the  plexus  retiformis, 
from  which  emerge  about  a  dozen  efferent  canals,  or  vasa  efferentia,  to 
pass   out   to   the   head    of   the   epididymis.      Within    the    latter    these 


Fig.  549. 


Testicle  and  epididymis  of  the  human  subject.  a.  Testicle,  b.  Lobules  of  the  testicle  c  Vaaa 
recta,  d.  Rete  testis,  e.  Vasa  efferentia.  /.  Cones  of  the  globulus  major  of  the  epididymis,  g  Epi- 
didymis h.  Vas  deferens,  i.  Vas  aberrans.  m.  Branches  of  the  spermatic  artery  to  the  testicle  and 
epididymis,  n.  Ramification  of  the  artery  upon  the  testicle  and  epididymis,  o.  Deferential  artery,  p. 
Anastomosis  of  the  deferential  with  the  spermatic  artery.  (KiiLUKER,  Hmidbiich  der  Gea-ebelthre,  Leip- 
zig, 1867,  S.  523.) 

efferent  canals  form  the  spermatic  cones,  which  finally  give  rise  to  one 
convoluted  tube,  constituting  the  body  and  tail  of  the  epididymis,  the 
latter  of  which,  as  just  mentioned,  becomes  the  spermatic  duct.  The 
spermatic  duct  passing  through  the  inguinal  canal,  leaves  the  latter  at 
the  internal  abdominal  ring,  and  descending  backward  and  downward, 
passes  forward  to  form,  together  with  the  duct  of  the  seminal  vesicle, 
the  ejaculatory  duct,  the  latter  terminating  in  the  prostatic  urethra. 
The  seminiferous  tubules,  about  thirty  inches  in  length  when  unravelled, 
and  the  y^tti  of  an  inch  in  diameter,  consist  of  a  fibro-membranous 
wall  lined  with  a  delicate  layer  of  soft  polyhedra  nucleated  cells, 
the  sperm  cells,  which  elaborate  the  spermatic  or  seminal  liquid, 
of  which  about  half  a  drachm  is  emitted  during  the  orgasm.  The 
latter  is  a  faintly  alkaline  liquid,  slightly  heavier  than  water,  becoming 
jelly-like  first,  and  then  hardening  after  emission.  Of  a  thousand 
parts,  perhaps  one  hundred  are  solid.  Chemically  but  little  is  posi- 
tively known  of  its  composition ;  phosphates  appear,  however,  always  to 

:,7 


898 


REPRODUCTION. 


be  present,  notably  magnesium  phosphate.  Physiologically  the  essential 
portion  of  the  spermatic  fluid,  upon  which  its  fecundating  powers 
without  doubt  depend,  are  the  spermatozoa  that  it  contains.  Indeed, 
if  the   seminal  liquid  be   deprived  of  its  spermatozoa,  it  is    rendered 

entirely  inoperative  as  regards  impregnation.  Of  the  sperm  cells  just 
mentioned,  which  elaborate  the  sperm,  some  are  larger  than  others, 
and  it  would  appear  that  the  development  of  the  spermatozoa  appearing 
first  at  the  age  of  puberty  and  afterward  up  to  ninety  years  of  age,  and 
longer,  takes  place  only  within  these  larger  cells,  the  granular  nuclei  of 
which  divide  (Fig.   550)  and  subdivide,  one  of  the  nucleoli  of  each 

Pig   •">•">  1 


rammatic  view  of  development  of  spermatozoa. 


Spermatozoa  of  man.     h,  ap- 
parent  nucleus.  6,  body.  J,  tail. 


nucleus  assuming  the  form  of  a  spermatozoon,  which  is  set  free  by  the 
deliquescence  of  the  cell  wall  enclosing  it.  The  spermatozoa  (Fig.  551), 
discovered  by  Hammins  or  Von  Hammen  in  1677,  and  described  by 
Leeuwenhock,  resemble  the  flagellate  animalcule  for  which  they  Avere 
first  taken.  A  spermatozoon  consists  of  an  ovoidal  head,  apparently 
containing  a  nucleus,  about  the  g^th  of  an  inch  in  length,  and  of  a  fila- 
mentary appendage  or  tail  the  ^-yth  of  an  inch  in  length,  which  vibrates 
with  astonishing  rapidity.  The  movements  of  the  spermatozoa  are 
arrested  by  water  and  cold,  retarded  by  acids,  and  favored  by  alkalies. 
The  spermatic  fluid,  with  the  spermatozoa,  passes  from  the  testicles  by 
the  spermatic  ducts  to  the  seminal  vesicles,  where  it  becomes  mixed 
with  the  secretion  of  the  latter,  the  nature  and  use  of  which  are,  how- 
ever, doubtful,  as  no  secreting  glands  are  found  in  these  vesicles ;  its 
use  may  be  to  dilute  the  mixed  spermatic  fluid.  The  spermatic  fluid 
having  accumulated  in  the  seminal  vesicles  is  thence  introduced  during 
coition,  still  further  mixed  with  the  secretion  of  the  prostate  gland, 
of  the  glands  of  Cowper,  and  of  the  urethra,  the  use  of  which  is  not 
known,  by  an  ejaculatory  effort,  into  the  vagina  of  the  female,  the 
spermatozoa  by  their  vibrating  movements  passing  up  into  the  Fallo- 
pian tubes,  and  even  the  ovaries,  as  shown  by  the  development  of  the 
ovum  in  those  situations  in  cases  of  extra-uterine  pregnancy.  In 
order    that   coition   should  be    accomplished,    it    is    essential   that    the 


MALE    GENERATIVE    APPARATUS.  899 

penis  should  be  erect.  This  is  brought  about  through  its  blood  supply 
being  very  much  increased  by  the  stimulation  of  the  vaso-dilator  fibres 
of  the  nervi-erigentes,  the  latter  arising  probably  from  the  second 
sacral  nerves.  The  centre  of  erection,  situated  in  the  cord,  can  be 
reflexly  stimulated  either  by  impressions  made  upon  the  genital  organs, 
or  upon  the  mind.  The  ejaculatory  effort  is  due  to  the  simultaneous 
contraction  of  the  bulbo  urethroe,  ischio-cavernous,  and  transverse 
perinseus  muscles,  due  to  the  reflex  stimulation  of  the  ejaculatory 
centre  of  the  spinal  cord,  situated  in  the  lumbar  region. 


CHAPTER   LVI. 

REPRODUCTION.— {Concluded.) 

Impregnation  of  the  Ovum  and  Development  of  Embryo. 

As  a  matter  of  fact,  nothing  is  known  as  to  the  manner  in  which  the 
ovum  is  impregnated  in  the  human  female,  or  of  the  early  stages  of  the 
development  of  the  embryo.  Since  the  primitive  ova  of  all  animals  are, 
however,  alike,  and  the  mature  eggs  of  ordinary  mammals  undistinguish- 
able  from  that  of  the  human  female,  and  as  the  spermatozoa  of  the  mam- 
malia and  animals  generally  differ  from  each  other  unessentially,  it  is  to 
he  inferred  that  the  process  of  impregnation  in  the  human  female  is  the 
same  as  that  observed  in  animals.  Further,  as  the  human  foetus  of  about 
three  weeks  old  (Fig.  552)  differs  but  little  from  that  of  the  rabbit  at  about 


Fig.  552. 


Fig.  553 


Embryo  of  man. 
<j.  Eye.   m.  Mid-brain,   o.  Ear. 


Embryo  of  rabbit. 
Spinal  marrow,    w.  Vertebral  column,    k.  Visceral  arches.   (HiKCKEL.) 


ten  days  (Fig.  553),  there  can  be  little  doubt  that  the  stages  intermediate 
between  that  of  the  egg  and  that  of  three  weeks  old,  through  which  the 
human  embryo  passes,  are  essentially  the  same  as  the  corresponding  stages 
through  which  the  rabbit  embryo  passes  from  the  stage  of  the  egg  to  that 
represented  in  Fig.  553,  or  the  corresponding  stages  in  the  development 
of  the  dog,  hog,  etc.,  or  even  bird,  reptile,  or  fish.  Assuming,  then, 
that  the  development  of  man,  in  the  early  stages,  is  the  same  as  that  of 
a  rabbit,  for  example,  we  will  describe,  as  illustrating  the  former,  the 
development  of  that  animal,  as  based  principally  upon  the  researches  of 
Bischoft* '  and  Van  Beneden,2  up  to  the  period  that  it  begins  to  differ 
from  man.  The  act  of  impregnation  in  the  rabbit,  and  in  all  animals 
in  which  impregnation  has  been  observed,  consists  in  the  passage  of  one  or 
more  spermatozoa  (Fig.  554)  through  the  vitelline  membrane  of  the  egg 


1  Entwiekliings  Geschichte  des  Kaninchen-Eies,  Braunschweig,  1842. 

2  La  maturation  de  l'oeuf,  etc.,  d'apres  des  rechercb.es  faitea  chez  le  lapin,  Bruxelles   1875 


IMPREGNATION     OF    OVUM. 


901 


into  the  vitellus,  the  germinal  vesicle  in  consequence  immediately  disap- 
pearing. The  first  effect  of  fecundation  appears,  then,  to  be  the  reducing 
of  the  distinctly  nucleated  egg  to  the  condition  of  a  monera-like  ball  of 
protoplasm  (Fig.  555),  hence  the  name  of  monerula,  given  by  Hpeckel, 
to  this,  the  first  stage  of  the  development  of  the  embryo.      It  will  be 


Fig.  554. 


Fig.  555. 


Passage  of  spermatozoa  into  vitellus. 

(H.ECKEL.) 


Monerula  of  rabbit.     (Hjeckel.) 


observed,  also,  that  the  inner  yelk  (c?),  or  protoplasm,  has  receded  some- 
what from  the  cell-wall  or  zona  pellucida  (2),  and  that  the  latter  is 
covered  with  several  concentric  layers  (h)  of  an  albuminous  nature  de- 
posited during  the  passage  of  the  egg  through  the  Fallopian  tube.  The 
egg,  after  fecundation,  does  not  remain  in  this  unnucleated  condition 
long,  a  new  nucleus  and  nucleolus  appearing.  The  latter  has,  however, 
an  entirely  different  morphological  significance  from  the  germinal  vesicle 
and  spot  of  the  primitive  or  unimpregnated  egg,  being  developed,  in  all 
probability,  by  the  fusion  or  coalescence  of  the  head  of  the  spermatozoa 
or  pronucleus  with  the  remains  of  the  germinal  vesicle,  probably  the 
nucleolus  or  female  pronucleolus,  the  latter  coming  to  the  surface  of  the 
ovum,  as  it  were,  to  meet  the  spermatozoan.  While  there  is  no  doubt 
that  the  new  nucleus  and  nucleolus  are  due  to  the  fusion  in  some  way 
of  the  spermatozoin  with  the  old  germinal  vesicle,  or  part  of  the  same, 
the  exact  details  of  the  process  not  having  yet  been  worked  out,  at  least 
satisfactorily,  Ave  will  not  dwell  further  upon  it.  It  may  also  be  added 
that  though  one  spermatozoin  only  appears  to  enter  into  the  formation 
of  the  new  nucleus,  and  suffices,  therefore,  for  fecundation,  there  can 
be  no  doubt  that  numerous  spermatozoa  pass  into  the  vitellus  during  the 
act  of  impregnation.  The  author  has  observed  this  too  often  in  the  ova 
of  the  lower  forms  of  life,  as  well  as  in  some  of  the  higher,  to  have  any 
doubt  himself  as  to  the  fact,  whatever  its  significance  may  be.  With 
the  appearance  of  this  new  nucleus  and  nucleolus  (n,  Fig.  556),  the  egg 
passes  from  the  first  or  monerula  stage  to  that  of  the  cytula  stage,  as  it  is 
called  by  Haeckel,  or  parent  cell  stage,  from  the  fact  of  its  being  the  parent 
of  all  the  future  cells  of  which  we  have  seen  the  tissues  of  the  body  consist. 
Shortly  after  the  appearance  of  the  nucleus  and  nucleolus  the  process  of 


902 


REPRODUCTION, 


the  cleavage,  segmentation,  or  furrowing  of  the  vitellus  begins — that  is, 
the  vitellus  subdivides  into  two  spheres,  each  of  which  is  provided  with 
a  nucleus  and  nucleolus  (Fig.  557).  The  two  spheres,  so  formed  by 
fission,  subdividing  into  four  (Fig.   558),  and  the  four  into  eight,  the 


Fig.  556. 


Fig.  557. 


Cytula  of  rabbit.     (H.sckel 


Segmentation  of  vitellus  in  rabbit      (H^ckel.) 


eight  into  sixteen,  and  so  on,  the  original  single  vitellus  becomes  finally 
transformed  into  a  mulberry-like  mass  of  vitelline  spheres,  the  vitelline 
membrane  remaining,  however,  undivided.  These  cells  are  not  of  the 
same  size  and  are  differently  affected  by  reagents.     The  larger  cells 


Fig.  558. 


Segmentation  of  vitellus  in  rabbit  continued.     (H.teckel.) 

originally,  the  smaller  ones  finally,  arrange  themselves  in  the  centre,  the 
smaller  ones  at  the  periphery  and  in  a  single  row,  the  latter  enclosing 
the  former,  as  a  cup,  its  contents.  The  egg  now  reaches  its  gastrula  stage 
(Fig.  559).  Shortly  afterward,  however,  through  one  of  the  larger  inner 
cells  being  drawn  inward  the  mouth  (o)  of  the  gastrula  disappears,  and 
the  latter  now  forms  a  ball  consisting  of  larger  cells  within  and  covered 
by  a  single  layer  of  small  vesicles  without.  Fluid,  formed  probably 
through  the  deliquescence  of  some  of  the  cells,  appears  between  the  inner 


DEVELOPMENT    OF    EMBRYO. 


903 


cells  and  the  layer  of  outer  ones ;  the  latter  is  expanded  into  a  one-layered 
globular  vesicle,  the  inner  cells  remaining  as  a  ball  of  cells  adhering  to 
the  outer  layer  at  the  point  where  the  mouth  of  the  gastrula  was  situated. 
The  inner  cells  now  lose  their  ball-like  form,  and  becoming  flattened, 


Gastrula  of  rabbit,  in  longitudinal  section.     (Hjeckel.) 

assume  a  discoidal  shape,  spreading  themselves  out.  The  gastrula,  so 
modified,  is  now  known  as  the  blastodermic  vesicle  (Fig.  560),  and  con- 
sists, as  shown  in  section,  of  the  original  zona  pellucida  or  cell-wall  (a) 
which  we  shall  henceforth  designate  as  the  chorion,  of  a  single  layer  of 


Fig.  500. 


Fig.  561. 


<v — : 


Blastodermic  vesicle  of  rabbit  seen  in  section. 

(HaCKEL.) 


Blastodermic  vesicle  of  rabbit,  seen  from  surface. 
(Kolliker,  after  Bisohoff.) 


cells  (b)  lying  next  to  the  chorion  and  constituting  the  wall  of  the  blas- 
todermic vesicle,  of  a  heap  of  cells  (c)  adhering  to  the  inner  surface  of 
the  wall.  The  latter  being  darker  in  color  than  the  cells  forming  the 
Avail  of  the  vesicle,  looks  like  a  dark  mass  when  the  blastodermic  vesicle 
is  viewed  from  the  surface,  the  cells  of  the  wall  then  appearing  like  a 
mosaic  (Fig.  561). 

The  changes  just  described  by  which  the  egg  is  transformed  into  the 
blastodemic  vesicle  appear  to  take  place  as  the  egg  passes  through  the 
Fallopian  tube. 


904 


REPRODUCTION. 


Formation  of  Blastodermic  Membrane. 

The  blastodermic  vesicle  does  not  remain,  however,  long  a  one-layered 
vesicle,  but  soon,  through  the  extension  of  the  disk-like  dark  cells  around 
to  the  opposite  pole  of  the  egg,  a  two-layered  vesicle;  and  further,  through 
the  development  of  a  third  layer  intermediate  between  the  external 
and  internal   one,  a  three-layered  vesicle  (Fig.  562),  not  including,  of 


Fig.  562. 


Fig.  563. 


Diagrammatic  view  of  ovum  of  rabbit,  consisting 
of  chorion,  enclosing  three-layered  blastodermic 
vesicle. 


Diagrammatic  view  of  ovum  of  rabbit  to  show 
formation  of  primitive  trace  (B)  by  fusion  of  blasto- 
dermic membrane. 


course,  the  chorion  (Z)  or  the  original  zona  pellucida  of  the  egg,  which 
now  presents  here  and  there  over  its  outer  surface  little  wart-like  villous 
processes.  The  three  layers  of  which  the  blastodermic  vesicle  now 
consists  (1,  2,  3,  Fig.  562),  are  known  from  without  inward  as  the 
external,  middle,  and  internal  blastodermic  membranes,  or,  more  briefly 
as  the  epiblast,  mesoblast,  and  hypoblast. 

Development  of  Primitive  Trace. 

Shortly  after  the  development  of  these  three  layers  through  the 
thickening  of  the  two  outer  ones,  there  appears  within  tolerably  well- 
defined  limits  an  opaque  oval-like  body  (Fig.  564,  b),  the  primitive 
trace1  or  double  shield,2  so  called  on  account  of  indicating  the  rudiment 
of  the  body  of  the  future  embryo,  the  remaining  portions  of  the  blas- 
todermic membranes  not  entering  into  the  formation  of  the  body  of 
the  embryo,  but  appropriated,  as  we  shall  see  presently,  to  the  formation 
of  the  true  and  false  amniotic  folds  and  umbilical  vesicle.  If  the  blas- 
todermic vesicle  be  viewed,  not  in  section,  but  from  the  surface,  the 
primitive  trace  will  be  seen  (Fig.  564,  b)  as  an  oval-like  structure,  lying 
in  the  centre  of  a  pellucid  area  (c),  so  called  on  account  of  the  latter 
being  surrounded  by  an  opaque  area  (<7),  the  whole  area  extending  from 
edge  to  edge  of  the  area  opaca  (d),  being  known  as  the  area  germinativa, 
which    at    this    period,    while  oval-shaped,    is  at  its    first    appearance 


1  Von  Baer  :  TTber Entwickelungs  Gescbiclite  der  Thiere,  Zweiter  Theil,  S.  fin,  S.  TOO.  Konisberg,  1837. 

2  Remak  :  Uutersuchungeu  iiber  die  entwickelung  der  Wirbelthiere,  S.  7.     Berlin,  1855. 


DEVELOPMENT    OF    PRIMITIVE    ORGANS. 


905 


round  in  form.  The  opacity  of  the  outer  portion  of  the  area  germina- 
tiva,  giving  rise  to  the  name  of  area  opaca,  is  due  to  the  development 
within  the  cells  of  this  part  of  the  area  germinativa  of  dark  protoplasmic 
granules.    If  viewed  by  reflected  light,  however,  as  in  Figs.  564  and  565, 


Fig.  564. 


Fig.  565. 


Primitive  trace  ot"  rabbit  (6).     Primitive   groove 
(a)    Area  pellucida  (c).  Area  opaca  (d).  (II.t.ckf.l.  t 


Lyre-shaped  primitive  trace  of  rabbit.     Letters 
,s  in  Fig.  605.     (H.f.ckel.) 


the  area  opaca  (d)  will  appear  light,  and  the  inner  portion  of  the  area 
germinativa,  or  the  area  pellucida  (c),  dark,  by  comparison  the  dark 
ground  being  visible  from  below. 

Development  of  Primitive  Organs. 

Shortly  after  the  development  of  the  primitive  trace  (Fig.  564,  b) 
within  the  area  pellucida  (c),  there  appears  along  its  central  line  a  delicate 
white  streak,  the  primitive  streak1  or  axis  plate,2  due  to  the  coalescence 
of  the  three  blastodermic  membranes  along  the  middle  line,  as  shown  by 
section  (Fig.  568,  B),  and  with  further  developments  within  the  latter  a 
delicate  groove  or  furrow  (a),  which  may  be  called  the  spinal  furrow, 
since,  as  we  shall  see  in  a  moment,  through  its  conversion  by  deepening 
and  closing  into  a  tube,  it  gives  rise  to  the  spinal  cord.  As  this  primitive 
groove  («)  deepens,  the  primitive  trace  (b)  and  area  pellucida  (<?)  lose 
their  oval  shape  and  become  lyre-or  sole-shaped  (Fig.  565) :  the  area  opaca 
(d),  however,  reassumes  its  original  round  shape.  Returning  now  to 
the  consideration  of  the  embryo  as  studied  by  transverse  section  (Fig. 
563),  it  will  be  seen  from  a  comparison  of  the  section  (Fig.  566)  made 
through  an  embryo  more  advanced  in  development  than  that  of  Fig.  604, 
that  not  only  the  primitive  groove  or  furrow  (mr)  is  much  deepened, 
but  that  the  external  blastodermic  membrane  rises  up  into  folds  (1'/), 
which  arching  over  the  dorsal  surface  of  the  embryo,  coalesce  in  the 
middle  line  and  form  the  amnion,  the  remaining  portion  of  the  external 


i  Von  Baer,  op.  cit.,  Erster  Theil.  S.  12. 


-  Remak,  op.  cit. 


906 


REPRODUCTION. 


blastodermic  membrane  receding  from  the  amnion  proper  as  the  false 
amniotic  folds  (/'),  until  they  finally  fuse  with  the  inner  surface  of  the 
chorion  (Fig.  566).     It  will  also  be  observed  that  the  middle  blasto- 


Pig.  566. 


Diagrammatic  view  uf  ovum  of  rabbit  to  show  primitive  furrow,  amniotic  folds,  splitting  of  mesoblast. 

dermic  membrane  or  mesoblast  has  split  into  two  layers  (Fig.  566,  2,  2'), 
of  which  layer  2,  or  the  skin  fibrous  layer,  unites  with  that  part  of  the 
external  blastodermic  membrane,  or  the  skin  sensory  layer,  out  of  which 

Fig.  567. 


In  all  the  figures  the  letters  indicate  the  same  parts,  h.  Skin  sensory  layer,  mr.  Spinal  tube.  hf.  Skin 
fibrous  layer,  w.  Primitive  vertebrae,  ck.  Notochonl.  c.  Body-cavity  (codoma)  df.  Intestinal  fibrous 
layer.     (M.^Intestiual  glandular  layer,     d.  Intestinal  cavity,     nb.  Navel  vesicle.     (Hjeckel.) 

the  primitive  spinal  tube  is  developed  to  form  the  parietes  of  the  body,  as 
shown  in  Fig.  567  (A,  E),  representing  in  section  the  embryo  successively 
advanced  in  development,  while  layer  2',  or  the  intestinal  fibrous  layer, 
in  adhering  to  the  internal  blastodermic  membrane,  or  layer  3,  forms  the 
fibro-muscular  wall  of  the  primitive  alimentary  canal  and  umbilical 
vesicle  (3),  the  internal  blastodermic  membrane,  or  the  intestinal  glan- 
dular layer,  giving  rise  only  to  the  mucous  membrane  lining  the 
same.  An  inspection  of  these  different  sections  will  show  also,  that  just 
as  the  primitive  neural  canal,  or  spinal  cord,  is  developed  through  the 


DEVELOPMENT    OF     PRIMITIVE    ORGANS. 


907 


primitive  groove  (mr)  being  transformed  into  a  tube,  which  later  becomes 
entirely  separated  from  the  external  blastodermic  membrane,  the  latter 
giving  rise  to  the  epithelium  or  epidermis  of  the  skin,  so  through  the 
deepening  of  the  furrow  (rf)  in  the  internal  blastodermic  membrane  the 
primitive  alimentary  canal  is  formed,  the  umbilical  vesicle,  originally 
part  of  the  same,  being  constricted  off  by  the  bending  downward  and 
inward  of  the  parietes  of  the  body. 


Fio.  568. 


Fig.  569. 


a.    Umbilical   vesicle.      6.    Amniotic  cavity.  Fecundated  egg,  with  allantois  nearly  complete. 

e.  Allantois.    (Daltos.)  ".  Inner  lamina  of  amniotic  fold.   6.  Outerlamina 

of  ditto.  c.  Point  wliere  the  amniotic  folds  come 
in  contact.  The  allantois  is  seen  penetrating  be- 
tween the  inner  and  outer  lamina?  of  the  amniotic 
folds.     (Dalton.) 

An  inspection  of  Figs.  566  and  567  will  also  show  that  as  the  primi- 
tive furrow  (mr)  of  the  external  blastodermic  membrane  is  formed 
there  is  developed  within  the  middle  blastodermic  membrane  a  rod  of 
cartilage  (ch),  the  notochord,  or  chorda  dorsalis,  which  represents 
the  axis  around  which  will  be  developed  the  bodies  of  the  future  verte- 
brae, the  neural  canal  being  finally  enclosed  by  a  bony  spinal  canal, 
through  ossification  of  that  portion  of  the  mesoblast  lying  above  and 
on  either  side  of  the  notochord.  The  embryo  of  the  rabbit  consists 
at  this  period,  then,  apart  from  the  enveloping  chorion  (Fig.  567,  E), 
of  two  tubes,  a  neural  one  above,  an  alimentary  tube  below,  separated 
by  a  rod  of  cartilage,  and  enclosed  by  the  walls  of  the  body,  the  space 
between  the  two  layers  of  the  mesoblast  representing  the  future  body 
cavity.  Resuming  what  we  have  just  endeavored  to  describe,  it  will  be 
seen  that  through  the  process  of  segmentation  the  vitellus  is  trans- 
formed into  a  mass  of  cells,  that  these  cells  dispose  themselves  as  three 
membranes  or  layers,  that  the  three  layers  give  rise  to  the  primitive 
organs  of  the  body,  out  of  which  the  remaining  organs  are  developed,  as 
shown  in  Table  LXXXIII. 


908 


REPRODUCTION. 


Table  LXXXIII. 


-Membranes  and  Layers  of  Embryo  and  Organs 
Developed  from  Them. 


Membranes. 

External  blasto- 
dermic membrane 
or  epiblast, 


Middle  blasto- 
dermic membrane 
or  mesoblast, 


Internal  blasto- 
dermic membrane 
or  hypoblast, 


Layers. 


(    Skin, 
(      sensory, 


Skin, 

sensory, 


Intestinal 
fibrous, 


Organs. 

Epidermis. 

Centra]  nervous  system. 

Primitive  kidneys. 

I  dermis. 

Peripheral  nervous  system. 

Osseous 

Muscular 

Testes. 

f  Vascular  system. 

|   Mesentery. 

|    Wall  of  alimentary  canal 

and  appendages. 
I   Ovaries. 


;    Intestinal      f  Epithelium  of  alimentary 
f    glandular,    i       canal  and  appendages. 


Fig.  570. 


Development  op  Amnion,  Allantois,  and  Umbilical  Vesicle. 

It  has  already  been  mentioned  that  that  portion  of  the  external 
blastodermic  membrane  not  entering  into  the  formation  of  the  em- 
bryo, rises  up  into  folds  (Fig.  569)  at  the  sides,  head,  and  tail  ends 
of  the  latter,  and  arching  over  its  back,  and  coalescing  in  the  middle 
line,  form  the  amnion  (a),  the  remaining 
peripheral  portions  of  the  extensive  blasto- 
dermic membranes  not  giving  rise  to  the  am- 
nion  receding  as  the  false  amnion  (b)  from  the 
true  one,  until  it  reaches  the  inner  surface  of 
the  chorion,  with  'which  it  ultimately  fuses. 
It  will  also  be  observed  from  Figs.  570  and 
571,  representing  the  progressive  development 
of  the  embryo  still  further  advanced,  that 
during  the  formation  of  the  amnion  (6)  there 
buds  out  as  an  outgrowth  of  the  posterior  por- 
tion of  the  intestine  a  vesicle,  the  allantois 
(Fig.  568, c),  which, growing  outward,  gradually 
extends  itself  around  the  entire  inner  surface  of 
the  chorion,  the  cavity  of  the  vesicle  being 
finally  obliterated  by  the  fusion  of  its  outer  and  inner  layers.  The  chorion, 
covered  with  villous  processes  (Fig.  571,  t)  at  this  stage  will  consist, 
then,  from  without  inward,  of  the  original  zona  pellucida  of  the  false 
amnion,  the  allantois.  As  the  allantois  develops,  bloodvessels  make  their 
appearance  in  it,  derived  from  the  vessels  of  the  foetus,  as  we  shall  see 
presently,  which,  in  extending  into  the  villous  processes  of  the  chorion, 
serve  to  convey  to  the  foetus  the  nutritive  material  introduced  by  osmosis 
from  the  uterine  blood  of  the  mother,  the  allantois  constituting,  in  fact, 
the  foetal  part  of  the  placenta.  With  the  establishing  of  the  allantois, 
and  the  consequent  nourishing  of  the  foetus  by  the  mother,  the  um- 
bilical vesicle  (Fig.  571,  d  s),  which,  up  to  this  time,  through  its  vessels, 


Fecundated  egg,  with  allantois 
fully  formed,  a.  Umbilical  vesi- 
cle. 6.  Amnion.  c.  Allantois 
(Dalton.) 


DEVELOPMENT    OF    AMNION,    ETC 


909 


nourished  the  same,  begins  now  to  diminish  in  size,  and  finally  disap- 
pears altogether.     As  the  human  embryo,  at  the  earliest  period  of  its 


Fig.  571. 


Diagrammatic  figures,  illustrating  the  development  of  the  mammalian  embryo  and  thefoetal  membrane. 
1.  The  blastodermic  vesicle  invested  in  the  zona  pellucida,  and  showing  at  its  upper  pole  the  embryonic 
area.  2.  Shows  the  pinching  off  the  embryo  from  the  yolk-sac,  and  the  formation  of  the  amnion.  3. 
Further  development  of  amnion,  and  commencement  of  allantois.  4.  Completion  of  amnion,  and  growth 
of  allantois.  The  false  amnion,  or  subgonal  membrane,  gives  off  villous  processes.  5.  The  allantois  has 
grown  all  round  the  vesicle,  and  gives  off  processes  into  the  villi  which  are  much  larger  than  before.  The 
yolk-sac  is  greatly  reduced  in  size.  a.  Epiblast  of  embryo,  a'.  Epiblast  of  non-embryonic  part  of  blasto- 
dermic vesicle.  «/  Allantois,  urn.  Amnion,  eh.  Chorion,  ch  2.  Chorionic  villi,  rf.  Zona  pellucida. 
d'.  Processes  of  zona.  <ld.  Embryonic  hypoblast.  df  Area  vasculosa.  dg  Yolk  stalk,  ds.  Yolk-sac. 
e.  Embryo,  hh  Pericardial  cavity,  i.  Non-embryonic  hypoblast,  leh.  Cavity  of  blastodermic  vesicle. 
ks.  Head-fold  of  amnion,  m.  Embryonic  mesoblast.  n.  Non-embryonic  mesoblast.  r.  Space  between 
true  and  false  amnion,  sh.  False  amnion,  or  subgonal  membranes,  ss.  Veil-fold  of  amnion,  st.  Sinus 
termiualis.     si.  Processes  of  zona  pellucida.     vl.  Ventral  body-wall  of  embryo.     (KollikeiO 


910 


REPRODUCTION 


existence,  as  observed  by  the  author,  and  by  others — that  is,  from 
about  twelve  to  fourteen  days  old — consists,  essentially,  of  the  same 
primitive  organs  and  appendages  as  that  of  the  rabbit,  there  can  be  no 
doubt  that  the  still  earlier  stages  of  its  development,  not  yet  actually 
seen,  are  essentially  the  same  as  those  just  described  as  taking  place  in 
the  rabbit. 

Development  of  the  Nervous  System, 

The  primitive  nervous  system  consists,  as  already  mentioned,  of  a 
tube  lying  between  the  external  blastodermic  membrane  and  the  noto- 


Fig.  572. 


Primitive  brain  and  spinal  tube  of  nmu, 
with  sixteen  pairs  of  primitive  vertebrae.  The 
brain  has  parted  into  five  bladders,  v.  Fore- 
brain,  z.  Twixt-brain.  to.  Mid-brain.  h. 
Hind-brain,  n.  After-brain,  a.  Eye-bladders. 
g.  Ear-vesicles,  c.  Heart,  dv.  Yolk-veins,  imp. 
Medullary  plates,  uw.  Primitive  vertebra. 
(Hjeckel.) 


Mb 


Diagrammatic  horizontal  section  of  a  vertebrate 
brain.  The  figures  serve  both  for  this  and  the  next 
diagram.  Mb.  Midbrain:  what  lies  in  front  of  this 
is  the  fore-,  and  what  lies  behind,  the  hind-brain.  It. 
Lamina  terminalis.  Ozf.  Olfactory  lobes.  Hmp. 
Hemispheres.  TJi.E.  Thalamencephalic  Pn.  Pineal 
gland.  Pij  Pituitary  body.  FM.  Foramen  of 
Monro,  os.  Corpus  striatum.  Tk.  Optic  thalamus. 
CO.  Crura  cerebri  :  the  mass  lying  above  the  canal 
represents  the  corpora  quadrigemina.  CJ.  Cerebel- 
lum. I — IX.  The  nine  pairs  of  cranial  nerves.  1. 
Olfactory  ventricle.  2.  Lateral  ventricle.  3.  Third 
ventricle.  4.  Fourth  ventricle.  +  Iter  a  tertio  ad 
quartum  ventriculum.    (Huxley.) 


chord,  and  running  from  one  end  of  the  body  to  the  other.  As  devel- 
opment advances,  however,  the  anterior  portion  of  the  primitive  neural 
tube  separates,  and  subdivides  into  three  vesicles  :  the  anterior,  middle, 
and  posterior  cerebral  vesicles ;  while,  through  the  further  subdivision 
of  the  anterior  vesicle  into  two,  and  of  the  posterior  vesicle   into  two 


DEVELOPMENT    OF    THE     NERVOUS    SYSTEM. 


911 


also,  soon  five  vesicles  are  developed  (Fig.  572),  which  are  known, 
from  before  backward,  as  the  prosencephalon,  thalamencephalon,  mes- 
encephalon, epencephalon,  and  metencephalon,  or  as  the  fore-brain, 
between  brain,  mid-brain,  hind-brain,  and  after-brain.  In  the  sending 
out,  anteriorly  and  laterally,  of  two  vesicles  (Figs.  573  and  574)  from 
the  anterior  vesicle  the  future  olfactory  bulbs  and  optic  cups  now  make 
their  appearance;   while  through  the  thickening  and  inward  growth  of 


Longitudinal  anil  vertical  diagrammatic  section  of  a  vertebrate  brain.     Letters  as  before.    Lamina 
leiminalis  is  represented  by  the  strong  black  line  joining  Pa  and  Pg.    (Huxlet.1 

the  walls  of  the  vesicles,  the  hemispheres  and  the  ganglia  of  the  brain 
are  developed,  the  intervening  passage-ways — that  is,  the  remnant  of  the 
cavities  of  the  original  cerebral  vesicles  becoming  from  before  backward 
the  lateral  and  third  ventricles,  the  way  from  the  third  to  the  fourth 
ventricle,  the  cavity  of  the  spinal  portion  of  the  primitive  neural  tube, 
persisting  as  the  canal  of  the  spinal  cord  of  the  adult. 

Table  LXXX IV.— Cerebral  Vesicles  and  Parts  of  Brain  Developed 

OUT  OF  THEM. 

f    Cerebral  hemispheres,  corpora 
J        striata,  corpus  callosum,  for- 
I        nix,  lateral  ventricles,  olfac- 
tory bulb  (Rhinencephalon). 

f   Thalami  optici,  Pineal  gland, 
pituitary  body,  third  ventri- 
(       cle,  optic  nerve  (primarily). 

(  Corpora  quadrigemina,  crura 
-j  cerebri,  aqueduct  of  Sylvius, 
(        optic  nerve  (secondarily). 

j  Cerebellum,  pons  Varolii,  an- 
{        terior  part  of  fourth  ventricle. 

Medulla  oblongata,  fourth  ven- 
tricle, auditory  nerve. 


I.  Anterior, 

Primary, 
Vesic  e, 


1.  Prosencephalon. 


Thalamencephalon, 

(Diencephalon.) 


II.  Middle,         | 

Primary,  ■>.  Mesencephalon, 

Vesicle,        i 

III.  Posterior,     {  4"  Epencephalon, 
Primary,      -j 

I    •").  Metencephalon, 


The  primary  cerebral  vesicles  with  the  secondary  parts  of  the  brain 
developed  out  of  them,  may  be  seen  synoptically  arranged  in  Table 
LXXXIV.  At  an  early  period,  of  development  these  five  different 
parts  of  the  brain  may  be  more  or  less  seen  through  the  membranous  head 
of  the  embryo  (Figs.  552  and  574).     Just  as  Ave  have  seen,  however, 


912 


REPRODUCTION, 


that  through  ossification  of  the  mesoblast  around  and  above  the  chorda 
dorsalis,  the  primitive  spinal  neural  canal  becomes  enclosed  in  a  bony 
one,  the  spinal  column,  so  through  the  ossification  of  the  mesoblast 
forming  the  primordial  cranium  surrounding  the  primitive  cerebral 
vesicles,  the  latter,  or  the  future  brain,  comes  to  be  enclosed  in  a  bony 


Fig. 


,..  The  zygomatic  arch.  ma.  The  mastoid  process,  mi.  Portions  of  the  lower  jaw.  M.  The  cartilage 
of  Meckel  of  the  right  side,  and  a  small  part  of  that  of  the  left  side,  joining  the  left  cartilage  at  the 
symphysis  T.  The  tympanic  ring.  m.  The  malleus,  i.  The  incus,  s.  The  stapes,  ste  The  stapedius 
muscle,  si.  The  styloid  process,  p,  h,  g.  The  stylo-pharyngeus,  stylohyoid,  and  styloglossus  muscles. 
stl.  stylo-hyoid  ligament  attached  to  the  lesser  cornu  of  the  hyoid  bone.  hy.  The  hyoid  bone.  th. 
Thyroid  cartilage. 

cavity,  the  skull.  There  are  three  marked  differences  though,  to  be 
noticed  in  the  development  of  the  skull  as  compared  with  that  of  the 
spinal  column.  First,  the  notochord  does  not  extend  entirely  through 
the  head  end  of  the  embryo,  but  stops  short  in  a  tapering  point  at  the 
pituitary  fossa.  Second,  the  mesoblast  does  not  split  into  skin  fibrous 
and  intestinal  fibrous  layers.  Third,  the  primordial  cranium  never 
exhibits  any  trace  of  segmentation  into  segments  or  vertebrae.  That 
the  embryo  skull  does,  nevertheless,  consist  of  segments  of  modified 
vertebrrje,  though  not  in  the  adult  in  the  sense  held  by  Goethe,1  the 
presence  of  visceral  or  branchial  arches  (Figs.  552  and  575)  clearly 
proves,  since  the  latter  are  morphologically  cranial  ribs  bearing  the  same 
relation  to  different  parts  of  the  skull  that  the  thoracic  ribs  bear  to 
the  vertebrae  to  which  they  are  attached.  As  the  primordial  cranium 
of  man,  however,  shows  no  trace  of  such  segmentation,  gives  no 
evidence  of  having  ever  consisted  of  vertebra1,  it  is  evident  that  the 
fusion  or  coalescence  of  the  same  must  have  taken  place  at  such  an 
early  period  in  the  development  of  the  vertebral  type  that  no  trace 
of  the  primitive  segmentation  of  the  skull  is  ever  seen  in  the  trans- 
itory condition   through  which  it  passes,  even   in  the  earliest  condition 


i  Virehow  :  Goethe  als  Naturforscher,  1861,  S.  103. 


VISCERAL    ARCHES.  913 

of  the  embryo.  The  study  of  the  embryonic  or  adult  skull  in  man  will 
not  enable  us,  therefore,  to  determine,  even  approximately,  the  number 
of  the  primitive  vertebrae  through  the  fusion  of  which  it  has  been 
developed.  The  researches  of  Gegenbaur1  go  to  show,  however,  that 
the  skull  of  the  shark  retains  to  some  extent  the  primordial  type  of 
segmentation,  in  the  fact  of  there  being  eight  or  nine  branchial  arches, 
and  that  the  nerves  emanating  from  the  brain,  excepting  the  olfactory 
and  optic,  bear  to  the  latter  the  same  relation  that  the  spinal  nerves 
bear  to  the  spinal  cord.  If  the  latter  be  the  case,  and  the  branchial 
arches  be  regarded  as  homological  with  so  many  ribs,  then  the  prim- 
itive cranium,  in  the  shark,  at  least,  must  have  been  developed  through 
the  coalescence  of  so  many  vertebras.  Returning  from  this  brief 
digression  upon  the  nature  of  the  primordial  cranium  in  man  to  the 
thread  of  development,  let  us  consider  what  becomes  of  these  branchial 
arches.  The  visceral  or  branchial  arches  resembling  those  of  fishes, 
the  intervening  spaces  between  them  being  perforated  by  gill-like  open- 
ings or  slits,  as  in  the  latter  animals,  are  four  in  number  in  man,  and 
symmetrically  disposed  (Figs.   552,  575,   576),  and  are  known  from 

Fig.  576.  Fig.  577. 


h 
Visceral  arches  in  man 


before  backward  as  the  first  or  mandibular  (u),  the  second  or  hyoid 
(h),  the  third  or  thyro-hyoid  (d),  the  fourth  or  subhyoid  (r).  Through 
the  fusion  at  the  middle  line  of  the  distal  ends  of  the  first  visceral 
arches  (Fig.  576,  u),  the  rudimentary  lower  jaw  (Fig.  577,  a)  is  devel- 
oped, the  permanent  jaw  being  developed  by  ossification  (mi,  Fig.  575) 
around  the  cartilages  of  Meckel  (M),  or  the  rod  of  cartilage  that  early 
appears  within  this  first  arch,  the  proximal  part  of  the  cartilages  of 
Meckel  not  related  to  the  formation  of  the  lower  jaw  becoming  eventu- 
ally the  malleus  (m)  of  the  middle  ear.  In  addition  to  the  changes  just 
described  as  occurring  in  the  first  or  mandibular"  arches,  there  grows 
from  the  root  of  each  of  the  latter,  forward  and  inward,  a  process 
(Fig.  576,  o),  the  superior  maxillary,  from  which  are  developed  the 
superior  maxillary  and  malar  bones,  and  a  pair  of  cartilaginous  rods 
which  ultimately  become  the  pterygoid  (o)  plate  of  the  sphenoid  and 
the  palate  bones,  which  lie  parallel  with  the  trabecular  cranii.  The 
latter  are  two  elongated  bands  of  cartilage  at  the  base  of  the  cranium, 
connected  with  the  primitive  auditory  capsule,  which  diverging  to 
enclose  the  pituitary  body  unite  beneath  the  anterior  end  of  the 
primordial  cranium,  to  form  the  septum  of  the  nose. 

1  Das  Kopfskelet  <ier  Selachier,  1872. 
58 


914 


REPRODUCTION. 


The  basis  of  the  cranium  consists,  therefore,  at  an  early  period  of 
development,  of  a  cartilaginous  rod  developed  around  the  notochord, 
and  continuous  where  the  latter  ends  with  the  trabecule  cranii,the  basi 
occipital,  basi  sphenoid,  and  presphenoid  hones  being  developed  in  it  by 
three  centres  of  ossification,  respectively,  the  vault  of  the  skull,  with 
the  exception  of  the  squaino-occipital — that  is,  the  frontal,  parietal,  and 
squamous  portion  of  the  temporal  bones — being  developed  directly  out 
of  membrane,  instead  of  out  of  cartilage.  Dming  the  development  of 
the  superior  maxillary  process  from  the  first  or  mandibular  arch,  as  just 
described,  there  grows  downward,  between  the  primitive  olfactory 
grooves,  later,  the  nostrils,  the  naso-frontal  process  (Fig.  576,  m)  or  the 
termination  of  that  part  of  the  investment  of  the  head  situated  beneath 
the  fore-brain  (v).  In  this  way  a  large  cavity  is  formed,  bounded  by 
the  naso-frontal  process  above,  the  superior  maxillary  process  at  the 
sides,  and  the  primitive  lower  jaw  below,  which  later,  through  the  inward 
growth  and  coalescence  of  the  palatine  plates,  is  subdivided  into  a  mouth 
below  and  a  nasal  cavity  above,  the  latter  being  further  subdivided  into 
two  by  the  growth  of  the  septum  nasi — the  tongue  growing  from  the 
inner  surface  of  the  centre  of  the  first  gill  arch.  The  second  visceral 
arches,  or  hyoid  arches  (Fig.  576,  h),  growing  downward,  and  fusing 
on  the  middle  line,  give  rise  to  the  lesser  cornua  of  the  hyoid  bone,  the 
stylo-hyoid  ligament  (Fig.  575,  stl),  and  styloid  process  (st),  the  proxi- 
imal  portion  of  the  arch  being  transformed  into  the  stapes  (s)  and  incus 
(i)  of  the  middle  ear,  and  the  stapedius  muscle  (sta).  The  third  visceral 
arches,  the  thyro-hyoid  (Fig.  576,  d),  are  transformed,  through  fusion, 
into  the  body  and  greater  cornua  of  the  hyoid  bone.  The  fourth  visceral 
arches,  or  the  subhyoid  (Fig.  576,  r),  do  not  appear  to  be  developed  into 
any  particular  organ,  being  situated  in  that  part  of  the  embryo  which  in 
the  adult  becomes  the  neck,  and  which  is  absent  in  the  foetus.  It  has  just 
been  mentioned  that  the  branchial  arches  in  man  resemble  those  of  fish,  in 
that  the  intervening  spaces  are  perforated  by  slit-like  openings  or  clefts, 
through  which  the  water  passes  by  which  the  vascular  gills  attached  to 
the  arches   are  bathed  and  the  blood  aerated   in    the  latter    animals. 


Development  of  the  internal  ear.      (H^eckel.) 

Apart,  however,  from  the  fact  of  the  branchial  arches  in  man  never 
being  fringed  with  gills,  as  in  the  fish,  the  same  present  another  striking 
difference,  in  that  these  clefts  all  close  up,  save  the  first  one,  or  that 
intervening  between  the  mandibular  and  hyoid  arches,  which  persists  as 
the  tympano-Eustachian  tube — the  latter  being  finally,  in  the  adult,  cut 
off  from  the  exterior  by  the  growing  across  it  of  the  tympanic  membrane 


DEVELOPMENT    OF    EAR,    EYE. 


915 


Thus,  through  the  transformation  of  the  proximal  ends  of  the  first  and 
second  visceral  arches,  and  of  the  cleft  between  them,  the  ear  bones, 
meatus,  tympanic  membrane,  tympanum,  and  Eustachian  tube  are  formed, 
the  external  ear  being  developed  from  the  integument  near  the  first  and 
second  arches  ;  the  rudimentary  internal  ear  through  the  invagination 
of  that  part  of  the  epiblast  situated  immediately  above  the  upper  or 
proximal  ends  of  the  second  arch,  which,  in  time  closing  (Fig.  578, 
Afl,  B  h>),  becomes  a  vesicle.  The  latter,  the  rudimentary  vestibule, 
in  giving  off  successively  the  three  semicircular  canals  (Fig.  578,  O,  D, 
JE,  c,  cp,  est),  and  the  cochlea  (c),  originally  a  straight  tube,  develops 
into  the  internal  ear  of  the  adult.  It  will  be  remembered,  in  speaking 
of  the  functions  of  the  ear,  it  was  mentioned  that  the  transitory  stages 
through  which  it  passes  in  its  development  are  permanently  retained  as 
the  organ  of  hearing  in  the  lower  animals.  Like  the  ear,  the  eye — at 
least  the  anterior  part  of  it — appears  first  as  an  invagination  of  the  epi- 
blast (Fig.  579,  A,  1),  which  in  closing  up  (Fig.  579,  B,  2)  and  separating 
from  the  same  gives  rise  to  the  crystalline  lens  (2).      On  the  other  hand, 


Development  of  the  eye.     (Kemak 


through  the  invagination  of  the  optic  cup  or  vesicle — that  is,  the  peri- 
pheral portion  of  the  optic  nerve — by  the  indenting  into  it  of  the  lens, 
the  inner  surface  of  the  cup  becomes  the  retina  (4),  the  outer  the  tapetum 
nigrum  of  the  choroid  (5),  the  vitreous  humor  being  developed  through 
the  insertion  of  the  mesoblast  from  below  between  the  lens  and  the 
retina.  The  remaining  portions  of  the  eye  are  also  developed  out  of 
the  mesoblast,  through  the  latter  growing  around  the  ball  of  the  eye 
as  a  fibrous  capsule,  which  splitting  into  an  anterior  and  a  posterior 
layer,  gives  rise  to  the  sclerotic  and  cornea,  and  choroid  and  iris, 
respectively.  Though  the  brain  and  spinal  cord  are  developed  out  of 
the  epiblast,  the  cranial  nerves,  with  the  exception  of  the  olfactory  and 
optic,  which  are  outgrowths  of  the  anterior  cerebral  vesicle,  as  well  as 
the  spinal  nerves  and  sympathetic,  are  developed  out  of  the  mesoblast. 

Development  of  Alimentary  Canal  and  its  Appendages. 

The  primitive  alimentary  canal,  like  the  neural  canal,  extending  as  a 
straight  tube  from  one  end  of  the  body  to  the  other,  is  formed,  as  already 
mentioned,  through  the  pinching  oif  of  the  internal  blastodermic 
membrane  and  the  intestinal  fibrous  layers  of  the  middle  blastodermic 
membrane  covering  it,  and  by  the  bending  inward  and  downward  of  the 
parietes  of  the  body,  the  upper  portion  persisting  in  the  adult  as  the 


916 


REPRODUCTION. 


Fro.  :.S0. 


alimentary  canal,  the  lower  portion  remaining  only  temporarily  in  the 
embryo  as  the  umbilical  vesicle  (Fig.  580).  At  first  the  alimentary  tube 
is  closed  at  the  ends,  but  as  development  proceeds 
the  skin  at  both  its  extremities  invaginating,  deep 
furrows  are  formed,  which,  gradually  growing 
toward  the  blind  ends  of  the  intestinal  tube, 
finally  break  into  the  latter,  and  so  give  rise  to 
the  mouth  and  anus.  Such  being  the  manner  in 
which  these  apertures  are  formed,  it  is  evident 
that  their  lining  membrane  differs  from  that  of  the 
remaining  portion  of  the  alimentary  canal  in  being 
developed  out  of  epiblast  instead  of  hypoblast.  The 
mucous  membrane  of  the  mouth  being  then  in- 
vaginated  skin,  the  salivary  glands,  developed 
through  the  division  and  subdivision  of  its  follicu- 
lar glands,  must  be  regarded  as  being  essentially 
the  same  kind  of  glands  as  the  sudoriparous  and 
sebaceous  glands — that  is,  as  epidermal  in  origin.  Hence,  also,  the  fact 
of  the  teeth  of  certain  fishes  resembling  so  closely  their  dermal  spines, 


Human  embryo,  with  um- 
bilical vesicle ;  about  the 
fifth  week.     (Dalton.) 


Fig.  581. 


d- 


Three  stages  iu  the  development  of  a  mammalian  tuoth  germ.  a.  Oral  epithelium  heaped  up  over 
germ.  b.  Younger  epithelial  cells,  c.  Deep  layer  of  cells,  or  stratum  Malpighii.  d.  Inflection  of  epi- 
thelium for  enamel  germ,  e.  Stellate  reticulum.  /.  Dentine  germ.  <j.  Inner  portion  of  future  tooth  sac. 
h.  Outer  portion  of  future  tooth  sac.     i.  Vessels  cut  across,     h.  Bone  of  jaw.     (From  Frey.) 


DEVELOPMENT    OF    TEETH, 


917 


that  at  the  border  of  the  mouth  it  is  difficult  to  say  where  the  one  end 
and  the  other  begin.  Indeed,  teeth  are  simply  calcified  mucous  mem- 
brane the  invaginated  oral  epithelium  (Fig.  581,  1,  d),  giving  rise  to  the 
enamel,  the  submucous  papilla  (/)  below  to  the  dentine,  the  pulp  being 
made  up  of  a  matrix  of  connective  tissue  supporting  bloodvessels  and 
nerve  fibres.  The  structure  of  the  teeth  having  been  already  considered, 
it  will  not  be  necessary  to  dwell  further  upon  them,  merely  calling 
attention  to  Table  LXXXY.,  in  which  the  order  of  development  and 
appearance  of  the  temporary  and  permanent  teeth  is  synoptically  given, 
and  observing  that  while  the  permanent  teeth  are  thirty-two,  the  tem- 
porary teeth  are  only  twenty  in  number,  the  twelve  permanent  molar 
teeth  not  being  preceded  by  corresponding  temporary  ones. 


Table  LXXXV. — Order  of  Development  and  Appearance  of  Teeth. 


Temporary. 

(Intrauterine  life.) 

Kind. 

Date  of  appearance. 

Anterior  molar 

7th  week. 

Canine 

8th      " 

Central  incisors 

9th      " 

Lateral         " 

9th      " 

Posterior  molars 

(Eruption  after  birth. 

10th      " 

Central  incisors 

...... 

7th  month 

Lateral  incisors    . 

8th  to  10th      " 

Anterior  molars    . 

12th  to  18th       " 

Canines 

14th  to  20th       " 

Posterior  molars  . 

Permanent. 

18th  to  36th 

Kind. 

Date  of  appearance. 

First  molar  . 

..... 

6V    to    7th  month 

Central  incisors 

7th  to    8th      " 

Lateral  incisors 

8th  to    9th      " 

First  premolars 

9th  to  10th      " 

Second  premolars 

10th- to  11th      " 

Canines 

11th  to  12th      " 

Second  molars 

12J    to  14th      " 

Third 

16th  to  30th      " 

The  alimentary  canal  does  not  remain  long  in  the  human  embryo  a 
simple  straight  tube  ;  its  abdominal  portion  soon  expands  into  the  sto- 
mach, while  through  the  elongation  and  coiling  of  the  part  immediately 
succeeding  the  latter,  the  small  intestine  is  differentiated  from  the  large 
one.  It  has  been  mentioned  that  the  glandular  structures  of  the  ali- 
mentary canal  are  developed  out  of  the  hypoblast  or  its  lining  membrane. 
This  is  accomplished  through  the  invagination  of  the  latter  into  the  wall 
of  the  alimentary  canal,  formed,  it  will  be  remembered,  out  of  the  intes- 
tinal fibrous  layer  of  the  mesoblast.  The  simple  follicular  glands  so 
formed  either  remain  as  such,  or,  through  elongation,  become  simple 
tubular  glands,  or,  through  segmentation,  peptic  or  racemose  glands. 
The  liver  and  pancreas  arise  in  a  similar  manner,  the  only  essential 


918 


REPRODUCTION 


difference  being  that  these  glands  enlarge  enormously  and  recede  to  a 
considerable  extent  from  the  alimentary  canal,  with  which  they  remain, 
however,  through  life  in  communication  through  their  ducts.  In  the 
case  of  the  liver,  as  already  mentioned,  the  cells,  like  those  of  the 
remaining  alimentary  canal,  are  hypoblastic  in  origin,  the  fibrous  cap- 
sule and  vessels  mesoblastic,  the  bile-ducts  beginning  as  spaces  between 
the  cells. 

Development  of  the  Vascular  System. 

The  heart,  like  the  glands  just  mentioned,  is  also  an  appendage  of 
the  alimentary  canal,  but  differs  from  the  latter  in  being  developed  only 
out  of  the  mesoblastic  wall  of  the  same.  The  heart  is  originally  a 
mass  of  cells,  but  through  liquefaction  of  the  latter,  or  the  primi- 
tive blood-corpuscles,  is  soon  transformed  into  a  muscular  sac  or 
tube,  which  remains  for  a  short  time  connected  by  a  mesenteric  (Fig. 
582,  Tig)  with  the  wall  of   the  alimentary  canal,  of  which  it  is,   as 


Fig.  582. 


Diagrammatic  transverse  section  through  the  head  of  an  embryonic  mammal,  h.  Epidermis-plate. 
to.  Medullary  tui>e  (brain-bladder)  mr.  Wall  of  the  latter.  1.  Dermis-plate.  s.  Rudimentary  skull 
ch.  Notochord.  k.  Gill-arch.  mp.  Muscle-plate,  c.  Heart-cavity,  anterior  part  of  the  body-cavity 
(ccelomii).  d.  Intestinal  tube,  dd  Intestinal  glandular  layer,  df.  Intestinal  muscle-plate.  hy.  Heart- 
mesentery,  hw.  Heart-wall.  hlc.  Ventricle,  ub.  Aorta-arches.  «.  Transverse  section  through  the 
aorta.     (HiECKEL.) 

just  said,  an  outgrowth.  Coincidently  with  the  development  of  the 
heart,  as  just  described,  and  in  connection  with  it,  there  appears,  appa- 
rently through  fission  of  the  inner  and  outer  parts  of  the  intestinal 
fibrous  mesoblastic  wall  of  the  alimentary  canal,  the  two  primitive  aortee 
and  the  two  primitive  cardinal  veins,  respectively.  The  two  primitive 
aortee  uniting  then  divide  again,  the  two  branches  passing  along  the 
inner  surface  of  the  first  visceral  arches  and  curving  around  the  anterior 
portion  of  the  alimentary  canal,  unite  anteriorly  and  pass  as  one  tube 
into  the  heart  aorta.  At  first  there  are  but  one  pair  of  vascular  arches 
encircling  the  alimentary  canal ;  in  time,  however,  five  such  are  devel- 
oped, three  only  coexisting  at  one  period. 


TRANSFORMATION    OF    THE    VISCERAL    ARCHES.        919 


Fig.  58?. 


The  primitive  aorta  further  gives  off  lateral  branches,  of  which  two, 
passing  to  the  umbilical  vesicle,  are  known  as  the  vitelline  or  omphalo- 
mesenteric arteries,  while  through  the  twisting  of  the  heart  into  an 
S-like  shape,  the  auricles  become  uppermost,  the  ventricles  lowermost. 
Two  veins,  similarly  named,  return  from  the  umbilical  vesicle  to  the 
body  of  the  foetus,  and  pass  as  a  single  trunk,  the  sinus  venosus,  into 
the  heart.  Such  being  the  disposition  of  the  heart  and  the  primitive 
vessels,  it  follows  that  the  nutritive  material  of  the  umbilical  vesicle 
passes  by  the  vitelline  veins  to  the  heart,  and  thence  through  the  vas- 
cular arches  to  the  primitive  aorta  and  so  to  the  body  generally,  the 
circulation  being  completed  by  the  vitelline  arteries.  Neither  the 
heart,  aortic  trunk,  nor  vascular  arches  remain,  however,  long  in  the  con- 
dition in  which  they  have  just  been  described.  The  heart  soon  sub- 
divides into  a  right  and  left  heart  through  the  growth  of  a  longitu- 
dinal septum,  and  further  into  auricles  and  ventricles  (Fig.  583)  through 
the  growth  of  transverse  septa,  the  septum  be- 
tween the  auricles  remaining,  however,  incom- 
plete until  after  birth,  the  opening  so  caused  being 
known  as  the  foramen  ovale.  Coincidently  with 
the  development  of  the  cavities  of  the  heart 
through  the  growth  of  a  longitudinal  septum  in 
the  common  arterial  trunk,  the  latter  subdivides 
into  aorta  and  pulmonary  artery,  the  aorta  finally 
being  disposed  to  the  right,  the  pulmonary  artery 
to  the  left.  Finally  through  the  transformation 
of  the  third,  fourth,  and  fifth  vascular  aortic 
arches,  the  first  and  second  having  disap- 
peared, the  aorta  and  its  first  main  branches  and 
the  pulmonary  artery  are  developed,  the  change 
being  brought  about  through  the  atrophy  or 
hypertrophy  of  these  arches  respectively.  Thus, 
for  example  (Figs.  584-587),  through  the  persist- 
ence of  the  left  fifth  arch  (5),  the  right  disappear- 
ing, the  internal  half  of  it  becomes  the  pulmonary 
artery  (p),  the  external  half  the  ductus  arteriosus, 
the  left  fourth  arch  (4)  becoming  the  permanent 
aorta  and  giving  off  the  left  subclavian  artery  («), 
the  right  fourth  arch  developing  into  the  innomi- 
nate dividing  into  the  right  subclavian  and  right 
common  carotid,  the  left  common  carotid  being  given  off  by  the  aorta, 
the  third  left  arch  (3)  on  both  sides  entering  more  into  the  formation  of 
the  internal  carotid  than  of  the  external  one,  the  outer  connecting  por- 
tions of  the  third  and  fourth  arch  disappearing. 

With  the  establishing  of  the  allantois,  however,  and  the  dwindling 
away  of  the  umbilical  vesicle,  the  allantoic  or  second  circulation  gradu- 
ally replaces  the  vitelline  or  first  one.  The  allantoic  or  umbilical  veins, 
originally  two  in  number,  appear  to  be  developed  as  branches  of  the 
vitelline  veins,  which,  extending  themselves  through  the  allantois, 
finally  pass  into  the  villous  processes  of  the  chorion.  Shortly  after  the 
appearance  of  the  umbilical  veins,  the  right  one  disappears,  and  with  it 


Heart  and  hc.nl  of  an  em- 
bryonic dog,  from  the  front. 
a.  Fore-brain,  b.  Eyes.  c. 
Mid-brain,  tl.  Primitive  lower 
jaw.  e.  Primitive  upper  jaw. 
/.  Gill-arches,  g.  Right  auri- 
cle, h.  Left  auricle,  i  Left 
ventricle,  k.  Right  ventricle. 
(Bischoff.) 


920 


REPRODUCTION. 


the  right  vitelline  vein  and  that  part  of  the  left  vitelline  outside  of  the 
body  of  the  embryo.  The  mesenteric  portion  of  the  latter,  or  left 
omphalo-mesenteric  vein  (Fig.  588,  M),  enlarges,  however,  while  the  re- 


Pro.  584 


Pig.  586. 


/  u- 

/    fi 

</ 

/.P 

a  00 

artr 

A' 

ad — 

U.7V 

Metamorphosis  of  the  five  arterial  arches  in  the  human  embryo,  ta.  Arterial  stalk.  1,  2,  3,  4,  5,  the 
arterial  arches  from  the  first  to  the  fifth  pair.  <»'.  Main  stem  of  the  aorta,  aw.  Roots  of  the  aorta. 
In  Fig.  584,  three  of  the  arterial  arches  are  given  ;  in  Fig  585,  the  whole  five  (those  indicated  by 
dots  are  not  yet  developed) ;  in  Fig.  586,  the  first  two  have  again  disappeared  ;  in  Fig.  587,  the  perma- 
nent arterial  stems  are  represented.  The  dotted  parts  disappear,  s.  Subclavian  artery,  v.  Vertebral 
artery,  ax.  Axillary  artery  c.  Carotid  artery  (c',  outer,  <_■",  innor  carotid),  p.  Pulmonary  aitery 
(lung-artery).     (Rathke.) 

maining  portion  (0),  that  returning  from  the  umbilical  vesicle,  atrophies. 
At  the  same  time,  the  left  umbilical  vein  (Fig.  -588,  U)  becomes  very 


Fig.  588. 


Fig.  589. 


Diagrammatic  view  of  portal  and  umbilical  circu- 
lations. 


Diag  rammatic  view  of  portal  and  umbilical  circu- 
lations more  advanced  than  in  Fig.  588. 


much  enlarged,  and  as  it  is  a  branch  of  the  omphalo-mesenteric  vein,  it 
will  with  the  mesenteric  branch  of  the  same,  pass  as  one  trunk  (P  D)  to 
the  sinus  venosus  (S),  and  so  reach  the  heart  (H).    The  continuity,  how- 


DEVELOPMENT    OF    VENOUS    SYSTEM 


921 


ever,  of  this  trunk  due  to  the  union  of  the  umbilical  and  omphalo- 
mesenteric vein,  is  interrupted  by  the  development  of  the  liver  (L)  as 
an  investing  mass  around  it,  and  by  the  appearance  of  the  inferior  vena 
cava.  The  latter  may  be  regarded  as  the  backward  prolongation  of 
the  sinus  venosus  (S),  and  in  dividing  posteriorly  into  two  branches  gives 
rise  to  the  two  iliac  veins.  With  the  growth  of  the  liver  the  common 
trunk  (Fig.  589,  P),  which  may  now  be  called  the  portal  vein,  gives  off 
capillaries  (C  C),  which,  ramifying  through  the  liver,  pass  into  the  vena 
cava  by  a  distinct  vessel,  the  hepatic  vein  (Fig.  589,  H).  The  amount 
of  blood  circulating  through  the  hepatic  capillaries  (c  c)  at  this  period  is, 
however,  but  small,  since  little  blood  comes  from  the  intestines  through 
the  mesenteric  vessel  (M),  while  of  the  blood  passing  through  the  umbili- 
cal vein  (U),  the  greater  part  flows  directly  through  what  may  be  now 
called  the  ductus  venosus  (D)  into  the  inferior  vena  (I vc),  very  little  mix- 
ing with  the  blood  of  the  portal  vein  (P).  It  will  be  remembered  that 
the  single  aorta  formed  through  the  union  of  the  vascular  or  branchial 
arches,  passing  from  the  heart  along  the  inner  surface  of  the  visceral 
arches  soon  divides  into  the  two  primitive  aortse  that  run  along  toward 
the  posterior  end  of  the  body  on  either  side  of  the  notochord.  As 
development  proceeds,  the  point  of  division  of  the  aorta  is  carried  much 
further  back,  its  two  branches  becoming  the  iliac  arteries. 


Fig.  500. 


Fi<;.  591. 


Further  development  of  the  venous  system, 
The  cardinal  veins  ((')  are  diminished  in  si/.e. 
The  canal  of  Cuvier  (D)  on  left  Bide  much  atro- 
phied. Primitive  left  innominate  vein  (Li),  and 
primitive  vena  azygos  minor  vein  (c)  appearing. 
J.  Jugular  vein.   S.   Subclavian  vein.    (DaltON). 


6^  ^G 

Adult  condition  of  venous  system.  1.  Right 
auricle  of  heart.  2.  Vena  cavasuperioi 
Jugular  veins.  4, 4.  Subclavian  veins  5.  Vena 
cava  inferior.  6,  6.  Iliac  veins.  7.  Lumbar 
veins.  8  Vena  azygos  major.  9.  Vena  azygos 
minor.  10.  Superior  intercostal  vein.  (Dalton.) 


From  the  internal  part  of  the  latter,  that  which  becomes   later    the 
internal  iliac  arteries,  two  vessels  are  given  off,  which  passing   to    the 


922  REPRODUCTION. 

itllantois,  give  rise  to  the  umbilical  or  hypogastric  arteries.  In  the 
meantime  the  primitive  cardinal  veins  (Fig.  589,  C  C)  uniting  with  the 
jugular  veins  (J  .1).  pass  into  the  sinus  venosus,  and  so  to  the  heart, 
there  being  at  this  period  then  two  superior  venae  cavae,  a  disposition 
which  is  retained  during  life  in  the  elephant,  manatee,  rodents,  mono- 
feremes,  and  birds.  This  condition,  however,  is  only  a  transitory  one, 
since  a  vessel  (Li,  Fig.  590)  is  given  off  from  the  point  of  union  of 
the  left  jugular  and  subclavian  veins,  which  uniting  with  the  corre- 
sponding vessel  of  the  right  side  forms  the  superior  vena  cava  (2,  Fig. 
5^1),  the  left  primitive  superior  vena  cava  almosi  entirely  disappearing, 
being  only  represented  in  the  adult  by  the  coronary  sinus  and  a 
fibrous  band  descending  obliquely  on  the  left  auricle.  Such  being  the 
disposition  of  the  venous  system  with  the  establishment  of  the  allantois 
(Figs.  589  and  590),  or,  as  Ave  shall  see,  presently,  of  the  placenta,  the 
heart  in  the  meantime  having  become  four  chambered,  the  allantois  or 
second  circulation  will  be  as  follows :  The  blood  returning  from  the 
head  and  upper  extremities  will  pass  to  the  right  auricle  of  the  heart 
by  the  superior  vena  cava,  thence  by  the  right  ventricle  and  ductus 
arteriosus  to  the  aorta,  and  so  to  the  lower  extremities,  and  to  the 
allantois  by  the  umbilical  arteries.  The  latter  being  nourished  by 
blood  that  has  circulated  through  the  head,  etc.,  will  be  relatively, 
therefore,  poorly  nourished.  On  the  other  hand,  the  blood  of  the 
umbilical  vein  returning  directly  from  the  allantois  or  placenta  laden 
with  nutritive  material  and  oxygen  absorbed  from  the  maternal  blood 
will  pass  with  little  or  no  admixture  from  the  portal  blood  into  the 
right  auricle,  whence  guided  by  the  Eustachian  valve  it  will  pass 
through  the  foramen  ovale  into  the  left  auricle,  thence  into  the  left  ven- 
tricle, and  so  by  the  aorta  to  the  head,  hence  the  fact  of  the  latter 
being  so  much  better  developed  than  the  rest  of  the  body.  But  little 
blood  passes  through  the  lungs  in  the  foetus,  aeration  being  effected  by 
the  placenta ;  on  the  other  hand,  a  very  large  amount  traverses  the  liver, 
which  may  be  accounted  for  on  the  supposition  that  the  liver  acts  as 
a  decarbonizer  of  the  blood,  supplementing  in  this  way  the  want  of 
action  of  the  lungs.  At  all  events,  with  the  establishing  of  the  pul- 
monary respiration,  the  liver  becomes  smaller,  relatively,  while  in 
animals,  generally,  the  lungs  and  liver  are  in  an  inverse  ratio  as  regards 
size  and  functional  importance.  With  the  replacing  of  the  second 
or  allantois  circulation  by  the  adult  pulmonic  and  systemic  circula- 
tions the  foramen  ovale  closes,  the  ductus  arteriosus,  umbilical  vein,  and 
umbilical  arteries  shrivelled  up  into  cords,  the  internal  portion  of  the 
latter  remaining,  however,  pervious,  and  persisting  in  the  adult  as 
the  superior  vesicle  arteries,  while  the  part  of  the  allantois  remaining 
within  the   body  becomes  the  urinary  bladder  and  urachus. 

Development  oe  Respiratory  Organs. 

The  respiratory  organs  may  be  regarded  as  appendages  of  the 
alimentary  canal,  since  the  trachea  and  oesophagus  are  originally 
one  and  the  same  tube.  As  development  advances  the  trachea 
separates    itself    from    the    oesophagus,    the    upper    portion   becoming 


DEVELOPMENT    OF    THE    GENITO-U  R  IN  A  R  Y    ORGANS.      923 

the  larynx,  the  lower  subdividing  into  the  two  bronchi,  the  latter,  by 
a  process  of  fission  and  segmentation,  giving  rise  to  the  bronchial  tubes 
and  pulmonary  lobules. 


Fig.  592. 


Development  of  the  Gexito-urinary  Organs. 

The  genito-urinary  organs  are  so  intimately  associated  in  their 
development,  that  it  will  be  found  convenient  to  study  them  together. 
In  describing  the  structure  of  the  kindey,  it  was 
mentioned  that  however  complex  in  structure 
the  organ  may  appear  to  be,  it  consists  essen- 
tially of  a  tube  open  at  one  end,  from  which  are 
given  off  diverticula  terminating  in  blind  glob- 
ular-like expansions.  Such  a  primitive  type  of 
structure  is  presented  through  life  in  the  kidneys 
of  the  myxinoid  fishes,  and  as  a  transitory  condi- 
tion in  man,  in  the  early  period  of  development. 
The  common  duct  (Fig.  592,  iv),  running  from 
end  to  end  of  the  body  on  either  side  of  the 
notochord,  which  gives  off  the  primitive  urine 
tubes  (Fig.  592,  u),  is  known  as  the  Wolffian 
duct  (ic),  and  is  developed  most  probably  out  of 
the  skin  sensory  layer  (Fig.  593,  u)  by  invagina- 
tion and  constriction,  precisely  as  the  spinal  cord 
is  developed,  the  duct,  however,  receding  (Fig. 
594,  u)  farther  from  the  general  surface  of  the 
body  than  the  cord,  and  terminating  in  the  cloaca 
or  lower  portion  of  the  alimentary  canal.  Coin- 
cidently  with  the  development  of  the  Wolffian 
duct  and  its  diverticula,  or  the  primitive  kidneys, 
there  appears  in  the  mesoblast  (Fig.  594)  just 
at  that  part  where  the  latter  splits  into  the  intes- 
tinal fibrous  layer  (d),  and  the  skin  fibrous  layer 
(hf),  the  so-called  indifferent  gland,  the  cells 
of  which  differ  in  many  respects  from  those  of 
which  the  latter  layers  consist,  and  out  of  which 
the  germinal  epithelium  (g,  Fig.  595)  giving  rise 
to  either  ova  or  spermatozoa,  as  the  case  may  be, 
appears  to  be  developed.      Such  a    condition   of 

the  urinary  apparatus  does  not,  however,  remain  long,  there  being 
developed  out  of  the  posterior  portion  of  the  Wolffian  duct  near  where 
it  passes  into  the  cloaca  a  secondary  duct,  the  primitive  ureter, 
which  gradually  elongates  and  gives  off  diverticula,  which  become  the 
renal  tubules,  and  disposed  with  reference  to  the  bloodvessels  precisely 
as  the  diverticula  of  the  Wolffian  duct  were.  The  urine  excreted  by 
the  former,  however,  passes  into  the  posterior  part  of  the  stalk  of  the 
allantois,  or  the  urachus,  which  dilating,  is  retained  in  the  body  as  the 
primitive  bladder.  The  latter  in  time  separates  both  from  the  cloaca 
and  that  part  of  the  allantois  which  comes  away  as  the  umbilical  cord 
and  the  foetal  portion  of  the  placenta. 


Primitive  kidney  of  a 
human  embryo :  «.  The 
urine-tubes  of  the  primitive 
kidney.  w.  Wolffian  duct. 
"'.  Upper  end  of  the  latter 
(Morgagni's  hydatid).  m. 
Mullerian  duct,  m'  upper 
of  the  latter  (Fallopian  hy- 
datid), g.  Hermaphrodite 
gland,  becoming  either  tes- 
ticle or  ovary.      (KOBELT.) 


924 


REPRODUCTION. 


In  this  manner  the  permanent  kidneys  grow  out  of  and  replace  the 
primitive  ones  developed  out  of  the  Wolffian  duct.    The  latter,  however, 


Pig.  593 


Fin.  594. 


h.  Skin  sensory  layer,  n.  Spinal  tube. 
M.  Beginning  of  Wolffian  body,  x  Noto- 
chord.  c.  Body  cavity.  /.  Intestinal 
fibrous  layer,  d.  Intestinal  glandular 
layer,     a.  Intestinal  tube. 


a.  Primitive  spinal  cord.  r.  Notochord.  hf  Skin 
fibrous  layer,  w.  Vertebrae.  /.  Skin  sensory  layer. 
rm.  Dorsal  muscles,  bm.  Ventral  muscles,  g.  Mesen- 
tery, to.  Indifferent  sexual  gland,  d.  Intestinal 
fibrous  layer.    /.  Intestinal  glandular  layer. 


Fig.  595. 


Transverse  section  through  the  pelvic  region  and  the  hind  limbs  of  a  chick,  on  the  fourth  day  of  incu- 
bation (about  forty  times  the  natural  size),  h.  Skin  sensory  layer,  w.  Medullary  tube  n.  Spinal  canal, 
it.  Wolffian  body  or  primitive  kidneys,  x.  Chorda,  e.  Hind  lim'is.  b.  Allantoic  canal  in  the  ventral 
wall.  t.  aorta,  v.  Cardinal  veins,  a.  Intestine,  d  Intestinal-glandular  layer.  /.  Intestinal  fibrous 
layer,  hf  Skin  muscle  layer,  g.  Germ-epithelium,  r.  Dorsal  muscles,  e.  Body  cavity  (cseloma). 
(Waldeyek.) 

do  not  disappear,  but  split  (Fig.  596)  into  two  distinct  tubes,  the  outer 
still  called  the  Wolffian  duct  (w),  the  inner  the  Miillerian  duct  (m). 


FORMATION    OF    VAGINA    AND    UTERUS, 


925 


The  Wolffian  duct,  as  just  mentioned,  for  a  time  carries  off  the  urine 
excreted  by  its  tubules  from  the  blood,  but,  as  this  office  is  transferred 
to  the  ureter  and  permanent  kidneys,  it  gradually  is  transformed,  if  the 
individual  becomes  a  male,  into  the  epididymis  and  vas  deferens,  and 
will  hereafter  carry  to  the  urethra  the  spermatozoa  developed  by  the 
hitherto  indifferent  body  (ot),  now,  therefore,  a  testicle;  the  Miillerian 
ducts,  at  their  lower  distal  united  portion,  persisting  as  the  sinus  pocu- 
laris,  the  homologue  of  the  vagina ;  the  upper  proximal  portions  as  the 
so-called  hydatid  of  Morgagni.  On  the  other  hand,  if  the  individual 
becomes  a  female,  the  gland  (ot)  produces  eggs,  and  is  henceforth,  there- 
fore, an  ovary.  The  Miillerian  ducts  fuse  together  from  below  upward 
and  become  the  vagina,  uterus,  and  Fallopian  tubes ;  the  Wolffian  ducts 
persisting  in  an  atrophied  condition,  in  the  human  female,  as  the  par- 
ovarium, or  the  white  tortuous  tubes  in  the  broad  ligament  of  the  uterus; 
and  in  that  of  certain  animals,  the  pig,  as  the  ducts  of  Gaertner  opening 
into  the  vagina.  At  an  early  period  of  intrauterine  life  the  conjoined 
Wolffian  and  Miillerian  ducts  pass  as  the  genital  cord  (Fig.  596,  gc)  into 

Fig.  596. 


Diagram  of  the  Wolffian  bodies,  Miillerian  ducts,  and  adjacent  parts  previous  to  sexual  distinction,  as 
seen  from  before,  sr.  The  suprarenal  bodies,  r.  The  kidneys,  ot.  Common  blastema  of  ovaries  or  tes- 
ticles. W.  Wolffian  bodies,  w.  Wolffian  ducts,  m,  m.  Miillerian  ducts,  gc.  Genital  cord.  ug.  Sinus 
urogenitalis.     i.  Intestine,     cl.  Cloaca.     (Qi'ain  i 

the  expanded  stalk  of  the  allantoic,  or  urogenital  sinus  (ug) ;  the  latter, 
in  time,  emptying,  together  with  the  alimentary  canal  (/),  into  the  cloaca 
(cl),  or  cavity  common  to  both.  As  development  advances,  however, 
the  rectum  separates  from  the  cloaca,  and,  if  the  individual  becomes  a 


926  [REPRODUCTION. 

female,  a  further  differentiation  takes  place,  in  that  the  lower  united 
portion  of  the  Miillerian  ducts,  or  the  vagina,  terminates  in  an  opening 
distinct  from  that  of  the  urethra,  or  the  passage-way  from  the  bladder. 
The  latter,  in  the  case  of  the  individual  being  a  female,  will  pass  beneath 
the  clitoris,  or  female  penis,  the  two  adjacent  folds  of  skin  becoming  the 
labia  minora,  the  two  latter  external  ones  the  labia  majora,  the  ovaries 
lying  within,  in  the  body  cavity.  On  the  other  hand,  if  the  individual 
be  a  male,  the  urethra  passes  through  the  elongated  penis ;  the  under-skin 
of  which  is  formed  by  the  coalescence  in  the  middle  line  of  what,  in  the 
female,  constitute  the  labia  minora ;  the  scrotum  being  formed  through 
the  fusion  along  the  future  raphe  of  the  parts  corresponding  to  the  labia 
majora,  into  which  the  testicles  descend  by  passing  through  the  inguinal 
canal,  the  peritoneum  consequently  pushed  in  front  of  them  becoming 
the  tunica  vaginalis  testis.  Such  being  the  manner  in  which  the 
external  generative  organs  are  developed  in  the  two  sexes,  it  will  be 
readily  understood  why,  in  those  male  individuals,  on  the  one  hand,  in 
which  development  is  arrested  at  the  stage  at  which  the  external  genera- 
tive organs  in  the  two  sexes  are  alike ;  and  in  the  other,  in  those  female 
ones  in  which  the  clitoris  is  much  elongated,  that  such  should  be 
regarded  by  the  vulgar  as  hermaphrodites,  though  in  neither  case  is 
hermaphroditism  really  present.  Bearing  in  mind  what  has  just  been 
said  as  to  the  development  of  the  uterine  generative  organs,  it  is  readily 
conceivable,  also,  that  if  one  of  the  indifferent  bodies  of  early  ultra- 
uterine  life,  became  a  testicle,  and  the  other  an  ovary,  and  both  func- 
tionally active,  or  if  two  ovaries  and  two  testicles  were  developed  through 
the  subdivision  of  the  indifferent  bodies,  which  consisted,  probably,  of 
both  male  and  female  elements ;  and  further,  that  the  Wolffian  ducts 
became  vasa  deferentia,  and  the  Miillerian  ducts  the  vagina,  uterus,  and 
Fallopian  tube  or  tubes ;  that  the  same  individual  might  produce  ova 
and  spermatozoa,  and  that  an  egg  might  be  developed  in  the  uterus  of 
the  individual  producing  it  after  fecundation  by  its  own  spermatozoa, 
or  by  those  of  a  similar  or  normal  male  individual.  In  such  a  hypo- 
thetical case  there  would  be,  however,  either  a  penis  or  clitoris,  but  not 
both,  and  either  a  scrotum  or  labia  majora,  but  not  both.  While  a  con- 
dition, like  that  just  described,  is,  therefore,  within  the  limits  of  possi- 
bility, it  is  extremely  doubtful  whether  such  a  case  ever  actually  existed 
in  a  human  being,  though  hermaphroditism  obtains  in  many  of  the  lower 
animals,  mollusca,  worms,  etc.,  and  in  numerous  plants  ;  the  stamens 
and  pistil  of  a  flower  constituting  the  male  and  female  generative  organs 
respectively.  The  only  true  test  of  sex  being  the  power  of  producing 
ova  or  spermatozoa,  it  is  obvious  that  however  much  the  external  or 
internal  organs  in  any  one  individual  may  resemble  those  of  the  normal 
male  or  female  as  due  to  either  hypertrophy  or  arrest  of  development, 
that  such  modified  organs  cannot  be  taken  alone  as  an  evidence  of  sex. 

Development  of  Extremities. 

The  limbs  first  appear  as  bud-like  protuberances  from  the  sides  of  the 
body  (Fig.  595,  e),  those  giving  rise  to  the  upper  extremities  being 
developed  first.     While  covered  by  the  outer  or  skin  sensory  layer,  the 


DEVELOPMENT    OF    FCETUS.  927 

limbs  are  developed  more  especially  out  of  the  deeper  or  skin  fibrous 
layer,  through  its  cells  becoming  first  cartilage,  with  after-ossification  of 
the  same.  As  development  advances,  the  primitive  limb-bud  recedes 
from  the  body,  and  expanding  at  its  distal  extremity,  segments  the  divi- 
sions so  arising,  becoming,  hereafter,  the  fingers  and  toes — the  charac- 
teristic bones  with  the  correlated  muscles  being  gradually  developed  in 
the  same. 

Resume  of  Development  of  Fcetus. 

On  the  supposition  that  the  ontongeny  or  development  of  the  indi- 
vidual is  the  epitomized  phylogeny  or  history  of  the  race,  we  have  some 
explanation  of  the  fact  that  the  various  changes  through  which  the 
embryo  passes  represent  morphologically  the  permanent  condition  of 
lower  forms  of  life.  The  principal  changes  undergone  by  the  embryo 
during  its  development,  which  we  have  just  endeavored  to  describe  and 
account  for,  may  be  synoptically  resumed  about  as  follows  : 

At  the  twelfth  day,  the  ovum,  about  5  millimetres  (1th  of  an  inch)  in 
length,  consists  of  the  zona  pellucida  beset  with  small  villi,  and  enclosing 
a  two-layered  vesicle,  the  blastodermic  vesicle. 

At  the  fifteenth  day,  the  embryo,  about  2  millimetres  (the  y^th  of  an 
inch)  in  length,  exhibits  the  primitive  groove,  amnion,  allantois,  and 
umbilical  vesicles  ;  the  heart,  though  still  one-chambered,  is  present, 
and  the  first  or  vitelline  circulation  is  established,  and  the  rudiments  of 
the  Wolffian  duct  indicated. 

At  the  twentieth  day,  the  embryo,  about  3  millimetres  (Jth  of  an 
inch)  in  length,  presents  the  visceral  arches  and  perforated  clefts. 

At  the  twenty-first  day,  the  embryo,  about  4  millimetres  (-jUh  of  an 
inch)  in  length,  has  developed  rudimentary  eyes,  ears,  mouth,  three 
cerebral  vesicles,  and  the  heart  has  become  four-chambered. 

At  the  end  of  the  first  month  the  embryo  has  attained  a  size  of  12 
millimetres  (h  an  inch),  and  is  characterized  by  the  presence  of  distinct 
rudimentary  limbs,  the  whole  ovum  measuring  about  17  millimetres. 

At  the  end  of  the  second  month  the  embryo  is  about  25  millimetres 
(1  inch)  in  length,  and  weighs  about  4  grammes  (|th  of  an  ounce),  the 
whole  ovum  measuring  about  7  centimetres  (2.4  inches).  By  this  time 
the  vitelline  vessels  and  right  umbilical  vein  are  obliterated,  the  future 
fingers  and  toes  are  indicated,  the  outer  ear  has  appeared,  nose  and  eye- 
lids are  present ;  the  umbilical  cord  is  about  16  millimetres  (§d  of  an 
inch)  in  length,  and  ossification  has  begun  in  the  lower  jaw,  clavicle,  ribs, 
vertebral  bodies;  permanent  kidneys  present,  but  sex  still  indistinct. 

At  the  third  month  the  foetus  is  about  10  centimetres  (4  inches)  in 
length,  weighs  about  20  grammes  (%-d  of  an  ounce) ;  a  difference  of  sex 
is  indicated  by  the  external  genitals,  the  umbilical  cord  is  7  centimetres 
(2.8  inches),  and  the  placenta  begins  to  be  formed. 

At  the  fourth  month  the  foetus  is  17  centimetres  (7  inches)  long, 
weighs  120  grammes  (4  ounces) ;  umbilical  cord  is  19  centimetres  (7 
inches)  long,  and  weighs  80  grammes  (2.6  ounces). 

At  the  fifth  month  the  foetus  is  about  20  centimetres  (8  inches)  in 
length,  and  weighs  284  grammes  (9  ounces) ;  the  hair  of  the  head  and 
of  the  body,  or  lunigo,  is  quite  distinct,  and  covered  with  the  vernix 


928 


REPRODUCTION. 


caseosa;  the  umbilical  cord  is  about  31  centimetres  (12  inches)  long, 
ami  the  placenta  weighs  178  grammes  (6  ounces). 

At  the  sixth  month  the  foetus  is  28  centimetres  (11  inches)  long,  and 
weighs  634  grammes  (20  ounces),  and  meconium  appears  in  the  intestines. 

At  the  seventh  month  the  foetus  is  about  35  centimetres  (11  inches) 
long,  and  weighs  1218  grammes  (2|  pounds);  the  eyes  are  open,  one 
testicle  has  descended  into  the  inguinal  canal,  and,  if  born  at  this 
period,  is  viable. 

At  the  eighth  month  the  foetus  is  42  centimetres  (16  inches)  in 
length,  and  weighs  between  1  and  2  kilos  (2. 2  to  4.4  pounds);  one 
testicle  has  descended  into  the  scrotum. 

At  the  end  of  the  ninth  month,  or  at  full  term,  the  foetus  is  about  51 
centimetres  (20  inches)  in  length,  and  weighs  3^  kilos  (7  pounds). 

Development  of  the  Placenta. 

Up  to  the  present  moment  nothing  has  been  said  as  to  the  changes 
undergone  by  the  mucous  membrane  of  the  uterus  after  the  ovum  has 
passed  into  the  cavity  of  the  same.  These  changes,  which  must  now  be 
at  least  briefly  considered,  appear  to  differ  rather  in  degree  than  in  kind 
from  those  exhibited  by  the  mucous  membrane  during  menstruation, 
the  essential  difference  being  that  the  mucous  membrane  during  preg- 
nancy is  hypertrophied  to  a  far  greater  extent,  and  more  of  it  is  finally 
cast  off  than  during  menstruation.  As  the  fecundated  egg  passes 
through  the  Fallopian  tube,  the  mucous  membrane  of  the  uterus  becomes 
tumefied,  vascular,  and  rugose,  projecting  as  rounded  eminences  into  the 
cavity  of  the  uterus  (Fig.  597),  the  uterine  tubules  at  the  same  time 
elongating  and  expanding  to  such  an  extent  that  their  open  mouths 
become  perceptible  at  the  surface.  The  mucous  membrane  so  modified 
is  a  thick,  soft,  velvety,  vascular  lining,  quite  different  from  that  of  the 


Fig.  597. 


Fio.  598. 


Impregnated  uterus,  with  projecting  folds  of 
decidua  growing  up  around  the  egg.  The 
narrow  opening,  where  the  edges  of  the  folds 
approach  each  other,  is  seen  over  the  most 
prominent  portion  of  the  egg.     (Dalton.) 


Impregnated  uterus:  showing  connection  be- 
tween villosities  of  chorion  and  decidual  mem- 
brane.    (Dalton  ) 


unimpregnated  condition ;  indeed,  so  much  so  that  the  decidua  vera,  as 
the  membrane  is  now  called,  was  supposed  at  one  time  to  be  of  new 
formation. 


VILLOUS    PROCESSES    OF    CHORION. 


929 


The  decidua  vera  is,  however,  only  the  hypertrophied  mucous  mem- 
brane of  the  uterus,  being  continuous  at  the  orifices  of  the  Fallopian 
tubes  with  the  mucous  membrane  lining  the  latter,  and  at  the  os  inter- 
num with  that  lining  the  cervix.  It  should  also  be  mentioned  that  at 
this  period  the  cavity  of  the  latter  becomes  so  filled  with  a  viscid-like 
mucus  that  the  passageway  to  the  vagina  is  blocked  up,  the  ovum 
within  the  cavity  of  the  uterus  being  thereby  protected  from  external 
influences.  The  impregnated  egg  having  reached  the  uterine  orifice  of 
the  Fallopian  tube,  passes  through  the  latter  into  the  cavity  of  the 
uterus  and  is  caught,  as  it  were,  between  a  pair  of  the  folds  of  the  de- 
cidua vera  and  retained  there  by  the  growing  downward  and  around  of 
the  latter,  until  the  ovum  is  completely  inclosed  by  the  same.  The 
reflected  folds  so  developed  are  known  as  the  decidua  reflexa  (Fig.  597), 
that  portion  of  the  decidua  vera  lying  between  the  ovum  and  the  wall 
of  the  uterus  as  the  decidua  serotina.  It  has  already  been  mentioned 
that  the  chorion  or  vitelline  membrane  of  the  ovum  at  an  early  period 
of  intrauterine  life  is  covered  with  small  villous-like  processes,  which 
in  time  become  vascular  through  being  penetrated  by  the  bloodvessels 
of  the  allantois.  The  villi,  when  examined  by  the  microscope  (Fig. 
599),  present  such  a  very  characteristic  appearance  that  their  presence 


Fig.  599. 


Fig.  fiOO. 


..    • 


Compound  villosity  of  human  chorion,  ramified  ex- 
tremity. From  a  three  months'  foetus.  Magnified 
thirty  diameters.     (Dalton.) 


Extremity  of  villosity  of  chorion,  more  highly 
magnified  ;  showing  the  arrangement  of  blood- 
vessels in  its  interior.     (Dalton.) 


may  be  accepted  as  positive  proof  of  the  existence  of  a  foetus,  as  much 
so,  indeed,  as  if  the  foetus  itself  had  been  found.  The  general  appear- 
ance of  a  villus  is  like  that  of  a  sea-weed,  originating  in  the  chorion  by 
a  trunk,  which  divides  and  subdivides  into  filamentous  branches,  swollen 
here  and  there  and  terminating  in  rounded  extremities,  and  consisting 
internallv  of  a  finelv  granular  substance  containing  nuclei.  At  first  the 
villous  processes  of  the  chorion  are  without  vessels,  but  with  the  estab- 

59 


930 


REPRODUCTION, 


lishment  of  the  allantois  they  become  vascular  through  prolongation  of 
the  terminal  allantoic  vessels,  which  (Fig.  000)  are  disposed  in  loops. 
As  development  advances,  however,  the  chorion  loses  its  villi,  except  at 
that  part  of  it  in  contact  with  the  decidua  scrotinia  (Fig.  601),  hut  here 


Fig.  601. 


Fig.  602. 


Pregnant  uterus:  showing  the  formation  Pregnant  human  uterus  audits  contents,  about  the  end 
of  the  placenta  by  the  local  development  of  of  the  seventh  mouth;  showing  the  relations  of  the  cord, 
the  decidua  and  the  chorion.     (Dalton.)  placenta,  and  membrane.     1.   Decidua  vera.     2.  Decidua 

reflexa.     3.  Chorion.     4.  Amnion.     (Dalton  i 


the  villi  are  much  developed,  dividing  and  subdividing  and  insinuating 
themselves  as  they  grow  into  the  mucous  membrane  or  decidua  serotina 
of  the  uterus.  The  latter  in  the  meantime  hypertrophies,  grows  down- 
ward, around,  and  between  the  villous  processes  of  the  chorion  (Fig.  603— 
605,  y),  its  capillaries  (vc)'  at  the  same  time  becoming  enormously  dilated, 
being  finally  transformed  into  sinuses  into  and  from  which  pass  a  uterine 
artery  (ua)  and  vein  (uv).  The  wall  of  the  sinus  eventually  fusing  with 
that  of  the  villous  process  of  the  chorion  (v),  and  the  latter  with  the  wall 
of  the  capillary,  eventually  the  maternal  blood  in  the  sinus  (vc)  is  sepa- 
rated from  the  foetal  blood  in  the  villous  (fv)  by  a  membrane  so  thin 
as  not  to  exceed  the  4  ^0  6 th  of  an  inch  in  thickness,  which  readily 
permits  of  the  osmosis  of  nutritive  materials  and  oxygen  from  the 
mother's  blood  into  that  of  the  foetus,  and  of  effete  materials  from  the 
blood  of  the  foetus  into  that  of  the  mother,  though  at  no  time  is  there 
any  connection  between  maternal  and  foetal  vessels.  The  organ  so 
formed,  with  nutritive  and  respiratory  functions,  is  called  the  placenta, 
and  evidently  consists  of  two  parts,  foetal  and  maternal,  the  allantois 
and  decidua  serotina,  which,  however,  become  so  intimately  united  that 
eventually  they  are  inseparable,  and  are  cast  off  as  such  during  labor  as 
the  "  after-birth."  As  development  proceeds,  the  amnion  becoming  dis- 
tended with  the  fluid  given  off  by  the  foetus,  consisting  principally  of 
water,  some  urea  and  alkaline  salts,  fuses  about  the  fifth  month  of  preg- 


TERMINATION    OF    FGETAL    LIFE 


931 


nancy  with  the  clecidua  reflexa.  The  latter,  in  turn,  fusing  about  the 
seventh  month  of  pregnancy  with  the  decidua  vera,  it  so  comes  that 
at  the  end  of  pregnancy  the  foetus,  suspended  from  the  placenta  by  the 
umbilical  cord,  floats  in  the  amniotic  fluid,  the  enclosing  sac  of  which, 
consisting   of   the  three   layers    just  mentioned,   now   fused  together. 

Fig.  603. 


- 


Fig.  604. 


Fig.  605. 


««.  Uterine  artery,      uc.  Uterine  capillary. 


uv.  Uterine  vein. 


ils.  Decidua  serotina.     ck.  Chorion. 


v.  Villous  processes  of  chorion,    fv.  Foetal  vessels.    (Eecolaki.) 

With  the  rupture  of  the  latter  and  the  escape  of  the  water,  etc.,  the 
child  is  born,  and  that  life  begins,  which  it  has  been  the  object  of  this 
work  to  endeavor  to  describe. 


INDEX. 


4  BSORPTION,  188 
A     by  rectum,  200 

by  stomach,  200 

condi t  on  favoring,  209 

formation  of  lymphatics  in.  100 

of  oxygen,  438 

resume  of,  211 

veins  as  a  means  of,  189 

villi,  uses  of,  in,  194 
Accommodation,  783,  801 
Acid,  hippuric,  524 

phosphoric,  529 

uric,  524 

volatile,  in  urine,  528 
Acids  of  bile,  171 
Acoustics,  physiological,  822 
Action  of  diaphragm,  406 

of  hear;,  271-286 

of  ocular  muscles,  808 

of  ribs  in  respiration,  408 
.K-  "tonometer,  436 

Ai^e,  influence  of,  on  temperatur  •.  47"> 
Air  cells  of  lungs,  400 
Albumen,  69 

in  blood,  260 
Albuminose,  70 

Alimentary  canal,  development  of,  915 
Alkaline  urine,  533 
Alkalinity  of  blood,  212 
Allantois,  908 
Alveoli  of  lungs,  400 
Amniotic  fold,  906 
Amceba,  45 

characteristics  of,  45 

movements  of,  45 
Amoeboid  movements,  45 
Amount  of  blood,  214 
in  brain,  706 

of    heat    produced    in    twentv-four 
hours,  493 

of  oxygen  absorbed,  441 

of  perspiration,  755 

of  urea,  518 

of  uric  acid,  524 

of  urine,  514 

of  water  in  b'o.id,  242 
Anelectrotonus,  609 
Analysis,    colorimetric,    of  haemoglobin, 

"  250 

of  blood  by  spectrum,  254 

spectroscopic,  of  haemoglobin.  253 


Anastomosis  of  veins,  363 
Animal  foods,  composition  of,  86 
heat,  470 

amount  of,  produced  in  twenty- 

fo  :r  hours,  493 
conditions   influencing  expendi- 
ture of,  474,  503 
age  and  sex,  475 
atmospheric  humiditv.  480 
baths,  481,  505 
clothing,  505 
food,  470 

glandular  action,  477 
mental  action,  477 
muscular  action.  477 
temperature,  478 
time  of  day,  475 
correlation  of,  and  mechanical 

work,  501 
expenditure  of,  499 
in  various  animals,  471 
production  of,  484 

calorimeter     for    studying, 
485 
regulation  of,  499 
specific  heat  of  tissues,  488 
thermometers       for      studvin^, 
473 

metastatic,  473 
Anterior  columns  of  spinal  cord,  623 
Aphasia,  719 
Apncea,  467 

Apparatus   for   counting    red    blood-cor- 
puscles, 216 
induction,  545 
respiratory,  443 
Appendages  of  skin.  737 
Aquaeductus  vestibuli,  868 
Aqueous  humor,  782. 
Area  opaca,  905 

pellucida,  905 
Arterial  blood,  color  of,  213 
gases  in,  259 
pressure,  325 
schema,  305 
Arteries,  293 

changes  in  shape  of,  299 
coats^of,  293 
contractility  of.  '2'.'~ 
dilatation  of,  299 
elasticity  of,  295 


934 


INDEX. 


Arteries,  elongation  of,  299 

function  of,  293 

demonstrations  of,  375 

increased  diameter  of,  293 

nourishment  of,  293 

tonicity  of,  297 

vaso-vasorum  of,  293 
Artificial  respiration,  423 
Asphj'xia,  467 

Attachments  of  pericardial  sac,  265 
Attraction,  capillary,  205 
Auricles  of  heart,  265 
Axis-cylinder  of  nerves,  537 


BATTERIES,  545 
Baths,  influence  of,  on  temperature, 
481 
Beer,  composition  of,  97 
Bile,  159 

acids  of,  171 
cholesterin,  174 
coloring  matter  in,  174 
composition  of,  170 
function*  of,  161 
origin  of,  175 
salts,  171 

tests  for,  172 

Gmelin's,  173 
Pettenkofer's,  172 
Biliverdin,  72 
Binocular  vision,  806 
Blastoderm,  903 

formation  of,  904 
Blood,  212 

alkalinity  of,  212 
amount  of,  in  body,  214 

in  brain,  706 
as  a  cause  of  heart's  action,  291 
coagulation  of,  236 

as  a  cure  for  hemorrhage,  238 
buffy  coat  in,  237 
causes  of,  237 
corpuscles  in,  236 
crassamentum  in,  236 
effect   of  sodium    sulphate    on, 
240 
of  temperature  on,  238 
explanation  of,  239 
ferment  in  the,  241 
fibrin  in,  236 
fibrinogen  in,  240 
forms  of,  236 
in  arteries,  238 
inside  the  body,  238 
in  veins,  238 
length  of  time  of,  237 
liquor  sanguinis  in,  236 
outside  the  body,  238 
paraglobin  in  the,  240 
plasmin  in,  240 
process  of,  236 
rapidity  of,  237 
serum  in,  236 
water  in,  236 


Blood,  color  of,  213 
arterial,  213 
brightness    of,     depending     on 

form  of  corpuscles,  213 
variations  in,  213 
venous,  213 
composition  of,  242 
albumen,  260 
corpuscles,  247 
excrementitious  matters,  262 
fatty  matters,  261 
fibrin,  260 
gases,  255 

method  of  obtaining,  255 
varieties  of,  255 
in  arterial,  259 
in  venous,  259 
haemin,  251 

crystals  of,  251 
method  of  obtaining,  251 
haemoglobin,  248 

chemical     constituents    of, 

2J9 
colori  metric      analysis     of, 

250 
function  of,  255 
method  of  obtaining,  248 
spectroscopic  analysis,  253 
varieties  of  crystals,  249     ■ 
in  various  animals,  246 
method     of    determining     the, 

242 
saline  matters  in,  261 
spectrum  analysis  of,  254 
water,  amount  of,  in,  242 
constituents  of,  214 
corpuscles  of,  214 

effect  of  liver  on  the  formation 

of,  230 
in  capillaries,  350 
red  marrow  of  bone  as  a  source 

of,  231 
varieties  of,  214 
course  of,  through  heart,  271 
in  lungs,  401 
pressure,  309,  313,  321 

effects  on,  of  respiration,  422 
in  capillaries,  357 
in  veins,  364 
quantity  of,  213 

modes  of  estimation  of,  213 
specific  gravity  of,  212 
supply  of  lungs,  400 
temperature  of,  212 

variations  in,  212 
velocity  of,  341 
Body,  calcium  carbonate  in,  53 
phosphate  in,  52 
potassium  chloride  in,  52 
>odium  carbonate  in,  53 

chloride  in,  51 
water  in,  50 
Bones  of  middle  ear,  857 
Brain,  fissures  of,  704 
Branches  of  facial  nerve,  663 


INDEX. 


935 


Branches  of  pneumogastric  nerve,  671 
Brightness  of  blood  color,  213 
Bronchi,  399 

Bronchial  mucus,  composition  of,  398 
Butty  coat   in   the  coagulation  of  blood, 

Bulbs  of  nerves,  542 
Burdach,  columns  of,  624 


CALCIUM  carbonate  in  body,  53 
phosphate  in  body,  52 
Calibre  of  capillaries,  352 
Canula  for  artificial  respiration,  424 
Capacity  of  heart,  277 
of  respiration,  430 
Capillaries,  246 

blood  corpuscles  in,  350 
calibre  of,  352 

variations  in,  352 
causes  of,  353 
capacity  of,  349 
circulation  in, 350 
diameter  of,  347 
discovery  of,  346,  387 
distribution  of,  348 
pressure  of  blood  in,  357 
structure  of,  348 
velocity  of  blood  in,  352 
Capillary  attraction,  205 

forces,  359 
Carbonic  acid  exhaled,  438-458 

production  of,  461 
Cardiograph,  274,  279 
Cartilages  of  larynx,  840 
Cartilagin,   71 
Casein,  71 

Causation  of  sleep,  721 
Cause  of  electrical  current  in  nerve,  572 
Causes  of  flow  of  blood  in  veins,  365 

heart's  action,  289 
Cavity  of  larynx,  841 
Cell,  definition  of  a,  44 
description  of  a,  44 
nucleolus  of,  44 
nucleus  of,  44 
reproduction  of  a,  4"> 
varieties  of,  44 
Cells  of  nerves,  539 

of  spinal  cord,  62  1 
Centre,  vasomotor,  732 
Centres  in  spinal  cord,  6  19 
Cerebellum.  696 
Cerebral  hemispheres,  702 

amount  of  blood  in,  706 
comparative     development     of, 

110 
composition  of,  708 
convolutions  of,  702 
development  of,  710 
fissure  of  Rolando,  703 

of  Sylvius,  703 
fissures  of,  703,  704 
gray  matter  of,  702 
injury  to,  709 


Cerebral  hemispheres,  Island  of  Reil,  703 
lobes  of,  704 

localization  of  functions,  715 
weight  of,  707 
white  matter  of,  7<  >li 
Cerebral  vesicles,  development  of,  911 
Cerebrum,  702 
Cervical  ganglia,  727 
Changes  i  n  shape  of  arteries,  299 

of  food,  destructive,  75 

of  tissue,  destructive,  75 
Chemical  changes  during  contraction  of 
muscle,  576 

composition  of  cells,  49 

constituents  of  haemoglobin,  249 
of  white  corpuscles,  223 

structure  of  body,  43 
Chiasm  of  optic  nerves,  769 
Cholesterin,  174 
Chordae  tendineae  of  heart,  268 
Choroid  coat,  771 
Chyle  and  lymph,  193 

composition  of,  193 
Ciliary  muscles,  773 

process,  772 
Circulation,  discovery  of,  372 

in  capillaries,  350 

in  veins,  369,  370 

of  blood,  264 

velocity  of,  341 
Circulatory  system,  346 

capillaries  of,  346 
Circumvallate  papilhe,  7<>5 
Clarke,  columns  of,  624 
Clothing,   influence  of,  on   temperature, 

505. 
Coagulation  of  blood  (see  Blood),  236 
(/oats  of  arteries,  293 

of  veins,  361 
Cochlea,  867 

Coffee,  composition  of,  93 
Color  of  blood,  213 
Colori metric   analysis    of    haemoglobin, 

250 
Coloring  matter  of  bile,  174 

of  urine,  513 
Colors,  sensation  of,  814 
Colostrum,  752 

Columnar  carneae  of  heart,  269 
Columns  of  spinal  cord,  623 
Comparative  development  of  cerebrum, 
710 

physiology,  value  of,  37 
Composition  of  animal  foods,  86 

of  beer,  97 

of  bile,  170 

of  blood,  85,  242 

of  brain,  70s 

of  bronchial  mucus,  398 

of  cells,  49 

of  coffee,  93 

of  colostrum,  752 

of  corpuscles,  247 

of  cow's  milk,  92 

of  flour,  91 


936 


INDEX 


Compostion  of  food,  89 

of  gastric  juice,  L37 

of  hair,  747 

of  human  milk,  751 

of  nasal  mucus,  398 

of  ox  flesh,  87 

of  oyster,  87 

of  perspiration,  755 

of  potato,  87 

of  saliva,  118 

of  spinal  cord,  623 

of  tea,  93 

of  urine,  512 

of  vegetable  foods,  86 

of  wine,  97 
Conditions  favoring  absorption,  209 

influencing  production    of  carbonic 
acid,  456 

which  modify  animal  heat,  474 
Constituents,   chemical,  of  haemoglobin, 
249 

of  blood,  214 

of  urine,  515 
Contents  of  large  intestine,  L85 

of  pericardial  sac,  265 

of  small  intestine,  179 
Contractility  of  arteries,  297 

of  veins,  369 
Contraction  of  muscles,  875 
Convolutions  of  brain,  702 
Coordinating  powers  of  cerebellum,  699 
Cranial  nerves,  6-33 

oculo-motor,  653 

olfactory,  653 

optic,  653 

pathetic,  654 
Crassamentum    in    the    coagulation    of 

blood,  236 
Crura  cerebri,  689 

function  of,  689 
Crystallin,  71 
Crystalline  lens,  781 
Crystals    of    haemoglobin,    varieties    of, 
249 

of  hsemin,  251 

of  urea,  516 

of  uric  acid.  526 
Cord,  spinal,  623 
Cornea,  770 

Cornua  of  spinal  cord,  625 
Corpora  Arantii,  270 

quadrigemina,  G94 

striata,  690 
Corpus  luteum,  893 

Corpuscles,  blood,  red  marrow  of  bone 
as  a  source  of,  231 

in  coagulation  blood,  236 

of  blood,  214 

effect  of  liver  on  the  formation 
of,  230 

varieties  of,  314 
Correlation  of  heat  and  mechanical  work, 

501 
Corti,  rods  of,  869 
Counting  of  red  blood-corpuscles,  215 


Course  of  blood  through  heart,  271 
of  facial  nerve,  662 
glosso-pharyngeal  nerve,  662 
hypoglossal  nerve,  685 
pneumogastric  nerve,  669 
spinal  accessory  nerve,  682 
of  sympathetic  nervous  system,  724 

Cow's  milk,  composition  of,  92 

Current,  electrical,  572 

Czermak's  rabbit  holder,  326 

DEFECATION,  186 
Deglutition,  120 
Dentals  in  speech,  853 
Dermis  or  true  skin,  739 
Destruction  of  red  corpuscles  in  spleen, 

230 
Destructive  changes  of  food,  75 

of  tissue,  75 
Development  of  embryo,  900 
of  liver,  166 

of  primitive  organs  in  embryo,  905 
of  protococcus  pluvialis,  47 
of  red  blood-corpuscles,  222 
Diameter  of  capillaries,  347 
of  eyeball,  770 
of  red  blood-corpuscles,  219 
Diaphragm  as  a  respiratory  muscle,  404 
Diastole  of  heart,  271 
Dicrotic  pulse,  311 

Difference  of  heart  fibres  from  ordinary 
muscle  fibres,  266 
in  respiration  in  sexes,  41") 
Differential  rheotome,  599 
Diffusion  of  liquids,  208 
Digestion,  99,  186 
deglutition,  115 
gastric,  124 

juices,  124 
influence  on  heart's  action,  287 
insalivation,  115 
intestinal,  146 
juices,  148 
bile,  159 
pancreatic,  153 
mastication,  99 

muscles  of,  109 
Dilatation  of  arteries,  299 
Discovery  of  the  capillaries,  346,  387 
of  the  circulation,  372 

history  of,  372 
of  the  pulmonary  circulation,  377 
of  the  systemic  circulation,  381 
of  white  blood-corpuscles,  223 
Disintegration    of  red    blood-corpuscles, 

222 
Distribution  of  capillaries,  348 

of  spinal  nerves,  637 
Divisions  of  ear,  855 
of  heart,  265 
of  nervous  system,  535 
of  spinal  cord,  623 
Ducts  of  mammary  glands,  150 
Dynamic  electricity,  595 
Dyspnoea,  467 


INDEX. 


937 


EAR,  855 
divisions  of,  855 
external,  855 

function  of,  855 
structure  of,  855 
Eustachian  tube,  860 
internal,  860 

aquseductus  vestibuli,  868 
basilar  membrane,  872 
cochlea,  867 
endolvmph  in,  869 
labyrinth  of,  868 
membrane  of  Reissner,  869 
modiolus  of,  871 
rods  of  Corti  of,  869 
saceulus  of,  868 
scala  tympani,  869 
vestibuli,  869 
semicircular  canals,  807 
structure  of,  866 
utriculus  of,  868 
middle,  856 

bones  of,  857 
function  of,  850 
structure  of,  856 
powers  of,  861 
Elasticity  of  veins,  362 
Elastin,  72 

Electrical  current,  572 
Electricity,  static,  595 

dynamic,  595 
Electrodes,  non-polarizable,  572 
Electromotive  force  of  nerve,  572 
Electrotonic  current,  596 
Electrotonus,  596 
Eleventh  nerve,  682 
Elongation  of  arteries,  299 
Embryo,  development  of,  900 
Embryonic  layers,  908 
membranes,  908 

organs  developed  from,  908 
Endocardium,  267 
Endolvmph  in  ear,  869 
Endosmometer,  203 
E  pi  blast,  808 
Epidermis,  739 
Epididvmis,  896 
Epiglottis,  841 

Estimation  of  quantity  of  blood,  213 
Eustachian  tube,  860 
Excrementitious  matters  in  blood,  262 
Excretion  of  urine,  529 
Exhalation  of  carbonic  acid,  438,  458 
of  organic  matter,  456 
of  watery  vapor,  456 
Expenditure  of  heat,  499 
Expiratory  muscles,  412 
External  ear,  855 
Extremities,  development  of,  926 
Eye,  770 

development  of,  915 

FACIAL  nerve,  661 
branches  of,  663 
course  of,  662 


Facial  nerve,  functions  of,  661 

Fallopian  tubes,  889 

Fat,  quantity  of,  in  various  foods,  61 

in  tissues,  59 
Fatty  matters  in  blood,  261 
Feces  in  large  intestine,  185 
Feeding  of  white  blood-corpuscles,  223 
Female  generative  apparatus,  888 
Fibre4  of  heart,  266 

of  muscle,  875 
Fibrin,  70 

in  blood,  260 

in  coagulation  of  blood,  236 
Fick's  spring  kymograph,  336 
Fifth  nerve,  656 
Filiform  papilla?,  767 
First  nerve,  653 
Fissures  of  brain,  704 

of  medulla  oblongata,  627 

of  Kolando.  703 

of  spinal  cord,  623 

of  Sylvius,  703 
Flour,  composition  of,  91 
Flow  of  blood  in  veins,  365 
Foetal  derivation  of  white  corpuscles,  225 
Follicles  of  hair,  746 
Food, 80 

composition  of,  89 

destructive  changes  of,  75 

kinds  of,  85 

quality  of,  88 

quantity  of,  88 

use  of,  83 
Foramen  ovale  in  cochlea,  870 

rotundum,  870 
Force,  capillary,  359 

of  nerve,  electromotive,  572 
Form  of  corpuscles,  effect  on  blood  color, 
213 

of  medulla  oblongata.  * ; '2 7 
Forms  of  coagulation  of  bio  d,  236 

of  nerve  cells,  539,  540 
Formula  for  uric  acid,  524 
Fourth  nerve,  654 
Fungiform  papilla?,  766 


GALVANOMETERS,  572 
Ganglia,  725 
Gases  in  blood,  255 
Gastric  digestion,  124 
glands,  131 
juice,  action  of,  138 

duration  of,  143 
composition  of,  137 
Gelatinous  fibres  of  Remak,  538 

substance  of  Ro  ando,  624 
Generative  apparatus,  female,  888 

male,  896 
Genito-urinarv    tract,    development   of, 

923 
Glands,  896 

of  large  intestine,  181 
of  stomach,  131 
Globulin,  71 


938 


1  NDEX, 


Glomeruli  of  kidney,  f)1 1 

G-losso-pharyngeal  nerve,  668 
course  of,  669 
functions  of,  669 

Glottis,  SI  I 

Glycogen,  17G 

Gmelin's  test  for  bile,  17:! 

Goll,  columns  of,  624 

Graafian  follicle,  890 

Gray  matter  of  brain,  702 
of  spinal  cord,  '124 

Gustation,  765 

Gutturals  in  speech,  858 


HM MATIN,  72 
Haemin,  251 
Haemodromometer,  339 
Haemodynamometer,  323 
Haemoglobin,  248 

functions  of,  255 
Hairs,  745 
Harvey,  372 
Hearing,  powers  of,  861 
Heart,  265 

action  of,  271,  286 
causes  of,  289 
frequency  of,  286 
influence  of  digestion  on,  287 
of  position  on,  287 
of  respiration  on,  288 
of  sleep  on,  288 
of  temperature  on,  288 
of  vagus  on,  673 
in  various  animals,  286 
auricles  of,  263 

thickness  of,  272 
capacity  of,  277 
chordae  tendineaa,  268 
columnae  carne;e,  269 
corpora  Arantii,  270 
course  of  blood  through  the,  271 
diastole  of,  271 
divisions  of,  265 
endocardium  of,  267 
fibres  of,  266 
movements  of,  271 
papillary  muscles  of,  269 
position  of,  265 
rhythm  of,  273 

method  of  determining  the,  274 
sac  of,  265 

attachments  of,  265 
contents  of,  265 
description  of,  265 
sinus  of  Valsalva,  270 
sounds  of,  282 
systole  of,  271 
valves  of,  269 

functions  of,  271 
movements  of,  271 
ventricles  of,  265 

thickness  of,  272 
weight  of,  277 
work  done  by,  281 


Heat,  animal,  470 

produced  in  twenty-four  hours,  493 
value  of  foods,  495,  497 
Ilenle,  loop  of,  511 
Hepatic   vein,   proportion    of   corpuscles 

in,  230 
Hippuric  acid,  527 
Human  milk,  751 
ovum,  47,  &«79 
Hunger  and  thirst,  80 
Hyaloid  tumor  of  eye,  781 
Hydrostatic  bellows,  319 
Hymen,  889 
Hypoblast,  808 
Hypoglossal  nerve,  585 
course  of,  685 
distribution  of,  685 
functions  of,  685 
origin  of,  685 

TLEO-CzECAL  valve,  181 

JL     Impregnation  of  ovule,  900 

Incessures  of  Lautennann,  538 

Indican  in  urine,  528 

Induction  apparatus,  545 

Insalivation,  1 15 

Inspiratory  muscles,  404 

Intensity  of  sound,  825 

Intercostal  muscles  in  respiration,  413 

Intermaxillary  hone,  106 

Internal  ear,  866 

development  of,  912 
Intestine,  large,  180 

contents  of,  185 

feces  in,  185 

glands  of,  181 

valve  of,  181 
small,  contents  of,  179 
Intestinal  digestion,  146 
Invertebrates,  nerves  of,  538 
red  blood-corpuscles  of,  221 
respiration  in,  391 
Iris,  773 

Iron,  quantity  of,  in  spleen,  230 
Island  of  Reil,  703 


-) 


UICE,  bile,  159 
gastric,  124 

composition  of,  137 
intestinal,  148 
pancreatic,  153 


IfATELECTROTONUS,  609 

IV     Keratin,  72 

Kidneys,  508 

function  of,  508 
glomeruli  of,  511 
Henle,  loop  of,  511 
Malpighian  bodies  of,  510 
structure  of,  509 
uriniferous  tubules,  511 

Kinds  of  food,  85 


INDEX, 


039 


Kymograph,  331 

Fick's  spring,  336 

LABIALS  in  speech,  853 
Labvrinth  of  ear,  868 
Lacteals,  189 
Lacunar  type  of  circulation  in   spleen, 

Large  intestine,  181 
Larynx,  395,  840 

cartilages  of,  840 

cavity  of,  841 

function  of,  395 

mechanism  of,  842 

muscles  of,  840 

position  of,  840 

shape  of,  840 

vibrations  in,  845 
Latent  period,  545 
Lautennann,  incessures  of,  538 
Law,  Ohm's,  545 

Hitter's,  621 
Liquids,  diffusion  of,  208 

miscibility  of,  207 

Liquor  sanguinis  in  coagulation  of  blood, 
236 

Liver,  163 

as  a  source  of  white  corpuscles,  231 

development  of,  166 

effect  of,  on  formation  of  cornuscle* 

230  K 

structure  of,  163 

in  lower  animals,  168 
Lobes  of  brain,  704 
Lobules  of  lungs,  400 
Locality   for    production    of   white   cor- 

puscles,  226 
Localization  of  functions  of  brain,  715 
Ludwig's  respiratory  apparatus,  446 
Lumbar  ganglia,  729 
Lungs,  399 

air-cells  of,  400 

number  of,  400 
alveoli  of,  401 
blood  in,  401 

sipply  of,  400 
elasticity  of,  414 
lobules  of,  400 
Lymph  and  chyle,  193 
composition  of,  193 
Lymphatics,  190 

ALE  generative  apparatus,  896 
epididymis,  896 
glands,  896 
prostate,  896 
semen,  897 

seminiferous  tubules,  897 
spermatic  curds,  896 
spermatozoa,  898 
testicles,  896 
tunica  albuginea,  896 
JMalpighian  bodies,  510 

corpuscles  in  spleen,  229 


Mammary  glands,  750 
Manometer,  differential,  335 

frog,  Brubaker's.  328 
Marrow,  red,  of  bone'as  a  source  of  blood 

corpuscles,  231 
Mastication,  99 

muscles  of,  109 
Maxillary  bones,  105 

articulation  of,  105 
Mechanical   work  done    during   respira- 
tion, 427  F 
Mechanism  of  lar.nx,  842 
Medulla  oblongata,  627 
Medullary  nerves,  537,  651 
functions  of,  632 
pairs  of,  652 

number  of,  652 
varieties  of,  652 
Melanin,  72 

Membranes,  embrvonic,  908 
Membrane  of  Reissner,  869 
Menstruation,  895 
Mesoblast,  808,  906 
Metastatic  thermometers,  473 
Metronome,  417 
Middle  ear,  856 
Milk,  human,  751 
Miscibility  of  liquids,  207 
Modiolus  of  ear,  87 
Movements  of  heart,  271 
of  respiration,  416 
of  white  corpuscles,  223 
Mucosin,  71 

Mucous  membrane  of  stomach,  131 
Mucus,  bronchial,  composition  of,  398 

nasal,  composition  of,  398 
Muscle  pla*ma,  880 
i  Muscles,  875 

contraction  of,  875 

apparatus  for  studying,  878 
chemical  changes  during,  876 
curves  of,  877 

physical  changes  during,  876 
sounds  produced  by,  879 
fibres  of,  875 
myosin  of,  880 
ocular,  action  of,  808 
of  larynx,  840 
of  mastication,  109 
of  respiration,  404,  410,  412 
plasma  of,  880 
sarcolemma  of,  875 
sheath  of,  875 
striss  of,  875 
varieties  of,  875 
Musculin,  71 
Myograph,  276 

pendulum,  545 
spring,  545 
Myosin,  880 


YTAILS,  743 

11      Nasal  mucus,  composition  of,  398 

Negative  variation,  596 


940 


INDEX, 


Nerve,  eleventh,  682 

force,  velocity  of,  545 

ninth,  668 

seventh,  661 

tenth. 669 

twelfth,  685 
Nerves,  535 

axis-cylinder  of,  537 

bulbs  of,  542 

cells  of,  539 

forms  of,  530,  540 

cranial,  653 

gelatinous  fibres  of  Remak,  538 

incessures  of  Lautennann,  538 

medullary,  537,  651 

neurilemma,  538 

nodes  of  Ranvier,  538 

non-medullary,  538 

of  invertebrata,  538 

of  spinal  cord,  630 

of  vertebrata,  538 

optic,  769 

peripheral  distribution  of,  540 

sheath  of  Schwann,  538 

substance  of  Schwann,  537 

tactile  corpuscles  of,  542 
Nervous  system,  534 

definition  of,  535 
development  of,  910 
divisions  of,  535 
structure  of,  534 
sympathetic,  724 
Neural  tract,  906 
Neurilemma,  538 
Nodes  of  Ranvier,  538 
Non-medullary  nerve-,  538 
Non-polarizable  electrodes,  572 
Nose,  761 

Nourishment  of  arteries,  293 
Nuclei  of  white  blood-corpu;cles,  223 
Nucleolus  of  a  cell,  44 
Nucleus  of  a  cell,  44 
Number  of  air  cells,  400 

of  respirations,  426 

of  sudoriferous  glands,  753 

of  white  blood-corpuscles,  233 
in  spleen,  229 


OCULAR  muscles,  action  of,  808 
Oculo-motor  nerve,  653 
Ohm's  law,  545 
Olfaction,  761 
Olfactory  nerves,  652 
tracts,  762 

origin  of,  762 
termination  of,  763 
Olivary  bodies,  627 
Oncometer,  735 
Optic  nerves,  652,  769 

thalamus,  692 
Optics,  physiological,  783 
Organic  matter,  exhalation  of,  456 
Organs  developed  from  embryonic  layers 
908 


Organs  of  body,  development  of,  908 

of  reproduction,  885 

of  vision,  769 
Origin  of  hile,  175 

of  optic  nerves,  769 

of  hypoglossal  nerve,  685 

of  olfactory  tracts,  762 

of  pneumogastiic  nerve,  669 

of  spinal  accessory,  682 

of  urea,  521 

of  uric  acid,  525 
Osmosis,  202 
Ostein,  71 
Ovaries,  889 
Ovule,  887 
Ovum,  47,  888,  891 
Ox  flesh,  composition  of,  87 
Oxygen,  absorption  of,  438 
Oyster,  composition  of,  87 


PAPILLARY  muscles  of  heart,  269 
Paraglobulin  in  the  coagulation    of 
blood,  240 
Paramcecium  caudatum,  46 
Pairs  of  medullary  nerves,  651 
Pancreatic  juice,  153 
Pancreatin,  71 
Papillae,  circum vallate,  765 

filiform,  767 

fungiform,  766 

of  skin,  740 
Pathetic  nerve,  654 
Pediastrum  pertusum,  47 
Pendulum  myograph,  545 
Pepsin,  71 

Perception  by  sitrht,  817 
Pericardial  sac,  265 
Period,  latent,  545 
Peripheral  distinction  of  nerves,  540 
Perspiration,  754 
Pettenkofer's  test  for  bile,  172 
Phosphoric  acid  in  urine,  528 
Physical  changes  during  contraction  of 
muscles,  876 

structure  of  body,  43 
Physiologica:  acoustics,  822 

optics,  783 
Pitch  of  sound,  826 
Placenta,  development  of,  928 
Plasma,  muscle,  880 

Plasmin  in  the  coagulation  of  blood,  240 
Plethysmograph  of  Mosso,  355 
Pleura?,  401 
Plexus,  solar,  728 
Pneumogastric  nerve,  669 

branches  of,  771 

course  of,  669 

function  of,  669 

influence  of,  on  heart,  613 

origin  of,  669 
Pneumograph,  416 
Pons  Varolii,  629,  688 

definition  of,  688 

function  of,  688 


INDEX, 


941 


Portal  vein,  proportion  of  corpuscles  in, 

230 
Position,  influence  of,  on  heart's  action, 
287 
of  heart,  265 
of  tongue,  840 
of  valves  of  heart,  285 
of   white  blood-corpuscles   in    blood 
streams,  224 
Posterior  columns  of  spinal  cord,  623 
Potassium  chloride  in  body,  52 
Potato,  composition  of,  87 
Powers  of  hearing,  861 
Pregnancv,  effect   on   white   corpuscles, 

224 
Pressure,  arterial,  325 
blood,  309, 313,321 
in  capillaries,  357 
in  veins,  364 
Primitive  trace,  904 
Principles,  chemical  composition  of,  56 
nitrogenous,  55 
non-nitrogenous,  55 
organic,  55 
Process  of  coagulation  of  blood,  236 
Production  of  animal  heat,  484 

of  carbonic  acid,  461 
Proportion    of    white    blood-corpuscles, 
223,  231 
and   red  corpuscles    in     hepatic 
vein,  230 
in  portal  vein,  230 
Prostate  gland,  896 
Protamceba,  45 

Protective  appendages  to  eye,  819 
Protococcus  pluvialis,  47 
Proximate  principles  of  organic  origin, 
55 
of  the  third  class,  66 
resume  of,  77 
Pulmonary  circulation,  discovery  of,  377 
Pulmonic  circulation  of  blood,  264 
Pulp  of  spleen,  229 
Pulse,  dicrotic,  311 

transmission  of,  309 
wave  length  of,  310 
Pump  for  artificial  respiration,  424 
Pyramids  of  medulla  oblongata,  627 

QUADRIGEMINAL  BODIES,  694 
functions  of,  695 
Quality  of  food,  88 

of  sound,  831 
Quantity  of  blood,  213 

modes  of  estimating,  2] 3 
of  calcium  carbonate  in  body,  53 

phosphate  in  body,  52 
of  fat  in  various  foods,  61 

tissues,  59 
of  food,  88 
of  iron  in  spleen,  230 
of  potassium   chloride  in  body,  52 
of  sodium  carbonate  in  body,  53 
chloride  in  body,  51 


Quantity  of  starch  in  various  foods,  57 
of  sugar  in  various  foods,  58 
of  water  in  body,  50 


RANVIER,  nodes  of,  538 
Rapidity  of  circulation,  370 
in  veins,  369 
of  coagulation  of  blood,  237 
Rate  of  the  heart  beat,  281 
Ratio  of  brain  to  spinal  cord,  645 
Ration  of  U.  S.  soldier,  92 
Reaction  of  urine,  513 
Rectum,  absorption  by,  200 
Red  blood-corpuscles,  214 

counting  of,  2 1 5 

apparatus  for  the,  216 
development  of,  222 

fiom  white  corpuscles, 
225 
diameter  of,  219 

in  various  animals,  219 
difference  in  size,  in  various 
animals,  219 
from  white,  224 
disintegration  of,  222 
number  of,  215 
of  invertebrates,  22] 
of  vertebrates,  221 
shape  of,  217 
structure  of,  214 
study  of,  217 
corpuscles  in  spleen,  230 
marrow  of  bone  as  a  source  of  blood 
corpuscles,  231 
Reflex  action,  647 

nature  of,  647 
Refraction,  783 

Regnault's  and  Reisel's  respiratory  ap- 
paratus, 443 
Regulation  of  heat,  499 
Reil,  island  of,  703 
Reissner's  membrane,  869 
Remak,  gelatinous  fibre  of,  538 
Reproduction,  885 

consideration  of,  885 
corpus  luteum,  893 

of  menstruation,  893 
of  pregnancy,  893 
development  of  embryo,  900 

alimentary  canal,  915 
allantois,  908 
amniotic  folds,  906 
area  opaca  in,  905 

pellucida  in,  905 
blastoderm  in,  903 
cerebral  vesicles,  911 
epiblast,  808 
extremities,  926 
eye,  915 

genito-urinary  organs,  923 
hypoblast,  808 
internal  ear,  912 
mesoblast  in,  808,  906 
nervous  system,  910 


942 


INDEX. 


Reproduction,  development  of  embryo- 
neural  tract,  700 
of  organs,  908 
placenta,  5)28 
primitive  organs,  905 
primitive  truce  in,  904 
respiratory  organs,  922 
segmentation    of  ovum   in 

902 
skull,  912 
teeth,  916 

va-cular  system,  918 
Graafian  follicle  in,  890 
human  ovum  in,  879 
impregnation  of  ovule,  900 
menstruation,  895 
methods  of,  885 
of  cells,  4"> 
organs  of,  888 
hymen,  889 
ovaries,  889 
uterus,  888 

Fallopian  tubes,  889 
walls  of,  889 
vagina,  889 
ovaries  in,  892 
ovule  in,  887 
ovum  in,  888,  891 
spermatozoa  in,  888 
Resemblance  of  chyle  to  blood,  228 
Resistance  of  nerve,  585 
Respiration,  391 

absorption  of  oxygen  in,  438 

amount  of,  441 
apncea  in,  467 
apparatus,  433 
artificial,  423 

canula  for,  424 
pump  for,  424 
asphyxia  in, 467 
bronchi,  structure  of,  399 
capacity  of,  430 

spirometer  for  testing,  430 
carbonic  acid  exhaled,  determination 

of,  453 
complemental  air  in,  432 
conditions  influencing  production  of 

carbonic  acid,  456 
difference  of,  in  sexes,  415 
dyspnoea  in,  467 
effects  on  blood  pressure,  422 
exhalation  of  carbonic  acid,  438,  458 
of  organic  matter,  436 
of  watery  vapor,  456 
Graham's  law  in,  435 
in  invertebrata,  392 

forms  of,  393 
influence  on  heart's  action,  287 
larynx  in,  function  of,  395 

structure  of,  395 
lungs,  air-cells  in,  400 
number  of,  400 
alveoli  of,  401 
blood  in,  401 

supply  of,  400 


Respiration,  lungs,  functions  of,  399 
tubules  of,  400 

varieties  of,  400 
mechanical  work  done  during,  427 
movements  of,  416 

effects  of,  on  blood  pressure,  422 
tracings  of,  421 
muscles  of,  action  of,  412 
diaphragm  as  a,  404 

action  of,  406 
expiratory,  412 
inspiratory,  404 
intercostal,  413 

varieties  of,  414 
scaleni,  411 
number  of,  426 
pleurae,  401 

production  of  carbonic  acid,  461 
residual  air  in,  432 
ribs  in  function  of,  407 

action  of,  408 
sounds  of,  425 

temperature  of  expired  air  in,  464 
tidal  air  in,  431 
trachea  in,  function  of,  397 
structure  of,  397 
Respiratory  apparatus,  443 

organs,  development  of,  922 
Restiform  bodies,  627 
Rete  mucosum,  741 
Retina,  776 
Rheocord,  602 
Rheotome,  differential,  599 
Rhythm  of  heart,  273 
Ribs,  action  of,  in  respiration,  408 
function  of,  in  respiration,  407 
Ritter's  law,  621 
Rods  of  Corti,  869 
Rolando,  fissure  of,  703 

gelatinous  substance  of,  624 
Roots  of  spinal  nerves,  630 
Running,  883 

SAC  around  heart,  265 
Sacral  ganglia,  729 
Saline  matters  in  blood,  261 
Saliva,  114 

composition  of,  118 

function  of,  lis 
Salivary  glands,  114 
Salts  of  bile,  171 
Sarcolemrna  of  muscle,  879 
Scala  tympani,  869 

vestibuli,  869 
Scaleni  muscles,  411 
Schwann,  sheath  of,  538 

substance  of,  537 
Sclerotic  coat,  770 
Sebaceous  glands,  748 
Second  nerve,  653 
Segmentation  of  ovum,  902 
Semen,  897 

Semicircular  canals,  867 
Seminiferous  tubules,  8 
Sensation  of  sight,  809 


INDEX. 


943 


Sensation  of  colors,  814 

Sense  of  taste,  765 

Sensibility,  tactile,  758 

Serum,  in  coagulation  of  blood,  236 

Seventh  nerve,  661 

Sex,  influence  of,  on  temperature,  475 

Sexes,  difference  in  respiration,  415 

Shape  of  larynx,  840 

Sheath  of  muscle,  875 

of  Schwann,  538 
Sight,  sensation  of,  809 

perception  by,  817 
Sinus  of  Bakalva,  271 
Size  of  white  blood-corpuscles,  223 
Skin,  737 

appendages  of,  737 

dermis  or  true,  739 

description  of,  737 

epidermis,  739 

functions  of,  737,  754 
perspiration,  754 
amount  of,  755 
composition  of,  755 

hairs,  745 

follicles  of,  746 
composition  of,  747 

layers  of,  738 

nails,  743 

papilla?  of,  740 

rete  mucosum  of,  741 

sebaceous  glands  of,  748 
matters  of,  749 

sensibility  of,  758 

sudoriferous  glands  of,  752 
number  of,  753 
Skull,  development  of,  912 
Sleep,  causation  of,  721 

influence  on  heart's  action,  287 
Small  intestine,  contents  of,  179 
Sodium  carbonate  in  body,  53 

chloride  in  body,  51 

sulphate,  effect,   on    the  coagulation 
of  blood,  240 
Solar  plexus,  728 
Soldier,  ration  of,  92 
Sound,  825 

intensity  of,  825 

pitch  of,  825 

quality  of,  825 
Sounds  of  the  heart,  282 

respiration,  425 
Specific  gravity  of  blood,  212 

of  urine,  513 

heat  of  tissues,  488 
Spectroscopic    analvsis    of    hsemoglobin, 

237 
Spectrum  analysis  of  blood,  254 
Speech,  851 

dentals  in,  853 

gutturals  in,  853 

labials  in,  853 

mode  of,  852 
Spermatic  cord-,  896 
Spermatozoa,  888,  898 
Sphygmograpb,  301 


Sphygmograph,  uses  of,  302 
Spinal  accessory  nerve,  f>82 
cour.-e  of,  682 
functions  of,  682 
origin  of,  682 
Spinal  cord,' 623 

anterior  column  of  623, 
as  a  nervous  centre,  639 
cells  of,  624 
columns  of,  623 
of  Goll,  624 
of  Clarke,  624 
of  Burdach,  624 
composition  of,  623 
cornua  of,  635 
course  of  fibres  of,  629 
divisions  of,  623 
extent  of  623 
fissures  of,  623,  627 
form  of,  627 
functions  of,  634 
gelatinous     substance     of,    Ro- 
lando, 624 
gray  matter  of,  624 
medulla  oblongata,  627 
nerves  of,  630 
roots  of,  630 
distribution  of,  637 
nerve  centres  in,  619 
olivary  bodies,  627 
pons  Varolii,  629 
posterior  columns  of,  623 
pyramids  of,  627 
ratio  of  brain  to,  645 
restiform  bodies,  627 
reflex  action  of,  647 
weight  of,  623 
Spinal  nerves,  630 

functions  of,  634 
Spirometer,  430 
Spleen,  228 

a  lymphatic  gland,  229 
as  a  source  of  white  corpuscles,  231 
iron,  quantity  of,  in,  230 
lacunar  type  of  circulation  in,  229 
Malpighian  corpuscles  of,  230 
number  of  white  corpuscles  in,  229 
pulp  of,  229 

red-blood  corpuscles  in,  230 
structure  of,  229 
vascularity  of,  229 
Spring  myograph,  545 
Starch,  quantities  of,  in  various  foods,  57 
Static  electricity,  595 
Stethometer,  418 
Stomach,  absorption  by,  250 
digestion  in,  137 
experiments  on,  129 
function  of,  125 
glands  of,  131 
juices  of,  135 
mucous  membrane  of,  131 
of  Alexis  St.  Martin,  126 
Strength  of  veins,  363 
Stria?  of  muscle,  *75 


944 


INDEX. 


Striated  bodies,  690 
Stromuhr,  Lud wig's,  340 
Structure  of  body,  43 

in  lower  animals,  168 
of  bronchi,  399 
of  capillaries,  348 
of  external  ear,  855 
of  internal  ear,  866 
of  kidneys,  509 
of  larynx,  395 
of  liver,  163 
of  middle  ear,  856 
of  nervous  system,  534 
of  red  blood-corpuscles,  214 
of  spleen,  229 
of  trachea,  397 
of  veins,  361 

of  white  blood-corpuscles,  223 
Substance  of  Schwann,  537 
Sudoriferous  glands  of  skin,  752 
Sugar,  quantities  of,  in  various  foods,  58 
Suprarenal  body  as  a  source  of  white  cor- 
puscles, 232 
Sylvius,  fissure  of,  703 
Sympathetic  nervous  system,  724 

effects   of   division    of  cer- 
vical sympathetic,  731 
ganglia  of,  725 
cervical,  727 
lumbar,  729 
sacral,  729 
solar  plexus,  728 
vasodilator  nerves,  733 
vasomotor  centre,  732 
Systemic  circulation  of  blood,  264 

discovery  of,  381 
System,  nervous,  534 
Systole  of  heart,  271 


TACTILE  corpuscles,  542 
sensibility,  758 
Taste  765 

bird's,  765 

circum vallate  papillae,  765 
filiform  pa  pit  lie,  767 
fungiform  papillae,  766 
sense  of,  765 
Tea,  composition  of,  93 
Teeth,  100 

development  of,  916 
enamel  of,  103 
pulp  of,  105 
Temperature,  478 

atmospheric  influence  on  bodily,  478 
effect  on  coagulation  of  blood,  238 
influence  of  baths  on,  481 
of  food  on,  476 
of  glandular  action  on,  477 
of  mental  action  on,  477 
of  muscular  action  on,  477 
of  sex  and  age  on,  475 
of  time  of  day  on,  475 
on  heart's  action  on,  287 
of  blood,  212 


Temperature  of  expired  air,  464 
of  various  animals,  471 

Ten- ion  of  gases  in  blood,  437 

Tenth  nerve,  669 

Termination  of  olfactory  nerves,  763 

Testicles,  896 

Tests  for  bile,  172 

Thalami  optici,  692 

Thermometers  for  studying  animal  heat, 
473 

Thickness  of  ventricles  of  heart,  265 
of  auricles  of  heart,  265 

Third  nerve,  653 

Thirst  and  hunger,  80 

Thoracic  duct,  189 

Thymus  gland  as  a  source  of  white  cor- 
puscles, 232 

Thyroid  gland  as  a  source  of  white  cor- 
puscles, 234 

Tidal  air,  431 

Tissue,  distinctive  changes  of,  75 

Tongue,  765 

functions  of,  765 

Tonicity  of  arteries,  297 

Trachea,  397 

function  of,  397 

Tracings  of  respiration,  421 

Tracts,  olfactory,  762 

Transformation  of  white  corpuscles  into 
red,  225 

Transmission  of  pulse  wave,  309 

Trigeminus,  656 

Tubules,  uriniferous,  511 

Tunica  albuginea,  896 

Twelfth  nerve,  685 


UREA,  72 
derivation  of,  72 
determination  of,  516 
Uric  acid,  524 
Urine,  512,  524 

alkaline,  formation  of,  533 
amount  of,  514 
coloring  matter  of,  513 
composition  of,  512 
constituents  of,  515 
definition  of,  512 
excretion  of,  529 

method  of,  530 
hippuric  acid,  527 
indican  in,  528 
influence  of  exercise  on,  519 
phosphoric  acid  in,  529 
reaction  of,  513 
specific  gravity  of,  513 
urea  in,  515 

amount  of,  518 
crystals  of,  516 
determination  of,  516 
origin  of,  521 
uric  acid  in,  524 

amount  of,  in,  524 

in  various  animals,  524 
crystals  of,  526 


INDEX. 


945 


Urine,  uric  acid  in,  formula  for,  524 
origin  of,  525 

volatile  acids  in,  528 
Uriniferous  tubules,  511 
Urrosacin,  72 
Use  of  food,  83 

of  villi  in  absorption,  104 
Uterus,  888 
Utriculus  of  ear,  868 


yAGINA,  sgg 
V      Vagus  nerve,  669 
Valsalva,  sinus  of,  271 
Value  of  food  for  heat,  495,  497 
Valves  of  heart,  269 

position  of,  285 

of  large  intestine,  181 

of  veins,  361 
Variation  in  calibre  of  capillaries,  352 

in  number  of  white  corpuscles,  224 

in  temperature  of  blood,  212 

negative,  596 
Varieties  of  cells,  45 

of  crystals  of  hasmoglobin,  249 

of  gases  in  the  blood,  255 

of  lobules  of  lungs,  400 

of  muscle,  875 
Vascularity  of  spleen,  229 
Vascular  system,  development  of,  918 
Vasodilator  nerves,  733 
Vasomotor  centre,  732 
Vaso-vasorum  of  arteries,  293 

of  veins,  361 
Vegetable  foods,  composition  of,  86 
Veins,  361 

anastomoses  of, 

as  a  means  of  absorption,  189 

blood  pressure  in,  361 

circulation  in,  rapidity  of,  369 

coat  of,  369 

contractility  of,  369 

elasticity  of,  362 

flow  of  blood  in,  365 
causes  of,  365 

sets  of,  361 

strength  of,  363 

structure  of,  361 

valves  of,  361 

vaso-vasorum  of,  361 
Velocity  of  the  blood,  341 
in  capillaries,  352 

of  nerve  force,  545 
Venous  blood,  color  of,  213 

gases  in,  259 
Ventricles  of  heart,  265 
Vertebrates,  nerves  of,  533 

red  blood-corpuscles  of,  221 
Vibrations  in  larynx,  845 


Villi,  structure  of,  195 

uses  of,  in  absorption,  194 

Vision,  169 

binocular,  806 

Vitreous  humor,  781 

Vivisection,  39 

Voit's  respiratory  apparatus,  447 

Volatile  acids  in  urine,  52 

WALKING,  883 
Walls  of  uterus,  889 
Water,  amount  of,  in  blood,  242 
in  coagulation  of  blood,  236 
quantity  of,  in  body,  50 
Watery  vapor,  exhalation  of,  456 
Weight  of  brain,  707 
of  heart,  277 
of  spinal  cord,  623 
Whippe,  545 
White  blood-corpuscles,  223 

chemical  constituents  of,  223 
derivation  of,  225 

foetal,  225 
difference  from  red,  224 
discovery  of,  223 
effect  of  acetic  acid  on,  223 

of  alkalies  on,  223 
effect  of  pregnane v  on,  224 
feeding  of,  223 
identit}r  with    those   of  lymph 

and  chyle,  224 
liver  as  a  source  in,  231 
locality  for  production  of,  226 
movements  of,  223 
nuclei  of,  223 
number  of,  223 
in  spleen,  229 
variations  in.  224 
position  of,  in  blood  stream,  224 
production  of,  231 
proportion  of,  to  red,  223 

variations  in,  224 
size  of,  223 

spleen  as  a  source  of,  231 
structure  of,  223 
suprarenal  body  as  a  source  of, 

232 
thymus  gland  as  a  source  of,  232 
thyroid  gland  as  a  source  of,  234 
transformation  into  red,  226 
White  matter  of  brain,  702 
Wine,  composition  of,  '.'7 
Work  done  by  heart,  281 


ZONA  opaca,  905 
Zona  pellncida,  905 


60 


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